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Lecture 14

ANP1107 Lecture 14: Lecture 14

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Anatomy and Physiology
Jackie Carnegie

Anatomy and Physiology of the Male Reproductive Systems • Gross and Microscopic Anatomy of the Testes The testes are located in the scrotum, the sac of skin and superficial fascia outside the abdominopelvic cavity at the root of the penis. The scrotum is more heavily pigmented than the rest of the body and has sparse hairs. The midline septum splits the scrotum and provides one compartment (testis). The exterior position provides essential temperature of 3°C lower than the core. This lower temperature allows for normal spermatogenesis. There are two tunics in the testes: i) Tunica Vaginalis: outer, 2-layered, extension of the peritoneal membrane ii) Tunica Albuginea: fibrous capsule of testis (white coat), septal extensions divide each testis into 250-300 wedge shaped lobules -each lobule consists of 1 to 4 coiled seminiferous tubules The darts and cremaster muscles in the testes controls how close the testes are to the body for temperature regulation. This protects testes from temperature changes. Leydig cells are interstitial cells that produce androgens (testosterone). They are located in between the seminiferous tubules, in the tissue of the testes. The testes blood supply comes from testicular arteries (branch from abdominal aorta). Testicular veins form the pampiniform plexus, acting as a venous drain. This has close association with the arteries to cool the blood as it enters the testes. The spermatic cord consists of blood and lymph vessels, nerves, and the vas deferens. Pathway Followed by the Sperm • 1) Epididymis (~3.8cm) -the epididymis is the head caps of the superior part of testis, it receives sperm from efferent ductules -the body and tail contain highly coiled duct of the epididymis -the sperm that enters the epididymus are immature and nonmotile -it takes 20 days for the sperm to traverse the epididymus, during this time they gain the ability to swim -the walls of the epididymis contract during ejaculation, sperm that do not get ejaculated for a long period of time (>month) get broken down and recycled 2) Ductus (Vas) Deferens (1/testis, ~45cm) -the ejaculatory duct passes into the prostate gland and then into the urethra, each vas deferens propels sperm out during ejaculation -a vasectomy is a cut in the vas deferens to prevent sperm from entering the ejaculatory pathway 3) Urethra -terminal portion of the pathway, serves both urinary and reproductive functions -prostatic urethra: portion where the urethra is surrounded by the prostate gland -membranous urethra is a short area where it traverses the urogenital diaphragm -spongy (penile) urethra runs through the penis and opens to the outside at the external urethral orifice Male Reproductive Accessory Glands • Accessory glands produce secretions that, along with sperm, make up semen. These include: i) Seminal Vesicles (2) -posterior wall of bladder, about the shape and size of little finger -contribute about 70% of semen volume (yellow, viscous, alkaline, fructose, critic acid, coagulating enzyme, prostaglandins) -sperm and seminal fluid exist in the ejaculatory duct ii) Prostate Gland (1) -single gland, size and shape of chestnut, encircles urethra inferior to bladder -milky secretion (close to 1/3 semen volume, contains enzymes, role in activating sperm, also contains PSA) -secretion to prosthetic urethra via several ducts during ejaculation iii) Bulbourethral Glands (2) -pea-sized, inferior to prostate, thick/clear mucus to spongy urethra before ejaculation -secreted first (pre-cum), cleans out the ejaculation pathway of urine and acts as lubrication • Penis as a Copulatory Organ The penis delivers sperm into the female reproductive tract. The external genitalia consists of the penis and the scrotum, while the penis is the attached root and free shaft of body and its enlarged tip is the glans penis. Internally, the penis contains: -spongy urethra -2 corpora cavernosa -3 corpora of erectile tissue -1 mid ventral corpus spongiosum • Semen Secretions provide a transport medium, nutrients (ie. fructose, citrate) and chemicals (ie. prostaglandins) which protect and activate the sperm. The sperm has a pH of 7.2-7.6 which neutralizes the acidic pH (3.5-4) of the vagina. Cells of the Male Reproductive System • The normal rate of sperm production is 2x10^8 sperm/day. The testis are a source of both germ cells and hormones, and is composed of: i) seminiferous tubules: sertoli cells and spermatogenesis intermediates, 80% of testicular mass ii) leydig cells: synthesize androgens (testosterone) in the presence of luteninizig hormone • Hormones a) A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adrenal cortex, hence cortico-) and sex steroids (typically made in the gonads or placenta). -ie. estradiol, testosterone, aldosterone, and cortisol Cholesterol is the precursor of the five major classes of steroid hormones: progestagens, glucocorticoids, mineralocorticoids, androgens, and estrogens. These hormones are powerful signal molecules that regulate a host of organismal functions. b) The amino acid-derived hormones (ending in '-ine') are derived from tyrosine and tryptophan and include epinephrine and norepinephrine (produced by the adrena
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