Embryology 1 - Gametogenesis

Question 1

a working definition of ‘sex’

Answer 1

blending genetic characteristics of two individuals of the n^th generation to create the (n+1)^th generation

Question 2

disadvantages of sex

Answer 2

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 - the red queen syndrome
each individual has a new mix of genes that determine its environmental interactions

Question 4

female gametes

Answer 4

not many, large gametes - ova
provide nurture - yolk, placenta, milk

Question 5

male gametes

Answer 5

many small gametes - spermatozoa
provides nurture behaviourally or not at all

Question 6

general strategy of sexual reproduction

Answer 6

single gametes fuse to form a single cell which then divides many times

Question 7

germ line

Answer 7

produce gametes

Question 8

somatic cells

Answer 8

produce everything other than gametes

Question 9

what does myoid mean

Answer 9

muscle like

Question 10

spermatogonia

Answer 10

stem cells
some differentiate into spermatocytes which differentiate into sperm cells

Question 11

sertoli cells

Answer 11

provide metabolic support

Question 12

spermatogenesis

Answer 12

proliferation of germ line stem cells by mitosis
reduction to haploid state by meiosis
differentiation into mature spermatozoa

Question 13

mitotic proliferation

Answer 13

begins at puberty
produces about 10,000 sperm per second
typically about 10^8 sperm/ml of semen

Question 14

where does mitotic proliferation take place

Answer 14

in the basal side of the tubule - the side furthest from the lumen

Question 15

what does the hypothalamus secrete for mitotic proliferation

Answer 15

gonadotrophin releasing hormone - GnRH

Question 16

what does the anterior pituitary gland secrete for mitotic proliferation

Answer 16

follicle stimulating hormone (FSH) and luteinising hormone (LH)

Question 17

what does FSH act on

Answer 17

sertoli cells

Question 18

what does LH act on

Answer 18

leydig’s cells

Question 19

what does testosterone act on

Answer 19

sertoli cells

Question 20

what would an immune response against sperm result in

Answer 20

subfertility

Question 21

when does sperm production begin

Answer 21

at puberty

Question 22

what prevents sperm cells reaching immune system

Answer 22

immune cells on luminal side
continuous tight junctions

Question 23

orch-

Answer 23

prefix for testis
e.g. orchidectomy, cryporchidism
named after orchid

Question 24

maturation of sperm

Answer 24

sperm are shed and flow to epididymis (by moving passively along tubules) which alters seminal fluid
epididymal secretions (glycoproteins etc) activate sperm and make them capable of swimming

Question 25

features of the female reproductive system

Answer 25

uterus vagina oviduct = fallopian tube ovary cervix uteri

Question 26

when do females have germ line stem cells

Answer 26

as foetuses but not as children or adults

Question 27

rate of female gamete production

Answer 27

13 per year

Question 28

rate of male gamete production

Answer 28

150 billion per year

Question 29

what are primordial follicles

Answer 29

oocytes surrounded by less differentiated squamous granulosa cells and are derived from oocyte nests

Question 30

what are primary follicles

Answer 30

oocytes surrounded by a single layer of cuboidal granulosa cells that have initiated follicle development

Question 31

what type of cells are granulosa cells

Answer 31

somatic cells

Question 32

when does the pituitary gland start producing FSH

Answer 32

puberty

Question 33

what is stimulated by FSH

Answer 33

some follicles resume development a surge each month promotes development in around 50 or more follicles

Question 34

what happens during the primary follicle phase

Answer 34

oocyte grows and synthesises rRNA and mRNA. does not progress further through meiosis

Question 35

what is a ripening follicle

Answer 35

results in an increase in oestrogen levels, as oestrogen is secreted by follicular cells

Question 36

what happens during the ripening follicle phase

Answer 36

oocyte synthesises a glycoprotein zona pellucida, and granulosa cells multiply

Question 37

what are granulosa cells linked by

Answer 37

cytoplasmic bridges

Question 38

what do granulosa cells secrete

Answer 38

follicular fluid - forms fluid-filled 'antrum'

Question 39

what does the developing follicle depend on

Answer 39

receiving a surge of LH from pituitary gland thecal cells bind LH. cells dies without LH surge

Question 40

what does the LH surge stimulate

Answer 40

further maturation of the follicle to become a Graafian follicle at the surface of the ovary

Question 41

what kind of process is follicle death

Answer 41

an active process - will destroy itself

Question 42

what does atretic mean

Answer 42

dying follicle from 'atresia' - withering

Question 43

process of preovulatory growth following LH surge

Answer 43

primary oocyte > completion of meiosis 1 > secondary oocyte > arrest in meiosis 2 > connection with granulosa lost takes about 12 hours

Question 44

what happens once oocyte is mature

Answer 44

digests way out of edge of ovary and enters fallopian tube

Question 45

when is meiosis 2 complete

Answer 45

never unless fertilisation occurs

Question 46

what do the remains of the ruptured follicle become

Answer 46

the corpus luteum - looks yellow

Question 47

what does the corpus luteum do

Answer 47

produces hormones - progesterone, oestrogen - that prepare the lining of the uterus to receive an embryo unless woman is pregnant, the CL dies after around a week

Question 48

what is the early antral stage

Answer 48

a 'make or break' time for each follicle survival depends on adequate stimulation by FSH

Question 49

what happens if the antral follicle does not receive enough FSH

Answer 49

the follicle matures further to become a Graafian follicle at the surface of the ovary becomes more sensitive to FSH, makes a signal back to pituitary gland with oestrogen to reduce FSH levels

Question 50

what do falling FSH levels prevent

Answer 50

recruitment of further follicles in that cycle - dominant follicle has increased sensitivity so still has enough FSH stimulation even with lower serum levels

Question 51

how many follicles usually mature

Answer 51

one

Question 52

what do oestrogen detection blocking drugs do

Answer 52

drive higher and longer duration production of endogenous FSH, and more follicles mature

Question 53

what does FSH ultimately do

Answer 53

prevents atresia at critical stage

Question 54

what does LH ultimately do

Answer 54

drives ovulation and maintains corpus luteum