mitosis and meiosis Flashcards
primordial germ cells
diploid cells that arise through mitosis. Arise in the primitive streak and migrate via the gut of an embryo to the developing gonads
once in the gonad:
oogonium
spermatogonium
stages of spermatogenesis
spermatogonium(d)->spermatogonia(d)->primary spermatocytes(d)->secondary spermatocytes(h)->spermatids(h)->spermatozoa
stages of oogenesis
oogonium(d)->primary oocytes(d)->enlarged primary oocyte(d)->secondary oocyte(h)->mature ovum(h)
spermatocytogenesis
germ cell->spermatids (immature sperm)
spermiogenesis
1-golgi phase -Golgi body enzymes form the acromosome
2-acrosomal phase-acrosome condenses around the nucleus
3-tail phase-centriole elongates to form the tail
4-maturation phase-loss of excess cytoplasm
spermiation
mature spermatozoa are released from the protective Sertoli cells into the lumen of the seminiferous tubule
the resulting spermatozoa are now mature but lack motility, rendering them sterile.
the non-motile spermatozoa are transported to the epididymis in testicular fluid secreted by the Sertoli cells and peristaltic contraction
storage in the vas deferens aided by secretion by the seminal gland, the sperm finally gain motility
still need to undergo capacitation in order for them to become fertile
sperm transport in female reproductive tract
a glycoprotein coat over the acrosome prevents the sperm from fertilising the egg. Capacitation of the sperm happens due to enzymes FPP and heparin which removes the coat and allows sperm to bind to egg
FPP is produced in the prostate gland as a component of seminal fluid.
high levels of active FPP prevent capacitation
ejaculate is deposited in the anterior vagina near the cervical os
hypergonadotrophic hypogonadism
issues with the testes or ovaries
hypogonadotrophic hypogonadism
issues with the hypothalamus or pituitary gland
LH surge
re-starts meiosis in the oocytes which becomes haploid
activates enzymes -dissolve follicle wall and promotes vascular leakage so that antrum swells and bulges
follicle ruptures
ovulation
oestrogen production dives
The corpus luteum
ruptured follicle transforms into corpus luteum
-yellow:from cholesterol …precursor of steroid hormones
CL secretes progesterone -dominant hormone and second Half of cycle
progesterone
inhibits FSH and LH so stopping further follicle development and ovulation in current cycle
prepares uterus for pregnancy
luteal phase
progesterone dominates and keeps LH and FSH down
negative feedback dominates
the corpus luteum : if fertilisation does not occur
CL degenerates progesterone falls uterus loses its endocrine support menstruation FSH and LH get to work again on the follicles
the corpus luteum if fertilisation does occur
CL maintained by hCG from the chorion
becomes the CL of pregnancy
maintains uterine lining until placenta takes over as main producer of progesterone at 3 months
oestrogen prepares the way …
uterine phase
promotes growth of endometrium and myometrium
promotes formation of progesterone receptors
progesterone acts on the oestrogen primed endometrium
uterine phase
loosens and softens connective tissue-makes implantation easier
promotes secretion of nutrients
quietens uterine activity
dysmenorrhea
painful periods
menorrhagia
heavy or prolonged periods
oligomenorrhoea
light periods
mechanism of action of the combined pill
low dose of oestrogen - decreased FSH from anterior pituitary -decreased development of follicle -no ovulation progestogen -makes cervical mucus sperm-unfriendly -decreased LH from anterior pituitary -decreased GnRH from hypothalamus -decreased motility of Fallopian tube
progestogen-only pill
low dose progestogen taken continuously
makes cervical mucus inhospitable to sperm
hinders implantation
-through its effect on endometrium and on the motility and secretion of the Fallopian tubes
menstruation-ceases initially but returns after prolonged use
main adverse effects-breakthrough bleeding and irregular masses
