reproduction Flashcards
sex determination males
SRY gene, located on the Y chromosome, codes for TDF (testis determining factor), causes the development of the testes.
examples of sterioid hormones
testosterone, estrogen and progesterone
testosterone
produced by the developing testes in the fetus, causing pre-natal development of male genitelia. during puberty, testosterone stimulates teh development of secondary sexual characteristics and sperm production
estrogen
causes pre-natal development of the female reproductive system, during puberty, it causes the development of female secondary sexual characteristics,
progesterone
prepares the uterus during the menstrual cycle for the implantation of an embryo and supports pregnancy
scrotum
holds the testis outside the body
edididymis
stores sperm until ejaculation
prostate gland
secretes an alkaline fluid that is added to sperm at the start of ejaculation and helps the sperm swim
seminal vesicle
secretes an alkaline fluid at the end of ejaculation containing proteins that make the semen sticky
negative feedback
stabilizing effect. a rise in levels causes a decrease in production
positive feedback
a rise causes further rises; a fall causes further falls
FSH
stimulates the growth of eggs, stimulates the secretion of estrogen by the follicle wall
LH
triggers the relase of an egg from the ovary. triggers the production of estrogen and progesterone
menstruation
1-5. FSH rises at a peak and stimulates the development of folliceles and the secretion of estrogen. estrogen causes an increase in FSH receptors (positive)
follicular phase
1-14. after menstruation, estrogen stimulates the repair and thickening of the endometrium. at high levels, estrogen stimulates the secretion of LH and inhibits the secretion of FSH, leading to a fall in estogen (negative)
luteal phase
15-28. Progesterone rises and promotes the thickening and maintenace of the endometrium. high levels of prog and est inhibit FSH and LH secretion (negative). prog and est eventually fall if no embryo has been formed. FSH levels rise again starting the next menstrual cycle
ovulation
day 14. LH rises to a sudden peak, stimulating the completion of meiosis in the oocyte and partial digestion of the follicle wall allowing to burst open. LH also promotes the devlopment of the follicle after ovulation into the corpus luteum which secretes estrogen and progesterone
down regulation
first step of in vitro. using a drug to stop thesecretion of FSH and LH, and eventually the secretion of est and prog, thus suspending the menstrual cycle
superovulation
second stage of in vitro. intramuscular injections of FSH and LH (higher than usual) given daily for 10 days, stimulating the development of many follicles.
egg retrival and fertilization
3rd stage of in vitro. when follicle are the right size, the eggs are retrived and mixed with sperm
establishing a pregnancy
4th stage of in vitro. if fertilization is successful, embryos are inserted in the uterus after 48 hours. extra prog is given as a tablet placed in the vagina to ensure that the uterus lining is maintained.
stages of gametogenesis
mitosis to generate a large number of cells, cell growth to have enough resources to undergo meiosis, meiosis to produce haploid cells, differentiation
spermatogenesis
outer layer (germinal epithelium - 2n) divides endlessly by mitosis to produce diploid cells (2n). diploid cells grow and become primary spermatocytes (2n). each cell carries out the second meiosis ll to produce two spermatids (n). spermatids become associated with sertoli cells (nurse cells) that help the spermatids develop into spermatozaa (n) - cell differentiation. sperm detach from the sertoli cells and are eventually carried out of the testis by the fluid in the center of the seminiferous tubule
structure of sperm
acrosome containign enzymes that digest the stuff around the egg. haploid nucleus containing 23 chr, mid piece containing mitochondria, tail pushing forward the sperm to allow it to swim
stages of oogenesis 1
germinal epithelium cells divide by mitosis. diploid cells grow into large primary oocytes and starts the first division of meiosis but stop during prophase l. primary oocytes and the single layer of follicle cells around it form a primary follicle. during a mentsrual cycle, some primary follicles start to develop, countinuing the first cycle of meiosis. cytoplasm of the primary oocyte divides unequally, forming a large secondary oocyte and a small polar body.
stages of oogenesis 2
secondary oocyte starts the secondary division of meiosis but stops at prophase ll. when the mature follicle bursts druing ovulation. after fertilization, the secondary oocyte completes meiosis ll to form an ovum and a second polar cell. both polar bodies degenerate.
zona pellucida
protects the egg cell and restricts sperm entry
cortical granules
hardens the zona pellucida to prevent polyspermy
comapring spermatogenesis and oogenesis
millions of sperm are produced daily, while only one egg is produced and released once a month. egg cells have a larger cytoplasm
stages in the fertilization of a human egg
arrival of sperm, binding of the sperm to the zona pellucida and triggering acrosome reaction. contents of acrosome are released to digest teh route to reach the egg. fusion as the sperm enters the egg. enzymes from cortical granules harden the zona pellucida to prevent polyspermy. mitosis is carried out by both egg and sperm, using same centrioles and microtubules, producing a two cell embryo
implantation
7 days after implanation, the embryo implants itself into the endometrium
hormonal control of childbirth
progesterone levels preventing contractions and ensuring growing drops after 9 months. oxytocin is secreted and estrogen is relased causing an increase in oxytocin receptors. when oxytocin binds, muscles contract. uterine contractions stimulates the secretion of more oxytocin (positive). cervix becomes wider, amniotic sac bursts, and baby is pushed. contractions countinue untill the plecenta is pushed out
function of the placenta
after 8 weeks, the embryo is known as a fetus. the fetus develops a placenta and an umbilical cord. the placenta contains placental villi embedded in the uterus wall. in the placenta, the fetus blood flows close to the blood of the mother in the uterine wall, facilitating the exchange if materian between maternal and fetal blood
inter-villous spaces
maternal blood flows through here, brought by uterine arteries and carries away by uterine veins
myometrium
muscular wall of the uterus used during childbirth
exchange of materials across the placenta (to fetus)
oxygen, glucose, lipids, water, minerals, vitamins, antibodies, hormones
exchange of materials across the placenta (to mother)
co2, urea, hormones, water
