Parts of the male genitalia: Male Genitalia: Anatomy, Function, and More
Male Genitalia: Anatomy, Function, and More
The male reproductive system includes both internal and external parts. Its primary functions are to:
- produce and transport semen, which contains sperm
- release sperm into the female reproductive tract during sex
- make male sex hormones, such as testosterone
Have you ever wondered what the different parts of the male genitalia are and what they do? Continue reading to learn more about the individual parts of the male genitalia, their function, and more.
Let’s begin by outlining the various parts of the male genitalia. We’ll then explain their functions in a later section.
The penis is an external part of the male reproductive system and is cylindrical in shape.
Its size can vary from person to person, but on average it’s about 3.6 inches long when flaccid (not erect) and 5 to 7 inches long when erect.
The penis has three different parts:
- Glans. Also called the head or tip of the penis, the glans is very sensitive and contains the opening of the urethra. In some men, a fold of skin that’s called the foreskin may cover the glans.
- Shaft. This is the main body of the penis. The shaft contains layers of erectile tissue. This tissue becomes engorged with blood when a man is aroused, causing the penis to become firm and erect.
- Root. The root is where the penis attaches to the pelvic area.
Like the penis, the scrotum is an external part of the male genitals. It’s a sac that hangs just behind the root of the penis. The scrotum contains the testicles and the ducts associated with them.
Men have two testicles, which are contained within the scrotum. Each testicle is oval in shape and is connected to the rest of the male reproductive tract via a duct called the epididymis.
Many areas of the male reproductive system are connected via a series of ducts. These include the:
- Epididymis. The epididymis is a coiled tube that connects the testicle to the vas deferens. One epididymis runs along the back of each testicle.
- Vas deferens. The vas deferens is a long tube that connects to the epididymis. Each epididymis has its own vas deferens. The vas deferens in turn connects to ejaculatory ducts.
- Ejaculatory ducts. The ejaculatory ducts connect to the vas deferens and small pouches called the seminal vesicles. Each ejaculatory duct empties into the urethra.
- Urethra. The urethra is a long tube that has connections with both the ejaculatory ducts and the bladder. It runs through the prostate gland and penis and opens at the glans.
The prostate gland is located internally just below the bladder. It’s about the size of a walnut.
These two small glands are found internally around the root of the penis. They’re connected to the urethra via small ducts.
Now let’s explore the functions of each part of the male genitals.
The penis has important functions for both the male reproductive tract and urinary tract:
- Reproduction. When a man is aroused, the penis becomes erect. This allows it to enter the vagina during sex. During ejaculation, semen comes out of the tip of the penis.
- Urinating. When the penis is flaccid, it can expel urine from the body.
The scrotum serves two functions:
- Protection. The scrotum surrounds the testicles, helping to keep them protected from injury.
- Temperature control. Sperm development is sensitive to temperature. Muscles around the scrotum can contract to bring the scrotum closer to the body for warmth. They can also relax to move it away from the body, reducing its temperature.
The functions of the testicles include:
- Sperm production. Sperm, the male sex cells that fertilize the female egg, are produced in the testicles. This process is called spermatogenesis.
- Making sex hormones. The testicles also produce the male sex hormone testosterone.
Each duct of the male reproductive system has a specific function:
- Epididymis. Sperm that are produced in the testicle move to the epididymis to mature, a process that takes about 12 days. Mature sperm are also stored in the epididymis until sexual arousal occurs.
- Vas deferens. During arousal, mature sperm move through the vas deferens and to the urethra in preparation for ejaculation. (It’s the two vas deferens ducts that are cut during a vasectomy.)
- Ejaculatory ducts. The seminal vesicles empty a viscous fluid into the ejaculatory ducts, which combines with sperm. This fluid contains components that give the sperm energy and stability. Fluid from the seminal vesicles makes up about 70 percent of semen.
- Urethra. During ejaculation, semen exits the urethra through the tip of the penis. When the penis is flaccid, urine can exit the body via this duct.
The prostate also contributes fluid to semen. This fluid is thin and milky in color. It contains components that help with sperm motility and stability.
Prostatic fluid also makes semen thinner, allowing sperm to move more efficiently.
The bulbourethral glands release a fluid into the urethra that provides lubrication and also neutralizes any residual urine that may be present.
Now that we’ve discussed the different parts of the male genitalia and how they function, let’s examine some of the common conditions that can affect this area of the body.
Sexually transmitted infections (STIs)
Some of the STIs that can affect the male reproductive system include:
- herpes simplex virus (HSV)
- human papillomavirus (HPV)
- human immunodeficiency virus (HIV)
Many times, these infections are asymptomatic, meaning there aren’t any symptoms.
