Overview of the Male Anatomy

Overview of the Male Anatomy | Johns Hopkins Medicine

The following is an overview of the male reproductive anatomy:

Scrotum. The bag of skin that holds and helps to protect the testicles. The testicles make sperm and, to do this, the temperature of the testicles needs to be cooler than the inside of the body. This is why the scrotum is located outside of the body.

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Testes (testicles). The testes are 2 small organs that are found inside the scrotum. The testes are responsible for making sperm and are also involved in producing a hormone called testosterone. Testosterone is an important hormone during male development and maturation for developing muscles, deepening the voice, and growing body hair.

Epididymis. A long tube that is located near each testicle. The epididymis is the tube which moves the sperm from the testicles.

Vas deferens. This is a tube in which the sperm is stored and it carries the sperm out of the scrotal sac. The vas deferens is between the epididymis and the urethra and connects these together.

Seminal vesicles. The sac-like glands that lie behind the bladder and release a fluid that forms part of semen.

Prostate gland. It is about the size of a walnut, and surrounds the neck of the bladder and urethra—the tube that carries urine from the bladder. It is partly muscular and partly glandular with ducts opening into the prostatic portion of the urethra. It is made up of 3 lobes: a center lobe with 1 lobe on each side. The prostate gland secretes a slightly alkaline fluid that forms part of the seminal fluid, a fluid that carries sperm.

Urethra. This is a tube that allows urine to flow outside the body. It is also the channel for semen to pass during ejaculation. The brain signals the bladder muscles to tighten. This squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals happen in the correct order, normal urination happens.

Penis. The external reproductive organ of the male. The penis is made up of 2 parts, the shaft and the glans. The glans is the tip of the penis, while the shaft is the main part of the penis and contains the tube (urethra) that drains the bladder. All boys are born with a foreskin, or a covering over the tip of the penis. Some boys are circumcised. This means that this covering of skin is removed. Other boys are not circumcised and may have skin that covers the tip of the penis.

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The Male Reproductive System: Organs, Function, and More

Written by WebMD Editorial Contributors

• How Does the Male Reproductive System Function?

The purpose of the organs of the male reproductive system is to perform the following functions:

• To produce, maintain, and transport sperm (the male reproductive cells) and protective fluid (semen)
• To discharge sperm within the female reproductive tract during sex
• To produce and secrete male sex hormones responsible for maintaining the male reproductive system

Unlike the female reproductive system, most of the male reproductive system is located outside of the body. These external structures include the penis, scrotum, and testicles.

• Penis: This is the male organ used in sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped part at the end of the penis. The glans, also called the head of the penis, is covered with a loose layer of skin called foreskin. This skin is sometimes removed in a procedure called circumcision. The opening of the urethra, the tube that transports semen and urine, is at the tip of the penis. The glans of the penis also contains a number of sensitive nerve endings.

  The body of the penis is cylindrical in shape and consists of three circular shaped chambers. These chambers are made up of special, sponge-like tissue. This tissue contains thousands of large spaces that fill with blood when the man is sexually aroused. As the penis fills with blood, it becomes rigid and erect, which allows for penetration during sexual intercourse. The skin of the penis is loose and elastic to accommodate changes in penis size during an erection.

  Semen, which contains sperm (reproductive cells), is expelled (ejaculated) through the end of the penis when the man reaches sexual climax (orgasm). When the penis is erect, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.

• Scrotum: This is the loose pouch-like sac of skin that hangs behind and below the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. The scrotum acts as a “climate control system” for the testes. For normal sperm development, the testes must be at a temperature slightly cooler than body temperature. Special muscles in the wall of the scrotum allow it to contract and relax, moving the testicles closer to the body for warmth or farther away from the body to cool the temperature.
• Testicles (testes): These are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord. Most men have two testes. The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm. Within the testes are coiled masses of tubes called seminiferous tubules. These tubes are responsible for producing sperm cells.

