HUB228 2024 Male Reproductive System PDF

Lecture 20 The Male Reproductive System B Nursing II HUB228 2024 Dept. Medical Biosciences University of the Western Cape  Introduction Why is the reproductive system unique? required for survival of species (not for survival of individua...

Lecture 20 The Male Reproductive System B Nursing II HUB228 2024 Dept. Medical Biosciences University of the Western Cape  Introduction Why is the reproductive system unique? required for survival of species (not for survival of individual) only becomes functional at puberty displays sexual differences on a grand scale Common functions of the male and female reproductive system: to produce and allow the union of gametes (sex cells) that contain www.jour.sc.edu specific genes - the random combination of these genes during sexual reproduction results in the birth of individuals with genetic differences  Introduction Functions of the male reproductive system: 1.to produce spermatozoa or sperm (male gametes) 2.to transfer spermatozoa to the female through copulation or coitus (sexual intercourse) 3.to produce and secrete sex hormones that - maintain male sex organs - contributes to male libido (sex drive) & sexual behaviour  Anatomy the male reproductive system consists of the following structures: 1. testes ] primary sex organ 2. ducts secondary 3. accessory glands sex organs 4. external genitalia (scrotum & penis)  Anatomy – the perineum perineum = specific portion of the pelvic region that contains the external genitalia & anal opening - is a diamond-shaped region between the pubic symphysis (anterior), coccyx (posterior) & ischial tuberosities (lateral) - is divided into two triangles by a set of muscles that run transversely between the two ischial tuberosities - the anterior/urogenital triangle contains the root of the penis & the scrotum - the posterior/anal triangle contains the anal opening  Anatomy – the scrotum scrotum = a fleshy pouch suspended inferior to the perineum, anterior to the anus & posterior to the base of the penis - a fibrous scrotal septum subdivides the scrotum internally into two scrotal cavities, each containing a testis - this separation normally prevents spread of infection/inflammation from one testis to the other - a serous membrane lining the scrotal cavity, called the tunica vaginalis, prevents friction between the opposing parietal (scrotal) and visceral (testicular surfaces) – think of the serous pericardium… - is externally subdivided at midline by irregular ridge called the perineal raphe Function of scrotum: 1) encloses & protects the testes 2) helps maintain constant temperature for spermatogenesis  Anatomy – the scrotum www.embarrassingproblems.co.uk  Anatomy – the scrotum an optimal testicular temperature of ± 35°C is required for the production & storage of spermatozoa this temperature is maintained by contraction & relaxation of two scrotal muscles 1) dartos muscle (= layer of smooth muscle in superficial fascia) 2) cremaster muscle ( = extension of internal oblique muscle that forms part of the covering of the spermatic cord; the spermatic cord being a small pocket of peritoneal cavity that accompanies the testes as they move through the body wall in utero)  Anatomy – the scrotum in cold air temperatures: → muscles involuntarily contract to pull testes closer to body, keeping them warm, scrotum has wrinkled skin in warm air/body temperatures: → muscles relax to allow testes to descend away from body, making them cool, scrotum has loose skin  Anatomy: the testes are small , ovoid organs, ± 5cm long, which are suspended by spermatic cords in the scrotum are surrounded by the tunica albuginea (thick, white capsule of fibrous c/t) whose septa divide each testis into 300-400 lobules each lobule contains 1-4 coiled seminiferous tubules (house developing sperm) each tubule forms a loop that is connected to the rete testis, which is connected to the epididymis via the efferent ductules  Anatomy & function: the testes seminiferous tubules are surrounded by stroma containing clusters of interstitial cells or Leydig cells (endocrine cells which secrete testosterone) the seminiferous tubules empty into a series of tubes and ducts that ultimately form the epididymis Function of testes: 1) are the gonads (primary sex organs) of the male reproductive system 2) are both exocrine & endocrine glands: - major exocrine secretion = sperm - major endocrine secretion = testosterone  Anatomy: the testes CLINICAL APPLICATION 1. testicular cancer is relatively rare but the most common cause of cancer in young men highest risk factor = uncorrected cryptorchidism (nondescent of the testes) – 10% of uncorrected cryptochid testes usually develops testicular cancer most common sign = painless solid mass in testis treatment: - early detection has an impressive cure rate ∴ self-examination should be practiced - surgical removal, followed by radiation therapy and chemotherapy cures 90% of testicular cancer  Anatomy: the testes CLINICAL APPLICATION 2. Inguinal hernias = protrusions of visceral tissues or organs into the inguinal canal the inguinal canals link the scrotal cavities with the peritoneal cavity & form during development as the testes descend into the scrotum in adulthood the canals are closed but the presence of the spermatic cords creates weak points in the abdominal wall that remain throughout life → inguinal hernias are therefore a relatively common condition that can develop commons.wikimedia.org  Anatomy: the ducts from the testes, sperm are delivered through a system of ducts: epididymis, ductus deferens, ejaculatory duct