When symptoms are present, they may include:
- discharge from the penis
- swelling or discomfort of the genitals
- lesions in the genital area
Consult with your doctor if you’re experiencing symptoms of an STI.
Uncircumcised men can experience problems involving the foreskin. These can include phimosis and paraphimosis.
Phimosis results from the foreskin being too tight. It can cause symptoms like pain, swelling, and redness around the tip of the penis.
Paraphimosis occurs when the foreskin can’t return to its normal position after being pulled back. This is a medical emergency. Along with the symptoms of phimosis, someone with paraphimosis can have restricted blood flow to their penis.
See your doctor if you have either of these conditions.
An enlarged prostate is a common condition in older men. It’s a benign condition, meaning that it isn’t cancerous. It’s unknown what causes an enlarged prostate, but it’s believed to happen due to factors related to aging.
Some of the symptoms of an enlarged prostate are:
- increase in urinary urgency or frequency
- a weak urine stream
- pain after urination
Treatment can include:
- lifestyle adjustments
Priapism is a long-lasting, painful erection. It happens when blood becomes trapped in the penis. A variety of things can lead to priapism, including:
- certain underlying health conditions
- specific medications
- injury to the penis
Priapism is a medical emergency that requires immediate attention. If it’s allowed to persist, it can lead to scarring of the penis and potentially erectile dysfunction.
Peyronie’s disease is a condition that results in scar tissue accumulating in the penis. This causes the penis to curve, which may be more noticeable when the penis is erect.
While it’s unknown what causes Peyronie’s disease, it’s believed to occur as a result of injury to the penis or damage from an autoimmune disease.
Treatment is typically recommended when pain is present or curvature interferes with sex or urination.
Male reproductive cancers
Cancer can develop in many parts of the male reproductive tract. Types of male reproductive cancer include:
- penile cancer
- testicular cancer
- prostate cancer
Possible symptoms include pain, swelling, and unexplained lumps or bumps. It’s important to note that symptoms can vary based on the location of the cancer.
Some risk factors are associated with the development of male reproductive cancers. Examples include:
- HPV infection
- a family history of a specific type of cancer
Talk to your doctor about any concerns you may have about male reproductive cancers.
Premature ejaculation happens when you’re unable to delay your ejaculation. When this happens, you ejaculate earlier than either yourself or your partner would like.
It’s not known what causes premature ejaculation. However, it’s believed to happen due to a combination of physiological and psychological factors.
There are a wide variety of treatments available, such as pelvic floor exercises, medications, and counseling.
Erectile dysfunction (ED)
A person with ED can’t get or maintain an erection. A variety of things can contribute to the development of ED, including:
- underlying health conditions
- certain medications
- psychological factors
ED can be treated with medications that help to increase blood flow to the penis. Some that you may be familiar with include sildenafil (Viagra) and tadalafil (Cialis).
Infertility can also affect men. Possible causes of infertility in men include:
- problems with sperm or sperm development
- hormone imbalances
- certain genetic conditions
Additionally, certain factors can increase a man’s risk of infertility. Following are a few examples:
- excess weight
- frequent exposure of the testicles to high temperatures
It’s always a good idea to talk to your doctor if you have any questions or concerns regarding your reproductive health.
Additionally, plan to make an appointment with your doctor if you notice:
- abnormal discharge from your penis
- pain or a burning feeling when you urinate
- bumps, sores, or lesions in your genital area
- unexplained pain, redness, or swelling in the area of your pelvis or genitals
- changes in urination, such as a weak urine stream or increased frequency and urgency of urination
- curvature of your penis that’s painful or interferes with sex
- an erection that’s prolonged and painful
- changes in your libido or your ability to get or maintain an erection
- problems with or changes in ejaculation
- problems conceiving after 1 year of trying
The male genitals have many parts. Some are external, such as the penis and scrotum. Others are inside the body, such as the testicles and prostate.
The male genitals have several functions. These include sperm production, making male sex hormones, and depositing sperm into the female reproductive tract during sex.
There are a variety of conditions that can impact the male genitals. Examples include STIs, enlarged prostate, and erectile dysfunction.
If you have questions about your reproductive health or notice concerning symptoms, make an appointment with your doctor to discuss them.
Anatomy, Abdomen and Pelvis, Penis – StatPearls
Peter Sam; Chad A. LaGrange.
Author Information and Affiliations
Last Update: July 25, 2022.
