8.6: Endocrine Glands – Biology LibreTexts

Organs with Secondary Endocrine Functions

There are several organs whose primary functions are non-endocrine but that also possess endocrine functions. These include the heart, kidneys, intestines, thymus, gonads, and adipose tissue.

The heart possesses endocrine cells in the walls of the atria that are specialized cardiac muscle cells. These cells release the hormone atrial natriuretic peptide (ANP) in response to increased blood volume. High blood volume causes the cells to be stretched, resulting in hormone release. ANP acts on the kidneys to reduce the reabsorption of Na⁺, causing Na⁺ and water to be excreted in the urine. ANP also reduces the amounts of renin released by the kidneys and aldosterone released by the adrenal cortex, further preventing the retention of water. In this way, ANP causes a reduction in blood volume and blood pressure, and reduces the concentration of Na⁺ in the blood.

The gastrointestinal tract produces several hormones that aid in digestion. The endocrine cells are located in the mucosa of the GI tract throughout the stomach and small intestine. Some of the hormones produced include gastrin, secretin, and cholecystokinin, which are secreted in the presence of food, and some of which act on other organs such as the pancreas, gallbladder, and liver. They trigger the release of gastric juices, which help to break down and digest food in the GI tract.

While the adrenal glands associated with the kidneys are major endocrine glands, the kidneys themselves also possess endocrine function. Renin is released in response to decreased blood volume or pressure and is part of the renin-angiotensin-aldosterone system that leads to the release of aldosterone. Aldosterone then causes the retention of Na⁺ and water, raising blood volume. The kidneys also release calcitriol, which aids in the absorption of Ca²⁺ and phosphate ions. Erythropoietin (EPO) is a protein hormone that triggers the formation of red blood cells in the bone marrow. EPO is released in response to low oxygen levels. Because red blood cells are oxygen carriers, increased production results in greater oxygen delivery throughout the body. EPO has been used by athletes to improve performance, as greater oxygen delivery to muscle cells allows for greater endurance. Because red blood cells increase the viscosity of blood, artificially high levels of EPO can cause severe health risks.

The thymus is found behind the sternum; it is most prominent in infants, becoming smaller in size through adulthood. The thymus produces hormones referred to as thymosins, which contribute to the development of the immune response.

Adipose tissue is a connective tissue found throughout the body. It produces the hormone leptin in response to food intake. Leptin increases the activity of anorexigenic neurons and decreases that of orexigenic neurons, producing a feeling of satiety after eating, thus affecting appetite and reducing the urge for further eating. Leptin is also associated with reproduction. It must be present for GnRH and gonadotropin synthesis to occur. Extremely thin females may enter puberty late; however, if adipose levels increase, more leptin will be produced, improving fertility.

Endocrine Glands – an overview

VIII Endocrine System

The endocrine system consists of the glands of the body that secrete the chemical substances known as hormones. Hormones are secreted into the bloodstream and are carried by the blood to other parts of the body, where their actions are exerted. The major endocrine glands include the hypothalamus, pituitary, thyroid, parathyroid, adrenal gland, kidney, pancreas, ovaries, and testes. Because hormones are secreted into the blood, they have the potential to reach all cells in the body. However, they act only on those “target” cells with specific receptors designed to recognize and respond to a particular hormone. Hormones have some regulatory effect on virtually every system in the body. In-flight and postflight values described below are all mean values, and are compared to preflight values.

Cortisol is produced in the adrenal cortex in response to stress and has many effects on human physiology. Plasma cortisol levels were decreased by 27% after Apollo missions, while levels in urine were increased by 24%. Urinary cortisol levels were increased in-flight and postflight during Skylab, and postflight in Salyut-6, while plasma values for cortisol were generally not significantly altered after either mission. Spacelab-1 astronauts also showed an elevation of cortisol levels in the urine, indicating that the adrenal glands are activated during spaceflight. Interestingly, however, adrenocorticotropic hormone (ACTH), which is released by the anterior pituitary and controls the release of cortisol from the adrenal cortex, showed no change in urine concentration. Plasma ACTH levels were decreased by 24% in Apollo crew immediately postflight and were decreased slightly in Skylab crew in-flight and postflight. There were no significant changes in Salyut-6 or Spacelab-1.

Thyroxine, which is involved in growth, and insulin, which regulates glucose concentration in the blood, were found to be increased in plasma sampled postflight after Skylab, Apollo, and Salyut-6 missions. Yet, plasma insulin levels were found to be decreased in Skylab samples taken in-flight. During the 17-day-long STS-78 mission, the exercise-induced release of growth hormone was suppressed, while in other studies of postflight missions growth hormone was found to be elevated. These contrary hormone levels may simply indicate different levels of stress following landing.

Blood samples from the 125 crewmembers on the first 24 NASA space shuttle flights were tested for levels of cholesterol, triglycerides, very low density-lipoprotein cholesterol (VLDL-C), low-density-lipoprotein cholesterol (LDL-C), and high-density-lipoprotein cholesterol (HDL-C). Only HDL-C levels decreased on the day of landing. Measurements taken 3–23 days after spaceflight revealed significant decreases in total cholesterol, LDL-C, and HDL-C. The increase in thyroxine, growth hormone, and insulin levels seen during postflight and reduced physical activity may have contributed to these alterations.

Vitamin D hormone, calcitonin, and parathyroid hormone are potent activators of bone remodeling. Changes in their levels could affect bone cell activity of astronauts and lead to space-induced osteoporosis (bone destruction). During the 8-day NASA Spacelab-2 mission, vitamin D hormone levels increased initially, but normalized in all astronauts by the end of the seventh day of flight. In contrast, levels of parathyroid hormone, calcium, phosphorus, and albumin remained normal throughout the mission. Others have indicated that low levels of serum testosterone may also lead to bone remodeling.

Urine concentrations of epinephrine and norepinephrine, hormones that contribute to nervous system regulation, were decreased in-flight during Skylab, but increased postflight. Blood and urine concentrations of these hormones were also increased postflight in Salyut-6 crew, but in Apollo crew, urine epinephrine levels were decreased postflight.

The regulation of electrolytes in the body, especially sodium and potassium, is another function of the endocrine system. Antidiuretic hormone (ADH) increases water retention, but it is unclear whether ADH levels are altered during spaceflight. Since the fluid shifts in-flight result in a loss of fluid from the blood and the interstitial spaces, it may be that decreases in body mass seen during the first few days of flight are strictly due to fluid loss via the digestive system and not diminished ADH activity.

With a lowered fluid volume in the body, levels of sodium, potassium, and other electrolytes (including chloride, calcium, magnesium, phosphorus, and phosphate) also should be altered to maintain a constant salt concentration. Postflight fluid levels would then need to be reestablished to preflight levels, so fluid and electrolyte retention or excretion would reverse. Calcium and phosphorus retention or excretion is usually indicative of bone metabolism. In Apollo crew, a 7. 3% decrease in serum potassium and 4.5% decrease in magnesium were seen immediately after flight. There were no significant changes in serum sodium or chloride. Yet, in urine taken during the first 24 hr after recovery, significant decreases in sodium, potassium, chloride, and magnesium concentrations were seen.

Aldosterone is released by the adrenal glands in response to elevated plasma potassium levels, reduced sodium levels, and low arterial blood pressure. Aldosterone causes an increased retention of sodium and excretion of potassium, both of which are also important in nervous system function. Angiotensin I is produced in response to kidney reflexes and stimulates the production of aldosterone by the adrenal glands. In Apollo crewmembers, angiotensin I values in plasma increased 488% and urinary aldosterone increased 57% during the first day following recovery. As a result, there was a 32% decrease in urine volume accompanied by a 20% increase in osmolarity (concentration of salts). Despite these changes, postflight sodium and potassium levels were not significantly altered in serum.

Angiotensin I was generally elevated in the plasma of Skylab crew in-flight, although not always significantly, and potassium was increased in-flight and immediately after recovery. Plasma aldosterone levels varied in-flight but were significantly increased postflight. Plasma levels of sodium, chloride, osmolarity, and ACTH were lower in-flight than preflight. In-flight, urinary sodium, potassium, chloride, calcium, phosphates, serum osmolarity, and aldosterone were significantly increased.

During long-term missions (from 18 to 366 days) on board the Salyut and Mir, metabolite studies showed generally a reduction in body water and electrolytes, as well as changes in blood hormone levels and urinary hormone excretion. The crews of two Life Sciences Space Shuttle missions showed no changes in ACTH, growth hormone, insulin-like growth factor I, and C-peptide. However, free 3,5,3′-triiodothyronine prostaglandin E2 (PGE2) and its metabolite, PGE-M, were decreased during spaceflight. The plasma amino acid distribution patterns of four crewmembers of the 1993 SLS-2 Columbia Shuttle mission showed changes between flight day 2 and flight days 8 and 12. With increasing time in space, there was an increase in the concentration of the amino acids leucine and isoleucine. On the day of landing, the concentration of the total essential amino acids and especially that of the branched-chain amino acids were decreased. This may be simply part of the reduced body protein levels observed or may be a consequence of the hormonal changes seen.

