6. SPERMATOGENESIS Flashcards
1
Q
What do the testes do?
A
- The testes is made up of mainly seminiferous tubules (90%)
- Spermatogenesis occurs in these seminiferous tubules
- Seminiferous tubules = Tightly coiled, 600nm long
- –> Lead to epididymis & vas deferens
2
Q
What are the tight junctions between sertoli cells?
A
- Walls of seminiferous tubules have sertoli cells which are tall, columnar endothelial cells
- Tight junctions between sertoli cells = ADLUMINAL COMPARTMENT
- Adluminal compartment forms an enclosed environment for spermatogenesis to occur
- contains secretions rom sertoli cells
3
Q
What is found in the spaces between seminiferous tubules?
A
- Leydig cells
- blood vessels
- lymphatic vessels
- interstitial fluid
4
Q
What are the 4 cell precursors for spermatoazoa?
A
- Spermatogonia ->
- Primary Spermatocyte ->
- Secondary spermatocyte
- Spermatid
- Spermatazoa
5
Q
What are spermatogonia?
A
- SPERMATOGONIA are primary germ cells found in the basement membrane
- DIPLOID CELLS
- Capable of mitosis or meiosis
- Mitosis = produce more spermatogonia
- Meiosis = produce primary spermatocytes
6
Q
What are the two types of spermatogonia cells?
A
- A d (A dark) - Mitosis
- A p (pale) - Meiois
- A pale cells committed to Meiosis, which then become B cells
- These B cells from primary spermatocytes
A p cell –> B cell –> Primary spermatocyte
7
Q
**What are primary spermatocytes?
A
- PRIMARY SPERMATOCYTES move into the adluminal compartment between sertoli cells
- 46 XY DIPLOID
- DNA replication occurs form sister chromatids
- Sister chromatids exchange genetic material before Meiosis I
8
Q
What are secondary spermatocytes?
A
- SECONDARY SPERMATOCYTES are HAPLOID 23X & 23Y
- Meiosis I forms haploid 23x & 23y
- chromosomes are arranged as sister chromatids which don’t separate
9
Q
What are spermatids & spermatozoa?
A
- SPERMATIDS produced from MEIOIS II
- 4 HAPLOID spermatids produced
- Round spermatids differentiate into elongated spermatids
- SPEMATOZOA = mature sperm extruded into lumen
10
Q
What are the three stages of spermatogenesis & how long does a cycle last?
A
- Mitotic proliferation of spermatigonia
- Meiosis & spermatocyte development
- Spermiogenesis - elongation of spermatid, loss of cytoplasm & arrangement of cellular components
- Each cycle lasts 16 days & takes 74 hours
11
Q
What is a synctium in sperm development?
A
- Each division from a spermatogonia to a spermatid is incomplete because the spermatids are still connected by bridges known as SYNCTIA (individual = synctium)
- The synctia allow for synchronous development
- The synctia are at various stages in their development, so there will always be a constant supply of spermatozoa
12
Q
Describe the effect of the HPG axis in males
A
Hypothalamus
I (GnRH)
Pituitary
I (FSH & LH)
Testes
(testosterone, DHT, androgens)
- LH = Leydig cells -> Testosterone
- FSH = Sertoli cells
13
Q
What are the effects of testosterone produced by the Leydig cells?
A
- Circulates in the body to produce secondary effects
- Testosterone binds to Androgen Binding Protein (ABP), which transports it to seminiferous tubules
- Testosterone binds to androgen receptors within Sertoli cells to cause spermatogenesis
14
Q
What’s the importance of FSH for Sertoli cells?
A
- FSH is needed to maintain a normal number of sertoli cells proportions
- Sertoli cells express FSH receptors, they convert androgens into oestrogen
15
Q
How can anabolic steroids interfere with negative feedback of the HPG axis in males?
A
- Anabolic steroids will acta s sex steroids
- So high kevels of anabolic steroids can cause negative feedback, resulting in decreased FSH & LH
- However, FSH is needed to maintain normal numbers of Sertoli cells. A drop in FSH can lead to testicular atrophy as the Sertoli cells are lost