The penis is a male organ that is used for reproduction and urination which is located within the urogenital triangle between the perineal membrane superiorly and deep perineal fascia inferiorly. Its composition divides it into 3 parts: the glans, body, and root. Dorsally, it is composed of the paired corpora cavernosa and ventrally the corpus spongiosum which contains the urethra. The anatomical positions of the penis are according to the erect penis with the dorsal direction being closer to the head and ventral direction being closer to the feet. The tunica albuginea is a fibrous sheet which encapsulates the cavernous body. Buck’s fascia, also known as deep fascia of the penis is superficial to the tunica albuginea and is the continuation of the deep perineal fascia which covers the corpora cavernosa and corpus spongiosum together. The spongy urethra is contained within the corpus spongiosum. The crura of the penis is between the 2 corpora cavernosa in the median plane externally. The corpora cavernosa is separated by the septum of the penis internally. The attachment of the penis consists of the bulb, crura, and ischiocavernosus and bulbospongiosus muscles, which collectively makes up the root of the penis. The bulb of the penis and crura contain erectile tissue. The middle portion of the penis is suspended and known as the body of the penis. The body of the penis lacks muscles and consists mostly of corpora cavernosa, corpus spongiosum, and spongy urethra with supporting skin, connective tissue, and blood, lymph, and fascia. The distal part of the penis is known as the glans penis. The proximal portion of the glans is termed the corona. The neck of the corona glans separates it from the body of the penis. The tip of the glans contains the opening to the urethra, known as the meatus. There is loose connective tissue between the thin skin of the penis and the tunica albuginea. The prepuce or foreskin is the second skin layer that covers the glans penis. The frenulum of the prepuce connects it to the urethral surface of the penis glans. The suspensory ligament of the penis is part of the deep fascia that arises from the anterior surface of the pubic symphysis. The fundiform ligament of the penis descends in the midline from the linea alba anterior to the pubic symphysis and splits to surround the penis and then unites and blends inferiorly with the dartos fascia forming the scrotal septum. 
Structure and Function
The 2 main functions of the penis are intercourse and urination. For intercourse, the penis must be erect. Erection occurs via parasympathetic innervation which allows engorgement of the corporal bodies. The bulbospongiosus and ischiocavernosus muscle compress the veins to prevent them from draining blood from the corpora cavernosa. The erectile tissue of the cavernosum becomes firm and enlarged when the erection occurs. The emission phase is due to the sympathetic response and occurs when semen exits the vas deferens to the ejaculatory ducts where fluid from the seminal glands are added. They then continue onto the prostatic urethra where the prostatic fluid is added. The ejaculation phase is due to the sympathetic response and is when semen exits from the urethra through the external urethral orifice. After ejaculation, the penis becomes flaccid again due to the sympathetic stimulation and constriction of the coiled helicine arteries and relaxation of the bulbospongiosus and ischiocavernosus muscles allowing blood to drain from the cavernous spaces. 
The other function of the penis is to drain urine from the body. Urine starts draining from the bladder into the bladder neck where the internal urethral sphincter will relax to allow urine to pass via involuntary control of the parasympathetic system. Urine will then pass into the prostatic urethra and the membranous urethra. The external sphincter will relax to allow urine to pass from the membranous urethra into the spongy penile urethra, then into the navicular fossa and out of the urethra through the external urethral orifice.
The male penis is derived in the fetus from the genital tubercle. The genital tubercle starts developing to become the phallus due to the influence of androgens from the testis. The elongation process drags the urethral folds ahead to become the lateral walls, which belongs to the urethral groove. The epithelial lining, which is from the groove, develop into the urethral plate. The penile urethra is created when both the urethral folds enclose on top of the urethral plate. This process usually occurs towards the end of month three. The urethra’s most distal part is created at the end of month 4 and ends at the external urethral meatus. The 2 urethral folds come together and fuse, this part will eventually become the spongy body. Then above the spongy body, there will be 2 cavernous bodies that arise, which will eventually become the corpora cavernosa.
Blood Supply and Lymphatics
The branches of the internal pudendal arteries are the main supplier of blood to the penis. The dorsal arteries of the penis run along the dorsal vein between the corpora cavernosa to supply the fibrous tissue surrounding the corpora cavernosa, corpus spongiosum, spongy urethra, and penile skin. The deep arteries of the penis run in the center of each corpora cavernosa to supply the erectile tissue of the penis. The helicine arteries of the penis are branches of the deep arteries of the penis which are coiled when the penis is flaccid. The arteries of the bulb of the penis supply the bulbous part of the corpus spongiosum, urethra, and bulbourethral gland. The superficial and deep branches of the external pudendal arteries supply the penile skin.