The internal organs of the male reproductive system, also called accessory organs, include the following:

• Epididymis: The epididymis is a long, coiled tube that rests on the backside of each testicle. It transports and stores sperm cells that are produced in the testes. It also is the job of the epididymis to bring the sperm to maturity, since the sperm that emerge from the testes are immature and incapable of fertilization. During sexual arousal, contractions force the sperm into the vas deferens.
• Vas deferens: The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports mature sperm to the urethra, the tube that carries urine or sperm to outside of the body, in preparation for ejaculation.
• Ejaculatory ducts: These are formed by the fusion of the vas deferens and the seminal vesicles (see below). The ejaculatory ducts empty into the urethra.
• Urethra: The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of ejaculating semen when the man reaches orgasm. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.
• Seminal vesicles: The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move. The fluid of the seminal vesicles makes up most of the volume of a man’s ejaculatory fluid, or ejaculate.
• Prostate gland: The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra, which carries the ejaculate to be expelled during orgasm, runs through the center of the prostate gland.
• Bulbourethral glands: Also called Cowper’s glands, these are pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra.

The entire male reproductive system is dependent on hormones, which are chemicals that regulate the activity of many different types of cells or organs. The primary hormones involved in the male reproductive system are follicle-stimulating hormone, luteinizing hormone, and testosterone.

Follicle-stimulating hormone is necessary for sperm production (spermatogenesis), and luteinizing hormone stimulates the production of testosterone, which is also needed to make sperm. Testosterone is responsible for the development of male characteristics, including muscle mass and strength, fat distribution, bone mass, facial hair growth, voice change, and sex drive.

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Anatomical structure of the male reproductive organs

Organs of the genitourinary system

The term “genitourinary” explains that this system consists of two components: urinary and genital. The combination of these two subsystems into one indicates a close relationship between the organs of this system, and in the male body this relationship is more closely manifested than in the female, since the male urethra (urethra) performs a dual function: urine excretion and ejaculation. Therefore, the urologist deals with the pathology of the male genitourinary system and the female urinary system.

The urinary system includes: kidneys, ureters, bladder, urethra. Kidneys In their shape, the kidneys resemble beans (or beans). The average size of the kidneys in an adult is 10 x 6 cm. The right kidney is usually located slightly lower than the left, since it is located under the liver. The kidneys are surrounded by fatty tissue, which, along with the surrounding muscles and ligaments, hold them in place. This explains why in thin people, as well as due to sudden weight loss, a disease such as nephroptosis can occur – omission of the kidney.

Kidneys consist of two layers. Superficial – cortical, and deeper – cerebral. On the section of the kidney, you can see the medulla is a system of tubules (tubules). The function of the tubules is to collect and divert urine into the pelvis. The pelvis is a combined collector of all tubules of the kidney. It opens into the gate of the kidney, in which, in addition to the pelvis, there is also an artery and a vein.

The basic unit of the kidney is the nephron. This is such a glomerulus, it consists of the very initial “cup-shaped” end of the tubule, which is entangled with capillaries, through which blood continuously circulates. Due to blood pressure and the membrane properties of the capillary walls, plasma is filtered from the blood into the glomerulus – that is, the liquid part of the blood without erythrocytes, leukocytes and other blood cells, which, normally, do not pass through the membrane, as well as some substances (sugar, protein, etc.) But in certain diseases, these blood components are filtered through the glomerular membrane and are found in the urine.

So, the main function of the kidneys is to “filter” the blood. The kidneys are the main organ that cleanses the blood of all toxins and metabolic products. When they become ill, this filtering function is disturbed, which leads to accumulation in the blood and poisoning of the body with its own metabolic products. It is worth noting that some drugs and their metabolic products are excreted from the body through the kidneys.

Ureters

The ureters are a downward extension of the pelvis and are a tube about 30 cm long. The lumen of the ureter is 5-6 mm. But this width is not constant and the lumen of the ureter narrows in three places – the so-called physiological narrowing. The significance of these narrowings lies in the fact that small kidney stones can get stuck in them. The ureters empty into the bladder.

Bladder

The bladder is an extensible reservoir, the wall of which contains a muscular layer and is lined with a mucous membrane from the inside. The ureters flow into the bladder. The average bladder capacity is 300 to 600 ml.

