S3) Gametogenesis Flashcards
What are the starting cells for spermatogenesis and how long are they available for?
- Spermatogonia
- 70 years
Spermatogonia divide by mitosis to give rise to two types of cells.
Identify and describe them
- Ad spermatogonium: reserve stock (resting)
- Ap spermatogonium: maintain stock (active)
What do ap spermatogonia do?
From puberty onwards, ap spermatogonia produce type B spermatogonia which give rise to primary spermatocytes
Briefly describe the process of spermatogenesis
What is spermiation?
Spermiation is the release of spermatids into the lumen of seminiferous tubules
What is spermiogenesis?
Spermiogenesis is when a haploid spermatid differentiates into a spermatozoon
Outline the steps involved in spermiogenesis
⇒ Spermiation
⇒ Spermatid remodelling (seminiferous tubule)
⇒ Spermatid moves through rete testis and ductuli efferentes and into the epididymis
What is the spermatogenic cycle?
Spermatogenic cycle is the time taken for reappearance of the same stage (of spermatogenesis) within a given segment of the seminiferous tubule
How long is the spermatogenic cycle in adult humans?
16 days
What is the spermatogenic wave?
Spermatogenic wave is the distance (in the tubule) between the same stage of spermatogenesis
How does the spermatogenic wave move?
Waves move in corkscrew-like spirals towards the inner part of the lumen
How do spermatids reach the epididymis in the process of spermiogenesis?
- Spermatids are non-motile
- Transported by Sertoli cell secretions assisted by peristaltic contraction
Identify the different structures in the pathway for the delivery of sperm
Seminiferous tubules → Rete testis → Ductuli efferentes → Epididymis → Vas deferens → Urethra
Identify the contents of seminal vesicle secretions (~70%)
- Amino acids
- Citrate
- Fructose
- Prostaglandins
Identify the contents of prostate gland secretions (~25%)
- Proteolytic enzymes
- Zinc
What is the function of the bulbourethral gland (<1%)?
Secrete mucoproteins to help lubricate and neutralise acidic urine in distal urethra
What is the overall contribution of sperm to semen?
2-5% of overall volume
How many sperm are there per ejaculate?
200-500 million
Which glands secrete into the urethra?
- Prostate gland
- Bulbourethral gland
Which gland secretes into the vas deferens?
Seminal vesicle
What is sperm capacitation?
- Sperm capacitation refers to the physiological changes spermatozoa must undergo in order to fertilise an egg
- The final maturation step for sperm