and urethra, which opens to the outside at the tip of the penis 1) Epididymis a 7m long tubule that consists of a head, body & long tail that “hug” the external surface of the testes; tail connected with epididymis smooth muscle lining wall contracts during emission to expel sperm into the ductus deferens, which leaves the scrotum in the spermatic cord “old”/damaged sperm are www.e-rham.com eventually phagocytosed  Anatomy: the ducts Functions of epididymis: a) site of sperm functional maturation (1-3 weeks) - but sperm still immobile & incapable of successfully fertilizing an oocyte a) stores & conveys sperm to ductus deferens - through fluid movement and peristaltic contractions of smooth muscle in wall of the epididymis  Anatomy: the ducts 2) Ductus deferens or vas deferens a 40-45cm long tubule that emerges from the tail of the epididymis & runs upwards through the inguinal canal into pelvic cavity to approach the prostate gland its end enlarges to form the ampulla, which is joined by a short duct from the seminal vesicle to form the ejaculatory duct  Anatomy: the ducts Functions of ductus deferens: a) stores sperm until ejaculated b) conveys sperm (via ejaculatory ducts) to urethra by peristaltic contractions during emission  Anatomy: the ducts CLINICAL APPLICATION a vasectomy (“cutting the vas”) is a simple & effective birth control procedure - a small incision is made into the scrotum (where part of the ductus deferens lies) and then the duct is cut through and ligated (tied-off) - this procedure causes a man to be “sterile”  although the man can still produce sperm, a vasectomy interrupts the route of the sperm to the www.nlm.nih.gov exterior  Anatomy: the ducts 3) Ejaculatory duct POSTERIOR a short 2cm passage that projects into the prostate gland empties into the urethra within the prostate gland Functions of ejaculatory duct: a) receives sperm b) receives additives from the seminal vesicles to produce seminal fluid  Anatomy: the ducts 4) Urethra is the 18-20cm terminal portion of the duct system, extending from the bladder to the distal end of the penis passes through the prostate gland, where it is joined by the two ejaculatory ducts is divided into three parts: - the prostatic urethra, - the membranous urethra - the spongy/penile urethra Functions of urethra: a) conducts semen to the body exterior b) conducts urine to the body exterior  Anatomy: the penis composed of three regions: glans penis, body and root 1) Glans penis - is the expanded distal end that surrounds the external urethral sphincter - composed of a mass of erectile tissue, the corpus spongiosum - a loose fold of skin called the prepuce/foreskin covers the glans penis & is snipped off during circumcision - preputial glands in the inner surface of the prepuce secretes smegma, a waxy material that can be a nutrient source for bacteria → NB to wash are thoroughly & frequently to avoid inflammation/infection (circumcision helps lower the incidence)  Anatomy: the penis 2) Body/shaft, - is the tubular, movable portion - contains three columns of erectile tissue (a maze of vascular channels incompletely separated by partitions of elastic connective tissue & smooth muscle fibers): o the corpora cavernosa forms the dorsum & sides of the penis o the corpus spongiosum forms the ventral portion of the penis & expands to form the glans penis, also surrounds spongy urethra - parasympathetic division of the ANS responsible for an erection, when nitric oxide released by postganglionic neurons in blood vessel wall causes vasodilation and the vascular channels become engorged with blood  Anatomy: the penis 3) Root of the penis - Is the fixed portion that attaches the penis to the body wall & consists of: o the bulb of the penis, which is an expansion of the corpus spongiosum at the base of the penis o the crus (“legs”) of the penis, which is an expansion of the corpora cavernosa that attaches the penis to the coxae Functions of penis: a) contains the urethra b) copulatory organ  Anatomy: the penis CLINICAL APPLICATION impotence is the inability to achieve & maintain an erection as a result of: - psychological factors (fear or anxiety) - medication - alcohol abuse - secondary to cardiovascular or nervous system problems that affect BP or blood flow to penile arteries  Anatomy: the accessory glands Functions of accessory glands: - the seminal vesicles, prostate POSTERIOR gland and bulbourethral glands produce the bulk of the semen (alkaline fluid containing sperm plus accessory gland secretions that dilutes & transports sperm) 1) Seminal vesicles: - contributes to 60% of semen volume; discharges into ejaculatory duct - secretes slightly alkaline fluid that neutralizes the acidic environment of the urethra and vagina - fluid contains: o fructose (nutrient) When sperm are mixed o prostaglandins (stimulates with seminal vesicle muscle contraction along male secretions, they become & female tracts) highly motile - step 1 in o fibrinogen (for clotting within the process of vagina after ejaculation) capacitation  Anatomy: the accessory glands 2) Prostate: - contributes to 20-30% of semen volume; discharges into POSTERIOR the prostatic urethra - secretes a slightly acidic milky fluid that activates and enhances motility of sperm - fluid contains: o seminalplasmin (an antibiotic that helps prevent urinary tract infections) o citrate (nutrient) o enzymes (for fibrin formation) o prostate-specific antigen (PSA) 3) Bulbourethral/Cowper’s glands: - secretes a thick, sticky, alkaline mucus that o neutralizes urinary acids in urethra o lubricates the urethra & end of glans penis  