BIOL 0800 Reading- Chapter 17 Flashcards
What are the major sex hormones (gonadal steroids) in the male and female systems?
Testosterone, estradiol/progesterone
What hormone group does testosterone belong to?
Androgens: testosterone produced in testes, other less-potent androgens produced in adrenal cortex
What are the three major estrogens?
Estrone, estriol, and estradiol
Where are estrogens produced?
Ovaries and placenta
Which is the predominant estrogen?
Estradiol
How does estriol differ from estradiol and estrone?
Found only in pregnant women, produced only by placenta
How are all estrogens produced?
By aromatase from the precursor androgens
Where is progesterone produced?
Ovaries at specific times of menstrual cycle
How do all steroid hormones act?
Bind to intracellular receptors, which binds to nucleus DNA to alter mRNA function rate: changes protein synthesis rate
Which is the first hormone in the chain of controlling reproductive function?
GnRH: gonadotropin releasing hormone
Where does GnRH come from?
Hypothalamus; goes to anterior pituitary visual hypothalamo-pituitary portal blood vessels
What triggers secretion of GnRH?
Action potentials in GnRH-producing hypothalamic neuroendocrine cells: pulsatile pattern
Why is it important that action potential to neuroendocrine cells of the hypothalamus are pulsatile for secretion of GnRH?
Because the cells of the anterior pituitary that secrete gonadotropins become insensitive to GnRH in high concentrations
What two anterior pituitary hormones does GnRH stimulate?
Gonadotropins: FSH and LH
What do FSH and LH do in both sexes?
Stimulate maturation of sperm/ova; stimulate sex hormone secretion
What is the dual function of the gonads?
Gametogenesis and secretion of sex hormones
What is the first stage in gametogenesis?
Proliferation of primordial germ cells: mitosis, all have 46 chromosomes, ready to be split into gametes by meiosis
When does germ cell proliferation occur in males vs females?
Females: in fetal development; Males: in puberty and continues throughout life
What is the second stage of gametogenesis?
Meiosis: germ cells divide twice to produce haploid cells with 23 chromosomes each
What are Barr bodies?
When there are two X chromosomes, the nonfunctional one condenses into a nuclear mass: sex chromatin/Barr Body
What level of sex differentiation is controlled by the genes?
Only the presence of ovaries/testes: all other characteristics are controlled by presence/absence of proper hormones
What determines formation of testes rather than continued formation of ovaries?
SRY gene: codes for SRY protein that activates a sequence of events in the urogenital ridge; only found on Y chromosome
What are the two components of the primitive reproductive tract?
Mullerian ducts and Wolffian ducts
Which duct, Mullerian or Wolffian, persists in males vs females?
Wolffian for male, Mullerian for female
What is MIS?
Mullerian-inhibiting substance: secreted by the testes along with testosterone; gene is encoded on the SRY gene of the Y chromosome
The testes secrete testosterone and MIS to begin male sex differentiation. What does testosterone do to help differentiation?
Stimulates differentiation of Wolffian ducts into epididymis, vas deferens, ejaculatory duct, and seminal vesicles
What hormones stimulates differentiation of Wolffian ducts into epididymis, vas deferens, seminal vesicles, and ejaculatory duct?
Testosterone
What is DHT?
Hormone produced from testosterone: stimulates formation of a penis and scrotum
What hormone causes the testes to descend into the scrotum?
Testosterone
What is cryptorchidism?
Failure of the testes to descend into the scrotum
What happens in Y-less, SRY-less, MIS-less females?
Mullerian ducts develop into fallopian tubes and uterus; Wolffian ducts degenerate without testosterone, and vagina/external genitalia develop
What is androgen insensitivity syndrome?
Genotype is XY, testes are present but androgen-receptor gene is mutated: testes secrete MIS and testosterone, so Mullerian ducts degenerate, but Wolffian ducts can’t respond to testosterone, so they also degenerate and vagina/external genitalia develop as in females
What is congenital adrenal hyperplasia?
Production of too much androgen in fetus, due to mutation in gene for enzyme in cortisol synthetic pathway: decrease in cortisol, increased ACTH, increased androgen production; results in masculinized XX fetus
What are sexual dimorphisms?
