Embryology Flashcards
what is the definition of sex?
sex is the blending of characteristics of two individuals of the nth generation to create the n+1th generation
what are the disadvantages of sex?
you need to find a partner
dilution of a “perfect” set of genes
advantages of sex
each individual has a new mix of genes that give it immunity to pathogens (red queen hypothesis)
each individual has a new mix of genes that determine its environmental interactions
what are the two sets of cells?
somatic (cells in the rest of the body
germ line (gametes)
what type of epithelium is found in seminiferous tubules?
multi-nucleated
where are the most mature sperm cells found?
nearest the middle of the tube
what is spermatogenesis?
spermatogonia (stem cells) differentiate into spermatocytes which undergo meiosis and become spermatozoa and go on to become sperm cells
what stimulates spermatogenesis?
follicle-stimulating hormone (FSH) directly stimulates
luteinising hormone (LH) stimulates the production of testosterone which stimulates spermatogenesis
when does mitotic proliferation begin?
at puberty
where does mitotic proliferation take place?
basal side of the tubule (furthest side from the lumen?
what is the acrosome and what does it store?
head of the sperm cells
contains information for fertilisation
what do sertoli cells do?
sperm cells live in the sertoli cells and are protected from the immune system
what happens when sperm cells mature?
sperm are shed and flow to the epididymis via gentle peristalsis
secretions from the epididymis activate the sperm and make them capable of swimming
do adult women have germ line stem cells?
no, only men do
when are oocytes (egg cells) produced?
during foetal life, they then enter into meiosis
how many oocytes complete meiosis?
one egg per month completes meiosis from around the ages of 12-50
what is the primordial follicle?
the primordial follicle is an oocyte arrested in meiosis 1 which is surrounded by granulosa cells (they look after the follicle)
what happens to the primordial follicle at puberty?
when FSH is produced the primordial follicles become primary follicles, only 50 per month resume development
what happens when the primary follicle develops?
the oocyte grows and synthesises rRNA and mRNA
what does the primary follicle develop into?
it becomes a ripening follicle, the oocyte synthesises a glycoprotein zona pellucida (surrounds the oocyte) and granulosa cells multiply
what do granulosa cells secrete?
follicular fluid, which forms the fluid-filled antrum (surrounds the oocyte and zona pelludica)
what happens after the formation of the antrum?
theca gains LH receptors
granulosa cells gain FSH receptors
together they activate hormone secretion from the cell
what happens if there is not adequate stimulation by FSH?
the follicle will die
what happens if the follicle does receive enough stimulation from FSH?
the antral follicle matures further to become a graafian follicle at the surface of the ovary
what happens once a graafian follicle develops?
it becomes more sensitive to FSH, there is negative feedback to the pituitary and there is a reduction in FSH levels. this prevents further recruitment of follicles, usually only one follicle matures
how do fertility drugs work?
block oestrogen detection which drives a higher and longer period of production of FSH and more follicles mature
what drives ovulation?
surge in LH levels
what occurs following a surge in LH?
completion of meiosis 1, arrest in meiosis 2 and connection with granulosa cells is lost
only takes around 12 hours
how does the mature oocyte leave the ovary?
it digests its way out of the edge of the ovary, and enters into the fallopian tube
when does meiosis 2 complete?
it never completes unless fertilisation occurs
what does the remains of the follicle become?
corpus luteum
what us the function of the corpus luteum?
produces progesterone and oestrogen
prepares the uterus lining for embryo implantation
unless the woman becomes pregnant the corpus luteum dies after a week or so
what maintains the corpus luteum?
LH
what are the phases?
menstrual - days 1-5
proliferative - days 5-14
secretory - days 14-27
ischemic - days 27-28