The deep dorsal vein of the penis receives blood from the venous plexus which receives drained blood from the cavernous spaces. The superficial dorsal vein drains blood from the skin and subcutaneous tissue of the penis.
The skin of the penis and all of the perineum excluding the glans penis drain lymph to the superficial inguinal nodes. The lymphatics of the intermediate and proximal parts of the urethra and cavernous bodies drain into the internal iliac lymph nodes. The distal spongy urethra and glans penis drain to the deep inguinal nodes.
The penis innervation is from spinal cord segments of the S2 to S4. These cord segments pass through the pelvic splanchnic nerves. The spinal ganglia of S2 to S4 passes through the pudendal nerves. The dorsal nerve provides sympathetic plus sensory innervation to the penis. The pudendal nerve branches to become the dorsal nerve of the penis. The nerve runs next to the dorsal artery and supplies the skin and glans penis also. The glans penis has a copious amount of sensory nerve endings. The root of the penis has innervation from the ilioinguinal nerve. The cavernous nerves have parasympathetic fibers that innervate the helicine arteries which supply erectile tissue.
The bulbospongiosus muscles cross the pelvic outlet intersecting with the superficial transverse perineal muscles. These structures support the perineal body and pelvic viscera. The bulbospongiosus muscles compress the bulb of the penis and the corpus spongiosum which can aid in emptying the spongy urethra. The anterior fibers of the muscle surround the proximal part of the body of the penis. These fibers can increase the pressure on the erectile tissue in the root of the penis for erections. The bulbospongiosus muscle can compress the deep dorsal veins to prevent drainage of the cavernous spaces and help promote erection of the penis. The root of the penis contains the crura which is encircled by the ischiocavernosus muscle. The muscle can push blood to the distal parts of the corpora cavernosa and help with erections. The muscle can also lead to compression of the deep dorsal vein of the penis as it is leaving the crus of the penis and restrict venous outflow to help with erections.
Hypospadias is a fairly common physiologic variant. The external urethral orifice opens on the ventral portion of the glans penis or the body of the penis. This is due to a failure of the urogenital folds to fuse correctly. This causes urine to be excreted through this opening instead of the external urethral meatus. Epispadias occurs less commonly and is a result of urethral meatus which is found on the dorsal side of the penis. Epispadia is most commonly associated with bladder exstrophy. Phimosis is when the prepuce fits too tightly over the glans and cannot be retracted. Micropenis is when the penis is 2. 5 standard deviations below the mean in length measured along the dorsal surface from the pubis to the tip of the penis stretched. It is thought to be due to insufficient androgen stimulation during the fetal period. Chordee is another congenital anomaly that is fairly common. Chordee is the downward curvature of the head of the penis that occurs during the fetal period. This curvature is most notable during an erection. Some patients with chordee may also have hypospadias, but this is not always the case. Chordee is usually not painful and may be treated with minor surgery.
Erectile dysfunction (ED), the inability to get or maintain an erection, is the most common penile disorder. This can be due to either psychological stress, organic disease, or a combination of both. Risk factors associated with erectile dysfunction include obesity, smoking, atherosclerotic disease, decreased activity, obstructive sleep apnea, diabetes, drugs as well as many other causes. Antidepressants and antihypertensive drugs are common drugs which lead to erectile dysfunction. The most common cause of erectile dysfunction is vascular issues. Thus the first line therapy is usually phosphodiesterase-5 inhibitors, such as sildenafil, vardenafil, and tadalafil. They work by increasing nitric oxide-induced vasodilation by increasing the cyclic guanosine monophosphate (GMP) levels. Phosphodiesterase inhibitors are contraindicated in patients taking nitrates due to vasodilatory effects of both drugs, which can lead to severe hypotension. Lifestyle modifications are usually indicated for the treatment of erectile dysfunction also. Weight loss, physical activity, and smoking cessation can improve erectile function. If initial therapy fails, there are second-line therapies such as vacuum-assisted mechanical devices, penile injections with alprostadil, or penile prosthesis.
