Gametogenesis, fertilization and the blastocyst

Question 1

Once eggs are released from ovary, where do they go through and what do they go to

Answer 1

Go through fimbrae to fallopian tube

Question 2

What are the parts of the Fallopian tube starting from the fimbrae

Answer 2

1) infundibulum
2) Ampulla
3) Isthmus
4) interstitial

Question 3

Where does fertilization happen

Answer 3

Ampulla

Question 4

What is the first entity that is present in female gametogenesis

Answer 4

Primary follicle

Question 5

What is the primary follicle

Answer 5

Primary oocyte is surrounded by a single layer of follicular cells

Question 6

What do primary follicles begin to develop into

-when does this happen

Answer 6

5-12 primary follicles develop and become growing follicles

-happens at the beginning of each monthly cycle

Question 7

What happens to the primary follicles after they become growing follicles

Answer 7

Follicular cells multiply and become several layered

-Also become separated from the ovum by a layer called the Septum Pellucidum

Question 8

What is the septum pellucidum

Answer 8

Layer that separates follicular cells from the ovum

Question 9

What do all but one of the growing follicles degenerate to become

Answer 9

Corpus atreticum/scar

Question 10

After all but one of the growing follicles becomes a corpus attreticum, what happens

Answer 10

The follicular cells of the remaining growing follicle secrete a fluid which produces a fluid-filled Antrum within the follicle

Question 11

What is the thecal layer of the growing follicle made from?

Answer 11

Made from the ovarian non-gamete cells surrounding the follicle

Question 12

What is the thecal layer divided into

Answer 12

• Vascular theca interna

- Avascular inactive theca externa

Question 13

What does the theca interna do

Answer 13

Produce oestrogen

Question 14

What is the mature follicle callled

Answer 14

Graafian follicle

Question 15

In the graafian follicle (mature follicle), what do the majority of the follicular cells form

Answer 15

Stratum granulosum

Question 16

What does the stratum granulosum produce

Answer 16

Progesterone

Question 17

What do the remaining of the follicular cells do

Answer 17

Remainder surround oocyte as the cumulus oophorus

Question 18

What is a secondary oocyte

Answer 18

• majority of the follicular cells have now formed the stratum granulosum
• The remainder of the follicular cells surround the oocyte as the cumulus oophorus

Question 19

What is formed after a graafian follicle

Answer 19

Secondary oocyte

Question 20

What happens after a secondary oocyte is produced

Answer 20

Mature follicle ruptures and releases an ovum

Question 21

What does the released ovum still have

Answer 21

Retains a covering of follicular cells which form the corona radiata

Question 22

What happens to the septum pellucidum after ovum is released

Answer 22

Septum pellucidum expands to become the zone pellucida

Question 23

What forms the corpus luteum

Answer 23

Cells of the theca interna and the stratum granulosum enlarge and become yellowish to form the corpus luteum

Question 24

What does the corpus luteum do?

-what did it do before ovulation

Answer 24

Secretes a large amount of progesterone

-THe follicle produced mainly oestrogen

Question 25

What is the life span of the corpus luteum is fertilization does not occur

Answer 25

12 days

Question 26

What degenerates if fertilization does not occur

Answer 26

Corpus luteum degenerates into the corpus albicans | - the cessation of its hormonal output leads to menstruation

Question 27

What happens if fertilization does occur

Answer 27

The corpus luteum is sustained by the HCG produced bu the conceptus and form a large corpus luteum of pregnancy

Question 28

What does a corpus luteum of pregnancy eventually form

Answer 28

Corpus albican

Question 29

In a sperm, what does the head consist of

Answer 29

Largely of a nucleus with a sparse cytoplasmic covering

Question 30

What is the acrosomal cap derived from

Answer 30

Golgi

Question 31

What does the acrosomal cap do

Answer 31

contain enzymes which help in the penetration of the ovum

Question 32

Main difference between spermatogenesis and oogenesis

Answer 32

spermatogenesis has mitosis followed by meiosis | -oogenesis has meiosis in ovaries and no mitosis

Question 33

What is the cytoplasmic:nuclear ratio in spermatogenesis vs in oogenesis

Answer 33

Spermatogenesis Low cytoplasmic:nuclear ratio Oogenesis High cytoplasmic:nuclear ratio

Question 34

How is the abdominal cavity different in males and females

Answer 34

Abdominal cavity is closed in males but it communicates with the exterior in females (vagina->Fallopian tube->abdominal cavity)

Question 35

After being in the cervix, where does the sperm go and what happens to it

Answer 35

sperm reaches the isthmus and becomes less motile

Question 36

What makes the sperm motile again? Where are these released from

Answer 36

Chemoattractants released from cumulus cells

Question 37

What does sperm require in the female reproductive tract

Answer 37

Requires capacitation | -during which acrosomal region loses glycoprotein coat

Question 38

What is fertilization 1

Answer 38

Shed secondary oocyte halted part way through 2nd meiotic division

Question 39

What is fertilization 2

Answer 39

Mature ovum- penetration by spermatozoon prompts completion of 2nd meiotic division

Question 40

What do acrosomal enzymes do

Answer 40

Help disperse corona radiata and aid penetration of zone pellucida. Plasma membranes of gametes fuse and male nucleus is 'injected'

Question 41

What is fertilization 3

Answer 41

Fertilized ovum is diploid again and the permeability of the zone pellucida is altered to prevent further penetration

Question 42

What is done to stop more sperm entering fertilized ovum?

Answer 42

Zona reaction- permeability of zone pellucida is altered to prevent further penetration

Question 43

Where are enzymes released from to digest sperm receptor proteins on ovum so they can no longer bind sperm

Answer 43

Enzymes released by cortical granules

Question 44

What is the circumvitelline space

Answer 44

Ovum has shrunk and there is a 'gap' between the zona pellucida and the ovum

Question 45

How are blastomeres formed

Answer 45

Mitosis

Question 46

What happens when there is further cleavage | -what is DNA and protein synthesis like

Answer 46

Cells continue to cleave to form progressively smaller blastomeres. There is DNA synthesis but virtually no protein made

Question 47

What is a morula

Answer 47

New solid balls of cells. Cytoplasmic:nuclear ration is now normal

Question 48

What is the zone pellucida like in a morula and why

Answer 48

Still persists to stop implantation

Question 49

What do morula cells undergo | -What happens to the zone pellucida

Answer 49

COmpaction- establishment of tight junctions between surface cells -the zone pellucida starts to split

Question 50

When does the blastocyst form

Answer 50

5 days after fertilization

Question 51

What does a blastocyst look like

Answer 51

Has an inner cell mass and a trophoblast

Question 52

When are 2 daughter cells (blastomeres) formed by mitosis

Answer 52

30h post fertilisation