male repro physio Flashcards
SRY gene
development of testes –> spermatagonia, sertoli cells (produce AMH), leydig cells (produce testosterone)
retention of wollfian ducts
results from testosterone (made from leydig cells)
regression of mullerian duct - results from AMH production by sertoli cells
DHT
testosterone stimulates the urethral epihtleium and primorordia along with GHT to formation of male-type external genitalia (prostate gland and penis)
what results in conversion to dihydrotestosterone in scrotum
5alpha reductase
testosterone production
Produced by Leydig cells of testes
Production begins in fetus by 8 weeks gestation
- Leydig cell production of testosterone is initially stimulated by hCG (human chorionic gonadotropic) which is structurally similar to pituitary LH (luteinizing hormone) before LH takes over
After production, androgens diffuse to target cells and bind to androgen receptors
Androgen receptor complex (AR) is a nuclear receptor which directs protein synthesis
– Binds T both DHT (unclear mechanism by which AR receptor differentiates in different cell types)
DHT production
Dihydrotestosterone (DHT) Production:
DHT is formed from testosterone by 5α-reductase-2 in peripheral tissues (urogenital tract, skin, hair folicles, liver); binds AR
T –> DHT (via 5α-reductase-2): Important role puberty changes
- Growth and activity of prostate gland
- Growth of penis
- Darkening and folding of scrotum
- Growth of pubic, axillary, facial, and body hair
- Increased muscle mass
5α-reductase-1: primarily expressed in skin, contributes to sebaceous gland activity and acne associated with puberty
Deficiency of 5α-reductase-2 results in ambiguous external genitalia
5α-reductase-2 inhibitors have benefited treatment of prostatic hypertrophy and prostatic cancer
actions of androgens
Androgenic:
- Fetal differentiation of male internal (T) and external genitalia (DHT)
- Growth, development of secondary sexual characteristics at puberty
- Maintenance of reproductive tract & production of semen
- Initiation and maintenance of spermatogenesis
Anabolic:
- Stimulation of erythropoietin synthesis
- Stimulation of sebaceous gland secretion
- Control of protein anabolic effects (nitrogen retention)
- Stimulation of linear body growth, bone growth and closure of the epiphyses
- Promotion of ABP synthesis
- Maintenance of secretions of sex glands
- Regulation of behavioral effects, including libido
leydig vs. sertoli cells
leydig cells = produce testosteorne (stimulated by LH)
- Note: hCG is structurally similar to LH and can act to stimulate Leydig cells
- T, DHT, and E: Negative feedback mainly on LH production
sertoli cells = nursing cells that help mature sperm (stimulated by FSH)
- also results in ABP
- spermatogenesis
- production of inhibin (neg. feedback on FSH)
sertoli cells
Supportive Function:
- Maintaining blood-testis barrier
- Phagocytosis
- Transfer of nutrients to sperm
- Receptors for hormones & paracrines
Exocrine Function:
- Fluid produced for sperm mobilization
- Production of ABP (Androgen binding protein)
- Spermination: release of sperm from seminiferous tubule
Endocrine Function:
- Expression of testosterone, ABP and FSH receptors
- Production of AMH (Antimϋllerian hormone)
- CYP19 Aromatase: testosterone –> estradiol-17β (local)
- Production of inhibin to regulate FSH levels
35 y/o male with infertility, has sparse facial hair and decreased sexual development. Testosterone is low, LH and FSH are elevated. Semen is low. Sperm concentration is low.
karyotype shows 47XXY = klinefelters
most common sx:
- infertility
- gynecomastia: swelling of the breast tissue in boys or men
look over the BSC questions
do it now.
primary hypogonadism
high gonadotropins (high FSH/LH ) androgen production reduced
