Flashcards in Repro Session 2 Deck (76):
Effect of oestrogen on GnRH secretion at moderate concentration?
reduces amount of GnRH released per pulse
Effect of oestrogen on GnRH secretion at high concentration?
promoted, producing a surge
what hormone reduces amount of FSH released in response to GnRH?
inhibin- produced by developing follicles in ovary granulosa cells, and seminiferous tubules, sertoli cells in testis
during antral phase of follicular development, what hormone do theca interna cells bind?
during antral phase of follicular development, what hormone do granulosa cells bind?
action of FSH on granulosa cells?
develop enzymes to convert androgens secreted by theca interna to oestrogens
what happens to release of steroids by corpus luteum as it grows, for any given LH concentration?
what enhances the effects of LH acting upon leydig cells?
prolactin and inhibin
where does testosterone act to promote spermatogenesis?
how does -ve feedback occur when testosterone levels rise?
testosterone inhibits GnRH secretion, reducing LH and FSH
reduces sensitivity of gonadotrophs to GnRH
so testosterone falls
what happens if spermatogenesis process too rapidly in terms of -ve feedback?
inhibin rises, and inhibin reduces secretion of FSH by acting on gonadotrophs in pituitary, and FSH is necessary to maintain Sertoli cells and make them responsive to tetosterone to promote spermatogenesis
what are the regulatory effects of testosterone?
maintenance of male internal genitali- prostate, seminal vesicles, vas deferens, epididymis
metabolic- anabolic action
behavioral- aggression, sexual activity
length of the luteal (waiting/secretory) phase?
how is sperm transport inhibited in the luteal phase?
action of progesterone on oestrogen primed cells, stimulating thickening and acidification of cervical mucus
which cells produce inhibins?
what happens to hormone secretion if conception occurs?
implanted embryo develops a placenta- secretes hCG- prevents corpus luteum regression, so oestrogen and progesterone continue to be secreted, supporting early wks of pregnancy, and maintaining suppression of ovarian cycle
what does the length of the luteal phase represent?
the lifespan of the corpus luteum
How does LH surge cause an ovum to be released?
LH stimulates collagenase which breaks down the theca externa (CT) of the pre-ovulatory follcle, so that it becomes weak and ruptures, releasing an ovum
why does progesterone increase prior to ovulation?
LH surge stimulates granulosa cells to secrete progesterone
where does oestrogen act via +ve feedback?
at both the hypothalamic neuroendocrine cells and anterior pituitary gonadotrophs
why does FSH also rise at when LH rises with the LH surge?
in response to GnRH signal
why is another LH surge prevented when the corpus luteum is formed during the luteal phase?
inhibitory effect of progesterone on the +ve feedback mechanism of oestrogen
how is the corpus luteum maintained in a normal cycle?
example of a drug that mimics action of dopamine, supressing release of prolactin?
how is the corpus luteum maintained initially in pregnancy?
by hCG secretion from placenta
what is menstruation triggered by?
loss of progesterone support from corpus luteum
where does inhibin act?
on the anterior pituitary gland
why does FSH tend to rise more than LH at beginning of menstrual cycle?
low inhibin levels release FSH from selective inhibition at anterior pituitary
uterine cycle is produced by...?
use of LHRH (GnRH) agonists?
in metastatic prostate cancer to overwhelm anterior pituitary gland and so reduce testosterone secretion that is necessary for growth of prostate cancer, as GnRH release from hypothalamus is normally pulsatile
what does prolactin do?
cause mammary glandular tissue growth and development, ductal proliferation, breast milk synthesis, and preparation of breast for lactation
what increases prolactin secretion?
oxytocin, oestrogen, sleep, stress, thyroid-releasing hormone
what decreases prolactin secretion?
suppressed by dopamine
GnRH receptor family?