Pregnant rats that were flown on 9- or 11-day spaceflights at the midpoints of their pregnancies and then returned to earth 2 or 3 days before delivery had more lordosis contractions during labor than did ground-based controls, but did not differ from the ground-based controls in the length of their labor, number of pups per litter, birth weights of the neonates, or mammary metabolism (measured in terms of mRNA expression of a major milk protein). However, in males, scientists have reported testicular dysfunction and a subsequent reduction in testosterone production. While this problem has been shown to be reversible, it may be of some consequence for reproduction for individuals staying for long periods at the proposed International Space Station.

What Is It & Definition

What is the pituitary gland?

Your pituitary (hypophysis) is a pea-sized endocrine gland at the base of your brain, behind the bridge of your nose and directly below your hypothalamus. It sits in an indent in the sphenoid bone called the sella turcica. The pituitary gland is one of eight interrelated major endocrine glands:

• Pineal gland.
• Pituitary gland.
• Thyroid gland.
• Thymus.
• Adrenal gland.
• Pancreas.
• Ovary (women only).
• Testis (men only).

The pituitary is often referred to as the “master gland” because it not only secretes its own hormones, it tells other glands to produce hormones.

Your pituitary gland is divided into two main sections: the front (anterior) lobe and the back (posterior) lobe. Connecting the hypothalamus and pituitary gland is a stalk of blood vessels and nerves. Through that stalk, the hypothalamus communicates with the anterior lobe via hormones and the posterior through nerve impulses.

The hypothalamus, which is above your pituitary gland, is the control center of some of your body’s basic operations. It sends messages to your body’s autonomic nervous system, which controls things like blood pressure, heart rate, respiration, body temperature, sleep-wake cycle and digestion. The hypothalamus also tells the pituitary gland to produce and release hormones.

What does the pituitary gland do?

Glands are organs that secrete hormones — the “chemical messengers” of the body — that travel through your bloodstream to different cells, telling them what to do. The major hormones produced by the pituitary gland are:

• ACTH: Adrenocorticotrophic hormone. Stimulates the production of cortisol, a “stress hormone” that maintains blood pressure and blood sugar levels.
• FSH: Follicle-stimulating hormone. Promotes sperm production and stimulates the ovaries to produce estrogen.
• LH: Luteinizing hormone. Stimulates ovulation in women and testosterone production in men.
• GH: Growth hormone. Helps maintain healthy muscles and bones and manage fat distribution.
• PRL: Prolactin. Causes breast milk to be produced after childbirth. It also affects hormones that control the ovaries and testes, which can affect menstrual periods, sexual functions and fertility.
• TSH: Thyroid-stimulating hormone. Stimulates the thyroid gland, which regulates metabolism, energy and the nervous system.
• Oxytocin: Helps labor to progress, causes breast milk to flow, affects labor, breastfeeding, behavior and social interaction and the bonding between a mother and child.
• ADH: Anti-diuretic hormone, or vasopressin. Regulates water balance and sodium levels.

Hormones are not released from the pituitary gland in a steady stream. They come in bursts, every one to three hours, and alternate between periods of activity and periods of inactivity.

What happens when the pituitary gland doesn’t work properly?

Your pituitary gland plays such an important role that a lot can go wrong if it overproduces hormones (hyperpituitarism) or under-produces hormones (hypopituitarism). Overproduction or underproduction can affect metabolism, growth, blood pressure, sex functions and more.

Pituitary disorders occur when your pituitary gland fails to function as it normally should, likely because of a tumor, which is an abnormal growth of cells. Expert endocrinologists determined that about one in five people will get a tumor in their pituitary gland (16% to 20% of the population). Thankfully, the tumors are usually noncancerous (benign). Cancers of the pituitary gland rarely happen. Sometimes a pituitary gland will even have a tumor for years that’s both benign and doesn’t cause any symptoms.

There are two types of tumors: functioning and nonfunctioning. A functioning tumor produces hormones itself and a nonfunctioning tumor does not. Nonfunctioning tumors are more common.

You should see an endocrinologist, a specialist in the pituitary gland, if you have a tumor. You may also need to see an ophthalmologist (eye doctor) and neurosurgeon (a surgeon who operates on the brain, the head and the nervous system).

What are the symptoms of a pituitary tumor?

Many symptoms may point towards a pituitary tumor. If the tumor is putting pressure on the gland, your symptoms could include:

• Headaches.
• Vision problems (including trouble with peripheral vision).

If the pituitary gland is not producing enough hormones, your symptoms could include:

• Fatigue.
• Dizziness.
• Dry skin.
• Irregular periods (women).
• Sexual symptoms (men).

Additional symptoms include:

• Mood changes.
• Irritability.
• Muscle weakness.
• Depression.
• Menstrual cycle changes.
• Erectile dysfunction.
• Infertility.
• Inappropriate breast growth.
• Inappropriate production of breast milk.

There are several conditions that involve the pituitary gland:

• Hypopituitarism: Hypopituitarism is when the pituitary gland doesn’t make enough hormones.
• Acromegaly (Gigantism): Gigantism is a very rare disorder caused when the pituitary gland produces too much growth hormone (GH).
• Diabetes Insipidus: This is a disorder affected by vasopressin, the antidiuretic hormone (ADH). If you have this disorder, your kidneys can’t retain water, which results in increased urination and increased thirst.
• Hypogonadism: Also known as testosterone deficiency, this condition is a failure of the testes to make testosterone and/or sperm.
• Prolactinoma: This is a type of tumor that causes the pituitary gland to produce too much of the prolactin hormone.
• Galactorrhea: Galactorrhea is when a man or a woman produces breast milk when they’re not breastfeeding.
• Cushing’s syndrome: This rare condition can happen when your body makes too much ACTH, which causes another gland in the body, your adrenal glands, to make too much cortisol. This condition can affect almost any tissue in the body.
• Adult GH deficiency syndrome: Problems resulting from this syndrome include changes in body composition due to changes in fat and muscle, bad cholesterol levels and loss of energy and/or interest in hobbies and social activities.
• Empty sella syndrome: The sella turcica is the bone structure that surrounds and protects the pituitary gland. Empty sella syndrome means that nothing appears, at first, to be inside that bone structure. The pituitary gland may be flat, smaller than normal, or regressed within the cavity because of an injury.
• Sheehan’s syndrome (postpartum hypopituitarism): Sheehan’s syndrome occurs when a woman has severe uterine hemorrhage during childbirth. Such severe blood loss causes some of the pituitary gland tissues to die.
• Craniopharyngioma: A craniopharyngioma is a rare tumor that puts pressure on the hypothalamus.
• Multiple endocrine neoplasia (MEN): MEN causes multiple glands to develop tumors.
• Lymphocytic hypophysitis: This is caused by immune cells that inflame the pituitary gland.

How are pituitary tumors treated?

Radiotherapy, medications and surgery may be necessary to treat a pituitary tumor.

• Radiotherapy — which may be performed before or instead of surgery — uses highly focused x-rays (Gamma knife or X-knife Linac), usually over several weeks.
• Medications are used to either reduce the levels of a particular hormone or replace a hormone that is under-produced.
• Surgery is called transsphenoidal surgery where the neurosurgeon makes an incision inside your nostril or under your upper lip. You’ll stay in the hospital for about five days after the tumor is removed. Recovery times vary. It could be as short as four weeks to as long as eight weeks. Regular follow-ups will be required.

Pituitary tumors can regrow.

Your pituitary gland affects vital areas of your body. If your pituitary gland doesn’t function properly, your skin, brain, reproductive organs, vision, mood, energy, growth and more could all be negatively affected. Your body depends on the hormones it produces and releases.

Contact your healthcare provider to address any symptoms that might point towards your pituitary gland.

Major Endocrine Glands Names Locations Products – Endocrine System Hormones And Their Sources

The main endocrine glands are the hypothalamus, pituitary (anterior and posterior), thyroid, parathyroid, adrenal (cortex and medulla), pancreas, and gonads. All these glands together form the endocrine system.

1. The hypothalamus is an endocrine organ located in the brain. The hypothalamus synthesizes hormones such as ADH and oxytocin. The hypothalamus also synthesizes and secretes regulatory hormones that control the endocrine cells in the anterior pituitary gland such as Gonadotropin-Releasing Hormone, Thyrotropin Releasing Hormone, Growth Hormone Releasing Hormone and somatostatin.

2. The pituitary gland, sometimes called the “master gland,” is located at the base of the brain. The pituitary has two distinct regions: the anterior pituitary and the posterior pituitary.