Peyronie disease is an abnormal curvature of the penis that is normally a benign condition but may be associated with painful erections or erectile dysfunction. The condition can resolve spontaneously, become stable, or worse. The underlying pathogenesis of Peyronie disease is not known. However, it is believed that repeated microtrauma to the penis leads to fibrin deposition due to microvascular injury. The fibrous plaques contain excessive collagen that causes focal inelasticity leading to the curvature of the penis. Several conditions have been associated with Peyronie disease such as Paget disease and Dupuytren contracture. The diagnosis of Peyronie disease is usually a clinical diagnosis, but imaging may be helpful. Current medical management of oral therapy for Peyronie disease include pentoxifylline, vitamin E, potassium para-aminobenzoate, colchicine, tamoxifen, and carnitine. Pentoxifylline is usually the first-line therapy. Intralesional drug therapy includes verapamil, interferon alfa-2b, and collagenase. Other treatments include penile traction therapy, iontophoresis, extracorporeal shockwave therapy, surgical straightening procedures, penile prosthesis placement, and radiation.
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The Penis, Vertical section of bladder, penis, and urethra. Contributed by Gray’s Anatomy Plates
The Penis, Diagram of the arteries of the penis, Corpus Cavernosum, Glans penis, bulbous branch. Contributed by Gray’s Anatomy Plates
The Penis, Veins of the penis. Contributed by Gray’s Anatomy Plates
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Disclosure: Peter Sam declares no relevant financial relationships with ineligible companies.
Disclosure: Chad LaGrange declares no relevant financial relationships with ineligible companies.
Male reproductive system – article Bozhedomov V.A.
From the book: Sukhikh G.T., Bozhedomov V.A. MALE INFERTILITY. A practical guide for urologists and gynecologists, M.: Eksmo, 2009; 240 with ill. – Medical practice.
The information is posted on the site with the permission of the author – prof. V.A. Bozhedomova.
- Etiology, pathogenesis and classification of male reproductive disorders
The male sex glands of a person (testicles – testis or orchis) perform two important functions: they form spermatozoa and sex hormones that affect the development of primary and secondary sexual characteristics.
The testicles have two anatomical and physiological compartments – inside and outside the seminiferous tubules. Each of them can also be divided into separate zones: intertubular compartment – into intravascular and interstitial; intratubular – into basal and adluminal (Fig. 1). These compartments differ in functions, biochemical and antigenic composition: for example, in the adluminal compartment of the seminiferous tubule, compared to the interstitium, the content of potassium ions and inositol is significantly higher, but, on the contrary, the content of protein and testosterone is lower.
Spermatozoa are formed inside the convoluted seminiferous tubules, whose own membrane is lined with sustentocytes (Sertoli cells) and germinal epithelium, from which mature male germ cells are formed. Sertoli cells are pyramidal in shape and reach the lumen of the convoluted tubule with their apex. On their lateral surfaces, bay-shaped depressions are formed, in which spermatogenic cells are located. Directly at the basement membrane of the tubule are spermatogonia, above – more differentiated spermatocytes and spermatids, at the end facing the lumen – directly spermatozoa. The process of transformation of stem spermatogonia into mature spermatozoa is called spermatogenesis.
Spermatogenesis is a complex process that is under the control of many genes. Its molecular mechanisms are currently under active study. About 2000 genes are known to be involved in the regulation of spermatogenesis. Most of them are in autosomes, about 30 genes are in the Y-chromosome.
Fig.1. Transverse section through the testis showing the presence of four compartments: vascular (V), interstinal (I), including lymphatic vessels and containing Leydig cells, basal (B) and adluminal (A) seminiferous tubule (according to Johnson, 2007).
The duration of spermatogenesis in humans is 62+8 days.
Spermatogenesis is divided into three phases. It includes a series of successive mitotic divisions (proliferation), reduction division meiosis and morphological and biochemical cell metamorphosis (spermiogenesis). As a result of successive mitotic divisions from stem spermatogonia, through the morphological stages of cell differentiation, called spermatogonia A light, A dark and B, spermatocytes of the first order are formed. They enter meiosis. In the prophase of meiosis I, crossing over occurs in these cells – the exchange of sections of homologous chromosomes, i.e. “mixing” of hereditary information received from the father and mother. The cells formed after the first reduction division are called spermatocytes of the second order. They contain haploid, i.e. half set of double-stranded chromosomes (23 D-chromosomes). After the second meiotic division, spermatid cells are formed containing 23 single-stranded chromosomes (23 S-chromosomes). Genetically, spermatids do not differ from mature spermatozoa, but the chromatin in them is not yet sufficiently compactly packed, and there are no specific organelles necessary for fertilization. Later, in the process of spermatogenesis, spermatids form an acrosome, condensation of heterochromatin occurs, centrioles and mitochondria are located in the middle part, and a flagellum is formed. Excess cytoplasm forms residual bodies. During chromatin condensation, histones are replaced by transitional proteins and other protamines; as a result, the compactness of DNA increases by more than 20 times compared to somatic cells. As a result of the formation of heterochromatin at the stage of oblong spermatids and spermatozoa, the transcriptional activity of most genes stops.