GPCRs- PLC induced DAG and IP3 second messenger system
when is the number of oocytes at its maximum?
by about 20 wks gestational age
enzyme within granulosa cells that converts androgens to oestrgens?
over which time period do follicles in the ovary begin further development each day?
between puberty and the menopause
where do the ovaries lie?
on lateral walls of pelvic cavity, paired organs
what is the ovary covered by?
squamous epithelium- layer of peritoneum
what does the cortex of the mature ovary contain?
germ cells in various stages of development
what does the medulla of the ovary contain?
nerves, blood vessels, CT and stromal cells
what happens to the ovarian stromal cells at the outer margin of the developing follicle?
they differentiate to produce the theca folliculi
what happens with continued coalescence of fluid filled spaces between granulosa cells in follicle?
results in a follicle with a number of fluid filled spaces, which will ultimately form a single large antrum (A). Now a tertiary follicle and oocyte surrounded by a few layers of granulosa cells known as the corona radiata. As the antrum becomes larger, the oocyte is pushed to one side of the follicle where it will sit on a peg of granulosa cells called the cumulus oophorus.
name given to the few layers of granulosa cells surrounding oocyte of tertiary follicle
what happens to the cumulus oophorus just before ovulation?
starts to break down and the oocyte together with its surrounding corona radiata floats free in the follicular fluid of the graafian follicle
why is blood contained in the centre of the corpus luteum?
from ruptured theca vessels during ovulation
what happens to the granulosa cells and theca interna cells to form the corpus luteum?
granulosa cells transformed into granulosa lutein cells by LH, which secrete progesterone. The theca interna cells become theca lutein cells and secrete oestrogen. GL cells are large cells, often apparently vacuolated and with a very pale staining periphery.
what is the corpus albicans?
the regressed form of the corpus luteum
will contract and are usually resorbed
What is a corpus nigricans?
a pigmented structure formed by a regressing corpus luteum if process of removing erythrocytes from the centre by phagocytosis is incomplete
what are the main parts of the fallopian tube?
fimbriae- capture released ovum
infundibulum- where fimbriae are attached
ampulla- wide segment in which fertilisation normally occurs
intramural part- within the uterine wall
isthmus- narrow, medial segment of uterine tube adjacent to uterus
ectopic pregnancy more dangerous in intramural or isthmus than ampulla, maybe as narrower so more tube unable to withstand stretch in that location and mass bleeding occurs with tearing?
* peritoneal cavity is open to external environ in a female via infundibulum of the fallopian tubes
where is the folding of the epithelium of the fallopian tube most pronounced?
in the ampulla
what does wall of fallopian tube comprise?
inner mucosa- epithelium and LP, muscular layer (muscularis) and outer serosa
epithelium of fallopian tubes?
simple columnar ciliated- most numerous in infundibulum and ampulla, and non-ciliated peg cells- secretory cells- mucus produced that provides nutritive material for ovum, increase in number as tube approaches uterus
muscularis of fallopian tubes?
inner, relatively thick circular layer and outer thinner longitudinal layer across much of length, though 3 layers seen in isthmus where muscle thicker
epithelium lying on LP in endometrium of uterus?
LP- glands and CT elements
structure of myometrium?
4 layers of smooth muscle
blood supply of uterus?
paired uterine arteries which branch to form the arcuate arteries located in the myometrium. The arcuate arteries give rise to two sets of branches:
straight arteries which ramify in the stratum basalis
coiled arteries which supply the stratum functionalis.
stratum layers are the 2 layers of the endometrium
2 layers of the stratum functionalis of the endometrium
outer compact and deeper spongy layers
importance of cells lining the glands of the stratum basalis in the endometrium
will form a new functional layer after previous functional layer shed completely in menstruation
3 stages of the uterine cycle?
a proliferstive phase primarily under the control of oestrogen
a secretory phase primarily under the control of progesterone
a menstrual phase caused by the sudden drop in progesterone levels
what happens to the endometrium during the proliferative phase of the uterine cycle?
the stratum functionalis regenerates from cells lining the glands in the stratum basalis which remain intact during menstruation. The growth in depth of the s. functionalis leads to increasing length of the endometrial glands which are straight, unbranched tubular glands at this stage. Cells surrounding the developing glands, the stromal cells, proliferate and by the end of this stage the spaces between the endometrial glands are lacked with these stromal cells.
what happens to the endometrium during secretory phase of uterine cycle?
