Flashcards in GU phys Deck (45)
Formation of the testes after conception?
- first 40 days gonads of males and females are similar
- cells that give rise to spermatogonia and oogonia migrate from yolk sac to developing embyryonic gonads
- Testis-determining factor (TDF) promotes the conversion to the testes - seminiferous tubules appear w/in 43-50 days following conception - produce:
germinal cells - sperm
nongerminal cells - sertoli cells
leydig cells: appear about day 65 - these secrete testosterone - beings at 8th wk and peaks at 12-14th wk - this masculinizes embryonic structures - testosterone then declines to very low levels until puberty
- testes descend into scrotum shortly b/f birth
structure, formation of testes?
- testes (male gonads): 2 egg shaped structures outside abdominal cavity in the scrotum
- testes develop in abdominal cavity and then descend through the inguinal canal into pouch of peritoneum (tunica vaginalis)
- 80% spermatogenesis and 20% testosterone production
- arteries, veins and nerves
- 2 stages:
7-12 wks fetal life (AMH)
7-9 months fetal life (testosterone)
- undescended testicle - higher risk for testicuar cancer
Scrotum fxn, components?-
- temp control and protection
- houses testes
- dartos muscle (wrinkles em): smooth muscle - change in temp - can modify surface area, also sep. testes
- cremaster muscle: (elevates em) - skeletal muscle
Components of testes? Passage of sperm?
- composed of several hundred lobules
- each contains one or more colied seminiferous tubules - site of sperm production
- tubules lead into efferent ducts and become the rete testis
- 10,000-20,000 efferent ducts emerge to join the epididymis (further maturation occurs)- sperm still can't swim, so they rely on peristaltic movements of ductal walls of epididymis
- spermatozoa continue migration through vas deferens - the ampulla serves as storage reservoir for sperm - until ejaculation
How long can sperm live in ampulla of vas deferenes after vasectomy?
- 42 days
accessory organs - fxn?
- seminal vesicles: secrete fluid high in fructose and prostaglandins (increase peristaltic contractions, he;ps sperm get through cervical mucus)
- prostate gland: add alkaline fluid during ejaculation - easer fertilization (urine and vagina acidic)
- bulbourethral glands (cowper glands): on either side of membranous urethra - secrete alkaline fluid
Components of penis?
- shaft that ends in tip - glans
- loose skin of penis shaft folds to cover the glans (foreskin)
- corpora cavernosa - 2 lateral compartments
- corpus spongiosum - ventral compartment
Negative feedback of hypothalamus and pituitary? When does testosterone gradually decline?
- will inhibit GnRH from hypothalamus and inhibits ant. pituitary response to GnRH - inhibin secretion inhibits ant. pituitary release of FSH
- male - testosterone - leads to negative feeback of LH and and GnRH prod. - maintain a relatively constant secretion of LH and FSH
- declines gradually in men over than 50, inhibin inhibits FSH secretion
- aromatization rxn producing estradiol in brain is reqd for negative feedback effects
What is responsible for initiation and maintenance of body changes in puberty? What are other fxns of this hormone?
- testosterone and derivatives are responsible for initiation and maintenance of puberty
- stimulate growth of muscles, larynx, bone growth until sealing of epiphyseal discs
- promotes hemoglobin synthesis
- act in paracrine fashion, responsible for spermatogenesis
Testes and relationship w/ hormones?
- seminiferous tubules: contain receptor proteins for FSH in sertoli cells, FSH stimulates spermatogenesis to occur
- Leydig cells: LH stimulates secretion of testosterone. Contain receptor proteins for LH
- androgens secreted by interstitial cells of leydig (20% of mass of testes) under influence of LH from ant. pituitary
- leydig cells not fully mature until about 10yo
- testosterone is sig. hormone responsible for male hormonal effects
How does testosterone determine the development of sex organs? What stim. the testosterone secretion?
- embryonically testosterone is THE determining factor in development of male or female genital organs and characteristics
- hCG - which is produced by placenta stim. testosterone secretion in the fetal testes
Testosterone and testes descent?
- stim. for descent of testes during last 2-3 months of preg.
- if male child is born with undescended testicles - admin of testosterone or LH, can cause testes to descend in usual maner if inguinal canals large enough (not usually done, 80-90% of undescended testes will descend by 1yo)
Testosterone's role in primary and secondary sexual characteristics?
