The male reproductive system consists of the following organs:
- testes
- ducts system (ductus deferens, ejaculatory ducts, urethra)
- accessory sex glands (seminal vesicles, prostate gland, bulbourethral gland)
- supporting structures (scrotum, penis)
The function of the testes is to produce sperm and secrete hormones, while the ducts system is responsible for the transportation and storage of sperm, assistance in sperm maturation, as well as conveyance of the sperm to the exterior.
The Scrotum
The scrotum acts as a supporting structure for the testes, consisting of loose skin and superficial fascia that hangs from the root of the penis. The left testis is suspended lower than the right testis. The spermatic cord passes up the scrotum’s back, through the inguinal ring, and into the pelvic cavity.
The external structure of the scrotum consists of rich sensory innervation, sebaceous glands, darker pigmentation, and sparse hair.
Within the internal structure of the scrotum is the scrotal septum (made up of the superficial fascia and the dartos muscle), which divides the scrotum into 2 sacs.
The testes are kept cooler by the following 3 structures:
- cremaster muscle of the spermatic cord – relaxes when warm, contracts when cool, thus raising or lowering the scrotum and testes
- dartos muscle in the scrotal wall – contracts and tautens the scrotum when cool
- pampiniform plexus of blood vessels in the spermatic cord – acts as countercurrent heat exchanger, cooling blood on its way to the testis
The Testes
The testes are paired oval glands measuring around 5cm long with a diameter of 2.5cm. Each testis weighs between 10-15g. During foetal development, the testes originate near the kidneys, from where they start descending through the inguinal canals towards and into the scrotum by the end of the 7th month of pregnancy.
The testis has a fibrous capsule known as Tunica Albuginea. Within the fibrous septa are up to 300 compartments known as lobules, each of which contains up to 3 sperm-producing seminiferous tubules. Between these tubules are clusters of interstitial cells which secrete testosterone.
The Seminiferous Tubules
The seminiferous tubules contain the following two types of cells:
- spermatogenic cells – produce sperm
- sertoli cells – support spermatogenesis
Sertoli Cells
Sertoli cells, a.k.a. sustentacular cells, support and protect spermatogenic cells through their development.
Leydig Cells
Leydig cells a.k.a. interstitial endocrinocytes, are found in clusters within the spaces between adjacent seminiferous tubules. They secrete testosterone.
The Ducts
Sperm cells pass through a number of ducts to exit the body. Once they leave the testes, sperm cells pass through the epididymis, ductus deferens, ejaculatory duct, and urethra.
EFFERENT DUCTULES – carry sperm from the posterior side of the testis to the epididymis thanks to ciliated cell clusters which assist the sperm through.
EPIDIDYMIS – whilst travelling through the epididymis, sperm cells mature, and are then stored in the epididymis’s tail, where they remain fertile for 40 to 60 days.
DUCTUS DEFERENS – sperm cells travel from the epididymis’s tail before uniting with the seminal vesicle duct.
EJACULATORY DUCT – allows the sperm cells through the prostate gland before emptying into the urethra.
SEMINIFEROUS TUBULES – open up into a collection of very short ducts known as straight tubules, which lead into the rete testis.
EFFERENT DUCTS – sperm moves into a series of coiled ducts within the epididymis.
DUCTUS EPIDIDYMIS – efferent ducts empty into a single tube a.k.a. ductus epididymis.
Accessory Sex Glands within the Male Reproductive System
Seminal Vesicles
Seminal Vesicles are a pair of glands associated with the ductus deferens, posterior to the urinary bladder base and anterior to the rectum. Seminal vesicles secrete an alkaline yellowish secretion, which helps in neutralising the acidic environment of the male urethra and the female reproductive tract. It totals about 60% of semen, containing Fructose (used for sperm ATP production), Prostaglandins (provide sperm motility and viability), and Clotting Proteins (promote semen coagulation following ejaculation).
Prostate Gland
The prostate gland is a single gland situated immediately inferior to the bladder, surrounding the urethra and the ejaculatory duct. It secretes a thin, milky, slightly acidic secretion totaling around 30% of semen, containing Citric Acid (used for sperm ATP production via Krebs’ cycle), Proteolytic Enzymes (promote breakdown of clotting proteins from the seminal vesicles), and Acid Phosphatase.
Bulbourethral a.k.a. cowper glands
Bulbourethral Glands a.k.a. Cowper’s Glands, are pea-sized glands located posterior to the prostate. They produce a clear, slippery fluid during sexual arousal, which helps lubricate the penis’s head in preparation for intercourse. It also neutralises the acidity of residual urine found in the urethra, since this acidity would be harmful to the sperm.
The Penis
The penis provides a passageway for sperm ejaculation and urine excretion through the urethra. It consists of the Root (attached portion), the Body (2 corpora cavernosa, and 1 corpus spongiosum), and the Glans penis.
Hormones related to the Male Reproductive System
ANDROGENS – masculinising steroid sex hormones eg. testosterone (normally secreted in both sexes)
OESTROGENS – feminising steroid sex hormones (normally secreted in both sexes)
PITUITARY GONADOTROPHINS – FSH (follicle-stimulating hormone) helps in maintaining spermatogenic epithelium and sertoli cells within the male, and LH (luteinizing hormone) stimulates testosterone production from the Leydig Cells within the testes.
Testosterone
Testosterone, which is the primary hormone in the testes:
- promotes male development
- is responsible for an inhibitory feedback response on the pituitary’s secretion of LH
- develops and maintains male secondary sex characteristics eg. body hair growth, larynx enlargement and voice deepening, increased stature, etc.
- exerts a protein anabolic, growth-promoting effect
- maintains gametogenesis, along with FSH
Testicular Function Control
FSH:
- maintains gametogenic function, along with androgens
- is tropic to the Sertoli cells
- stimulates secretion of androgen-binding protein and inhibin (inhibin feeds back to inhibit FSH secretion)
LH:
- stimulates testosterone secretion (testosterone feeds back to inhibit LH secretion)
- is tropic to the Leydig cells
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Claire is keen about public education on health-related subjects as well as holistic patient-centered care. She is also passionate about spreading awareness on the negative effects that domestic abuse leaves on its victims’ mental, emotional, social and physical wellbeing.
Claire aspires to continue studying following completion of her Nursing Degree, because she truly believes in lifelong education.
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