Spermatogenesis

Question 1

Why are Testes located outside the body?

Where does spermatogenesis occur?

What are the tubule walls composed of?

What is the space between tubules filled with?

Answer 1

• To reduce temperature and maintain sperm count
• Seminiferous tubules
• Tall, columnar endothelial SERTOLI cells, which have tight junctions, called the Adluminal compartment
• LEYDIG cells, Blood vessels, Lymphatics, Interstitial fluid

Question 2

5 Stages of Spermatogenesis:
1. What is the first cell? What type of cell is it?

What are its subtypes?

Where is it laid down?

2. What is the second cell?

What does it do?

3. What is the third cell?

What does it do?

4. What is the fourth cell? What occurs?
5. What is the fifth cell?

How are many cells able to develop into sperm at the same time?

How long does Spermatogenesis take?

What is the process controlled by?

Answer 2

1. Spermatogonia - Diploid germ cells capable of Meiotic/Mitotic division
   - Type A Dark → Type A Pale → Type B Spermatogonia
   - Foetus
2. Primary Spermatocyte - 46XY Diploid
   - Enters Meiosis I
3. Secondary Spermatocyte - 23X/Y Haploid
   - Enters Meiosis II
4. Spermatids - 4 Haploid Round Spermatids differentiate into Elongated Spermatids
5. Spermatozoa - Mature sperm extruded into lumen
   - During division, the cells remain connected by cytoplasmic bridges, forming a Syncytium, allowing for synchronous development
   - 74 days (~2 months)
   - Sertoli secretions

Question 3

HPG Axis:
Where are LH and FSH receptors found?

How does FSH affect Sertoli cells?

What is the affect of Anabolic steroids on this axis? What does this lead to?

Answer 3

• • LEYDIG cells contain LH receptors
  • SERTOLI cells contain FSH receptors that convert Androgens to Oestrogen
• FSH establishes and maintains a normal quantity of Sertoli cells
• Provide Negative feedback on HPG-axis = ↓FSH/LH levels = Testicular Atrophy (↓Sertoli cells)

Question 4

What are the vascular changes during an erection?

What does the Parasympathetic NS control?

What does the Sympathetic NS control?

What does the Somatic NS control?

Answer 4

• Vasodilation of Corpus Cavernosum and Partial constriction of venous return
• Erection
• Movement of sperm along ejaculatory duct (Epididymis, Vas deferens, Spongy urethra)
• Expulsion of glandular secretions, Excavation of Urethra

Question 5

How many sperm is made every day? How many is in the ejaculate fluid?

How many of the ejaculate sperm reach the egg?

What is the fluid from the Bulbo-urethral Gland called? What’s it like? What’s its function?

What does the fluid from the Seminal vesicles contain? What’s its function?

What is the fluid from the Prostate like? What does it contain? What’s its function?

Answer 5

• 300 million sperm/day and 120 million/ejaculate
• 99.9% lost before reaching ampulla of uterine tube for fertilisation; 120,000 get near the egg
• Pre-ejaculate - Clear, Viscous, High in salt
  o Lubricates urethra for Spermatozoa and Neutralises any acidic urine
• Proteins, Enzymes, Fructose, Mucous, Vitamin C, and Prostaglandins
  o High PH protects against acidic environment of vagina
• Milky, White fluid containing Enzymes, Prostatic acid phosphatase, and Prostate-specific antigen (for Liquefaction)
  o High Zinc conc. = Antibacterial