repro 3 Flashcards
what is the graph of a feedback loop?
-pulsatile activity in kisspeptin neurons stimulates GnRH neurons to release GnRH
-GnRH binds GnRH receptor on gonadotropes in the anterior pituitary to stimulate the release LH and FSH
-LH and FSH on the gonads to stimulate hormone secretion and facilitate gamete production
what are environmental factors that influence reproduction?
-least understood influence on reproductive hormones and gametogenesis
-difficult to study in males
the normal reproductive cycle in women easier because physiological uterine bleeding during menstrual cycle can be monitored
-nutritional status, physical activity, change of day/light cycles (travelling across time zones, night shift work)
what can environmental estrogen influence?
-can bind and activate estrogen receptors
-some are anti-estrogens that interfere with second messenger pathways
-may influence developing embryo/fetus
what are the male reproduction organs and graph?
what is the scrotum (external)?
-external sac testes migrate into
-sperm development requires temp 2-3F lower
-failure to descend: cryptorchidism (usually resolves itself in 1st year)
-unable to produce sperm but do still produce androgens
-moved to scrotum with testosterone treatment or surgically
what is male reproduction and the cross-sectional graph?
what is the prostate?
probably best known accessory gland due to its medical significance (also doesn’t stop growing)
-cancer of prostate, one of the most common form of cancers in men
-benign prostatic hypertrophy a problem in many men over 50
how is DHT involved in prostate development?
-administration of 5a-reductase inhibitor (finasteride) blocks DHT production, shrinks hypertrophied prostate
what are the testis?
produce sperm and hormones
-paired ovoid structures 2.5x5cm
what is the seminiferous tubule?
site of sperm production
developing spermatocytes tack in columns from outer edge to lumen with sertoli cells between each column
-found in interstitial tissue produce testosterone during development then again after puberty
-basal lamina of tubule keep out large particles but allows testosterone to enter
what are sertoli cells?
-contain tight junctions with adjecent sertoli cells forming a blood-testis barrier between tubule lumen and interstitial space
-regulate sperm development
-“sustentacular cells” provide sustenance or nourishment
-produce a variety of substances: hormones (activin and inhibin); growth factors; enzymes; and androgen binding protein (ABP) which binds to testosterone to keep it in the tubule lumen
1 what do spermatogonium do in sperm production?
germ cells (spermatogonium) reside just inside the basal lamina of seminiferous tubules
-some remain here undergoing mitosis to produce more germ cells, some enter meiosis to become primary spermatocytes
-as spermatocytes differentiate to sperm they move towards the tubule lumen
-sertoli tight junctions break and reform around the migrating cells
-once reaching lumen, one spermatogonium becomes 4 spermatids
2 what are spermatids in sperm production?
spermatids remain embedded in apical membrane of sertoli cells while they complete transformation, losing most of their cytoplasm and developing a flagellated tail
-chromatin condenses
-microtubule extension
-acrosome, forms a cap over the nucleus
-mid piece: mitochondria for energy (for motility)
-spermatogonium to free sperm 64 days (200 million produced/day)
what is the final step in sperm production?
-spermatids released from sertoli cells before reaching maturity
-pushed out of tubule lumen by other developing sperm, bulk flow of other fluids and contraction
-mature in epididymis (epididymal cells secrete proteins) during 12 days or so days of transit time
spermatogenesis requires _________________ and _______________
gonadotropins and testosterone
-gonadotropins named originally for effect on female ovary
what does FSH bind to?
-FSH binds to receptor on sertoli cells causing them to generate paracrine molecules needed for spermatogonia mitosis and spermatogenesis
-also produce ABP and inhibin
what does LH target?
-LH targets the interstitial leydig cells resulting in production of testosterone
-essential for spermatogenesis and actions appear to be through sertoli cells but exact mechanism not completely understood
-spermatocytes do not have receptors for FSH, LH or androgens
difficult to study in vivo or in vitro
what is the spiderweb of when the hypothalamus secretes GnRH?
how do male accessory glands contribute to secretions of semen?
sperm leaving via vas deferens are joined by the secretions of accessory glands, the resulting mixture is known as semen, a liquid medium for delivering sperm (99% accessory)
-also protect reproductive tract from pathogens ascending urethra (IG’s, lysozyme)