The anterior pituitary produces seven hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Anterior pituitary hormones are sometimes referred to as tropic hormones because they control the functioning of other organs. While these hormones are produced by the anterior pituitary, their production is controlled by regulatory hormones produced by the hypothalamus. The antidiuretic hormone (ADH) (or vasopressin) and oxytocin are produced by neurons in the hypothalamus and transported to the posterior pituitary. They are released into the circulatory system via neural signalling from the hypothalamus. These hormones are considered to be posterior pituitary hormones even though they are produced by the hypothalamus since that is where they are released into the circulatory system.

3. The thyroid gland, one of the largest endocrine glands in the body, is located in the neck, just below the larynx and in front of the trachea. The thyroid gland produces the hormones T3 (triiodothyronine) and T4 (thyroxine). These hormones increase the metabolic activity of the body‘s cells.

4. The parathyroid glands are small endocrine glands that produce parathyroid hormone. Most people have four parathyroid glands; however, the number can vary from two to six. These glands are located on the posterior surface of the thyroid gland.

5. Adrenal glands are a pair of ductless glands located above the kidneys. The adrenal glands produce glucocorticoids and androgens, which are sex hormones that promote masculinity. Androgens are produced in small amounts by the adrenal cortex in both males and females. They do not affect sexual characteristics and may supplement sex hormones released from the gonads. The adrenal medulla contains large, irregularly-shaped cells that are closely associated with blood vessels. The adrenal glands also produce epinephrine (adrenaline) and norepinephrine (noradrenaline) in response to stress.

6. The pancreas is an elongated organ that is located between the stomach and the proximal portion of the small intestine. It contains both exocrine cells that excrete digestive enzymes and endocrine cells that release hormones. As an endocrine gland, the pancreas produces several important hormones, such as insulin and glucagon in the islets of Langerhans, which are secreted into the bloodstream to regulate blood sugar levels.

7. The pineal gland is a small endocrine gland in the brain. It is located near the center of the brain, between the two hemispheres. The main hormone produced and secreted by the pineal gland is melatonin.

8. The gonads are additional types of endocrine glands. They are the sex organs and include the male testes and female ovaries. Their main role is the production of steroid hormones. The testes produce androgens, which allow for the development of secondary sex characteristics and the production of sperm cells. The ovaries produce hormones, such as estrogen and progesterone, which cause secondary sex characteristics and prepare the body for childbirth.

Practice Questions

Khan Academy

ACE Inhibitors and the Renal Regulation of Blood Pressure

Cushing’s syndrome and the hypothalamic-pituitary axis

MCAT Official Prep (AAMC)

Online Flashcards Biology Question 23

Section Bank B/B Section Passage 7 Question 46

Section Bank B/B Section Passage 7 Question 51

Practice Exam 3 B/B Section Question 29

Sample Test B/B Section Passage 8 Question 41

Sample Test B/B Section Passage 8 Question 42

Sample Test B/B Section Passage 8 Question 43

Key Points 

• The hypothalamus synthesizes hormones and transports them to the posterior pituitary gland while also synthesizing and secreting regulatory hormones that control cells in the anterior pituitary gland.

• The anterior pituitary gland, regulated by the hypothalamus, produces seven tropic hormones, growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), which control the functioning of other organs.

• The posterior pituitary stores hormones produced by the hypothalamus (ADH and oxytocin) and release them into the bloodstream; the gland does not actually produce any hormones.

• The thyroid gland produces T3, T4 and calcitonin hormones.

• Parathyroid glands are responsible for the regulation of the body’s calcium and phosphorus levels by producing parathyroid hormone, which helps control calcium release.

• The two major hormones produced by the adrenal cortex are the mineralocorticoids, which regulate the salt and water balance, and the glucocorticoids, which can regulate blood glucose and the body’s inflammatory response.

• There are three main glucocorticoids: cortisol, corticosterone, and cortisone.

• The adrenal medulla produces the hormones epinephrine and norepinephrine; these hormones regulate heart rate, breathing rate, cardiac muscle contractions, blood pressure, and blood glucose levels.

• Glucagon and insulin are examples of hormones created by the pancreas that regulate the blood sugar levels.

• The pineal gland, a small endocrine gland in the brain, is responsible for producing hormone melatonin involved in the regulation of biological rhythms, mainly circadian rhythms.

• The gonads (the testes in males and ovaries in females) are responsible for the production of steroid hormones, such as testosterone, estrogen, and progesterone.

Key Terms

Hypothalamus: a region of the forebrain located below the thalamus that regulates body temperature, some metabolic processes and governs the autonomic nervous system

Glucocorticoid: any of a group of steroid hormones, produced by the adrenal cortex, that are involved in metabolism and have anti-inflammatory properties

Epinephrine: (adrenaline) an amino acid-derived hormone secreted by the adrenal gland in response to stress

Islets of Langerhans: regions in the pancreas that contain its endocrine cells

Exocrine: producing external secretions that are released through a duct

Androgen: the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates.

Oxytocin: a hormone that stimulates contractions during labor, and then the production of milk

Antidiuretic hormone: a hormone secreted by the hypothalamus to control water levels in the body

Parathyroid hormone: a hormone secreted by the parathyroid glands that regulate the calcium concentration of blood

Melatonin: a hormone that regulates the sleep-wake cycle

Endocrine Function – Hormonal and Metabolic Disorders

Q5 Prepare a Table having two columns depicting names of end

“hello everyone a welcome to yet another
little homework session
in today’s class we are going to be
doing a science problem so let’s begin
with the question
the question here is prepare a table
having two columns
depicting names of endocrine gland
and hormone separated by them so we have
to
name the endocrine glands
and the hormones it secretes
so let’s first know how many glands does
how many glands does endocrine have so
endocrine
have six glances so that means
we have hormones those gland secretes
also
so let’s begin with the glands
endocrine glands
endocrine
plants and hormones
and hormones
so let’s begin with the first endocrine
plant
first one is pituitary gland
plant
so the pituitary gland secretes the
growth hormone
growth hormone
so pituitary glands secretes growth
hormone
now the next one second one is
thyroid so thyroid gland
thyroid
thyroid now thyroid gland secretes
thyroxine thyroxine
now the third one third one
is adrenal
adrenal now adrenal gland secretes
adrenaline
adrenaline
now the fourth one
pan cream yes so pancreas secretes
what yes insulins
so pancreas secretes
insulins
now the fifth one fifth one is
testes testes
and testes secrets testosterone
testosterone
now the last gland that is ovaries
over race
now what does ovary secretes ovary
secretes
ostrogen and progestery
ostrogen
i
so friends see we have here our six
glands so let’s just summarize it again
the first gland is pituitary
and it secretes growth hormone second
is thyroid and it secretes thyroxine
third one is adrenal and it secretes
adrenaline fourth one is pancreas
it secretes insulin
fifth one is testis it secretes
testosterones sixth one is ovaries
and it secretes ostrogen and
progesterone
so friends i hope you have understood
the solution of this question
if you have any doubts or queries please
comment below and if you like this video
give it a big thumbs up
and for further such videos please
subscribe to the channel
till then thank you all”

Top 8 Types of Classical Endocrine Glands

The following points highlight the top eight types of classical endocrine gland. The types are: 1. Hypothalamus 2. Pituitary Gland 3. Pineal Gland 4. Endocrine Pancreas 5. Thyroid Gland 6. Parathyroid Gland 7. Thymus Gland  8. Adrenal Gland.

Classical Endocrine Glands: Type # 1. Hypothalamus:

The hypothalamus is anatomically basal part of diencephalon. It forms the walls and lower part of the third ventricle of brain. In mam­mals, neurosecretory cells are highly aggre­gated in this region. It controls the entire endocrine mechanism within the body through pituitary gland.

Hence it can be popularly called as super master gland. It secretes various releasing hormones which in turn stimulate specific cells of pituitary for secretion of pituitary hormones.

Anatomy of Hypothalamus:

Hypothalamus lies in close contact with optic chiasma, the infundibulum, median eminence and mammillary body. The vascular link between the median eminence and the pituitary gland is known as the hypothalamohypophysial portal sys­tem (Fig. 4.1).

Histology of Hypothalamus:

Within the hypothalamus, huge clusters of neurosecretory cells present called hypothalamic nuclei which are lo­cated around the third ventricle.

In mammals, hypothalamus consists of paired neurosecretory hypothalamic nuclei like anterior hypothalamic (AH), suprachiasmatic (SC), ventromedial (VM) dorsomedial (DM), posterior hypothalamic (PH), supra optic (SO), Para-ventricular (PV), Periventricular and actuate nuclei (AN).

These nuclei are responsible for secretion of different releasing hormones from hypothala­mus. The hypothalamic hormone secretion is controlled by neural activity or feedback mechanism (Fig. 4.2, 4.3 & 4.4).

Hypothalamic hormones (see Table 4.1) go from the neurons to the blood capillaries of the portal system and then to the target cells of the pituitary.

Classical Endocrine Glands: Type # 2.

Pituitary Gland:

In vertebrates, pituitary gland is known as ‘Master gland’, because it initiates all the physiological functions, as well as controls the secretions of other endocrine glands. This gland was identified by Vesalius in the 16th century. After that its biological func­tions worked out by Aschner (1910), Smith (1926), Riddle (1933) etc. Holmes and Ball (1974) studied the ultra-structural details.

