48 Male Reproduction (W)

Question 1

Identify and describe the functional roles and characteristics of each of the structures of the male reproductive system: testes, ducts, seminal vesicles, prostate, mucus secreting glands, penis.

Answer 1

• Testes: endocrine (testosterone) and exocrine (spermatazoa)
• Sertoli Cells: Blood-testis barrier, helps spermatogensis, produces androgen binding protien, elaborates aromatase enzyme, produces inhibin
• Leydig Cells: produces testosterone. Human chorionic gonadotropin initially stimulizes. Then at puberty (after quiescent period), LH stimulates leydig to make testosterone.
• Ducts:
  
  • Epididymus: Sperm become motile by activation of CatSper. Maturation process occurs here.
  • Vas Deferens: Ampulla is where seminal vesicles and vas deferens meet (site of sperm storage).
• Seminal Vesicles: secretory glands produces a majority of the fluid portion. Alkaline mucoid material. Fructose is the energy source for sperm. Prostaglandins alter cervical environment and promote reverse peristalsis. Fibrinogen produces coagulation of semen. Seminogelin.
• Prostate: Growth regulated by testosterone. Secretes thin, milky, fluid rich in calcium, citrate, acid phosphatase, profibrinolysin, and HCO3. Prostatic acid phosphatase used as marker for semen. Profibinolysin dissolves the clot of ejaculate, freeing the sperm. HCO3 neutralizes the acidic environment of the cervix.
• Mucus Secreting Glands:
  
  • Bulbo-urethral (Cowper’s) gland
  • Glands of Littre (along urethra) secrete thin, watery mucous to cleanse lumen of urethra and act as a lubricant
• Penis: Has 3 cylindrical sinuses encased by tunica albuginea. Corpus cavernosum is bilateral Ventral side is Corpus Spongiosum surrounding the urethra. Glans penis at distal aspect of penis rich in sensory fibers.

Question 2

Identify and describe the processes and factors influencing spermatogenesis and spermiogenesis

Answer 2

• Spermatogensis: (initiated/maintaind by sertoli cells)
• Spermatogonium goes thru mitosis to form primary spermatocyte. Then Primary goes thru first meiotic division to form secondary spermatocye. Secondary goes thru second meiotic division to form spermatid. Needs sertoli cells.
• Spermiogensis: process of cellular differentiation from spermatid to functionally immature spermatozoa. Needs sertoli cells, testosterone. The sertoli cells are under FSH influence. Sertoli cells are also responsive to testosterone.

Question 3

Identify and describe the characteristics and functional roles of spermatozoa and their components.

Answer 3

• Head: contains the compacted DNA. Covered by the acrosome which is a cap filled with lysosome. Acrosome reaction is letting the enzymes out to degrade the material surrounding the ovum
• Body: contains mitochondria
• Tail: flagella-like structure providing locomotion. Dynein deficiency results in infertility

Question 4

Identify and describe the physiological processes controlling testicular function, including the actions of testosterone, dihydrotestosterone, inhibin, GnRH, FSH, LH and prolactin.

Answer 4

• GnRH: Hypothalamus releases in pulsatile fashion but inhibited by LH/FSH thru DA, NE, and opiod peptides. Pituitary rapidly adapts to exposure of GnRH. High testosterone inhibits release of GnRH as well.
• FSH: needed for sertoli cells to function thru spermatogensis. Inhibin from sertoli cells inhibits release of FSH at level of pituitary.
• Testosterone: needed for sertoli cells to function, produced by Leydig Cells. HCG early stimulus for leydig cells to produce. Prohormone that is converted to dihydrotestosterone by 5-alpha reductase. DHT affects male hair pattern growth/loss. Masculinization of the fetus. Spermatogensis b/c sertolic cells need it. Secondary male sexual characteristics. Increases erythropoiesis and LDL, lowers HDL.
• Prolactin: Produced by anterior pituitray enhances LG action of Leydig cells. Too much will do the opposite, however.
• Inhibin: produced by sertoli cells that suppresses the release of pituitary FSH (Feeback inhibition)
• LH: From anterior pituitary to leydig cells  initiates testosterone creation. Gonadotropin. Directly inhibited at the pituitary by testosterone.

Question 5

Identify the various components of semen and describe their sources and functional significance.

Answer 5

Semen is the fluid portionof ejaculate composed of 60% seminal vesicles and 39% prostate secretions. pH is around 7.2.-8 with motility at 6.3.

Question 6

Identify and explain the various stages and mechanisms involved in the male sexual act.

Answer 6

• Erection: Parasympathetic activity of active dilating arterioles and passive constricting venules. The mechanisms release Ach promoting formation of cGMP in vascular smooth muscle and reduce release of norepinephrine. Active smooth muscle relaxation mediated by NO induced cGMP (help in check by PDE5). Sildenafil (viagra) blocks PDE5 maintaining a high concentration of cGMP
• Secretory Stages: Parasympathetic activity eliciting mucous secretions from bulbourethral and glands of littre
• Emission: Efferent sympathetic activity via hypogastric plexus. Contraction of proximal epididymis, vas deferens, and ampulla  forcing sperm into internal urethra. Also contraction of periurethral bladder muscles to stop retrograde ejaculation.
• Ejaculation: The filling elicits reflexive series of rthymic contractions of bulbocavernosus muscles resulting in expulsion. Under sympathetic control.
• Resolution: After, the sympathetic activity promotes a decreased arterial dilation with loss of boner.

Question 7

Identify and describe the major pathophysiological conditions affecting the male reproductive system.

Answer 7

• Obstruction of tubular network: due to infection, vasectomy, or prostatic hypertrophy
  
  • Testes:
    
    • Hypogonadism:
    • Orchitis: mumps or STDS
    • Cryptorchidism: undescended testes
  • Vascular: Varicocele
• ED (Impotence) due to spinal trauma, neuropathy (diabetes), endocrine imbalance, drug induced