Sex-linked differences in appearance or form within a species
What are Leydig cells?
Interstitial cells that lie in small connective-tissue spaces between seminiferous tubules in the tests: synthesize and release testosterone
What male reproductive structure produces sperm?
Seminiferous tubules
What male reproductive structure produces testosterone?
Leydig cells
What is the rete testis?
The network of interconnected tubes formed when the seminiferous tubules converge
What is the epididymis?
The structure attached to the outside of the testis; carries efferent ductules from the rete testis to the vas deferens
What is the vas deferens?
Large, thick-walled tubule lined with smooth muscle: bound with vessels/nerves in the spermatic cord (which passes to the testis through the inguinal canal from the abdominal wall)
What are the seminal vesicles?
Two large glands behind bladder that join the two vas deferens to form the two ejaculatory ducts
What happens after the seminal vesicles join the vas deferens to form the ejaculatory ducts?
Ejaculatory ducts enter the prostate gland and join the urethra, coming from the bladder
What is the prostate gland?
Doughnut shaped: surrounds upper part of urethra to secrete fluid into it
What are the bulbourethral glands?
Lie below the prostate: drain into the urethra as it leaves the prostate
Which male reproductive structures secrete semen?
Prostate gland and seminal vesicles
What do the bulbourethral glands contribute to semen?
Small amounts of lubricating mucoid secretions
What are spermatogonia?
Undifferentiated germ cells
What are primary spermatocytes?
The cells that result from the final mitotic division and differentiation in the series of spermatogonium proliferation
How does the male reproductive system maintain spermatogonia supply if the spermatogonia are converted into primary spermatocytes?
Not all of them do: one of the cells of each clone drops out of the mitosis-differentiation cycle to remain as a stem cell spermatogonium
What are secondary spermatocytes?
Cells formed from the first meiotic division of primary spermatocytes: contain 23 two-chromatid chromosomes
What are spermatids?
Cells formed from the second meiotic division of primary spermatocytes, or the division of the secondary spermatocytes: contained 23 one-chromatid chromosomes
What is the final phase of spermatogenesis?
Differentiation of spermatids into spermatozoa
What is the acrosome?
A protein filled vesicle with several enzymes needed for fertilization
What are Sertoli cells?
Cells that extend from the basement membrane of the seminiferous tubules to the lumen; joined to adjacent Sertoli cells by tight junction; form an unbroken ring around the outer circumference of seminiferous tubule: tight junctions divide the tubule into two compartments: basal compartment and central compartments
What are the two compartments of the seminiferous tubule lumen?
Basal compartment (between basement membrane and tight junctions) and central compartment (between tight junctions and including the lumen)
What is the Sertoli cell barrier?
The blood-testes barrier: prevents movement of chemicals into seminiferous tubule lumen
Where does mitotic cell division/differentiation of spermatogonia occur?
Basal compartment of the seminiferous tubule
Where do meiotic divisions of primary spermatocytes occur?
Central compartment of the seminiferous tubule
What do the Sertoli cells do in the seminiferous tubules?
Serve as route for nutrients for developing germ cells, secrete most of fluid in seminiferous tubule lumen
What is ABP?
Androgen-binding protein: binds testosterone secreted by Leydig cells so it can cross the Sertoli cell barrier to enter the seminiferous tubule
What is the pathway for sperm after production in the central compartment of the seminiferous tubules?
Through the rete testis to the efferent ductules to the epididymis to the vas deferens for storage in the vas deferens/epididymis
What generates sperm movement as far as the epididymis?
Secretion of fluid by the Sertoli cells; creates pressure and moves the sperm/fluid
What generates sperm movement through the epididymis?
Peristaltic contractions of smooth muscle in epididymis and vas deferens: sperm are gathered in tight mass, since fluid was reabsorbed from the epididymal lumen
What neural input is needed for erection?
Inhibition of sympathetic input; activation of nonadrenergic, noncholinergic autonomic neurons to arteries: release nitric oxide to release arterial smooth muscle and allow vasodilation
What kinds of neurons release NO to the arteries of the penis to allow vasodilation for erection?
Nonadrenergic, noncholinergis autonomic neurons