The name pituitary is derived from Latin word “Pituita” means mucus.

Development of Pituitary Gland:

This gland is developed from two embryological primordia. The pos­terior pituitary (neurohypophysis) is derived from infundibular region of diencephalon and anterior pituitary (adenohypophysis) is developed from the buccal epithelium.

Buccal epithelium gives an evagination, called Rathke’s pouch. At the sometime, infundibulum shows downward projection to­wards Rathke’s pouch from the floor of dien­cephalon. Ultimately both the walls fuse to­gether. Thereafter Rathke’s pouch losses its connection from the surface epithelium. Cells of the Rathke’s pouch proliferate to give rise to the histological details of ante­rior pituitary.

Accordingly nerve fibres grow into the infundibulum from hypothalamus and give rise the neurosecretory cells of poste­rior pituitary. Continued proliferation of cells of Rathke’s pouch leads to the reduction of lumen of the pouch to a residual cleft or inter-glandular cleft.

Infundibular growth fi­nally forms the stalk of pituitary gland, by means of which the gland is connected with the diencephalon. Thus the gland remains under the hypothalamus, hence it is known as hypophysis. It is connected with the 3rd ventricle of diencephalon. This gland is placed in a concavity of sphenoid bone called sellaturcica (Fig. 4.5).

External Anatomy of Pituitary Gland:

1. The pituitary gland is very small and red­dish or pinkish in colour.

2. Pituitary Gland is more or less oval in shape.

3. Sizes vary from 2-10 µm in length and 0.5-0.7 mm in thickness.

4. Anatomically it is divided into two parts—Adenohypophysis and neurohy­pophysis.

5. Pituitary gland is innervated by sympathetic nerves and blood vessels (Fig. 4.6).

Description of Adenohypophysis:

Adenohypophysis in most important part of pituitary and it constitutes about 75% of the gland. It is glandular in nature and secretes various kinds of hormones. Histologically it is divided into three parts—pars distal is, pars inter-media and pars tuberalis.

(A) Pars Distalis:

1. It is the main part of adenohypophysis.

2. This part of the gland is composed of ir­regular masses and cords of epithelial cells separated by sinusoids and sup­ported by loose framework of connec­tive tissue.

3. Routine staining of pars distalis with orange-G, PAS, Mallory Aniline blue etc. reveals two major varieties of gland cells like chromophobe cells and chromophil cells which constitute about 60% of glan­dular part of Pars distalis (Fig. 4.7).

(a) Chromophobe cells:

These types of cells are not stained with any dye. These cells have less cytoplasmic and lack secretory granules. E.M. structure shows that chromophobe cells contain very fine basophilic granules. Some histologists believe that these cells are embryonic con­dition of chromophil cells.

(b) Chromophil cells:

These types of cells take up both acid and basic dye. Thus these cells are further divided into acidophil and basophil cells.

Among these acidophil cells are about 85% and basophil cells are about 15%.

These cells secrete different type’s hor­mones.

Following types of chromophil cells are identified:

1. Acidophil cells: It is of two types (a) STH cells (b) LTH cell

(a) STH cells:

These cells ovoid or round in shape. Nucleus is central in posi­tion and cytoplasm is packed with acidophil granules. Size of the gran­ules varies from 350-400 mµ. Histo-chemically orange-G positive. It secretes STH hormone which is pro­tein in nature.

(b) LTH cell:

These cells are ovoid or el­lipsoidal in shape. Nucleus is at the centre and cytoplasm is packed with large granules. Sizes vary from 600- 900 mµ. Histo-chemically orange-G positive. It secretes protein hormone prolactin or LTH.

2. Basophil cells:

These cells are of four types: (a) FSH cells (b) LH/ICSH cells (c) TSH cells (d) ACTH cells.

(a) FSH cells:

These cells are large, round in shape. The nucleus is slightly wrinkled and the cytoplasm is packed with dense spherical gran­ules. Sizes vary from 150-300 mµ. These cells secrete hormone FSH which is glycoprotein in nature. His­tologically orange-G negative.

(b) LH/ICSH cells:

These cells are round or polygonal in shape. Nucleus is wrinkled. Size of the cytoplasmic granules vary from 100-300 mµ. These cells secrete glycoprotein hor­mone, LH in case of female and ICSH in males. Cells are histo-chemically orange-G negative.

(c) TSH cells:

These cells are irregular in shape and nucleus is round and centrally placed. Cytoplasmic gran­ules are fine and measured about 100-140 mµ. These cells secrete gly­coprotein hormone TSH. It is orange- G negative.

(d) ACTH cells:

These cells are round and small in sizes with central round nucleus cytoplasmic granules are very fine and comparatively low in number and measured about 100 mµ. They secrete glycoprotein hormone ACTH. Histo-chemically they are or­ange-G negative (Fig. 4.8) & (Table 4.2).

(B) Pars Inter-media:

This zone is anatomically associated with the neural lope and separated from pars distal is by inter-glandular cleft.

Anatomical variations:

1. It is absent in whales and dolphin;

2. In desert mammals it is well developed.

3. In man pars inter-media is reduced.

Histology of Pituitary Gland:

It consists of basophilic and chromo-phobic cells. It consists of melano­cyte cells and fibrous tissue. E.M. study re­veals that nucleus of melanocyte is round and central in position. Several mitochon­dria, ER, Golgi bodies are well apparent. Cytoplasm is filled up with secretory gran­ules (Fig. 4.9).

(C) Pars Tuberalis:

It lies adjacent to pars distalis and pars inter-media. It is very close to the infundibulum stalk. It is separated from infundibulum by fibrous connective tissue. The main com­ponent of pars tuberalis in cuboidal or short columnar cells. These cells contain lipid and glycogen droplets. Hence they are Sudan black-B and PAS “+”ve. Actual endocrine function is not clear.

Description of Neurohypophysis:

Neu­rohypophysis is nervous in origin. Anatomi­cally it constitutes three parts—pars nervosa, median eminence and infundibulum.

Histology:

(A) Pars nervosa:

It is the main component and histologically following elements are found:

1. Pituicytes:

It is a type of neurosecretory cell. Cell is slightly elongated with dis­tinct cell body. Nucleus is round oval in shape with prominent chromatin materi­als. Dendritic processes are absent. Axonic process is slightly elongated and terminal portion is comb like in appear­ance.

Mitochondria, ER, Golgi appara­tus etc. are well apparent. Secretory vesicles and yellowish brown pigments are scatteredly distributed within the axonic process. Cells are Bromophenol Blue positive.

2. Mast cells:

These are round cells with central nucleus.

3. Herring bodies:

Non-nucleated nerve fi­bres aggregate together to form herring bodies.

4. Neuroglial cells:

Polygonal or round neuroglial cells or distinct between the pituicytes.

5. Nerve and sinusoids:

These are well ap­parent.

(B) Infundibulum:

It is the stalk of pituitary. It is made up of neuroglial cells. Blood sinu­soids and few neurosecretory cells present.

(C) Median eminence:

It is made up of hy­pothalamic cells neuroglia and blood ves­sels.

Classical Endocrine Gland: Type # 3.

Pineal Gland:

Pineal gland is an important endocrine gland in case of higher vertebrates. The name is derived from its pinecone like structure. This gland receives its stimuli through vision, hence it is also known as third eye. This gland was first discovered by Herophilus about 2000 yrs. ago.

Decartes (1646) said that it was the “seat of soul” and receives stimuli through eye. Lamer (1948) first established the biological function of this gland. He administrated pineal extract of cow into the amphibian skin and showed bleaching action on the skin.

Development of Pineal Gland:

Pineal gland is embryo- logically derived from neuroectoderm of the di-encephalic roof. The gland remains its con­nection with the diencephalon by a thin stalk.

Anatomy of Pineal Gland:

1. This gland is located on the dorsal sur­face of the brain (Fig. 4.11).

2. It is embedded in between the cerebellum and cerebrum.

3. The shape is flattened stalk like structure hence it is called epiphysis (Fig. 4.12).

4. It has sympathetic innervation.

Histology of Pineal Gland:

Pineal gland consists of two types of major cells—Pinealocytes and As­trocytes. Besides these connective tissue cells, mast cells, nerve fibres etc. also present.

EM Structure of Pinealocytes (Fig. 4.13)

The following points highlight the main features of Pinealocytes:

Features:

1. It is a neuro secretory cell.

2. It has nucleated cell body like structure and also possess short and long processes like neuron.

3. It is surrounded by plasma-membrane which is lipoprotein in nature.

4. Nucleus is slightly irregular in shape. It has prominent nucleolus and little RNA.

5. GER shows peripheral localization whereas SER are apparent near nucleus.

6. Free ribosomes are distributed in the cy­toplasm.

7. Golgi apparatus are prominent with vesicles and measure about 40-100 nm.

8. Mitochondria are very long (4-5.8 µm) and has elongated tubular cristae.

9. Centrioles are absent.

10. Lipid droplets and electron dense vesicles are apparent in the cytoplasm.

11. Dendrite like two short processes pre­sent.

12. Axon like long process has comb like ending.

13. Parallely arranged electron dense micro­tubules present and is known as synap­tic ribbon. Each tubule has electron dense core about 120 nm diameter.