Increasing levels of progesterone lead to further development of the endometrium. The glands grow more than the surrounding lamina propria and so become coiled. The degree of coiling is so great that in section the glands appear to have a saw tooth appearance as seen here. Towards the end of this stage their are also changes in the stroma or lamina propria
The stroma becomes oedematous, and the stromal cells start to develop into decidual cells (the stage of decidualisation the diagram above) In this image the small nuclei belong to developing decidual cells and the empty spaces indicate the oedema. If fertilisation occurs, then the decidual cells contribute to the formation of the placenta and also secrete prolactin.W
Why does falling pregesterone levels cause the endometrium to break down?
Falling levels of progesterone lead to spasm of the spiral arteries. The stratum functionalis is therefore deprived of nutrients and dies (becomes necrotic). the spasm of the arteries is believed to be due to locally released prostaglandins. As the coiled arteries do not go into spasm the stratum basalis remains and in the next cycle proliferates to form a new stratum functionalis
what does the cervix connect?
the uterine cavity with the vagina, and extends between the internal ostium of the uterus, and external ostium of the uterus- uterine canal
what happens to the simple columnar epithelium lining the uterine canal of the inner aspect of the external ostium?
the epithelium abruptly changes to non-keratinised stratified squamous. Note that the cervical canal contains many mucous secreting glands underlying the epithelium.
describe the vagina
The vagina is a fibromuscular tube connecting the cervix to the exterior consisting of a mucosa, submucosa and muscular layer which contains both smooth and skeletal muscle.
The epithelium is non-keratinised stratified squamous. The epithelial cells accumulate glycogen under the influence of oestrogen. This glycogen provides a substrate for the numerous lactobacilli found within the vagina. Its metabolism accounts for the normally acid pH of the vagina- prevent candida albicans overgrowth
The vagina lacks glands; it is lubricated by mucous produced by cervical glands and also by the vestibular glands which open into the vestibule.
At puberty the junction between the cervical and vaginal epithelia occurs at the external ostium. There is a gradual movement of this junction from this site into the cervical canal during reproductive life
what is a lactiferous duct?
a duct transporting milk from the mammary glands to the nipple of the breast. Tree branched system connecting lobules
What happens to the breasts during puberty in the female?
Under the influence of oestrogens, the breast enlarges due to the accumulation of adipose tissue and the duct system (lactiferous ducts) becomes much enlarged
epithelium lining breast ducts?
The ducts (D) are lined by a cuboidal to columnar epithelium which changes to stratified squamous at level of the lactiferous sinuses; ducts are surrounded by myoepithelial cells
why might tenderness of the breast occur as part of the menstrual cycle?
The mammary glands are stimulated further during each menstrual cycle as the oestrogen peak induce duct proliferation which in turn leads to enlargement and sometimes oedema and tenderness
how do oestrogen and progesterone affect breast during pregnancy?
Maximal development of the breast occurs during pregnancy with oestrogen resulting in in proliferation of the duct system whilst progesterone influences development of the secretory tissues.
basic components of a mature mammary gland?
alveoli (hollow cavities, a few millimeters large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells. These alveoli join to form groups known as lobules. Each lobule has a lactiferous duct that drains into openings in the nipple. The myoepithelial cells contract under the stimulation of oxytocin- from PP, excreting the milk secreted by alveolar units into the lobule lumen toward the nipple
where is the anterior pituitary derived from?
what is happening to FSH during the pre-ovulatory phase?
FSH still being inhibited by inhibin produced by the granulosa cells, LH surge then occurs due to +ve feedback from oestrogen, and FSH rises slightly at this point due to effect of GnRH
importance of progesterone inhibiting +ve feedback of oestrogen in luteal phase?
prevent any more follicles from developing as FSH release suppressed