Reproductive Physiology Flashcards
oogenesis
the production, growth, and maturation of an egg, or ovum
how does oogenesis begin?
in the fetal ovaries, stem cells called oogonia produce primary oocytes
primary oocytes
diploid cells resulting from mitosis & differentiation of oogonia during fetal development
what phase of meiosis are primary oocytes in?
prophase of meiosis I; they are unchanged from the way they were produced in the fetus
- a number of primary oocytes restart meiosis early in the menstrual cycle and become secondary oocytes
secondary oocytes
after completing meiosis I, these are produced along with a polar body and one will be released into the fallopian tube
when does meiosis II end?
at exactly the time the sperm contacts the egg for fertilization
ovarian cycle
cyclic changes that occur in the ovaries for the development of eggs
what are the phases of the ovarian cycle?
follicular and luteal phase
follicular phase
where the egg and surrounding cells (follicle) develop up to the point of ovulation
luteal phas
where leftover bits of follicle remain and secrete hormones (progesterone) to prepare the lining of the uterus (endometrium) for a fertilized egg
granulosa cells
the majority of the cells surrounding an oocyte in a follicle; develop alongside oocyte and become more cuboidal, will start secreting estrogen, will develop secondary follicle around the follicle + has fluid-filled chambers (antrum)
when is oocyte development stalled?
halfway through meiosis II
corpus luteum
leftover support cells secreting copious amounts of estrogen and progesterone, yellow due to cholesterol
corona radiata
the layer of granulosa cells that surround an oocyte after is has been ovulated
how does a primordial follicle become a primary follicle?
under the influence of LH and FSH, formation of cuboidal granulosa cells from flat cells and zona pellucida
zona pellucida
proteinaceous cells that forms around the ovum, barrier sperm need to make through
how do primary follicles transition to secondary follicles?
when granulosa cells secrete follicular fluid and form an antrum
how do secondary follicles transition to mature follicles?
when the antrum becomes one continuous fluid-filled space allowing for separation from oocyte from support cells
homeostasis in the ovary
- negative feedback
1. low blood estrogen lvls feed back to hypothal. to release GnRH, which talks to ant. pit. to tell it to release LH and FSH
2. LH stimulates estrogen production which inhibits release of GnRH
3. granulosa cells can make copious amounts of estrogen which can stim. GnRH (+ve feedback in midst of -ve feedback)
4. LH surges causing follicle rupture and egg release
luteinizing hormone (LH)
secreted by the pituitary gland to promote production of hormones from the gonad
follicle stimulating hormone (FSH)
secreted by the pituitary gland to stimulate maturation of gametes
stratum basalis of endometrium
permanent layer - builds the functional layer after each menstruation
stratum functionalis of the endometrium
layer of uterus that sheds during menstruation
myometrium
muscle layer of the uterus
endometrium
inner lining of the uterus
what is the purpose of the menstrual cycle?
to prepare the lining of the uterus for a fertilized egg to implant
how long is the menstrual cycle?
from 21-40 days, usually about 28 days on average
development of stratum functionalis
due to the proliferation of the endometrial stroma and elongation + growth of endometrial glands which provide nutrition for a zygote
phases of menstrual cycle
menstrual, proliferative, secretory
menstrual phase
stratum functionalis sloughs off due to lack of estrogen and progesterone; days 1-4
proliferative phase
stratum functionalis starts to grow, arteries starting to develop, endometrial glands begin to show up; driven by estrogen prod. by developing follicles before ovulation
secretory phase
progesterone talks to endometrial glands to start secreting zygote food, progesterone necessary in conjunction w/ estrogen to keep stratum functionalis alive
- if no implantation, reduced estrogen and progesterone levels and regression of stratum functionalis
linkage of ovarian and menstrual cycle
- hormones of ovarian cycle drive menstrual cycle
- estrogen secretion by follicles drive progression of endometrial lining
corpus hemorrhagicum
as folllicle ovulates, some blood vessels will burst, resulting in some blood loss from surface of the ovary
- it secretes the estrogen and progesterone to maintain uterine lining during secretory phase
- talks to endometrial glands to start making zygote food and maintain structural integrity of epithelium blood vessels
corpus luteum and implanation
- can only last 2 weeks if no implantation
- undergoes apoptosis and regression, left w/ scar on ovary where support cells used to be (corpus albicans)
- causes reduction in hormones and regression of stratum functionalis
corpus albicans
degenerated corpus luteum w/ scar tissue
maintaining the endometrium
- pregnancy stops degeneration of corpus luteum; implanting egg and placenta will release hCG
- it acts like LH and stimulates corpus luteum to prod. lots of progesterone and little estrogen
- progesterone inhibits uterine contractions and disintegration of stratum functionalis that precedes menstrual flow
human chorionic gonadotropin (hCG)
hormone produced by the placenta to sustain pregnancy by stimulating the ovaries to produce estrogen and progesterone
fertilization window
day before to two days after ovulation
when is it too late for implantation?
about last 10 days of menstrual cycle in secretory phase; by the time fertilized egg arrives at endometrium and causes hCG secretion, the endometrium will already be entering the menstrual phase
parts of the sperm cell
head, midpiece and tail
acrosome
contains vesicles of digestive enzymes for penetrating the zona pellucida
nucleus of sperm
has the haploid number of chromosomes
midpiece of sperm
contains mitochondria supplying energy for the flagellum
flagellum of sperm
provides motive power for sperm to swim
spermatogenesis
the production of sperm cells; stem cells (spermatogonia) constantly divide + undergo meiosis to give mature sperm, continues throughout lifetime
sperm count threshold for fertility
20 million sperm/mL of semen
what is semen mostly made of?
fluids secreted by the prostate, seminal vesicles and bulbourethral glands
seminal vesicles
two small glands that secrete a fluid rich in glucose and clotting proteins that nourishes and helps sperm move; alkaline to neutralize vaginal pH
prostaglandins
modified fatty acids that stimulate the sperm to swim and uterus to contract
prostatic secretions
thin acidic/neutral fluid which provides medium for sperm to swim, citric acid, and protein digesting enzymes
bulbourethral glands
release alkaline fluid into urethra to neutralize acidic urine and some mucus to decrease sperm damage during ejaculation
similarities between both processes of gamete manufacture
- reliance on pituitary gonadotropins (FSH, LH)
- hormones produced by ovary or testes feedback on the pituitary to decrease gonadotropin production
hypothalamic-pituitary-gonadal (HPG) axis
the hypothalmus detects low levels of sex steroids to cause release of GnRH, which communicates to ant. pit. to release gonadotropins
- sex steroids provide -ve feedback on hypothal.
- cycles up and down throughout the day
fertilization
male: sperm need to get past cervix, up uterus and into Fallopian tube
female: egg has to be in uterine tube, cervical mucus cannot be too thick, endometrium must be ready for implantation of blastocyst