Types:

There are two types of pinealocytes—

1. Light pinealocytes:

These are many and large cell types. Nucleus is greatly lobulated. Cytoplasm is basophilic and is de­void of glycogen. SER are more in num­bers in these cells. Ribosomes are more prominent. These cells are chiefly found near capillary endothelium. Synaptic rib­bon is prominent.

2. Dark pinealocytes:

These are few in number and comparatively small in sizes. Nucleus is comparatively less lobulated. Large amount of glycogen droplets present in the cytoplasm. These are dis­tributed near synaptic neurons.

EM Structure of Astrocytes (Fig. 4.14)

1. Present in between the pinealocytes and

2. These are small stellate shaped cells and are supposed to be modified neuroglial cells.

3. Nucleus is elongated and dense in na­ture.

4. Corpora arenacea

5. Have few mitochondria, Golgi bodies, ER and ribosomes.

6. Occasional deposition of glycogen drop­lets.

Note:

In human, pineal body often con­tains corpora arenacea, which are extracel­lular mineralized concentric organisation and mainly consist of calcium phosphate and carbonates. Function is not clear (wood, 1981) (Fig. 4.15).

Classical Endocrine Glands: Type # 4.

Endocrine Pancreas:

Pancreas is a very important gland in verte­brates. This gland contains both exocrine and endocrine parts hence it is called as Mixocrine gland. The endocrine part was first described by Langerhans in 1869, hence it is popularly known as Islets of Langerhans. In mammals, this gland is well developed.

Development of Endocrine Pancreas:

Pancreas is derived from endodermal lining of the duodenum.

Anatomy of Endocrine Pancreas:

1. The gland is elongated leafy structure lies in between the duodenal loop and is con­nected with the intestinal wall by pan­creatic duct (Fig. 4.16).

2. The gland is creamy white or light pink in colour.

3. The gland can be divided into a head, body and tail.

4. The head is an expanded portion that lies in the C-shaped curve of duodenum. It is joined to the duodenum by connective tissue.

5. The centrally located body and tapering tail extend to the left.

6. The pancreatic duct extends through the length of the gland and empties into the duodenum.

7. It is well vascularized and innervated by nerve fibres.

Histology of Endocrine Pancreas:

1. The gland is invested by thin fibrous tis­sue.

2. Internally consists of exocrine and en­docrine components and the ratio is 85:15.

3. Exocrine units or acini are basophilic in nature. Each acinus is lined by simple epithelium and the lumen of acinus is very narrow. The acinal cell contains basophilic zymogen granules in the cy­toplasm.

4. Islets of Langerhans are the endocrine units and are scatteredly distributed among the acini.

5. Islets are well vascularized mass of cells.

6. Shapes of islets vary and sizes vary from 20-300 µn.

7. Islets are whitish in colour and internally consist of blood sinusoids. Number of islets varies in species to species, for in­stance in man, there are about 1 million islets (Fig. 4.1 7).

8. After light microscopy, three types of cells are identified after Mallory Azan method—

9. Electron microscopy reveals that islets cells are of two categories—

(a) Major cells:

Three types, α, β and δ cells.

(i) α-cell:

Cells are tall and cylindrical. Cytoplasmic granules are about 250 nm in diameter. Each granule is in­vested by lipoprotein membrane. Granule is oval is shape and bears light eccentric cone. Nucleus is lobulated type. Cytoplasm contains Golgi complex, ER, ribosomes and filamen­tous mitochondria (Fig. 4.19).

(ii) β-cell:

Cells are more or less round or irregular in shape with central round nucleus. The cytoplasmic granules are hexagonal and lined by double layered membrane. Granules are about 300 nm in diameter with dense crystalline core. Cells contain more ER and free ribosomes than a-cells. Golgi bodies and mitochon­dria are apparent (Fig. 4.20).

(iii) δ-cell:

Cells are large spindle shaped. Cytoplasmic granules are very large and are about 325 nm in diameter. Each granule is lined by smooth membrane and contains ho­mogeneous matrix. Few glycogen and lipid droplets are visible. Cyto­plasmic inclusions like ER, ribo­somes, mitochondria, Golgi bodies are apparent. Nucleus is elliptical in shape (Fig. 4.21).

(b) Minor cells: Three types

(i) PP cells:

These cells are found in be­tween the duct of acini. They secrete pancreatic polypeptide.

a. It inhibits bile secretion

b. It inhibits enzyme secretion

c. Inhibits HCO^–₃ secretion.

(ii) Di cells:

Cells are columnar type and granules are 1.18 nm in diameter. Scatteredly distributed and secrete vasoactive intestinal polypeptide.

a. It increases enzyme secretion.

b. Increases bile secretion.

(iii) Ec cells:

Secrete exo-chromaffin hor­mone.

Remark:

In mammals, pancreatic islets are called β-islets, because of more in num­bers of β-cells (Fig. 4.18).

Classical Endocrine Gland: Type # 5.

Thyroid Gland:

The thyroid gland is one of the important en­docrine gland in vertebrate series. Its hor­mone is important in tissue differentiation, metamorphosis and iodine metabolism. From evolutionary standpoint, through iodine bind­ing capacity it is believed that thyroid gland is evolved from the endostyle of protochordates.

Kendall (1918) isolated the active com­ponent of the thyroid called thyroxine. The thyroid is unique among vertebrate endo­crine glands in that it stores its hormones extracellularly.

Development of Thyroid Gland:

Thyroid gland develops from the endoderm of the cephalic portion of alimentary canal of embryo. A sac like diverticulum first appears in the mid-ventral surface of the pharynx at the level of 2nd pair of pharyngeal pouches. The diverticu­lum expands and remains attached with the pharynx by a narrow solid duct, called thy- roglossal stalk. Later the stalk atrophies and the gland remains free (Fig. 4.22).

Anatomy of Thyroid Gland:

In mammals, thyroid gland is lobed in nature and lies on either side of up­ per part of trachea, just below the cricothy­roid cartilage. In man both the lobes are con­nected by Isthmus Bridge. The gland is oval or pear shaped. The gland is light pink in colour and is covered by fibrous capsule.

The size of the gland varies in species to spe­cies. For instance, in human, the gland mea­sures about 2.5-4 cm in length and 1.5-2 cm in width and 1-1.5 cm in thickness. Normal weight of the gland in human is 15-40 gm. It is well vascularized by thyroid artery and is innervated by sympathetic nerve fibres from cervical region of spinal cord (Fig. 4.23).

Histology of Thyroid Gland:

On light microscopy:

The gland is in­vested by outer capsule which is made up of white fibrous connective tissue. Internally it consists of many thyroid follicles. For in­stance, in rat there are about 100,000 thy­roid follicles. The follicles are of various sizes which vary from 15-150 µm in diameter. Large follicles are usually distributed to­wards the periphery and smaller are present near the centre.

Each follicle is lined by simple epithe­lium and epithelium is made up of cuboidal cells. Very thin basement membrane present outside the follicular epithelium. The lumen of the follicle is filled up with homogeneous, gelatinous material which is eosinophilic in nature after H-E stain.

Colloid is protein in nature is secreted by epithelial cells. Thyroid follicles are separated by con­nective tissue. Within the meshes of connec­tive tissue few lymphocytes, histocytes, sec­tions of blood vessels and nerves present (Fig. 4.24).

On Electron microscopy:

Electron mi­croscope reveals that follicular cells contain Golgi apparatus near the luminal end. Mito­chondria, ER and lysosomes are scattered throughout the cytoplasm. Nucleus is well apparent at the centre of the cell. There are fine terminal bars at the apical side of the follicular cells. Cells are held together with the help of terminal bars.

Histo-chemically lipid droplets, different proteins laden granules are observed. There are two types of cell are found chief follicular cells and Para follicular cells or C-cells. Chief follicular cells are the main constituent of follicular epithelium. Para follicular cells may occur within the follicular epithelium or in the regions between or ad­jacent to the follicles (Fig. 4.25).

In this article we will discuss about Comparative account of chief follicular cells and Para follicular Chief follicular cells. After reading this article you will learn about: 1.Chief follicular cells 2.Para follicular cell

Chief follicular cell:

1. Luminal side bears microvilli

2. Comparatively large in number.

3. Comparatively less number of mitochondria.

4. Has less oxidative enzyme.

5. Nucleus is round.

6. Enlargement of Golgi apparatus from TSH treatment

7. Cytology not altered by high blood calcium level.

8. ER larger in diameter.

9. Secretes T₃ and T₄.

10. Binds antibody to thyroglobulin.

Para follicular cell:

1. Microvilli absent.

2. Comparatively small in number.

3. Comparatively mitochondrial rich.

4. Has high concentration of oxidative enzyme.

5. Nucleus is irregular in outline.

6. Golgi apparatus prominent.

7. Degranulation due to high blood calcium level.

8. Comparatively less in diameter.

9. Secretes calcitonin.

10. Binds antibody to calcitonin

Classical Endocrine Glands: Type # 6.

