Gametogenesis - Oogenesis and Spermatogenesis

Question 1

where do the oocytes and sperm come from?

Answer 1

derived from a group of specialised cells called primordial germ cells

Question 2

when can the cells begin to be identified in the embryo?

Answer 2

4 to 6 weeks of gestation so after gastrulation has occurred and its these primordial germ cells that are going tp migrate through the embryo to find their new homes in the developing gonads to create oocytes and sperm

Question 3

what are primordial germ cells?

Answer 3

-undergo lots of mitotic division within the gonads to populate testes and ovary with cells required to make gametes
-the cells are diploid
-they enter into meiosis to generate haploid gametes capable of fertilisation

Question 4

when are the gonads present in the embryo?

Answer 4

around week 7 of development

Question 5

what are the starting cells known as for oogenesis?

Answer 5

oogonia

Question 6

where are oogonia produced?

Answer 6

by PGC’s dividing by mitosis, they begin meiosis but only get to the point of prophase 1

Question 7

what happens when oogonia start meiosis?

Answer 7

they enter into the first meiotic prophase and then become arrested. meiosis halts at this stage and they lie dormant.
-they only get to the point of prophase 1 and then become arrested and remain in the developing ovary

Question 8

what causes the arrest of oocytes in the first meiotic prophase?

Answer 8

-lack of right type of cell cycle proteins at early stages
-cyclic AMP and cyclic GMP have an important role

Question 9

how long are primary oocytes arrested for?

Answer 9

until puberty but can be arrested for up to 50 years

Question 10

what makes up the primordial follicle?

Answer 10

supporting cells (follicular cells)
primary oocyte

Question 11

what are follicular cells?

Answer 11

epithelial cells that surround the developing follicle

Question 12

when should the primary follicle stage be reached?

Answer 12

about 5 months of fetal development
7 million primary follicles present

Question 13

how many primordial follicles resume development each month after puberty?

Answer 13

between 5 and 12

Question 14

what is follicular atresia?

Answer 14

degeneration of these follicular cells

Question 15

when is it called a secondary oocyte?

Answer 15

when it completes meiosis 1

Question 15

what happens to the follicular cells in response to hormone stimulation?

Answer 15

they thicken up and divide, help support developing oocyte

Question 16

when is the oocyte arrested for the second time?

Answer 16

metaphase 2

Question 17

as only 1/4 daughter cells will develop into a mature oocyte, what are the other cells known as?

Answer 17

polar bodies

Question 18

what are polar bodies?

Answer 18

much smaller
really only contain nuclear material
oocyte keeps most of it

Question 19

when does meiosis 2 occur?

Answer 19

if it is fertilised

Question 20

what happens during the second mitotic division of an oocyte?

Answer 20

will give rise to fertilised egg and another polar body which will degenerate

Question 21

which types of cells are thought to be partially responsible for some cases of teratoma?

Answer 21

primordial germ cells (PGC’s)

Question 22

which area of a testes does spermatogenesis take place?

Answer 22

seminiferous epithelium

Question 23

what are spermatogonia?

Answer 23

the stem cell population of the tesis
immature cells that don’t do much until puberty
divide to populate testis

Question 24

what is the dominant hormone in the testes at puberty?

Answer 24

testosterone

Question 25

what does testosterone have a major influence on?

Answer 25

seminiferous epithelial epithelium

Question 26

what do the spermatogonia divide into?

Answer 26

type A and type B

Question 27

what do type B spermatogonia produce?

Answer 27

produce the sperm

Question 28

what are type A spermatogonia?

Answer 28

identical spermatogonia
keep the starting material going by mitotic division

Question 29

what does mitotic division of type B spermatocyte produce?

Answer 29

a primary spermatocyte
round cell again that is haploid

Question 30

what type of spermatogonia enters meiosis?

Answer 30

primary spermatocyte

Question 31

what happens during meiosis 1 in sperm?

Answer 31

primary spermatocyte turn into secondary spermatocyte that are diploid sperm

Question 32

what happens during meiosis 2 in sperm?

Answer 32

secondary spermatocytes form 4 identical spermatids
spermatids are haploid and go on to form cells

Question 33

what are the supporting cells of spermatogenesis?

Answer 33

Sertoli cells
leydig cells
pertibular cells

Question 34

what is spermiogenesis?

Answer 34

differentiation to the final form
change to the structure

Question 34

what are the stages of spermiogenesis?

Answer 34

formation of acrosome
condense nucelar material into the head of the sperm
flagellum formation

Question 35

what is an acrosome?

Answer 35

a little hat or cap that forms over the top of the nucleus contains enzyme that helps the sperm penetrate the oocyte at fertilisation

Question 36

what is the function of the mid piece of sperm?

Answer 36

mainly contain mitochondria to help power the movement of sperm through the reproductive tract

Question 37

what cells phagocytose the cytoplasm that is removed from the sperm?

Answer 37

sartori cells

Question 38

how many mature oocytes are produced in life?

Answer 38

around 400

Question 39

in which stage of meiosis arrested in the primary oocyte?

Answer 39

prophase 1

Question 40

how many polar bodies are formed in oogenesis?

Answer 40

three