reproduction

Question 1

sex determination males

Answer 1

SRY gene, located on the Y chromosome, codes for TDF (testis determining factor), causes the development of the testes.

Question 2

examples of sterioid hormones

Answer 2

testosterone, estrogen and progesterone

Question 3

testosterone

Answer 3

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

Question 4

estrogen

Answer 4

causes pre-natal development of the female reproductive system, during puberty, it causes the development of female secondary sexual characteristics,

Question 5

progesterone

Answer 5

prepares the uterus during the menstrual cycle for the implantation of an embryo and supports pregnancy

Question 6

scrotum

Answer 6

holds the testis outside the body

Question 7

edididymis

Answer 7

stores sperm until ejaculation

Question 8

prostate gland

Answer 8

secretes an alkaline fluid that is added to sperm at the start of ejaculation and helps the sperm swim

Question 9

seminal vesicle

Answer 9

secretes an alkaline fluid at the end of ejaculation containing proteins that make the semen sticky

Question 10

negative feedback

Answer 10

stabilizing effect. a rise in levels causes a decrease in production

Question 11

positive feedback

Answer 11

a rise causes further rises; a fall causes further falls

Question 12

FSH

Answer 12

stimulates the growth of eggs, stimulates the secretion of estrogen by the follicle wall

Question 13

LH

Answer 13

triggers the relase of an egg from the ovary. triggers the production of estrogen and progesterone

Question 14

menstruation

Answer 14

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)

Question 15

follicular phase

Answer 15

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)

Question 16

luteal phase

Answer 16

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

Question 17

ovulation

Answer 17

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

Question 18

down regulation

Answer 18

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

Question 19

superovulation

Answer 19

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.

Question 20

egg retrival and fertilization

Answer 20

3rd stage of in vitro. when follicle are the right size, the eggs are retrived and mixed with sperm

Question 21

establishing a pregnancy

Answer 21

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.

Question 22

stages of gametogenesis

Answer 22

mitosis to generate a large number of cells, cell growth to have enough resources to undergo meiosis, meiosis to produce haploid cells, differentiation

Question 23

spermatogenesis

Answer 23

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

Question 24

structure of sperm

Answer 24

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

Question 25

stages of oogenesis 1

Answer 25

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.

Question 26

stages of oogenesis 2

Answer 26

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.

Question 27

zona pellucida

Answer 27

protects the egg cell and restricts sperm entry

Question 28

cortical granules

Answer 28

hardens the zona pellucida to prevent polyspermy

Question 29

comapring spermatogenesis and oogenesis

Answer 29

millions of sperm are produced daily, while only one egg is produced and released once a month. egg cells have a larger cytoplasm

Question 30

stages in the fertilization of a human egg

Answer 30

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

Question 31

implantation

Answer 31

7 days after implanation, the embryo implants itself into the endometrium

Question 32

hormonal control of childbirth

Answer 32

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

Question 33

function of the placenta

Answer 33

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

Question 34

inter-villous spaces

Answer 34

maternal blood flows through here, brought by uterine arteries and carries away by uterine veins

Question 35

myometrium

Answer 35

muscular wall of the uterus used during childbirth

Question 36

exchange of materials across the placenta (to fetus)

Answer 36

oxygen, glucose, lipids, water, minerals, vitamins, antibodies, hormones

Question 37

exchange of materials across the placenta (to mother)

Answer 37

co2, urea, hormones, water