Parathyroid Gland:

Parathyroid gland is anatomically associated with thyroid gland. It is responsible for cal­cium and phosphorus metabolism. The first anatomic description of this gland was given by Sand storm (1880).

Development of Parathyroid Gland :

Parathyroid gland is origi­nated from pharyngeal endoderm in associa­tion with 3rd and 4th pharyngeal pouches of mammals.

Anatomy of Parathyroid Gland:

1. In mammals, parathyroid glands are well developed and are embedded in the pos­terior surface of the thyroid gland.

2. Usually there are two parathyroids but four parathyroids are found in man, dog, cat, rabbit etc.

3. In man, four parathyroid are small oval bodies (6 x 3 x 2 mm) embedded in the thy­roid tissue. Total weight is about 140 mg.

4. The gland is well vascularized by supe­rior and inferior thyroid artery.

5. The gland is innervated by sympathetic nervous system (Fig. 4.26).

Histology of Parathyroid Gland:

1. Histologically the gland is made up of epithelial cells.

2. Two types of cells — Chief cells and oxyphil cells.

3. Chief cells are more numerous and com­prise about 99% of the Para thyroid’s cel­lular population cells are cuboidal in nature. The nucleus is round and cen­trally placed. Cytoplasm contains Golgi complex, ER, mitochondria and cytoplas­mic granules. Chief cells posses β-androgenic receptors as well as glucocorticoid receptors.

4. Oxyphil cells are large polyhedral in nature. These cells represent only about 1 % of the total parathyroid cellular popu­lation. These cells are eosinophilic cells rich in mitochondria.

5. Small colloidal vesicles and variable amounts of adipose tissue may be ob­served within the gland (Fig. 4.27).

Classical Endocrine Glands: Type # 7.

Thymus Gland:

Thymus is an important endocrine gland in mammals and plays an important role in im­mune mechanism at a young stage. It is rela­tively large organ at the time of birth and the maximum weight is attained in young age. For instance, in human children, the weight is about 30-40 gms. It undergoes age involu­tion and is partially replaced by fat and con­nective tissue.

Miller (1961) first recognized the immu­nological function of thymus. Good (1964), Cooper (1976), Londry et al. (1989), Kendeu (1990), Ritter and Crispe (1992) etc. studied the histology and endocrine functions of this gland.

Development of Thymus Gland:

Thymus gland arises as a thickening of the endodermal lining of pharyngeal pouches on each side. The thymic masses subsequently become separated from the pouches and remain as a separate gland. In mammals 3rd and 4th pouches are the sole contributors.

Morphological Description of Thymus Gland:

This gland lies between the posterior part of the thyroid gland and anterior end of pericardium. The gland lies on the surface of heart. It is bi- lobed structure. Each lobe is elongated flask shaped. The gland is well vascularized by blood vessels and lymph vessels. It is innervated by vagus nerve and cervical sympathetic nerves (Fig. 4.28).

Histology of Thymus Gland:

This gland is invested by a thin collagen connective tissue capsule. From the capsule connective tissue septa enter the gland and helps in the development of thymic lobules. Each lobule is of 0.5-2 mm in diameter. Each lobule comprises of dark stained peripheral zone, called cortex and central pale zone, called medulla. Within the gland, septa and trabeculae are formed by the connective tissue capsule extensions (Fig. 4.29).

(A) Cortex:

1. It is made up of loosely packed mass of cells. Cells are of different types.

2. The reticular cells are stellate type and have protoplasmic processes. The cells are acidophilic in nature, having oval nucleus (7-11 µm in diameters) with one or two nucleoli. EM study reveals that the processes are joined by desmosomes. The cytoplasm certain mitochondria, ER ribosomes, Golgi apparatus. Few vesicles are found, that are supposed to be lysosomes (Fig. 4.31).

3. Thymocytes, they are of large and small type. These cells are supposed to be modified lymphocytes. Cortex is consti­tuted by about 80% thymocytes.

Small thymocytes are more abundant than large thymocytes. Small thymocytes have dense round nucleus. Cytoplasm with few ribosomes, mitochondria and GER. Small type is about 7µm in diam­eter.

Large thymocytes have oval nucleus with rich chromatin material. Cytoplasm contains polyribosomes, few mitochon­dria, GER, vesicles and lipid droplets. They are more than 11µm in diameter.

4. A few plasma cells present.

5. Macrophages are scatteredly distributed in the cortex.

6. At the periphery of cortex and near the blood capillaries, the protoplasmic pro­cesses of reticulocytes form a continu­ous thin partition to separate the paren­chyma from blood capillaries, called blood-thymus barrier.

(B) Medulla:

1. It is the light stained central area of lob­ule.

2. Medulla is filled up with reticular cells, few thymocytes mast cells, eosinophil’s and very few macrophages.

3. Reticulocytes are of various shapes. Some have small cytoplasmic or large cytoplasmic filaments.

4. Small type thymocytes present.

5. Macrophages are rarely present.

6. Plasma cells are absent.

7. In the centre of medulla thymic or Hassal’s corpuscles present, which are concentrically arranged layers of modi­fied flattened reticular cells (Fig. 4.30).

Each corpuscle has a central calcified cell. Reticular cells are attached by desmosomes. Corpuscles are 100 µm or more in diameter. Each corpuscle in a section looks somewhat like a slice of onion.

Classical Endocrine Glands: Type # 8.

Adrenal Gland:

Adrenal gland is well known important en­docrine gland in vertebrate series. Anatomi­cally it is well developed in mammals. It performs various physiological functions. Eustachius (1563) first described adrenal gland in man. Addison (1855) first determined the clinical significance of the gland.

Development of Adrenal Gland:

Cuvier (1805) recognised two distinct regions in mammalian adrenal— cortex and medulla. Two components of this gland originate from different embryonic primordia. The cor­tex is derived from lateral mesoderm in close association with gonads.

The medulla differ­entiates from neural crest cells along with sympathetic ganglia. Hence cortical secre­tion is controlled by pituitary whereas med­ullary secretion is controlled by nervous stimulus.

Location of Adrenal Gland:

This gland is situated above the kidney hence it is known as supra renal gland (Fig. 4.32).

Anatomy of Adrenal Gland:

Light microscopic study:

The gland is oval or slightly triangular in nature. It is outerly covered by fibrous capsule. Histo­logically it consists of outer cortex and inner medulla (Fig. 4.33).

Cortex:

1. Cortex is made up of epithelial cells and is provided with blood sinusoids and nerves in section.

2. Cortex is histologically subdivided into 3 zones—zona glomerulosa, zona fasciculata and zona reticularis.

3. Zona glomerulosa:

This is the thin outer zone lies in parallel with outer fibrous capsule. It is made up of group of small columnar cells. These cells are arranged in clusters like bunch of grapes. This zone is light bluish in colour after H-E stain due to presence of basophilic granules.

The zona glomerulosa is not apparent in all mammals, like mice, lemurs and monkeys.

4. Zona fasciculata:

It is the widest middle layer of cortex. It is formed by polyhe­dral cells. Cells are arranged in the form of narrow columns or cords. Nuclei are larger and less dense. The cords of cells are surrounded blood sinusoids. Cyto­plasm contains brownish yellow pigment. After H-E stain, cytoplasm shows light pink in colour.

5. Zona reticularis:

It is the terminal sub-layer of cortex. It is made up of flat­tened irregular cells. Cells are arranged in irregular network fashion, this zone also contains few reticulin fibres. Hence this zone is called reticularis. Nuclei are dense in colour. After H-E stain, this zone looks much dark pink than fasciculata zone.

Medulla:

1. Medulla consists of large irregular cells.

2. Cells are packed with cytoplasmic gran­ules.

3. Large distinct nucleus present in each cell.

4. Large blood sinusoids are well apparent.

5. After H-E stain, medullary cells appear bluish in colour.

6. Medullary cells are also known as chro­maffin cells, because treatment of these cells with potassium dichromate or chro­mic acid results in formation of yellow­ish or brown oxidation product, the chro­maffin reaction.

The relative amounts of adrenocortical and medullary tissues vary in different spe­cies:

Additional zones:

Several unique adrenocortical zones are known in certain species of mammals. These zones may be conspicuous only at certain times in the life of an animal or in only one sex.

1. The Fetal zone:

In primates, a very con­ spicuous zone occupies the bulk of the adrenal gland prior to birth. Following birth this zone degenerates rapidly.

2. The mouse X-zone:

The cortex of the mouse adrenal contains a unique X-zone between zona reticularis and the me­dulla. The X-zone degenerates in males at puberty and in females of most nurse during the first pregnancy.

