repro Flashcards
what is the barr body?
in the XX genotype, only one chromosome active. Other chromosome forms a Barr body/sex chromatin nuclear mass. Can identify gender from skin cells. XY does not show this.
Where and when do male and female gonads develop from?
urogenital ridge
undifferentiated in week
testes develop in week 7
ovaries develop in week 11
why do only the tips of chromosomes undergo recombination in a male XY?
to avoid transfer of SRY gene from Y chromosome to X chromosome
describe the primitive reproductive tract
Wolffian and Mullerian tubes
common external opening
describe SRY gene influence
SRY gene produces SRY protein.
SRY stimulates primordial gonads to form testes
next the sertolli cells secrete Mullerian inhibiting substance MIS. causing duct to regress.
Leydig cells secrete testosterone which stimulates wolffian duct to form the epididymis, vas deferens, seminal vesicles and ejaculatory duct.
Testosterone also stimulates secretion of dihydrotestosterone. This causes development of the penis, scrotum and prostate.
testis descend into the scrotum, this is stimulated by testosterone
describe the testes
seminiferous tubules produce sperm
tubules converge to form the rete testis
leave testes via efferent ductules to the epididymis
leads on to the vas deferens
lumen filled with nutrient rich fluid secreted by Sertolli
surrounded by sertolli cell ring
basement membrane
leydig cells outside
describe the blood testis barrier
ring of sertolli cells with tight junctions
how long does spermatogenesis take
64 days
describe spermatogenesis
occurs at puberty
FSH and LH facilitate
spermatogonium located in the basal compartment (between basal membrane and tight junctions).
FSH on sertolli cells causes release of paracrine agents that lead to proliferation and differentiation of spermatogonium.
mitosis resulting in primary spermatocytes
not all spermatogonium are converted to primary spermatocytes but are reformed to stem cell spermatagonium. those that remain outside blood testis barrier are Type A. Type B cells go on to form primary spermatocytes.
primary spermatocytes undergo meiosis to form secondary spermatocytes as they emerge into the central compartment, passing through sertolli tight junctions
secondary spermatocytes undergo meiosis 2 to form four spermatids. Throughout this, movement from basement membrane through tight junctions, closer to lumen.
undergo spermatiogenesis where they form characteristic sperm cell structure. During this phase they embed themselves into the sertoli cell plasma membrane. once complete the sertolli cytoplasms retracts and spermatozoa cells released into the seminifeorus tubule.
- Golgi phase - formation of vesicles containing glycoproteins
- CAP phase vesicle forms the acrosome
- Acrosome phase where spermatazoon embeds itself in the sertoli layer and flagellum and midpiece develop.
- MATURATION embed in sertoli cell layer, with flagellum extending into seminiferous canal lumen. excess cytoplasm is pinched off. spermatazoon formed and released into seminiferous canal.
what are the roles of sertolli cells
secrete MIS in the embryological phase
secrete nourishing fluid into seminiferous tubule lumen. contains Androgen binding protein. binds to testosterone, keeps concentration of testosterone high.
respond to FSH and testosterone to release paracrine agents, these stimulate differentiation of spermatogonium.
form sertolli cell barrier
secrete inhibin to inhibit FSH
phagocytose defective sperm
what do the leydig cells do
secrete testosterone
also stimulates secretion of dihydrotestosterone in embyo
describe oogenesis
oogonia (primitive germ cells) divide by mitosis, finish at month 7.
7 million primary oocyte produced. these differentiate to form primary oocytes.
begins meiosis 1 arrested at metaphase 1.
at birth only 1 million primary oocyte
continues at puberty just before ovulation.
secondary oocyte formed and primary polar body, released by follicle at ovulation.
undergoes meiosis 2 but arrested in metaphase 2. Continues only if fertilised.
one cell receives most of the cytoplasm. net result is one ovum, whilst in spermatogenesis it is 4.
describe the HPG axis
hypothalamic pituitary gonadal axis
hypothalamus secretes GnRH
stimulates anterior pituitary to secrete FSH and LH
LH causes the THECA cells to convert cholesterol –> androstenedione.
Androstenedione diffuses into granulosa cells. FSH stimulates conversion of Androstenedione into oestrogen.
Oestrogen stimulates building of uterus wall. Between days 12-14 it stimulates FSH and LH. causes ovulation
Other times of the cycle in inhibits.
what are germ cells
cells that develop into ova and sperm
originate from the yolk sac of the hund guy
specialised cells
name the penile compartments
corpus cavernosum x 2
corpus spongiusum which transmits the urethra
how is the scrotum kept at 2* cooler temperature?
pampiform plexus
heat exchange mechanism in the blood vessels and air circulation
what is the epithelium of the rete testis?
simple cuboidal
what is the epithelium of the efferent ductules?
pseudostratified columnar
what is the epididymis lined by?
pseudostratified columnar with stereocilia
what is the epithelium of the vas deferens
pseudostratified columnar
out of the 2-5 ml fluid expelled during orgasm, how much is seminal, prostatic and sperm?
