Repro-Physiology Flashcards
What causes erection?
Parasympathetic impulses from S2-S4 cause NOS to form NO which causes smooth muscle relaxation, an efflux of calcium, and vasodilation to promote an erection.
This is maintained until norepinephrine allows calcium back into the cell, resulting in vasoconstriciton and PDE5 breaks down cGMP
What are PDE5 (phosphodiesterase 5) inhibitors that prevent breakdown of cGMP to help maintain an erection?
Sildenafil and Verdenafil FILL the penis
What are some AEs of PDE5 inhibitors?
Headache, flushing, dyspepsia, impaired blue-green color vision, and hypotension
“Hot and Sweaty,” but then Headache, Heartburn, and Hypotension
What stimulates ejaculation in a male?
Sympathetic nervous system via the hypogastric nerve stimulates emission and
the pudendal nerve stimulates ejaculation
Describe spermatogenesis
Spermatogonia are produced in the millions during gestation and line the periphery of seminiferous tubes (46,2N). Starting at puberty, these undergo many mitoses to produce primary spermacytes (46, 4N), which undergo meiosis I to form secondary spermacytes (23,2N), and the meiosis II to form spermatids (23,N). Following spermatogenesis, spermiogenesis causes maturation of spermatids to form mature spermatozoon via the loss of cytoplasmic contents and gain of an acrosomal cap
Full development takes 2 months
What other cells can be found within seminiferous cells?
Sertoli cells, aka nurse cells
What do Sertoli cells secrete?
They secrete:
inhibin which inhibits FSH production from the anterior pituitary
androgen-binding protein (ABP), which helps maintain local levels of testosterone
AMH which causes regression of the mullerian ducts during differentiation
What are the other roles of sertoli cells?
- support spermatogenesis
- form tight junctions to form the blood-testis barrier
- can transform testosterone into estrogen some via aromatase
T or F. Sertoli cells are temperature sensitive
T. There is decreased sperm and inhibin production when temp rises, such as in the case of varicocele and cryptorchidism
What are the roles of Leydig cells?
These are located in the intersitium between seminiferous tubules and secrete testosterone (unaffected by temperature)
What is Cililary dyskinesia and Kartagener syndrome marked by?
impaired sperm motility
Again, testosterone is made by leydig cells. What are the main roles of testosterone?
- differentiation of the male internal genital tract (except the prostate)- epididymis, vas deferens, seminal vesicles
- deepening of the voice at puberty
- libido
- closing of the peiphyseal plates (mainly via estrogen converted from testosterone)
- growth spurt at puberty (penis, seminal vesicles, sperm, muscle, RBCs)
How is DHT made from testosterone?
via 5a-reductase
What are the roles of DHT?
- differentiation of the external genitalia (penis, scrotum) and prostate
- balding and hair growth
- sebaceous gland activity
What are the results of extensive exogenous testosterone use?
Feedback inhibition of the HPG axis (at BOTH the anterior pituitary and the hypothalamus) which decreases sperm production and causes tesicular atrophy and azoospermia
What is azoospermia?
Azoospermia is the medical condition of a man when sperm count is equal or less than 15 million/ml in his semen
What are the main tissue sources of estrogen?
ovaries (via 17B-estradiol production), placenta (estriol), and adipose tissue (via aromatase)
How is estrogen made in adipose tissue?
from testosterone via aromatase
Give an overview of the two-cell production of ovarian estrogen
Pulsatile release of GnRH from the hypothalamus causes pulsatile LH release from the anterior pituitary which stimulates cholesterol (mainly from the liver LDL) mobilization and the action of cholesterol desmolase, which promotes conversion of cholesterol to androstenedione in THECA cells. Androstenedione then diffuses into granulosa cells, where FSH stimulates estrogen production from testosterone
How does estrogen work at a receptor tissue?
It binds to cytoplasmic receptors (alpha and beta) and translocates to the nucleus to induce transcription
What are the main functions of estrogen?
Estogen promotes development of the female genital tract, as well as follicle growth in the ovaries during the follicular phase of the menstrual cycle, and proliferation of the endometrium in the follicular phase
What are the effects of estrogen on cholesterol levels?
increases HDL but lowers LDL