Male Reproductive Physiology

Question 1

Describe the staes of spermatogenesis

Answer 1

• Spermatogenesis is a meiotic process that culminates in the formation of haploid spermatids
• Primordial germ cells:
  
  • Migrate into future testes and become:
    
    • Spermatogonia
• Spermatogonia
  
  • Begin mitotic division at puberty and become:
    
    • Primary Spermatocytes
• Primary Spermatocytes
  
  • complete the first half of meiosis and become
    
    • secondary spermatocytes
• Secondary Spermatocytes
  
  • Complete the second half of meiosis and become
    
    • Spermatids
• Spermatids
  
  • Undergo differentiation to become
    
    • Mature sperm

Question 2

Describe the location and function of Sertoli cells

Answer 2

• Location
  
  • Within the seminiferous tubules
• Function
  
  • Act as nurse cells (sustentacular cells) that surround primary spermatocytes and “nurse” them through the process of spermatogenesis and spermiogenesis (differentiation of spermatids into mature sperm)
  • Form estrogens and testosterone
    
    • Though to be important for spermiogenesis

Question 3

Describe the location and function of cells of Leydig

Answer 3

• Location
  
  • found in interstitial spaces in testes
• Function
  
  • Secrete testosterone
  • Stimulated by luteinizing hormone secreted by anterior pituitary
  • FSH is also necessary for spermatogenesis

Question 4

Describe the stages of Spermiogenesis

Answer 4

• Proacrosomal vesicles coalesce to form acrosome
  
  • Acrosome contains hyaluronidase and proteolytic enzymes
• Nucelus becomes condensed
• Acrosome caps nucleus
• Centrioles migrate to side of nucleus opposite of acrosome
• Distal Centriole begins to organize flagellum
• Mitochondria move to base of forming flagellum and wrap around it
• excess cytoplasm is sloughed off:
  
  • Residual body
• Sperm cells are stored in epididymis until ejaculated
• Sperm cells must remain in epididymis for a mimimum of 18 to 24 hours in order to gain motility
• Passage through the epididymis requires several days

Question 5

Describe the secretions and functions of the secretions of the seminal vesicles

Answer 5

• Paired structures behind prostate
• Secretes:
  
  • Fructose
  • Citric acid
  • Additional Nutrients
  • Prostaglandins
  • Fibrinogen
• During emission and ejaculation:
  
  • 60% of total volume of semen
  • Fructose provides energy for sperm
  • Prostaglandins make cervical mucous more receptive to sperm movement and may cause retro-peristaltic contractions of uterus and fallopian tubes

Question 6

Describe the secretions and functions of the secretions of the prostate gland

Answer 6

• During emission and ejaculation:
  
  • 30% of total volume of semen
  • Milky fluid containing calcium, citrate ions, phosphate ions, clotting enzyme, and profibrinolysin
  • Slightly alkaline fluid:
    
    • May help to neutralize acidity of other seminal fluids and vaginal secretions of the female

Question 7

List kinds of androgens and, source of androgens, and functions of androgens

Answer 7

• Androgens
  
  • Definition:
    
    • Any steroid hormone that has masculinizing effects
  • Include:
    
    • Testosterone
    • Dihydrotestosterone
    • Androstenedione
  • Can be synthesized in testes and adrenal glands from:
    
    • Cholesterol
    • Acetyl-CoA

Question 8

Source and function of testosterone

Answer 8

• Formed by intersititial cells of Leydig
• Function:
  
  • Responsible for distinguishing characteristics of masculine body
  • Stimulates descent of testes
  • Responsible for enlargement of external genitialia and formation of secondary male sexual characteristics
  • Associated with baldness
  • Responsible for hypertrophy of larynx
  • Increased skin thickness and secretion rate of sebaceous glands
  • Responsible for increase in protein formation and muscle formation
  • Responsible for increase in bone matrix and clacium retention
  • Responsible for increased BMR
  • Responsible for increased Hematocrit
  • Increases reabsorption of sodium in distal kidney tubules

Question 9

List the major hormones that control reproduction and list their specific functions

Answer 9

• Gonadotropin-Releasing Hormone
  
  • = LH-releasing hormone
  • Stimulates anterior pituitary to produce:
    
    • LH (Mostly)
    • FSH (Gonatropic hormones)
• Luteinizing Hormone (LH)
  
  • Activates cAMP second messenger system in target tissues
  • Causes Sertoli cells to secrete testosterone
    
    • Testosterone has a negative feedback effect on hypothalamus
• Inhibin
  
  • Secreted by Sertoli cells
  • Inhibites secretion fo FSH by anterior pituitary
    
    • also inhibits secretion of GnRH to a lesser extent
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