Urethra (urethra)

The urethra is a hollow tube that carries urine out of the bladder. The urethra in men and women is different: in men it is long and narrow (30 cm long, about 8 mm wide), while in women it is short and wide (3-4 cm long, 1-1.5 cm wide). These features of the structure of the urethra in women are the main reason that they often have inflammatory diseases of the bladder – cystitis, since the infection easily enters the bladder through the short female urethra. The lumen of the urethra is covered with a mucous membrane. Inflammation of this membrane – urethritis – occurs as a result of infection, both non-specific (conditionally pathogenic) and specific (gonorrhea, chlamydia, trichomoniasis, etc.).

Reproductive system. Male reproductive organs

Male internal genital organs

• Deferent ducts
• spermatic cords
• Seminal vesicles
• Prostate
• Bulbourethral gland

Male external genitalia

• Male urethra
• Scrotum
• Testicles
• Peritoneum of the pelvic cavity

Prostate (prostate)

The prostate is located directly under the bladder at its neck and covers the urethra with its thickness, i.e. the urethra passes through it. This is the so-called prostatic urethra. Both the ducts of the prostate and the ducts of the seminal vesicles open into it. The prostate is a glandular organ, meaning most of its tissue is glandular. In shape and size, the prostate resembles a chestnut.

The main function of the prostate is the production of a special transparent liquid – prostatic secretion (prostate juice), which is part of the semen. The composition of sperm is quite complex. Sperm is a mixture of secretions from a number of glands. In particular, in addition to spermatozoa, semen contains secretions of the prostate gland, seminal vesicles and glands of Littre and Cooper.

The secretions of the prostate gland attached to the seed have an alkaline reaction and an opalescent appearance, contain licitous grains, prostatic bodies, epithelial, granular cells and spermine, which gives the seed a translucent milky appearance and a specific smell. The discharge of the seminal vesicles is odorless, sticky, colorless, consists of epithelial cells, single leukocytes and formations similar to sago grains.

Secrets of the prostate and seminal vesicles liquefy thick semen, ensure the viability of spermatozoa and give them the necessary mobility.

Sperm has the appearance of a cloudy, gelatinous, stretchy liquid, and the white color is due to the presence of spermatozoa in it. The secretion of the testicles consists of spermatozoa and phosphate crystals.

Seminal vesicles

Seminal vesicles are peculiar convoluted sacs along the posterolateral surface of the bladder. The main function of the seminal vesicles is a reservoir of seminal fluid. In the seminal vesicles, the seminal fluid also undergoes some changes in order to become a full-fledged sperm. During sexual intercourse, during ejaculation, seminal fluid is ejected from the seminal vesicles through the ducts into the urethra, and, mixing with the juice of the prostate and the secret of other glands, is ejected through the external opening of the urethra.

The vas deferens

The vas deferens are thin tubes that lead from the testicles and empty into the seminal vesicles. Through them, the seminal fluid from the testicles enters the seminal vesicles.

Testicles

The testicles are a paired organ. They are located in the scrotum. In them, the formation and maturation of spermatozoa occurs. In addition, the testicles are the main organ in which the main male sex hormone, testosterone, is produced. It should be noted such an interesting fact that usually the left testicle is located slightly lower than the right one.

As already noted, the main function of the testicles is the production of spermatozoa. Spermatozoa are produced in them by special cells – Sertolli cells. In addition to these cells, there are also Leydig cells in the testicles, these are hormone-active cells that produce testosterone.

Each testicle consists of lobules filled with convoluted seminiferous tubules. On top of each testicle is an appendage that passes into the vas deferens. The functions of the testis are under the control of the anterior pituitary gland. It is worth noting the fact that such an arrangement of the testicles – the main, from the point of view of reproduction, genital organs – is associated with a special temperature regime, which is necessary for the maturation of spermatozoa in them. Those. for normal maturation of spermatozoa, a temperature of several degrees below body temperature is required. Therefore, such an important organ, from the point of view of storing and transmitting the genetic information of a species, is located in a not very reliable place – outside. However, many animals have a muscle that, in case of danger, raises the testicle and draws it into the abdominal cavity. In humans, it is underdeveloped.

