Spermatogenesis and semen evaluation Flashcards
What are the 3 goals of spermatogenesis?
- Produce spermatozoa (cells capable of fertilisation)
- Replenish supply of primordial stem cells
- Create genetic diversity
What are the 3 phases of spermatogenesis?
- Proliferation
- Meiotic phase
- Differentiation
What are the functions of sertoli cells?
- Nerve cells
- Provide nutrition to cells
- Remove waste
- Involved in hormonal regulation
The proliferation phase begins with what type of cell?
Spermatogonia
Describe the division and replication of cells in proliferation
- Mitosis
- Daughter cells are genetically identical to parent cells
- Diploid
- Some cells go back to the start to replenish stocks
In which compartment are spermatogonia present?
Basal compartment
The meiosis phase begins with which type of cell?
Primary spermatocytes
Describe the events of the meiosis phase
- Cross over and random assortment of DNA creates genetic diversity
- End up with haploid daughter cells which are genetically unique
In the bull how long is the primary spermatocyte lifespan?
18-19 days
What is the total length of spermatogenesis in the bull?
61 days
Which cells are produced at the end of the differentiation phase?
Spermatozoa
What is the function of the acrosome in the head of the spermatozoa?
Contains hydrolytic enzymes required for penetration of the zona pellucida
Name the 3 pieces that make up the tail of the spermatozoa
- Middle piece
- Principle piece
- Terminal piece
How can fertility be assessed externally?
- Scrotal circumference
- Palpation of testicle
Where do spermatozoa mature?
The head and body of epididymis
GnRH released from the hypothalamus has what effects?
Influences the anterior pituitary which releases LH and FSH
What is the role of LH?
- Acts on leydig cells which produce testosterone
- Testosterone has a negative feedback effect on Sertoli cells and the hypothalamus
What is the role of FSH?
- Acts on the Sertoli cells to regulate them
Which hormone is produced from Sertoli cells, what is the function of this hormone?
Inhibin
- negatively feedbacks to the anterior pituitary inhibiting GnRH, FSH and LH
How long does transport of spermatozoa through the epididymis take?
1-2 weeks
What should be recorded when evaluating semen?
Volume, colour, appearance, motility, density, any head/tail abnormalities, live:dead
A sperm score of 5 in a ram would have what appearance? Compare to a score of 0
5 = Thick and creamy 0 = Clear and watery
Describe 2 types of sperm defects
Primary vs secondary = classifying whether the defect occurred in the seminiferous tubule or after release into the lumen
Compensable vs non-compensable = will increasing the number of spermatozoa overcome the problem
Give examples of what spermatozoa are sensitive to
- Temperature
- Water
- Bright light
- Blood
- Cigarettes
