Oogenesis

Question 1

Oogenesis means differentiation of the ______ that are present in the _____ of the ____ into mature ova.

Answer 1

primordial germ cells (oogonia); cortex of the ovary

Question 2

Two stages of maturation in oogenesis are:

Answer 2

Prenatal and Postnatal maturation.

Question 3

During prenatal maturation, primordial germ cells (oogonia) undergo _____

Answer 3

Mitotic divisions.

Question 4

In prenatal maturation, PGCs (oogonia) arranged in clusters are surrounded by a layer of ______ called _____ which are derived from ______

Answer 4

A layer of flat epithelial cells called follicular cells, derived from the epithelium covering the ovary.

Question 5

At what stage of meiosis are primary oocytes arrested from near birth until puberty?

Answer 5

Prophase of the first meiotic division (prophase I).

Question 6

What is the range of the number of primary oocytes present at birth?

Answer 6

700,000 to 2 million.

Question 7

How many primary oocytes typically remain at puberty?

Answer 7

About 400,000.

Question 8

Approximately how many oocytes will be ovulated during a female’s lifetime?

Answer 8

About 400.

Question 9

With the onset of puberty, how many primordial follicles begin to mature each ovarian cycle and what happens to primary oocytes?

Answer 9

5-15 primordial follicles; primary oocytes begin to increase in size

Question 10

Describe the change in follicular cells as a primordial follicle matures. Follicular cells first change from ____ to ___, then form ____ around _____

Answer 10

Follicular cells change from flattened to cuboidal, then form a stratified layer of granulosa cells around the oocyte.

Question 11

Primordial follicle after differentiating becomes ____

Answer 11

Primary follicle

Question 12

____ form the theca folliculi

Answer 12

Stromal cells of the ovary

Question 13

What separates granulosa cells from the stromal cells in a primary follicle?

Answer 13

A basement membrane.

Question 14

What secrete zona pellucida in a primary follicle?

Answer 14

Granulosa cells and the oocyte

Question 15

**What key feature distinguishes the secondary follicle from the primary follicle?

Answer 15

Fluid-filled spaces appear between granulosa cells, which coalesce to form the follicular antrum.

Question 16

Fluid-filled spaces appear between granulosa cells in ___ follicle

Answer 16

Antral follicle or tertiary follicle.

Question 17

What is the mature follicle called?

Answer 17

Graafian follicle.

Question 18

How many chromosomes does the primary oocyte have?

Answer 18

46, XX chromosomes.

Question 19

What is the chromosomal composition of the secondary oocyte?

Answer 19

23 chromosomes, X.

Question 20

Daughter cells after first meiotic division are ___ (equal/unequal).

Answer 20

Unequal

Question 21

____ and ____ enter second meiotic division without _____

Answer 21

Secondary oocyte and first polar body; without DNA replication

Question 22

Secondary oocyte produced in first meiotic division and released during ovulation is arrested in ____ until ___ occurs

Answer 22

Metaphase of meiosis II; fertilization

Question 23

What condition is necessary for completion of second meiotic division?

Answer 23

Fertilization

Question 24

What are the products of second meiotic division in oogenesis?

Answer 24

Fertilized oocyte and Second polar body

Question 25

*In the Graafian follicle, what structure surrounds the oocyte?

Answer 25

The cumulus oophorus.

Question 26

What hormone surge triggers completion of meiosis I in the Graafian follicle?

Answer 26

LH (Luteinizing Hormone) surge.

Question 27

*What happens during ovulation?

Answer 27

The secondary oocyte arrested at metaphase II is released from the Graafian follicle into the fallopian tube.

Question 28

*What hormones does the corpus luteum produce?

Answer 28

Progesterone and estrogen.

Question 29

*What happens to the corpus luteum if fertilization does not occur?

Answer 29

It degenerates into the corpus albicans.

Question 30

How many mature oocytes result from the maturation of a single primary oocyte?

Answer 30

One mature oocyte.

Question 31

____ is conserved during oogenesis to form one large mature oocyte or ovum.

Answer 31

Cytoplasm

Question 32

*Why are polar bodies small and nonfunctional?

Answer 32

The cytoplasm is conserved to form one large mature oocyte, polar bodies receive minimal cytoplasm and degenerate.

Question 33

What are the two membranes of the mature ovum?

Answer 33

The inner thin vitelline membrane and the outer zona pellucida.

Question 34

Two or three layers of cells surrounding the zona pellucida externally when the ovum is shed from the follicle is _____

Answer 34

Corona radiata

Question 35

Compare size: sperm vs oocyte (ovum).

Answer 35

Sperm ~50 μm; Oocyte 117-142 μm.

Question 36

Compare mobility: sperm vs oocyte.

Answer 36

Sperm is highly motile; oocyte is immotile.

Question 37

The outer membranes covering mature oocyte (ovum) are:

Answer 37

Zona pellucida and corona radiata

Question 38

Compare cytoplasm: sperm vs oocyte.

Answer 38

Sperm contains little cytoplasm; ovum contains abundant cytoplasm

Question 39

The oocyte and sperm contain how many type of chromosome?

Answer 39

2 in sperm: 23,X or 23,Y. 1 in oocyte: only 23,X

Question 40

In what phase do the oogonia become arrested until puberty?

Answer 40

Meiosis I prophase.

Question 41

Which hormone spike restarts meiosis for the oogonia?

Answer 41

LH (Luteinizing Hormone).

Question 42

After the primary follicle takes in fluid and forms a large antrum, it is called what?

Answer 42

Antral follicle.

Question 43

The first meiotic division completes just before ovulation, forming a secondary oocyte. The second meiotic division begins immediately but finishes only if what occurs?

Answer 43

Fertilization takes place.

Question 44

What is the main function of the corpus luteum after ovulation?

Answer 44

To produce progesterone and estrogen to maintain the uterine lining.

Question 45

Follicular cells are derived from ____

Answer 45

Epithelium covering the ovary