Spermatogenesis begins periodically in different places of the testis, which ensures a continuous, rather than pulsating, as in women, gamete production pattern. All spermatozoa that are formed from one spermatogonium during spermatogenesis remain connected by cytoplasmic bridges, i. e. form syncytium. Developing spermatogenic cells form stable and successive populations of cells at different stages of differentiation. The successive change of such phases along the seminiferous tubule is called the wave of spermatogenesis. The organizing factor of spermatogenesis are Sertoli cells, which themselves change in accordance with the cycle. When spermatogenesis is completed, the cytoplasmic bridges between the maturing gametes are destroyed, the spermatozoa enter the lumen of the tubule and are passively transferred with the fluid flow. The fluid in the seminiferous tubules is a product of the Sertoli cells. Spermatozoa located in the convoluted seminiferous tubules are not yet capable of independent movement. Not all developing spermatozoa remain alive, at least half undergo apoptosis and subsequent phagocytosis while still in the testicles. The cytokine tumor necrosis factor-a takes part in this. They are also phagocytosed by Sertoli cells.
Sertoli cells perform another function – they form the blood-testicular barrier (HTB), which separates the basal and adluminal compartments inside the seminiferous tubules. Such a barrier prevents the antigens of developing spermatogenic cells that have passed the stage of meiosis from entering the bloodstream. The need for such protection is due to the fact that the elements of the synaptonemal complex, protamines, acrosome receptors and enzymes, and other spermatozoa differentiation antigens first appear only in the puberty period. Therefore, there is no tolerance towards them – immunological non-response, which normally occurs against autoantigens presented to immature T- and B-cells in the primary immune organs (bone marrow and thymus) in the prenatal and early postnatal periods. The main element of the GTB are three levels of tight contacts between adjacent Sertoli cells, through which, as through locks, maturing gametes move in the adluminal direction. In addition to the isolating function, Sertoli cells carry out active immunosuppression, obligately secreting a special substance – Fas-ligand, which causes apoptosis of T- and NK-cells that have penetrated from the testicle. The transforming growth factor-β3 synthesized by cells also has an immunosuppressive effect.
The intertubular testicular compartment contains interstitial endocrinocytes (Leydig cells), which synthesize most of the androgens circulating in the body (~ 95%), as well as blood and lymphatic vessels, nerves, and macrophages. Synthesized testosterone enters the blood, lymph and has a systemic effect on many types of cells that have receptors for it: muscles, skin, bones, neurons of the paraventricular nucleus of the hypothalamus, cavernous tissue of the penis, etc. At the same time, testosterone has effects in the testicle itself, affecting spermatogenesis. In the seminiferous tubule, testosterone enters bound to a special protein – androgen-binding protein (ABP), which is synthesized by Sertoli cells. Sertoli cells are the target for testosterone inside the seminiferous tubules. Under the action of the 5-alpha reductase enzyme, testosterone is converted to dihydrotestosterone (DHT), which has twice the affinity for the androgen receptor and therefore a greater biological effect. The interaction of testosterone and DHT with androgen receptors is necessary for Sertoli cells to perform their functions. In the absence of androgens, spermatogenesis is impaired at the stage of meiosis. Postmeiotic spermatogenic cells themselves lack such receptors; therefore, the effect of testosterone on maturing gametes is due only to the paracrine influence of Sertoli cells.
In addition to androgens, Leydig cells produce a certain amount of estrogens, which are formed from androgens under the action of aromatase, oxytocin, which stimulates the contraction of the vas deferens and ensures the movement of sperm along the epididymis, and the cytokine insulin-like growth factor 3 (Insl3), whose function in the testis is not yet clear .
The spematogenic and androgen-producing function of the testicles is under the control of the central nervous system (CNS), which integrates environmental factors and mental state, the interaction of the nervous, endocrine and immune systems (Fig. 2).
Fig.2 . Central regulation of testicular function. The patterns of GtrH production by the hypothalamus, LH and FSH by the pituitary gland, circadian rhythms of testosterone production are shown (according to Jockenhovel, 2004).
