reproduction Flashcards
functions of gonads (ovaries or testes)
produce gametes (spermatozoa or ova)
produce steriod “sex” hormones (mostly testosterone in males; mostly estradiol and progesterone in females)
testosterone belongs to a group of similar hormones having similar masculinizing actions called ____
androgens
in males, most of the testosterone is made by the ____ ; other less potent androgens are made by the ____ ____
testes
adrenal cortex
estradiol belongs to a group of similar hormones called ____ that are secreted in large amounts by the ____ and ____
estrogens
ovaries and placenta
estrone is an estrogen produced:
estriol is produced:
estrogens are produced:
by the ovaries and placenta
by the placenta, and is usually found only in pregnant women
from androgens by the enzyme aromatase
males produce ____ amounts of estrogens
females produce small amounts of ____ , most of which come from the ____ ____
small
androgens
adrenal cortex
progesterone is produced by the ____ and ____
it is an intermediate in the synthetic pathways for:
ovaries and placenta
adrenal steroids, estrogens, and androgens
all steroid hormones act via
intracellular receptors to alter the rate of formation of particular mRNAs and thus intracellular proteins
accessory reproductive organs
the system of ducts through which sperm or ova are transported and the glands lining or emptying into them (also included here are breats in females)
secondary sexual characteristics
the external differences between males and females (characteristic body shape, hair distribution, average adult height, etc.)
chain of hormones that largely controls reproductive function:
- ____ is released from the hypothalamus into the portal blood vessel leading to the anterior pituitary, where it stimulatess the relase of ……
- ____ ( ____ ____ and ____ ____ ) these travel in the blood to the gonads, resulting in ….
- the maturation of ____ or ____ and the stimulation of sex hormone secretion which exert many effects on all parts of the reproductive system (including the gonad from which they came) and on other body parts too
- the gonadal steriods exert feedback effects on the secretion of ____ , ____ , and ____
- gonadal protein hormones such as ____ also exert feedback effects on the anterior pituitary
- gonadotropin-releasing hormone (GnRH)
- gonadotropins (luteinizing hormone and follicle-stimulating hormone)
- sperm or ova
- GnRH, LH, and FSH
- inhibin
germ cells
cells that will develop or are developing into gametes
first stage of gametogenesis:
- primordial, undifferentiated germ cells (called ____ in males and ____ in females) first proliferate by ____ in which each of the two daughter cells resulting from the cell division receives a full set of ____ chromosomes identical to those of the original dividing cell
- this provides a supply of identical germ cells for the next stage (that is, it provides more spermatogonia or oogonia, some of which will eventually be called ____ spermatocytes or oocytes)
- in females, this mitosis occurs during ____ development; in males, it starts after ____ and continues throughout the rest of life
- spermatogia oogonia mitosis 46
- primary
- fetal
- puberty
second stage of gametogenesis:
- primary spermatocyte or oocyte divides by ____ which involves
- two successive divisions (with meiosis I producing two secondary ____ or one secondary ____ and one polar body, and meiosis II producing two ____ from each secondary spermatocyte or one ____ and another polar body from the secondary oocyte
- meiosis
- spermatocytes oocyte spermatids ovum
in meiosis I, the ____ chromosomes are dealt to the two cells being produced, so that each secondary spermatocyte or secondary oocyte contains ____ chromosomes
46
23
in meiosis II, a cell with ____ chromosomes gives rise to two spermatids with ____ each or an ovum with ____ and a polar body with ____
23
23
23
after meiosis II, the resulting sperm and ova are not genetically ____ to one another nor to the ____ germ cell that gave rise to them; thus the siblings from the same parents are far from being genetically identical
identical
primordial
seminiferous tubules
the walls of each tubule are formed from
sites of spermatogenesis in the testes
develop germ cells and sertoli cells
leydig (interstitial) cells
are in the connective-tissue spaces between the tubules
synthesize and release testosterone
the mitoitc cell division by spermatogonia in the walls of seminiferous tubules to produce primary spermatocytes begins
at puberty and continues throughout the rest of life
