Exam 4 (Lecture 57) - Male Reproduction 1

Question 1

What are the functions of Sertoli cells and Leydig cells in regard to spermatogenesis?

Answer 1

Sertoli cells:
- Facilitate sperm maturation
- Propel spermatogonia toward the central part of the lumen of the seminiferous tubules

Leydig cells:
- Support structure/scaffold
- Source of testosterone

Question 2

Describe the events in the two individual stages of spermatogenesis up to and including spermatidogenesis.

Answer 2

1) Spermatocytogenesis is the conversion of spermatogonia to spermatocytes
- Spermatogonia attached to the epithelium of the seminiferous tubules
- Sertoli cells then propel the spermatogonia toward the lumen of the seminiferous tubules
- Hormones from the Sertoli cells then cause the spermatogonia to mitotically divide and become
primary spermatocytes
- Mitotic process can occur up to six times
- Each division moves the spermatogonia toward the lumen

2) Spermatidogenesis = meiosis (2 steps)
- A primary spermatocyte then undergoes meiosis to form two secondary spermatocytes
- A secondary spermatocyte then undergoes meiosis to form two spermatids
- Spermatids are mono-chromosomal cells
- Mature spermatids are a hybrid of an epithelial cell and a sperm

Question 3

Describe the three differentiation phases of spermiogenesis (the steps AFTER spermatidogenesis).

Answer 3

1) The Cap Phase:
- The Golgi moves toward the distal pole
- The inner and outer acrosomal membranes are formed
- The axoneme forms from the distal centriole

2) The Acrosomal Phase:
- The nucleus elongates
- The proximal centriole becomes the neck
- The mitochondria migrate to the distal pole

3) The Maturation Phase:
- Mitochondria become trapped in the middle piece by the neck (proximal) and annulus (distal)
- The principle piece, containing the motility proteins (microtubules) becomes evident

Question 4

Describe the sperm activation steps that occur during storage and ejaculation.

Answer 4

Storage:
- Spermatozoa are mature spermatids that are released into the lumen and have moved to the
epididymis and vas deferens for storage
- These tubes secrete substances that keep sperm motility to a minimum
- Motility is activated during and after ejaculation

Ejaculation:
- Peristalsis of the vas deferens moves sperm from the epididymis to the urethra
- Urethral contractions move the sperm out of the penis
- Along the way, the epididymis, vas deferens and accessory glands add various components to the sperm
thus creating semen
- The vesicular glands (seminal vesicles in the horse) add fructose, citric acid, prostaglandins and fibrinogen
to the sperm
- Fructose and citric acid serve as nutrients for the sperm (TCA cycle)
- Fibrinogen is the precursor of fibrin, that can coagulate any type of cell
- The prostate adds alkalinity and a clotting enzyme
- The alkalinity immobilizes the sperm that are optimally motile at pH of 6
- The clotting enzyme converts fibrinogen to fibrin that clumps the sperm
- The prostate also adds profibrinolysin that is activated in the vagina
- The bulbourethral gland adds mucus to the ejaculate
- This mucus along with cholesterol that coats the sperm, protects the sperm and prevents excessive motility