- primary: causes penis, scrotum, and testes to all enlarge during puberty
molecularly almost all of these effects occur b/c of increased rate of protein formation -
distribution of body hair
skin: increases thickness, more prone to acne
bone growth, bone density, Ca retention
Disorders of embryonic sexual development?
- both ovarian and testicular tissue is present in body
- individual with either testes or ovaries but not both:
have accessory sex organs and external genitalia that are incompletely developed or inappropriate,
MC cause of female pseudohemaphroditism is congenital adrenal hyperplasia.
In the male, one cause is testicular feminizing syndrome: normal fxning tests, but lack receptors for testosterone
Causes of low testosterone?
- hypogonadism (testosterone less than 300)
- trauma to Leydig cells
- testicular tumors
Male reproductive fxns?
- male sexual act
Process of spermatogenesis? Sertoli cells contribution?
- spermatocytes divide into 2 stages, one of which is by process of meiosis to form 4 spermatids, each containing 23 unpaired x'somes
- spermatids mature for 2 months until they become spermatozoa
- fxn of sertoli cells: actually envelope spermatids for processing b/f release into lumen (protect and nurse sperm)
Fxn of sertoli cells?
- form blood-testes barrier:
prevents autoimmune destruction of sperm, produce FAS ligand which binds to FAS receptor on surface to T lymphocytes, triggering apoptosis of T lymphocytes - prevents immune attack
- secretes inhibin, FSH
- phagocytize residual bodies: may transmit information molecules from germ cells to sertoli cells
- secrete ABP - binds to testosterone and concentrates in the tubules
Hormonal control of spermatogenesis?
- formation of primary spermatocytes and entry into early prophase I, begin during embryonic development - spermatogenesis arrested until puberty
- testosterone reqd for completion of meiosis and spermatid maturation
- secrete paracrine regulators: IGF-1, inhibin, transforming growth factor
- FSH necessary in later stages of spermatid maturation
Pathway of sperm?
- sperm formed in seminiferous tubules (900 seminiferous tubules make up the testes)
- sperm emptied into epididymis (maturation) - sperm becomes fully motile (inhibitory proteins in epididymal fluid prevent motility until after ejaculation), and go through final maturation (becoming capable of fertilizing ovum)
- vas deferens - most of mature sperm is stored in Vas deferens (can maintain fertility for at least a month)
- prostate gland (seminal vesicle empties at this pt)
- onto urethra where it exits through the meatus
Process of spermatogenesis, where does this start?
spermatogenia to primary spermatocyte to secondary spermatocyte to spermatid to spermatozoa (sperm cell) - these are in seminiferous tubules along with sertoli cells
- starts at pituitary gland - FSH regulates conversion of spermatogonia into spermatocytes
testosterone is necessary for final maturation of sperm cells and this is stim. by LH, both LH and FSH from pituitary, begins at 14 and continues throughout life
Fxn of seminal vesicle?
- secrete mucoid material containing fructose, citric acid, prostaglandins, and fibrinogen: provides nutrients to sperm, prostaglandins thought to work on cervical mucus making it more receptive to sperm movement
What is semen? Max life span of sperm once ejaculated?
- semen: fluid from vas deferent, seminal vesicles, prostate gladns, as well as bulbourethral glands and glands of urethra
- once ejaculation has occurred, max life span of a sperm is only 24-48 hrs at body temp, may be stored for several wks at lower temp and preserved for yrs if frozen
- avg sperm count per ejaculate is about 400 mill, if this falls below 70 mill/3.5 ml person is likely to be infertile
What is oligospermia? Causes?
- sperm count of less than 20 mill/ml ejaculate
- decreased fertility caused by heat, pharmaceuticals, and ilicit drugs
Male contraception? Vasectomy?
- contraception: compounds that suppress gonadotropin secretion - testosterone and progesterone and GnRH antagonist (in the works)
- vasectomy: each ductus deferens is cut and ties, interferes with sperm transport, may develop anti-sperm abs - find diff route
Fxn of epididymis? Ductus deferens?
- maturational changes
- resistance to pH changes and temp
- storage of sperm b/t ejaculations
- ductus deferens:
carries sperm from epididymis into pelvic cavity
Secretion of seminal vesicles and prostate?
- seminal vesicles:
alkaline fluid, citric acid, Ca2+ , coag. proteins
Onset of puberty?
- 1st 10 yrs of life pituitary secretes almost no gonadotropins and consequently the testes secrete no testosterone
- following this, progressively increasing amts of gonadotropins released
- usually by 13 - male reaches adult sexual capability