The key role in this belongs to the hypothalamus – a small formation (1/150 of the mass of the brain) located in the diencephalon and connected by nerve fibers with many structures, primarily with the nuclei of the thalamus (thalamic thalamus) and the limbic system (hipocampus and cingulate gyrus), which play a key role in the formation of emotions. The hypothalamus produces special hormones that regulate the functions of the endocrine organs, the so-called. releasing hormones. The hormone that affects the reproductive system is a single gonadotropic releasing hormone (GT-RG). It is a decapeptide that enters the anterior lobe of the pituitary gland (adenohypophysis), and, acting on its specific cells, stimulates the production of gonadotropic pituitary hormones. Reproductive function is regulated by three pituitary hormones: follicle-stimulating (FSH), luteinizing (LH) and prolactin (Prl). FSH stimulates the development of germinal (actually sex) cells in the gonads, LH acts on the production of steroid hormones in the sex glands, Prl potentiates the action of the two described hormones on target cells. The synthesis of LH and FSH depends on the frequency and amplitude of pulse-like releases of GT-RH in the hypothalamus. Normally, GT-RG peaks occur at intervals of 90-120 min. With an increase in frequency, predominantly LH is synthesized, with a decrease – FSH. When peaks occur at intervals of less than 20 minutes, or secretion is observed in a constant mode, inhibition of gonadal function occurs as a result of depletion of secreting pituitary cells. Pulse secretion of LH completely repeats the pulsation of GT-RG, however, FSH emissions occur with a longer period. This is due to the different “lifespan” of hormones: the half-life of LH in blood serum is 50 minutes, and FSH is 180-200 minutes.
Gonadotropins secreted in the pituitary gland are carried with the blood throughout the body, and act on cells that have receptors that are sensitive to them. FSH binds to Sertoli cell receptors and stimulates their work: in the absence of FSH, there is a significant suppression of spermatogenesis and a decrease in the size of the testicles. LH binds to Leydig cell receptors and is needed for androgen synthesis: in the absence of LH, testosterone production is disrupted and spermatogenesis also stops. The intracellular mechanisms of action of gonadotropins on spermatogenesis are not completely clear. There is evidence that they prevent spontaneous apoptosis of spermatogenic cells. FSH and LH act synergistically, in particular, FSH stimulates the synthesis of androgen receptors in Sertoli cells, and androgens, in turn, stimulate FSH receptors. Simultaneously, sex steroids act on the secreting cells of the hypothalamus and pituitary gland, and thus regulate the pulsed secretion of GT-RH, LH and FSH in a feedback manner. The feedback formation also involves the growth factors inhibin B and activin A, products of Sertoli cells. Sertoli cells also continue to produce some mullerian inhibiting hormone (MIH), which plays a key role in the formation of the male reproductive system during the embryonic and fetal period. Prolactin and inhibin inhibit LH-stimulated androgen production.
The regulation of reproductive function also includes alpha-adrenergic blockers, endorphins, enkephalins and other neurotransmitters that provide control, or rather correction of the reproductive system from the central nervous system. For example, norepinephrine and dopamine have been shown to stimulate GT-RH production and sexual activity, while serotonin and endorphins inhibit it.
The epididymis / epididymis (epididymis) is a system of tubules filled with mature spermatozoa. Here they become capable of fertilization. In addition to biochemical “maturation”, in which glycerol-phosphorylcholine, carnitine and calcium ions play an important role, there is a significant increase in the concentration of spermatozoa in the seminal fluid due to the absorption of water. A special role belongs to the high concentration of dihydrotestosterone (DHT): if the DHT/T ratio in the peripheral blood is 0.1, in the testicular tissue fluid it is 1.0, then in the head of the epididymis it is already about 4.0. Fully formed morphologically, the spermatozoa in the tail of the appendage, however, remain immobile. This may be due to the presence of special inhibitory factors in the epididymal fluid, but it is more likely that specific stimulating factors contained in the secretion of the additional gonads are required to initiate mobility.
The vas deferens (ductus deferens) passes through the inguinal canal, and then along the side wall of the pelvis down and back, heading to the bottom of the bladder, where both ducts come together. In the final section of each vas deferens, its wall protrudes, as it were, forming lateral outgrowths, seminal vesicles (vesicula seminalis). Their folded mucosa produces a thick yellowish secretion that mixes with semen and thins it, nourishes and activates the spermatozoa. The pointed excretory duct of each seminal vesicle connects to the final section of the vas deferens and forms a vas deferens about two cm long, which pierces the prostate gland and opens into the prostatic part of the male urethra with a narrow opening located at the base of the seminal hillock.
The prostate gland (prostata / glandula prostatica) consists of 30-60 prostatic glands, the epithelium of which produces a liquid whitish secret – a component of sperm. The contraction of the muscular apparatus at the time of ejaculation (ejaculation) contributes to the ejection of secretions from the prostatic glands into the urethra.