Anatomy: the accessory glands CLINICAL APPLICATIONS prostatitis = inflammation of the prostate - the most common reason for men (especially elderly men) to consult a urologist - hypertrophy of prostate distorts the urethra, blocking the opening of the bladder & ∴ www.yourprostate.co.nz increasing the risk of bladder infection & kidney damage prostate cancer is the third most prevalent type of cancer in men - screening: digital examination & assay for PSA levels in blood - treatment: surgical removal www.nlm.nih.gov  Physiology: spermatogenesis spermatogenesis = the sequence of events in the seminiferous tubules of the testis that produces male gametes (spermatozoa) - takes ± 74 days, of which 50 days are spent in the seminiferous tubules - production rate: ± 400 million/day begins at 12-14yrs of age & continues throughout life: 1) interstitial cells ↑ in number 2) lumen develops in each seminiferous tubule  Physiology: spermatogenesis seminiferous tubules lined with two cell types: 1) spermatogonia (germ cells) − develop into sperm 2) Sertoli cells - nourish germ cells & protect them from auto-immune destruction by forming the blood-testes-barrier - produce a number of hormones including androgens, estrogens & inhibins  Physiology: spermatogenesis Steps in spermatogenesis: 1) spermatogonia (2n) at the basement membrane divide by mitosis 2) one of their offspring (2n) remains at the basement membrane to maintain the germ cell line, the other offspring (2n) gets pushed towards the lumen & becomes a primary spermatocyte (2n) 3) each primary spermatocyte divides by meiosis I to form two secondary spermatocytes (n) 4) each secondary spermatocyte divides by meiosis II to form two spermatids (n), which are converted into four spermatozoa (sperm) during a process called spermiogenesis Physiology: spermatogenesis  Physiology: hormonal control of spermatogenesis & testicular androgen production involves interactions between the hypothalamus, anterior pituitary gland & testes, a relationship called the brain- testicular axis 1) hypothalamus releases GnRH which stimulates anterior pituitary cells to secrete the gonadotropins (FSH & LH) into the blood stream 2) FSH stimulates spermato- genesis by binding to Sertoli cells & also stimulates Sertoli cells to secrete inhibin 3) LH binds to & stimulates interstitial cells/Leydig cells around seminiferous tubules to secrete testosterone Physiology: hormonal control of spermatogenesis & testicular androgen production 4) testosterone produced in seminiferous tubules is the final trigger for spermato- genesis & enters the blood stream to exert a number of effects at other body sites (development of sex organs & secondary sex characteristics) 5) testosterone inhibits hypothalamic release of GnRH & anterior pituitary release of FSH & LH secretion 6) inhibin, produced by Sertoli cells, also inhibits hypothalamic release of GnRH & anterior pituitary release of FSH & LH secretion 5 & 6 = negative feedback Physiology: hormonal control of spermatogenesis & testicular androgen production  Check your understanding The ______ secrete(s) a slightly acidic, milky fluid that contains seminalplasmin. a) prostate b) seminal vesicles c) bulbourethral glands d) vestibular glands e) Both c and d. True / False The spermatogonia (2n) located near the basement membrane of the seminiferous tubules, divide by meiosis.  Check your understanding The ______ secrete(s) a slightly acidic, milky fluid that contains seminalplasmin. a) prostate b) seminal vesicles c) bulbourethral glands d) vestibular glands e) Both c and d. True / False The spermatogonia (2n) located near the basement membrane of the seminiferous tubules, divide by meiosis. False  Check List Make sure you can define the following terms: copulation/coitus, cryptorchidism, vasectomy, impotence, prostatitis, spermatogenesis, spermiogenesis, brain-testis-barrier, brain-testicular-axis Make sure you can answer the following questions: 1. Describe the triangles of the perineum. (6) 2. Describe the structure and the functions of the scrotum. (4) 3. Name the scrotal muscles (2) and their function during changes in body temperature (4). 4. Describe the structure (4) and the functions of the testes (3). 5. Briefly describe the risk factors, signs and treatment of testicular cancer. (4) 6. State the functions of the epididymis. (2) 7. State the functions of the ductus deferens. (2) 8. Appreciate the implications of a vasectomy. 9. State the functions of the ejaculatory duct. (2) 10. Describe the three parts of the urethra (2) and state the functions of the urethra (2). 11. Describe the three regions of the penis (9) and state the functions of the penis (2).  Check List Make sure you can answer the following questions: 12. Describe the route sperm travel from their site of production to the external environment. (6) 13. State the functions of the accessory glands in general. (2) 14. State the function and contents in secretions from the seminal vesicles. (4) 15. State the function and contents in secretions from the prostate gland. (5) 16. State the function and contents in secretions from the bulbourethral glands (3). 17. Briefly describe the consequences of prostatitis. (3) 18. Name the blood antigen used to diagnose prostate cancer (1). 19. Name the two different cell types which line the seminiferous tubules of the testes and distinguish between their functions (5). 20. Name the cell type that surrounds the seminiferous tubules and state their function. (2) 21. Describe the four steps in spermatogenesis. (8) 22. Describe the functioning of the brain-testicular axis. (10)