60% seminal
30% prostatic
10% sperm and trace of bubourethral
what do prostate and seminal vesicle secretions contain?
buffer to protect sperm against vaginal acidic secretion
chemicals to increase sperm motility, fructose for energy
prostaglandins to stimulate female peristaltic action
describe the pathway of sperm
seminiferous tubule rete testis efferent tubules epididymis vas deferens seminal gland ejaculatory duct prostate bulbourethral gland urether penile urethra
what are the 2 divisions of the seminiferous tubule
basal compartment - from basement membrane and the tight junctions
central compartment, from tight junctions and including the lumen
how frequently is gonadotropin releasing hormone released from the hypothalamus in males?
every 90 minutes
how does GnRH trigger FSH and LH release?
hypothalami hypophyseal portal system
describe the hypothalamic pituitary gonadal axis in males
GnRH released every 90 minutes
release of FSH and LH from the anterior pituitary
FSH acts on sertolli cells to stimulate secretion of paracrine agents required to initiate spermatogenesis.
FSH also stimulates sertolli cells to release protein hormone INHIBIN which acts on the anterior pituitary to inhibit release of FSH.
LH acts on leydig cells to stimulate testosterone secretion.
testosterone acts locally by diffusing from interstitial space into the seminiferous tubule.
testosterone enters the sertoli cells where it helps to facilitate spermatogenesis
testosterone also inhibits LH secretion. 1) it acts on the hypothalamus to decrease the amplitude in GnRH burst. 2) acts directly on the anterior pituitary to decrease LH response to GnRH
describe the myometrium
smooth muscle bundles which orientate in various directions
what is the epithelium of the ovary?
simple cuboidal epithelium
what epithelium lines the fimbriae?
ciliated epithelium
what is the epithelium of the uterus
simple columnar ciliated epithelium
what is the epithelium of the cervix?
simple columnar epithelium
what is the epithelium of the vagina?
moist stratified squamous
keratinised towards the vulva end
state the differences between spermatogenesis and oogenesis
- oogensis not a continous process but disjointed
- in spermatogenesis both maturations occur in the testic wherease in females one occurs in ovary and one in fallopian tube after fertilisation
- 1 oocyte forms 1 ovum. 1 spermatocyte forms 4 spermatozoa
what are the changes which happen during puberty
before puberty
hypothalamic secretion of GnRH and GHRH is low
low levels of anterior pituitary FSH LH and GH release
low level gonadal sex steroids
at puberty
GnRH and GHRH increase
increase in FSH LH GH and sex steroids.
describe the physical features that change during male puberty
starts at 9-14 testicular enlargement pubic axillary and facial hair growth growth spurt spermatogenesis begins acne, body odour and mood change
describe the physical changes at female puberty
starts at 8-14 breast development pubic and axillary hair growth growth spurt menarche 2.5 years after puberty begin acne, body odour, mood change
describe the follicular phase of the menstrual cycle
Follicular phase
• Menstrual phase
- Oestrogen and progesterone are low because previous corpus luteum regressing.
- Secretion of FSH and LH released from inhibition.
- Around 10-15 of the preantral and early antral follicles are stimulated to mature into larger antral follicles.
• Proliferative phase
- A dominant follicle is selected.
- LH causes theca cells to produce androstenedione. Enzyme desmolase
- FSH enables granulosa cells to produce oestrogen from aldostenedione. Enzyme aromatase.
- FSH also induces formation of LH receptors on granulosa cells.
- Plasma oestrogen increases due to dominant follicle secretion
- Oestrogens stimulates endometrium to proliferate.
- FSH decrease (and LH to a lesser extent) due to oestrogen and inhibin (affects mainly FSH) negative feedback.
- Therefore atresia of the non dominant follicles occur.
- LH surge is initiated by increasing plasma oestrogen during the late follicular phase. Oestrogen acts to increase LH releasing cells to GnrRH on the anterior pituitary.
- High plasma LH acts on granulosa cells to stimulate ovulation
- Oocyte is induced to complete meiosis 1 and undergo cytoplasmic maturation.
- Follicle is stimulated to secrete digestive enzymes and prostaglandin
- Ovulation mediated via digestive enzymes and prostaglandin
describe the luteal phase of the menstrual cycle
day 14- 28-
Corpus luteum forms and under the influence of low but adequate LH levels, secretes oestrogen and progesterone and inhibin.
- Progesterone inhibits LH causing it to decrease after peak. It does this by inducing negative feedback on both the hypothalamus and anterior pituitary
- Progesterone and oestrogen stimulate edometrium to form the secretory endometrium. This starts to secrete glycogen, glycoproteins and mucopolysaccarides.
- Secretion of FSH and LH is inhibited, so no new follicles develop.
- Corpus luteum degenerates if no implantation occurs
- Plasma oestrogen and progesterone decreases
- Endometrium begins to slough at day 28 and a new cycle can begin
where is the oestrogen secreted?
by the granulosa cell during the follicular phase
after ovulation by the corpus luteum.
where is the progesterone secreted?
just before ovulation, by theca and granulosa cells produce small amounts.
after ovulation, corpus luteum is the major producer.
How is the GnRH input different in males and females?
in males release every 90 minutes
in females, levels change over course of menstrual period.
what enzyme is used by theca cells to synthesise androstenedione
desmolase
what enzyme is used by granulosa cells to synthesis oestrogen
aromatase
what occurs during menstrual phase
day 1-5 progesterone withdrawal stromal haemorrhafe granulocytes in stroma stromal and glandular gramentation
what are the 2 divisions of the follicular phase
menstrual 1-5
proliferative 5-14
what happens during the proliferative phase
menstrual flow ceases
endometrium and myometrium thickens due to oestrogen
oestrogen induces synthesis of progesterone receptors in endometrial cells.
what are the segments of the luteal phase
secretory phase 14-28
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