Bulbourethral glands (Cooper’s) (glandula bildourethralis) open into the lumen of the urethra, produce a viscous secret that protects the mucous membrane of the urethra from the irritating effect of urine.
Substances secreted by the prostate, Cooper’s glands, and seminal vesicles are added to the semen during its passage through the ejaculatory duct and urethra, thin it, increase the viability of the spermatozoa and activate them.
Anatomy of the male genital organs : Andrology : Services
From an anatomical point of view, the male genital organs are directly connected with the urinary system. They are divided into internal and external.
Male internal genital organs include: testicles, epididymis, vas deferens, bulbourethral glands, prostate and seminal vesicles.
External genital organs include the penis and scrotum.
In this article, we will briefly introduce you to all these organs.
Testis (testis) is a paired glandular organ, which is both an endocrine (secreting a secret into the blood – mainly testosterone) and an exocrine (producing a secret into the lumen of the vas deferens – spermatozoa) gland. It should be noted that the testicle is an autoantigen, that is, a foreign element for the body. Therefore, it is separated from the bloodstream by the blood-testicular barrier. If this barrier is violated, antisperm antibodies begin to be produced, which can lead to reduced fertility and even infertility. Therefore, injuries, inflammatory processes, surgical interventions, thermal effects are highly undesirable for the testicles.
The testicles are located in the scrotum and are covered with a common skin and fleshy membrane. The remaining membranes are formed as a result of protrusion of the abdominal wall and sheets of the peritoneum during the movement of the testicle from the retroperitoneal space to the peritoneum. During embryonic development, the testicle is laid in the abdominal cavity and only then descends into the scrotum.
The average size of the testicles in an adult male is 4-5 centimeters in length and 2.5-3 in width. The mass of each testicle is on average 20-30 grams.
Epididymis (epididymis) – a paired organ, has an oblong shape, is closely connected with the testis and is part of the vas deferens. Sperm production occurs in the testicles, but they mature in the appendages. Conditionally divided into head, body and tail. The epididymis is a kind of incubator and storage for spermatozoa. The process of spermatogenesis (creation of spermatozoa) occurs in the testicles and takes an average of 75-78 days, and they mature in the appendages.
Deferent duct (ductus deferens) is a paired organ, which is a direct continuation of the tail of the epididymis, and is part of Spermian cord (funiculus spermaticus), which is a kind of spermatic conduit from the epididymis to the seminal tubercle. It is through it that spermatozoa get to the place where the sperm is ejected.
Scrotum (scrotum) is an unpaired musculocutaneous organ divided by a vertical septum into right and left halves, in which the testicles are located. It plays the role of not only a container, but also a kind of radiator. The temperature of the testicles, for their normal functioning, should be slightly lower than body temperature. When the ambient temperature rises, the scrotum relaxes, allowing the testicles to cool. In the cold, on the contrary, the muscle that lifts the testicles pulls them up, thereby warming the body.
Penis (penis) – an unpaired organ used for sexual intercourse, passage of sperm into the vagina and removal of urine from the bladder through the urethra. It consists of a head, stem and root, which is attached in front of and below the pubic region at the base of the scrotum. The shaft of the penis consists of two cavernous and one spongy bodies. Cavernous tissue in its structure resembles a sponge. At a time when the penis is not erect, the partial pressure of oxygen in the cavernous bodies is very low and corresponds to venous blood. Only at the moment of erection the penis receives arterial blood and the corresponding amount of oxygen. The longer the penis is not erect, the less oxygen it receives and the worse it functions in the future. It was on this fact that the unique Pushkar-Segal method was developed for the treatment and prevention of erectile dysfunction. This method has been successfully used in our clinic for a long time.
The urethra (urethra) is an organ that removes urine and gonadal secretions. Consists of anterior (hanging) and posterior sections. It is a gap 5-6 mm wide. This is not a pipe, as many mistakenly believe. Normally, this gap is closed. A number of diseases can provoke complications leading to the transformation of the urethra into a tube, this is a very unpleasant situation, often requiring surgical treatment. If you notice urine leakage after urinating, contact your doctor immediately. In the early stages, you can do without surgery.
Prostate gland is an unpaired muscular-glandular organ weighing about 25 grams and having a volume of about 20 cubic centimeters. The prostate is often referred to as a man’s second heart. Indeed, in many respects, both erectile function and urination depend on her condition. Checking the condition of the prostate is very simple. And you need to do this at least once a year. In our clinic, TRUS of the prostate is performed on an expert class apparatus by doctors with many years of experience.
Seed tubercle – an elongated elevation located on the posterior wall of the prostatic urethra.