each stem cell spermatogonium undergoes a specified number of mitotic divisions to produce a clone of ____ ; a little differentiation occurs along the way, and cells resulting from the final mitotic division are called:
spermatogonia
primary spermatocytes
if all the cells in the clone produced by each stem cell spermatogonium followed the differentiation pathway, the spermatogonia would disappear, as all of them would be converted to:
this is prevented by, at an early point, one of the cells of each clone “dropping out” of the mitosis-differentiation cycle to:
primary spermatocytes
remain a stem cell spermatogonium (which will enter its own full sequence of divisions)
in spermatogenesis, meiosis I and II produce
4 enlarged spermatids from one primary spermatocyte
- in the final step of spermatogensis, spermatids differentation into ____ (sperm) ; this involves cell remodeling, including ____ :
- the sperm cell head is almost all ____ and contains the DNA; the tip of the nucleus is covered by the ____ , and protein- filled vesicle containing enzymes needed in fertilization
- most of the tail is a ____ (contractile filaments that produce movements capable of propelling the sperm)
- the body (midpiece) of the sperm contains ____ that provide the energy for movement
- spermatozoa elongation
- nucleus acrosome
- flagellum
- mitochondria
participation of sertoli cells:
- each sertoli cell extends from the base of the ____ ____ (where there is a basement membrane) all the way to the tubule’s ____
- sertoli cells send out extensions that join the extensions of other sertoli cells; ____ ____ are between the extensions of adjacent cells
- the ring of sertoli cells interconnected by tight junctions forms a ____ ____ ____ , which prevents the movement of many chemicals from the blood into the tubule lumen and thereby ensures proper conditions for germ cell development and differentation
- mitosis of spermatogonia occurs at the ____ of the seminiferous tubule; the primary spermatocytes then migrate through the tight junctions to eventually gain entry into the tubule’s ____
- when sperm formation is complete, the sertoli cells cytoplasm around the sperm ____, and the sperm are released in the ____
- seminiferous tubule lumen
- tight junctions
- blood testis barrier
- base lumen
- retracts lumen
other functions are sertoli cells:
- serve as the route by which _____ reach developing germ cells
- secrete most of the ____ found in the tubule lumen
- in response to ____ and to local ____ produced by leydig cells, secrete a variety of chemical messengers that function as paracrines to stimulate differentiation of the germ cells
- secrete the hormone ____
- secrete paracrines that affect ____ cell function
- ____ defective sperm
- secrete, during embryonic life, a substance that causes the primordial ____ duct system to regress
- nutrients
- fluid
- FSH testosterone
- inhibin
- leydig
- phagocytize
- female
from the seminiferous tubules, sperm travel through the ____ ____ , a network of interconnected tubes formed by the convergence of seminiferous tubules from different testicular areas
rete testis
after leaving the rete testis, sperm move into ____ ____ , which empty into the ____ , which is loosely attached to the testicular surface
efferent ductules
epididymis
the epididymis leads to the ____ ____ , a thick-walled tube lined with smooth muscle, which is bound together with blood vessels and nerves to form the ____ ____
vas deferens
spermatic cord
inguinal canal
slit-like opening that allows the spermatic cord to pass between the scrotum and abdominopelvic cavity
on each side of the body, the duct from a large, glandular ____ ____ joins the vas deferens to form an ____ ____ , which travels through the ____ ____ to join the ____ (which is coming from the urinary bladder and enters the penis after emerging from the prostrate
seminal vesicle
ejaculatory duct
prostate gland
urethra
in addition to fluid and sperm from the vas deferens, semen contains large amounts of fluid from the two ____ ____ and the ____ ____ , and small amounts from mucous glands, especially the two ____ ____
seminal vesicles
prostate gland
bulbourethral glands (cowper’s glands)
in addition to sperm, semen contains
nutrients
buffers for protecting sperm against the acidic vaginal secretions
chemicals that increase sperm motility
fibrinogen
prostaglandins
sperm are nonmotile early in the pathway, and movement as far as the ____ results from:
epididymis
the pressure created by fluid secretion from the Sertoli cells
fluid absorption as fluid travels through the epididymis
concentrates the sperm
peristaltic contractions of ____ and ____ ____ smooth muscle tissue propel the semen forward
epididymis
vas deferens
penis consists mostly of
