Testis Development Flashcards
Describe the development of fetal testis
On anki
What are the 2 types of staining used for testis histology
Haematoxylin & immunohistochemistry staining
In immunohistochemisrty staining, what colour do the gonocytes and what colour do the Sertoli cells stain?
Gono red & sertoli green
What gene induces Sertoli cell differentiation?
SRY
What do the Sertoli cells form? And what do they secrete?
Sex cords and tubules
Secrete Dhaka and PDGF-A to induce Leydig cell formation
The leydig cell
-found where
-2 populations of it
Found ininterstitial tissue between tubules
-2 populations in mammal; foetal/neonatal & adult
What is the function of the leydig cell? What hormone stimulates its release?
to make androgens, primarily testosterone, under the control of LH release from the anterior pituitary
Also makes INSL3
LH stimulate its release
What is testosterone and INSL3 essential for?
Testis descent
What are the 2 time peaks of androgen production in the leydig cell and what are they necessary for?
- In fetus (ensures masculinisation)
- In adult (necessary for fertility, sex drive and maintenance of secondary sex characteristics)
What is INSL3
Insulin-like growth factor
The Sertoli cell- controlled by…
Controlled by FSH release from the anterior pituitary and androgen release from Leydig cells
Name the three cells found in testis
Leydig cell
Sertoli cell
Peritubular myoid
Testis descent occurs before or after birth
Before birth
What is androgens role in testis descent?
Cause suspensions ligament to degenerate & Completes the shortening of the gubernaculum (with help of INSL3) & movement of testes into scrotum
What is Sertoli cell functions?
-Essential regulator of testis development; SRY acts to form SC
-forms the blood testis barrier; tight junctions between SC ‘seal off’ the lumen of the tubule, they prevent autoimmune attack of haploid germ cells
-secrete AMH; prevents paramesonephric duct development
-in adult, maintains the leydig cell
Peritubular myoid cell
-role
-dependant on what
-Contract tubules, & essential for normal spermatogenesis
-androgen dependant
Testis should be what temp less/more than body temp
Around 3C cooler
Describe testicular thermoregulation (counter current exchange)
Warm blood coming down via testicular artery is cooled by cool blood that is returning into body by testicular vein; wrap around one another to produce counter current exchange that allows blood to cool
Name other aids to thermoregeulation
-Tunica dartos- smooth muscle in scrotum capable of elevating testis to cooler conditions
-cremaster muscle- capable of short term contractions & short term elevation of testes during fear and excitement
An animal affected by failure of testis descent is called…
Cryptorchid
What is failure of testis descent caused by
Problems with AMH, androgens, CCRP or other factors
May be inherited
What is testis function controlled by?
-primarily by
endocrine regulation through LH and FSH
secretion from the anterior pituitary
-some input from ACTH, GH an thyroid hormones
Feedback from testosterone from testes is -ve or +ve?
Negative
Describe control of testis
1.LH acting on leydig cells releases testosterone
2. Testosterone acts on Peritubular myoid cells that act on Sertoli cells
3. Sertoli cells in turn act on leydig cells
4. FSH also acts on Sertoli cells
Summary of factors and hormones involved in testis
On anki
What is spermatogenesis
Generation of sperm-Massive amplification of cell numbers of sperm
Why must cell differentiation occur?
To generate a motile package
Describe process of spermatogensis
- Proliferation of spermatogonia- 1 cell produces 64 cells
- Enter period of meiosis during puberty- spermatogonia becomes primary spermatocyte
- Go through first meiosis to form secondary spermatocyte
- Secondary spermatocyte undergo second meiosis to form round spermatids- haploid with singl chromatids
- Spermatids develop into sperm cells by going through differentiation. Differentiate into elongated sperm cell (spermiogenesis)
Diagram on anki
How long does spermatogenesis take in:
-dog
-humans
-bull
-ram
56-93 days in dog
64d in human
60d bull
49d ram
Once a spermatogonium develops to meiosis then the next spermatogonium starts maturing behind it
Just know this
To ensure there is
continuous sperm
production each Sertoli
cell (SC) supports how many germ cells at different stages of cycle
20-30
How is spermatogenesis controlled?
Control through Sertoli cells
Epididymis
Function
Where does sperm enter
What does tail act as
Tube that Carries sperm and induces sperm maturation
• Non-motile, non-fertile sperm enter at the head and then become fertile and motile as they travel down the epidiymis
• The tail acts as a sperm storage area.
What kind of epithelium is found in epididymis?
Pseudostratified, columnar epithelium with stereolcilia Epithelium gets smaller towards the tail
Exocrine or endocrine accessory glads are found in testis?
Exocrine glands