Each testicle is covered with membranes in its half of the scrotum. There are seven in total. Sometimes, in case of accumulation between the layers of the testicles, dropsy (hydrocele) occurs.

Penis

The male penis is used for sexual intercourse and makes fertilization possible, as well as in the thickness of his spongy body passes the urethra, through which urine or semen is excreted. Those. the penis has a dual function: urination and procreation. The penis has a complex structure. In the upper part of it there are two cavernous bodies, and under them – a spongy body. The cavernous bodies are covered with a connective tissue protein membrane.

Cavernous bodies got their name for their special cellular structure, which looks like a cave. Such a structure is necessary to ensure an erection and sexual intercourse. Studies show that an erection occurs as a result of the expansion of the arteries that bring blood to the penis, the spasm of the veins through which this blood departs from the penis, and the relaxation of the cells of the cavernous bodies of the penis. Arteries, veins and cells of the corpora cavernosa are composed of smooth muscles. These muscles are affected by the so-called neurotransmitters – substances that are released during stimulation of the nerves that control the erection process.

After appropriate sexual stimulation, these substances lead to relaxation (relaxation) of the smooth muscles of the cavernous bodies of the penis, expansion of their arterial cells, which is manifested by a powerful increase in blood flow to the penis. Then the cells fill with blood, expand and compress the veins through which the blood drains, which leads to a further increase in intracavernous pressure, thereby causing an erection.

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Anatomy and physiology of the male genitourinary system

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Structure and function of male genital organs

Home » Urologist, andrologist » Structure and function of male genital organs

The male reproductive system is represented by external and internal genital organs. The external genital organs of a man include the penis (Penis) and testicles (Testis), located in the scrotum. The internal male genital organs include the prostate gland, seminal vesicles, and vas deferens.

Male external genitalia.

Penis (penis) . The penis consists of the so-called root, shaft and glans. The head of the penis is covered by a skin fold – the foreskin. The slit-like cavity between the head and the foreskin is called the preputial sac (Prepucium). Normally, the foreskin should move freely and expose the head of the penis.

Under the thin skin of the penis are the right and left cavernous (cavernous) bodies , under them is the urethra (urethra) . Around the urethra is spongy (spongiform) body . Cavernous bodies are enclosed in a strong, almost inextensible protein membrane.

In the glans penis and in the foreskin there is a large number of sensitive nerve endings, adequate stimulation of which is accompanied by excitation of the corresponding nerve centers in the spinal cord and brain. Visual, auditory, olfactory stimuli, mental images can also cause excitation of the nerve centers responsible for erection. As a result of the triggering of erection mechanisms, the arterial blood flow to the cavernous bodies of the penis increases several times, and due to the valve mechanisms, the venous outflow practically stops during an erection.

Testicles . In the testicles, spermatozoa are produced and mature (spermatogenesis occurs). The testicles also produce the male sex hormone, testosterone.

The testicles are located in the scrotum (Scrotum), which performs a thermoregulatory function to ensure normal spermatogenesis and maintain male fertility (fertility). The temperature of the scrotum is approximately two degrees below the axillary (axillary) and is about 34.5 ° C. Under conditions of overheating of the body, the cremasteric muscles lower the testicles, while the skin of the scrotum is significantly stretched, increasing heat transfer. In cold conditions, the testicles are pulled up to the root of the scrotum; the skin of the latter at the same time is reduced, saving a stable temperature of the testicles.

Fig. The structure of the male reproductive organs.

Male internal genital organs.

Prostate (prostate). The prostate is a gland that produces a secret (prostate juice) that is released during ejaculation and makes up a significant part of the semen volume. In addition, the prostate is the main organ where testosterone (male sex hormone) is metabolized. The prostate is located under the neck of the bladder, through it passes the initial section of the urethra (prostatic urethra).

Seminal vesicles . The seminal vesicles are paired organs located on either side of the upper lateral surfaces of the prostate, just below the bladder. The secret secreted by the seminal vesicles makes up the bulk of the semen volume.

Spermatic cords . The spermatic cord is a paired organ, in which blood vessels and nerves go to the testicle, as well as the vas deferens .