three cylindrical, vascular compartments that run its entire length
during sexual excitement, erection occurs as neural input to the arteries supplying the vascular compartments causes
the arteries to dilate, and the compartments become engorged with blood under high pressure
in male sexual excitement, the engorgement of blood passivley compresses
the veins draining the compartments, further increasing the local pressure
before erection, the main neural input to the arteries is ____ released from ____ neurons
norepinephrine
sympathetic
during erection, the sympathetic input is inhibited, and ____ neurons to the arteries that release the unusual transmitter ____ ____ become active; nitric oxide relases the arterial ____ ____
parasympathetic
nitric oxide
smooth muscle
the main receptors that initiate the erection reflex are ____ in the genital region, especially in the head of the penis
mechanoreceptors
during erection, sensory neurons carry impulses from the mechanoreceptors to the inferior parts of the spinal cord; interneurons here control
the outflow of neural signals to the penile arteries
ejaculation is a reflex initiated by sensory pathways from
penile mechanoreceptors traveling to teh spinal cord centers
ejaculaiton:
- a patterned sequence of impulses in ____ neurons leading from the spinal cord results in
- ____ , ____ ____ , ____ ____ , ____ , and ____ ____ smooth muscle contraction as a result of stimulation by ____ neurons; this empties semen into the urethra ( ____ )
- semen’s being expelled from the urethra by a series of rapid contractions of ____ smooth muscle and skeletal muscle as the base of the ____ ( the latter is controlled by somatic motor neurons)
- efferent
- epididymis, vas deferens, ejaculatory duct, prostate, and seminal vesicle sympathetic emission
- urethral penis
the GnRH-secreting neuroendocrine cells of the ____ fire a burst of action potentials about every 90 minutes to secrete pulses of GnRH
hypothalamus
GnRH reaches the ____ ____ via the portal blood vessels connecting the two structures, and triggers the release of both ____ and ____ from the same cell type; thus these hormones are released in pulses
anterior pituitary
LH and FSH
FSH acts mainly on the ____ cells to stimulate the secretion of paracrines required for ____
sertoli
spermatogenesis
LH acts mainly on the ____ cells to trigger ____ secretion
leydig
testosterone
testosterone secreted by leydig cells enters the blood to act hormonally/systemically, but it also acts locally, in a paracrine manner, by diffusing from the ____ ____ into the ____ ____ ;
it enters ____ cells, where it facilitates ____
interstitial spaces
seminiferous tubules
sertoli
spermatogenesis
negative hormonal feedback effects:
- testosterone inhibits ____ secretion by
- acting on the ____ to decrease ____ secretion
- and acting directly on the ____ ____ to decrease the ____ response to GnRH
- ____ released by sertoli cells, acts directly on the anterior pituitary to decrease ____ secretion
- LH
- hypothalamus GnRH
- anterior pituitary LH
- inhibin FSH
other effects of testosterone
- induces differentiation of male accessory reproductive organs and maintains their functions
- induces male secondary sex characteristics; opposes action of estrogen on breast growth
- stimulates protein anabolism, bone growth, and cessation of bone growth
- required for sex drive and may enhance aggressive behavior
- stimulates erythropoietin secretion by kidneys
some hormones must undergo changes within target cells to be effective; this is true for testosterone in many of its target cells:
in adult prostate cells, testosterone is converted to ____ catalyzed by the enzyme 5 alpha-reductase)
in certain other targets cells (for example in the brain), testosterone is converted to ____ (catalyzed by aromatase)
dihydrotestosterone
estradiol
some males lack 5 alpha-reductase or aromatase in some tissues, in such a case, they will exhibit
certain signs of testosterone deficiency but not others
the fetal differentiation and later growth and function of the entire male duct system, glands, and penis all depend on testosterone, following the loss of testicular function, what occurs
accessory organs decrease in size, the glands markedly reduce their secretion rates, the smooth muscle activity of the ducts is diminished, and sex drive - erection - and ejaculation are usally impaired
during childhood, the hypothalamus does not secrete significant amounts of ____ , for reasons not yet understood, at the time of ____ , GnRH secretion begins
GnRH
puberty
most if not all of the observable changes that occur at puberty depend on ____ or its metabolite ____
testosterone
DHT
