What controls the secretion of testestosteron from fetal testes?
What does testosterone act on in the male fetus?
CNS, hypothalamus development and GnRH release
What does GnRH-induced LH stimulae in male fetal periods/
Leydig cell development- androgen
Why does fetal hCG control fetal testosterone release?
HPG Axis not fully developed until hypothalamus is capable of secreting GnRH
What happens to fetal Leydig cells duing juvenile period?
They degenerate and decrease androgen levels
When does the Hypothalamus-pituitary-testes axis fully develop?
How do undifferentiated interstitial cells become Leydig cells? When does this occur?
Expression of LH Receptors
At puberty in males, increased sensitivity of LHR of Leydig cells =
Increased testosterone production
Inreased sensitivity of FSHR of sertoli cells during male puberty =
Proliferation of sertoli cells and germ cells = sperm formation
What compartmen of the testes is vascular?
Interstitial compartment containing Leydig cells
What is the site of hormone formation in the testes?
INterstitial Leydig cells
What cells make up 20% of fetal, newborn and adult testes?
What are some steroidogenic features of mature Leydig cells?
- Numerous mitochondria with vesicular/tubular cristae
- Abundant sER
-Numerous lipid droplets
What is the precursor molecule for all steroids?
What is the enzyme that converts Testosterone to DHT?
What is the enzyme that converts testosteron to estradiol?
What kind of receptor does testosterone act via?
In which tissues is testosterone converted into oestrogen?
Locally and in adipose tissue
What proteins does testosterone bind to?
Steroid-binding globulin (SBG) also known as Androgen Binding Protein(ABP) and albumin
Can testosterone bound to SBG exert androgenic effect? What about Albumin?
No, too tightly bound to exert change. Weakly bound to albumin so it is more available to exert change.
What is considered bioavailable testosterone?
Testosterone that is unbound + testosterone bound to albumin
What are the three androgens in order of potency?
Androstenedione -> Testosteron -> Dihydrotestosterone
What ligament is the testes suspended by before testicular descent? What receptors does it have?
Supsensory cranial ligament. It has androgen receptors.
What causes the descent of the testes?
Androgen stiulated rhythmic contractions of the gubernaculum via genitofemoral nerve.
What is the avascular compartment of the testis?
How long is the seminiferous tubules?
What is contained within the lamina propria surrounding the seminiferous tubules?
Undifferentiated fibroblast-like cells
Peritubular myoid cells, smooth muscle cells
Extracellular matrix, collagen
What is a histological featur of a leydig cell?
They have pale cytoplasm due to cholesterol lipid droplets.
What are histlogical feature of a sertoli cell?
Simple columnar-like extending from basement membrane to lumen. Have pale nucleus but a very dark densly basophilic nucleolus.
What makes up the Blood-testes barrier?
Multiple layers of gap and tight junctions between sertoli cells.