Spermatogenesis Flashcards
What are spermatogonia?
The ‘raw material’ for spermatogenesis
How long are spermatogonia available for?
Up to 70 years
How do spermatagonia divide?
Mitosis
What does mitotic division of spermatogonia give rise to?
- Ad spermatogonium
- Ap spermatogonium
What do Ad spermatagonium do?
Maintain stock
What do Ap spermatagonium do?
Give rise to primary spermatocytes
What happens to primary spermatocytes?
They divide by meiosis, giving rise to secondary spermatocytes
What do secondary spermatocytes give rise to?
Spermatids
What does each primary spermatocyte form?
4 haploid spermatids
What happens to spermatids once produced?
They are released into the lumen of the seminiferous tubules in a process called spermination
What happens to the spermatids as they pass down the seminiferous tubule?
They remodel
What path do spermatids take from the seminiferous tubule?
They pass through the rete testis and ductuli efferentes
Are sperm motile when passing through the seminiferous tubule to the ductuli efferentes?
No
If spermatids are non-motile, how can they pass through the seminiferous tubules to ductuli efferentes?
Transport via Sertoli cell secretions, assisted by peristaltic contraction, until they reach the epididymis
What happens to spermatids in the epididymis?
They form spermatozoa
What is sperm capacitation?
The final maturation step required before sperm become fertile
Where does sperm capacitation happen?
In the female genital tract
What happens in sperm capacititation?
- Removal of glycoproteins and cholesterol from sperm membrane
- Activation of sperm signalling pathways
What is involved in the activation of sperm signalling pathways?
Atypical soluble adenylyl cyclase and PKA
What does sperm capacitation allow?
Sperm to bind to zona pellucida of oocyte and initiate aerosome reaction
What must happen to human sperm for in vitro fertilisation?
It must first be incubated in capacitation media
What is the spermatic cycle defined as?
The time taken for reappearance of the same stage within a given segment of tubule
How long is the spermatic cycle in humans?
About 16 days
Why does the spermatic cycle occur?
Because not all stages in spermatogenesis are visible in a single cross-section of the seminiferous tubule
Why are not all stages in spermatogenesis not visible in a single cross-section of the seminiferous tubule?
Cells tend to appear in groups with the same maturation stages
What is the spermatogenic wave?
The distance between the ‘same stage’
Why can the spermatogenic wave be defined?
Because different stages in spermatogenesis are ordered in time as well as space, and each stage follows an orderly sequence along the length of the tubule
What is the rete testis?
Part of the testis
What is the role of the rete testis?
Spermatids move down rete testis to reach epididymis
What is the epididymis the location for?
Spermatozoa formation
Is the epididymis part of the testis?
yes
What structures are involved in the delivery of sperm?
- Seminal vesicles
- Prostate
- Bulbourethral glands
- Vas deferens
How does sperm enter semen?
It travels down the vas deferens
What % of semen does seminal vesicle secretions constitute?
70%
What do seminal vesicle secretions consist of?
- Amino acids
- Citrate
- Fructose
- Prostaglandins
What % of semen do prostate secretions constitute?
25%
What do prostate secretions consist of?
- Proteolytic enzymes
- Zinc
What are bulbourethral glands also called?
Cowper glands
What % of semen does bulbourethral glands secretions constitute?
1%
What do bulbourethral gland secretions consist of?
Mucoproteins
What is the function of mucoproteins?
- Helps lubricate
- Neutralises acidic urine in distral urethra
