Embryology

Question 1

what is the definition of sex?

Answer 1

sex is the blending of characteristics of two individuals of the nth generation to create the n+1th generation

Question 2

what are the disadvantages of sex?

Answer 2

you need to find a partner
dilution of a “perfect” set of genes

Question 3

advantages of sex

Answer 3

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

Question 4

what are the two sets of cells?

Answer 4

somatic (cells in the rest of the body
germ line (gametes)

Question 5

what type of epithelium is found in seminiferous tubules?

Answer 5

multi-nucleated

Question 6

where are the most mature sperm cells found?

Answer 6

nearest the middle of the tube

Question 7

what is spermatogenesis?

Answer 7

spermatogonia (stem cells) differentiate into spermatocytes which undergo meiosis and become spermatozoa and go on to become sperm cells

Question 8

what stimulates spermatogenesis?

Answer 8

follicle-stimulating hormone (FSH) directly stimulates
luteinising hormone (LH) stimulates the production of testosterone which stimulates spermatogenesis

Question 9

when does mitotic proliferation begin?

Answer 9

at puberty

Question 10

where does mitotic proliferation take place?

Answer 10

basal side of the tubule (furthest side from the lumen?

Question 11

what is the acrosome and what does it store?

Answer 11

head of the sperm cells
contains information for fertilisation

Question 12

what do sertoli cells do?

Answer 12

sperm cells live in the sertoli cells and are protected from the immune system

Question 13

what happens when sperm cells mature?

Answer 13

sperm are shed and flow to the epididymis via gentle peristalsis
secretions from the epididymis activate the sperm and make them capable of swimming

Question 14

do adult women have germ line stem cells?

Answer 14

no, only men do

Question 15

when are oocytes (egg cells) produced?

Answer 15

during foetal life, they then enter into meiosis

Question 16

how many oocytes complete meiosis?

Answer 16

one egg per month completes meiosis from around the ages of 12-50

Question 17

what is the primordial follicle?

Answer 17

the primordial follicle is an oocyte arrested in meiosis 1 which is surrounded by granulosa cells (they look after the follicle)

Question 18

what happens to the primordial follicle at puberty?

Answer 18

when FSH is produced the primordial follicles become primary follicles, only 50 per month resume development

Question 19

what happens when the primary follicle develops?

Answer 19

the oocyte grows and synthesises rRNA and mRNA

Question 20

what does the primary follicle develop into?

Answer 20

it becomes a ripening follicle, the oocyte synthesises a glycoprotein zona pellucida (surrounds the oocyte) and granulosa cells multiply

Question 21

what do granulosa cells secrete?

Answer 21

follicular fluid, which forms the fluid-filled antrum (surrounds the oocyte and zona pelludica)

Question 22

what happens after the formation of the antrum?

Answer 22

theca gains LH receptors
granulosa cells gain FSH receptors
together they activate hormone secretion from the cell

Question 23

what happens if there is not adequate stimulation by FSH?

Answer 23

the follicle will die

Question 24

what happens if the follicle does receive enough stimulation from FSH?

Answer 24

the antral follicle matures further to become a graafian follicle at the surface of the ovary

Question 25

what happens once a graafian follicle develops?

Answer 25

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

Question 26

how do fertility drugs work?

Answer 26

block oestrogen detection which drives a higher and longer period of production of FSH and more follicles mature

Question 27

what drives ovulation?

Answer 27

surge in LH levels

Question 28

what occurs following a surge in LH?

Answer 28

completion of meiosis 1, arrest in meiosis 2 and connection with granulosa cells is lost only takes around 12 hours

Question 29

how does the mature oocyte leave the ovary?

Answer 29

it digests its way out of the edge of the ovary, and enters into the fallopian tube

Question 30

when does meiosis 2 complete?

Answer 30

it never completes unless fertilisation occurs

Question 31

what does the remains of the follicle become?

Answer 31

corpus luteum

Question 32

what us the function of the corpus luteum?

Answer 32

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

Question 33

what maintains the corpus luteum?

Answer 33

LH

Question 34

what are the phases?

Answer 34

menstrual - days 1-5 proliferative - days 5-14 secretory - days 14-27 ischemic - days 27-28