3. The special zone:

One marsupial brush tailed opossum (Trichosurus vulpecula) possesses a large inner special zone only in adult female.

Electron microscopic study (Fig. 4.34) Cortex

1. Zona glomerulosa:

(a) Cells are comparatively smaller than other zones.

(b) Plasma membrane shows small mi­crovilli.

(c) Well developed smooth ER present.

(d) Golgi apparatus present in very close association with nucleus.

(e) Rich in mitochondria which possess shelf like cristae.

(f) Few lipid droplets are found in the cytoplasm.

2. Zona fasciculate:

(a) Cells are relatively larger and pos­sesses huge amount of lipid droplets in the cytoplasm.

(b) Golgi complex distinct.

(c) Mitochondria are many and tubular in shape.

(d) ER much more in concentration.

(e) Microvilli are well apparent on the surface membrane.

(f) Few cells are spongy in appearance, (Anderson 1984).

3. Zona reticularis:

(a) Cells are comparatively larger.

(b) Lipid droplets are few and scattered in cytoplasm.

(c) Elongated mitochondria are well ap­parent.

(d) ER and Golgi apparatus are distinct.

(e) Secretory vesicles present.

(f) Microvilli distinct.

Medulla:

1. Cells have smooth plasma membrane.

2. Microvilli absent.

3. Mitochondria, ER and Golgi apparatus distinct.

4. Cytoplasm contains dark granules each granule is enclosed by smooth lipopro­tein membrane. The diameter of the gran­ule is about 200 µm.

5. There are two types of cells are found nor epinephrine cells and epinephrine cells.

6. Granules of nor epinephrine cells are much more electron dense than epineph­rine cells.

Endocrine system – Petroclinic in St. Petersburg

Endocrinology – the science of the structure and function of the endocrine glands (endocrine glands), the products they produce (hormones), the ways of their formation and action on the human body; and also about diseases caused by dysfunction of these glands or the action of these hormones.

All organs of the endocrine system are responsible for the timely flow of hormones into the bloodstream.

Hormones act as catalysts for chemical processes in the body, that is, they regulate the rate of most chemical reactions, in addition, through hormones, our body regulates the work of most organs and systems in the body.When the functions of the endocrine system are disrupted, the natural balance of metabolic processes is disturbed, which leads to a huge number of diseases.

Often, endocrine pathologies can be caused by trauma, intoxication, or diseases of other organs and systems. In any case, timely treatment of diseases of this type and timely preventive measures will significantly reduce the risk of many diseases.

All organs of the endocrine system have glands that produce hormones.All glands represent a single system, which is controlled by the pituitary gland and hypothalamus.

Diseases such as diabetes, obesity, erectile dysfunction are directly related to dysfunction of the endocrine glands.

The root cause of the onset of diseases of the cardiovascular system, joints, gastrointestinal tract can also be a metabolic disorder, which depends on the malfunctioning of the endocrine system.

That is why taking care of the endocrine system is the first step to health and longevity.

Major endocrinological diseases:

• diabetes mellitus;
• utoimmune thyroiditis;

90,023 nodular goiter;

90,023 diffuse goiter;

• hyperparathyroidism;
• Itsenko-Cushing’s disease;
• Addison’s disease;
• acromegaly;
• adreno-genital syndrome;
• hyperprolactinemia;
• osteoporosis;

90,023 obesity.

The reasons for the development of diseases of the endocrine system can be both genetic anomalies in the development of the body, and inflammatory processes, various toxic poisoning, iodine deficiency, autoimmune diseases, tumors, etc.

This is only a small part of the diseases of the endocrine system.
The popularity of an endocrinologist at the present time can be easily explained: it is this specialist who deals with such serious diseases as diabetes mellitus, obesity, thyroid diseases.

With early detection and the appointment of the correct treatment, it is possible to avoid severe changes in the organs and systems of the body.
Timely started treatment can reverse the processes and restore dysfunctions of the endocrine glands.

For all questions, please contact the specialists of our center:
from 8-00 to 22-00 on weekdays and from 9-00 to 18-00 on weekends

Phone: +7 (812) +7 (812) 490-76-00 (multichannel)

90,000 Endocrine system diseases – medical center “YOUR DOCTOR” Mine

It is represented by the endocrine glands, which produce hormones and control the work of organs, systems and the whole organism.

Etiology of diseases
• Heredity.
• Pathological endocrine glands as a result of infectious diseases.
• In utero formed deficiencies of the endocrine glands.
• Improper blood supply or hemorrhagic damage to organs that secrete hormones.
• Changes in hormonal levels due to the inflammatory process.
• Autoimmune damage.
• Neoplasms in the endocrine glands.
Provoking factors
• Exposure to the body of toxic substances or radiation.
• Nutritional deficiencies.
• People over 40 years old.
• Overweight.
• Restriction of physical activity.
• The production of unnatural hormones, the reason for this is a gene mutation.
• Disrupted transport or exchange of hormones while carrying a child.
• Tissue resistant to hormones due to impaired receptor function.
Disease manifestations
• Unreasonable change in body weight up or down.
• Disturbances in the work of the heart and blood vessels.
• Improper functioning of the digestive system.
• Neurological manifestations.
• Pathological metabolism.
• General malaise.

The most common pathologies

• Thyroid adenoma. Formed inside the tissues of the organ. Has a benign nature. Characterized by weight loss, sweating, tachycardia, palpitations.
• Acromegaly. Individual parts of the body are pathologically enlarged, which is associated with excessive production of growth hormone. The disease leads to the formation of a tumor in the pituitary gland.
• Hyperthyroidism. It develops due to a high concentration of thyroid hormones and is manifested by an accelerated metabolism.
• Hypothyroidism. It develops with insufficient thyroid function. It manifests itself as a slowed-down metabolism, severe weakness, drowsiness, speech slowdown, weight gain.
• Obesity. It develops when the balance of incoming and outgoing energy is disturbed. This disease is talked about with an increase in body weight by 20 or more kg. The hypothalamic-pituitary regulation of digestion is impaired.
• Diabetes. Due to a deficiency of insulin and an increase in the concentration of sugar in the blood, metabolism is disturbed. It manifests itself in the form of intense thirst, increased appetite, weakness, dizziness and poor tissue regeneration.

E20-E35 Disorders of other endocrine glands

E20 Hypoparathyroidism

• E20.0 Idiopathic hypoparathyroidism
• E20.1 Pseudohypoparathyroidism
• E20.8 Other forms of hypoparathyroidism
• E20.9 Hypoparathyroidism, unspecified

E21 Hyperparathyroidism and other disorders of the parathyroid [parathyroid] gland

• E21.0 Primary hyperparathyroidism
• E21.1 Secondary hyperparathyroidism, not elsewhere classified
• E21.2 Other forms of hyperparathyroidism
• E21.3 Hyperparathyroidism, unspecified
• E21.4 Other specified disorders of the parathyroid gland
• E21.5 Disease of the parathyroid glands, unspecified

E22 Pituitary hyperfunction

• E22.0 Acromegaly and pituitary gigantism
• E22.1 Hyperprolactinemia
• E22.2 Syndrome of inappropriate secretion of antidiuretic hormone
• E22.8 Other conditions of pituitary hyperfunction
• E22.9 Pituitary hyperfunction, unspecified

E23 Hypofunction and other disorders of the pituitary gland

• E23.0 Hypopituitarism
• E23.1 Medication hypopituitarism
• E23.2 Diabetes insipidus
• E23.3 Hypothalamic dysfunction, not elsewhere classified
• E23.6 Other diseases of the pituitary gland
• E23.7 Disease of the pituitary gland, unspecified

E24 Itsenko-Cushing’s Syndrome

• E24.0 Itsenko-Cushing’s disease of pituitary origin
• E24.1 Nielson’s Syndrome
• E24.2 Itsenko-Cushing’s drug syndrome
• E24.3 Ectopic ACTH syndrome
• E24.4 Cushingoid syndrome caused by alcohol
• E24.8 Other conditions characterized by cushingoid syndrome
• E24.9 Itsenko-Cushing’s syndrome, unspecified

E25 Adrenogenital disorders

• E25.0 Congenital adrenogenital disorders associated with enzyme deficiency
• E25.8 Other adrenogenital disorders
• E25.9 Adrenogenital disorder, unspecified

E26 Hyperaldosteronism

• E26.0 Primary hyperaldosteronism
• E26.1 Secondary hyperaldosteronism
• E26.8 Other forms of hyperaldosteronism
• E26.9 Hyperaldosteronism, unspecified

E27 Other adrenal disorders

• E27.0 Other types of adrenal cortex hypersecretion
• E27.1 Primary adrenal cortex insufficiency
• E27.2 Addison’s crisis
• E27.3 Drug-induced adrenal cortex insufficiency
• E27.4 Other and unspecified adrenal cortex insufficiency
• E27.5 Adrenal medulla hyperfunction
• E27.8 Other specified adrenal disorders
• E27.9 Disease of adrenal glands, unspecified

