Endo - Testis & Male Reproductive Tract Flashcards
In males, where does LH bind?
Leydig cells in testis.
What do Leydig cells do?
Produce testosterone.
In males, where does FSH bind?
Seminiferous tubules & Sertoli cells in testis.
What do the seminiferous tubules do?
Spermatozoa – produce sperm.
What do Sertoli cells do?
Produces inhibin.
What does inhibin do in males?
Long loop negative feedback at anterior pituitary to stop FSH secretion (and stop sperm production).
What is the long loop negative feedback for LH?
Increased testosterone stimulates negative feedback in anterior pituitary.
How is testosterone transported?
Plasma proteins.
Some testosterone is free and unbound – can target androgen receptors and affect DNA / mRNA. Testosterone is a steroid hormone and is lipophilic.
What is 5’a-reductase?
Enzyme that changes testosterone to DHT (dihydrotestosterone).
What are the components of inhibin?
Alpha and Beta subunits bind and create inhibin.
What are the components of activin?
2 Beta subunits.
What does activin do?
Stimulates FSH secretion.
Usually located in pituitary cells to stimulate increase FSH. Not enough in blood stream.
What are the main secondary messengers of LH and FSH?
cAMP.
What does testosterone do in fetal development?
Development of:
- Epididymis
- Vas deferens
- Seminal vesicles
What does testosterone do in puberty?
Growth of:
- Penis
- Seminal vesicles
- Musculature
- Skeleton
- Larynx
What does DHT do in fetal development?
Development of:
- Penis
- Penile urethra
- Scrotum
- Prostate
What does DHT do in puberty?
Growth of:
- Scrotum
- Prostate
- Sexual hair
- Sebaceous glands (acne)
Why is there testosterone in utero at first?
hcG from placenta binds LH receptors to develop testosterone.
Why is testosterone important in utero?
Participates in future gender identification and future gender preference of the individual.
Why is testosterone needed at birth in male infants?
To cause descent of testis into scrotum. Need change in temperature to do this.
What is testosterone’s main role in puberty?
Growth of male genitalia.
What are the roles of GABA and glutamate in sex hormones?
GABA = inhibits GnRH glutamate = increases GnRH
In puberty, what are the levels of GABA and glutamate?
High glutamate.
Low GABA.
When does testosterone start to decrease after adulthood?
6th decade of life – Senescence.
