Reproduction: Spermatogenesis Flashcards
What is the optimal temperature for sperm production in the testes?
1.5-2.5°C below body temperature
What is the normal volume of the testes?
Between 15-25 ml
How is an orchidometer used to examine the size/volume of the testes?
- Orchidometer has different sized beads each with known volume
- Doctor will palpate a testicle as well as each of the beads on the orchidometer until they feel the same weight within the doctors hands
What structure are the testes mainly made up of?
Mainly made up of semineferous tubules (90% of each testicle made up of semineferous tubule).
What are some characteristics of the semineferous tubules?
- 600m worth of semineferous tubules within each testicle
- All of the tubules lead to the rete testis which connect to the epididymis which is connected to the vas deferens.
Within the walls of the semineferous tubule there are spermatogonia. What are spermatogonia?
Undiffererentiated germ cells on basement membrane that are able to undergo mitosis and produce more spermatogonia or under meiosis and differentiate into primary spermatocytes
What does the fact that the spermatogonia can undergo mitosis mean for sperm production in men?
It means that unlike women men can always continue to produce sperm so remain fertile trhoughout their lifetime
Briefly explain the process of how spermatogonia become mature sperm cells
- Spermatogonia go through mitosis to form primary spermatocyte
- Primary spermatocyte goes through meiosis I to form secondary spermatocyte
- Secondary spermatocyte goes through mitosis II to from spermatids
- Spermatids then form mature sperm cells
Within the semineferous tubules there are columns of sertoli cells what are the spaces between these columns of sertoli cells called?
Adluminal compartment
What cells/substances are within the adluminal compartment?
- Secretions from the sertoli cells
- Developing sperm cells (spermatogonia, primary and secondary spermatocytes)
What structure do the adluminal compartments forms?
They form the blood-testes barrier
Within the testes there are spaces between the semineferous tubules. What are these spaces filled with?
- Blood and lymphatic vessels
- Leydig cells
- Interstitial fluid.
What are the 3 types of spermatogonia?
- Type A dark spermatogonia
- Type A pale spermatogonia
- Type B spermatogonia
Explain how each of the 3 types of spermatogonia are formed?
- Type A dark spermatogonia formed from Type A dark spermatogonia undergoing mitosis
- Type A pale spermatogonia formed from the differentitaion of Type A dark seromatogonia
- Type B spermatogonia formed from Type A pale spermatogonia undergoing mitosis
Once the type B spermatogonia are formed what occurs to them and what is formed as a result?
- Type B spermatogonia move from basement membrane into the adluminal compartment and duplicate their DNA
- This causes formation of diploid primary spermatocyte
Once the spermatids are formed from the secondary spermatocytes where do they move into within the semineferous tubule?
- Once spermatids are formed they migrate from adluminal compartment towards the lumen of the semineferous tubule
What is Spermiogenesis?
The differentiation of the spermatids into the spermatozoa as they move into the lumen of the semineferous tubule
What changes occur to the spermatids as they differentitate into spermatozoa?
- Loss of cytoplasm
- Elongation
- Growth of tail and acrosome
- Movement of cellular contents
What does it mean when it says that the meiotic divisions of spermatogenesis are “incomplete?”
It means that each of the cells produced as a result of meiotic division are connected to each other via a cytoplasmic bridge which creates a synctium
What does the production of synctia during spermatogenesis mean for the cells cause its formation?
It means that each of the cells produced during the meiotic division sof spermatogenesis that form the synctia can develop together
Explain the effect LH has on spermatogenesis
- LH secreted from anterior pituitary binds to LH receptors on Leydig cells between semineferous tubules
- This causes cholesterol to be converted into androgens (mainly testosterone) by the leydig cells
- Testosterone then migrates to Sertoli cells within semineferous tubules
- This stimulates Sertoli cells to produce secretions that help/nuture developing spermatozoa
Explain the effect FSH can has on spermatogenesis
- FSH released from anterior pituitary will bind to FSH receptors on sertoli cells present within tight junctions of semineferous tubules
- Binding of FSH to Sertoli cells allows for them to stay alive/be maintained as Sertoli cells need FSH to survive
- Binding of FSH to sertoli cells also causes aromatase to convert androgens present in Sertoli cells to Oestrogens
What is testicular atrophy?
Condition is which the testes diminish in size and may lose function
How do anabolic steroids result in testicular atrophy?
- Anabolic steroids contain both natural and synthetic androgens
- These androgens produce negative feedback on hypothalamus and anterior pituitary which result in reduced secretion of GnRH, FSH and LH
- Reduced LH secretion leads to reduced Sertoli cell function, Developing spermatogonia less well nutured so less are produced.
- Reduced FSH secretion leads to reduction in no. of Sertoli cells present within semineferous tubules
- Both of these effects result in testicular atrophy