E28 Ovarian dysfunction

• E28.0 Excess estrogen
• E28.1 Androgen excess
• E28.2 Polycystic ovary syndrome
• E28.3 Primary ovarian failure
• E28.8 Other types of ovarian dysfunction
• E28.9 Ovarian dysfunction, unspecified

E29 Testicular dysfunction

• E29.0 Testicular hyperfunction
• E29.1 Testicular hypofunction
• E29.8 Other types of testicular dysfunction
• E29.9 Testicular dysfunction, unspecified

E30 Puberty disorders, not elsewhere classified

• E30.0 Delayed puberty
• E30.1 Premature puberty
• E30.8 Other disorders of puberty
• E30.9 Puberty disorder, unspecified

E31 Polyglandular dysfunction

• E31.0 Autoimmune polyglandular insufficiency
• E31.1 Polyglandular hyperfunction
• E31.8 Other polyglandular dysfunction
• E31.9 Polyglandular dysfunction, unspecified

E32 Thymus diseases

• E32.0 Persistent hyperplasia of the thymus gland
• E32.1 Abscess of the thymus
• E32.8 Other diseases of the thymus
• E32.9 Disease of the thymus gland, unspecified

E34 Other endocrine disorders

• E34.0 Carcinoid syndrome
• E34.1 Other states of intestinal hormone hypersecretion
• E34.2 Ectopic hormonal secretion, not elsewhere classified
• E34.3 Short stature [dwarfism], not elsewhere classified
• E34.4 Constitutional Tall
• E34.5 Androgen resistance syndrome
• E34.8 Other specified endocrine disorders
• E34.9 Endocrine disorder, unspecified

E35 * Endocrine gland disorders in diseases classified elsewhere

• E35.0 * Thyroid disorders in diseases classified elsewhere
• E35.1 * Adrenal disorders in diseases classified elsewhere
• E35.8 * Disorders of other endocrine glands in diseases classified elsewhere

Endocrine neoplasia is a single or multiple tumors of the endocrine glands.

Endocrine neoplasia are single or multiple tumors of the endocrine glands.The predisposition to the disease is inherited. The pancreas, pituitary gland, thyroid and parathyroid glands are mainly affected. Other organs are also affected: the nervous system and the digestive tract. The external manifestations of the disease are thickening of the lips, arachnodactyly, skeletal disorders, prognathism.

Treatment includes symptomatic therapy, but surgery is generally required. Often, specialists have to carry out total operations to remove the endocrine glands.

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INFLUENCE OF A COMBINATION OF PEPTIDE EXTRACTS OF ENDOCRINE GLANDS OF THE NORTHERN DEER (RANGIFER TARANDUS) ON THE PROCESSES OF CATECHOLAMINERGIC REGULATION OF ESTRAL FUNCTION IN RATS | Abaimov

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11. Malikova L.A., Fedotova I.B., Narkevich V.B., Klodt P.M., Kudrin V.S., Poletaeva I.I., et al. Effects of the novel anticonvulsant levetiracetam on the content of monoamines and their main metabolites in the brain structures of rats of the Krushinskii-Molodkina strain. Neurochemical J. 2008; 2 (4): 289-292.

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90,000 Major diseases of the endocrine system – causes, symptoms, tests for diagnosis

Endocrine disorders are numerous, and their development and symptoms are often unpredictable. The system of regulation of the activity of internal organs performs an important function, ensuring the production of special substances – hormones. Often, this system malfunctions, leading to the development of pathologies and diseases.

The endocrinologist is engaged in the identification of the causes and diagnosis of diseases. After consulting and examining the body, the doctor identifies how the disease is progressing and what treatment methods are relevant for a particular patient.

Qualified doctors from Novocherkassk and the Rostov region are receiving appointments at the Femina Medical Center for Women’s Health. Appointments are made by phone 8 8635 29 15 16.

List of major endocrine disorders

The function of hormones is of great importance for the physical, mental and physiological state of a person.Failure in the work of endocrine organs entails the development of pathological processes, which are accompanied by a change in the hormonal system:

• production disturbance – decrease or increase;
• slowdown in transport and suction;
• anomalous structure;
• increases resistance to hormonal action.

Similar processes affect all internal organs of a person, including the nervous system, leading to the development of various diseases.

Major endocrine disorders:

Signs and methods of diagnosis of endocrine diseases

The endocrine system consists of different endocrine glands, diseases also have a wide range of clinical manifestations.Often, the first signs of these diseases are attributed to fatigue after work or physical labor, stress, overeating. In this case, the disease progresses, and the defeat of the endocrine gland becomes chronic.

General signs of endocrine diseases:

• Increased fatigue during normal physical exertion;
• weakness, muscle spasms;
• a sharp decrease or increase in weight;
• rapid or slow heart rate, pain;
• febrile condition;
• increased sweating;
• excessive, unnatural excitability or, conversely, drowsiness;
• Frequent urge to urinate is an indirect symptom, each patient has his own norm;
• constant thirst;
• high blood pressure with headaches;
• decreased memory function;
• Constipation or diarrhea on a regular basis.

With a similar clinical picture, you should consult an endocrinologist. As additional survey methods are used:

• MRI;
• CT;
• X-ray of the skull;
• ultrasound.

Laboratory research:

• blood sugar test;
• blood biochemistry;
• glycosylated hemoglobin;
• glucose test;
• blood and urine tests for hormones.

A detailed examination of the body will allow diagnosing the disease at the first stage, leveling the pathology. You can make an appointment with an endocrinologist in Novocherkassk on the website of the Femina MC.

Manifestation and diagnosis of endocrine diseases in ophthalmopathy

Signs of endocrine disorders in ophthalmopathy are caused by the presence of pathology in the thyroid gland. This leads to the expansion of the list of characteristic manifestations:

• upward tightening of the eyelid, swelling;
• feeling of pressure and pain on the eyeball;
• dryness of the mucous membrane of the eye;
• failure in color perception;
• exophthalmos;
• conjunctivitis;
• limited movement of the eyeballs;
• rare blinking;
• Trembling and pigmentation of the eyelids.

Most cases do not lead to a complete loss of visual function, however, they can cause a decrease in vision, damage to the cornea, double image, and neuropathy.

If the clinical picture of the disease is pronounced, then a standard examination by an ophthalmologist is sufficient. The study included analysis of color vision and eye movement, optical media and perimetry. In unclear cases, ultrasound, MRI and CT are required.

90,000 Endocrine diseases: prevent in time – GBUZ “Starominskaya CRH” MH KK

Endocrine diseases: prevent in time

The field of study of endocrinology is the medical aspects of the structure and functioning of the endocrine glands (or endocrine glands), the study of biologically highly active substances produced by them – hormones and their effect on the body, as well as diseases arising from the disruption of the activity of these glands or the production of hormones.Endocrinology is closely related to almost all areas of clinical medicine, since hormones control the most important processes in the body: growth, maturation, reproduction, metabolism, and the proper functioning of organs and systems.

Modern trends in endocrinology are neuroendocrinology, which studies the relationship between nervous and endocrine regulation of the body, and gynecological endocrinology, which deals with the correction of hormonal disorders in the female body.

The endocrine system unites anatomically unrelated endocrine glands: pineal gland, pituitary gland, parathyroid glands, thyroid gland, thymus gland, pancreas, adrenal glands, gonads. Most diseases of the endocrine glands cause severe violations of vital functions, not excluding death, if you do not consult an endocrinologist in time.

The most pressing problems of modern endocrinology are the prevention, diagnosis and treatment of thyroid diseases (diffuse toxic goiter, thyroiditis, hypothyroidism, thyroid cysts), diabetes mellitus, diseases of the hypothalamic-pituitary system (acromegaly, gigantism, hypothalamic syndrome, diabetes insipidus, lactation problems , prolactinoma), adrenal diseases (adrenal insufficiency, adrenal tumors), dysfunctions of the gonads (endocrine infertility).Today, thanks to the knowledge and practical experience accumulated by endocrinology, it is possible to significantly improve the quality of life of patients with endocrine pathology.

Deterioration of the ecological situation, stress, unbalanced nutrition, weighed down heredity often cause disturbances in the functioning of the endocrine glands and lead to the development of endocrine diseases. Diseases of the endocrine system, as a rule, are long-term, severe. Therefore, it is important to prevent their occurrence in time, identify them as early as possible or prevent the development of their complications.

Consultation with an endocrinologist is necessary if:

• The closest relatives have any endocrine pathology: diabetes mellitus, thyroid diseases, etc.
• You are overweight
• you have symptoms: increased heart rate, sweating or dry skin, fatigue or irritability, thirst and increased urination, discoloration of the skin, etc.
• the child has mental, physical, sexual development retardation
• menstrual function is disturbed
• you are planning a pregnancy or have problems getting it
• You already have an endocrine disease and need monitoring and treatment.