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Embryology > Ovary and oogenesis > Flashcards

Ovary and oogenesis Flashcards

1
Q

Female gamete is called ……….., and the process of it’s production is ……………..

A

The female gamete is called ova, and the process of its production is oogenesis

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2
Q

Gametes are derived from …………

A

PGCs, primordial germ cells

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3
Q

The PGCs are formed in the …………….

A

Epiblast

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4
Q

The PGCs are formed in the epiblast during ……………. week

A

Second week

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5
Q

Formed PGCs move to …………..

A

The wall of the yolk sac

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6
Q

During ……… week PGCs begin to migrate from yolk sac to the gonads and arrive at …………… week

A

During 4th week PGCs begin to migrate from yolk sac to the gonads and arrive at 5th week

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7
Q

Ova are derived from ………..

A

Oogonia

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8
Q

………… is the female gonad

A

The ovary

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9
Q

All the oogonia to be used throughout fertile life of a female are produced before her birth. True or false

A

True

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10
Q

The oogonia undergo mitotic divisions, by the end of the …………. month, are arranged in clusters at the ovarian cortex.

A

Third month

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11
Q

The many rounded large cells called oogonia are contained in the …………… part of the ovary

A

The cortex

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12
Q

The oogonia arranged in clusters at the ovarian cortex are surrounded by ………. epithelial cells

A

Squamous/flat

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13
Q

All the oogonia in one cluster are from a single follicular cell. True or false

A

True

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14
Q

The total number of oogonia in the ovary reaches its maximum by the …………. month

A

5th month

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15
Q

What is the maximum number of oogonia in the ovary?

A

7 million

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16
Q

All surviving primary oocytes enters prophase of meiosis I, and are individually surrounded by a layer of ………….

A

Follicular cells

17
Q

A primary oocyte, with its surrounding flat epithelial cells, is called a …………..

A

Primordial follicle

18
Q

What is the state of all primary oocytes just before birth?

A

Close to the time of birth, all primary oocytes have started prophase of meiosis I, but instead of proceeding into metaphase, they enter the diplotene stage.

19
Q

Primary oocytes remain in prophase and do not finish their 1st meiotic division before puberty is reached. True or false

A

True

20
Q

Why do primary oocytes remain in prophase and not finish their 1st meiotic division before puberty is reached?

A

Oocyte maturation inhibitor (OMI), secreted by follicular cells.

21
Q

…………. Secrete OMI

A

Follicular cells

22
Q

The total number of primary oocytes at birth is about …………..

A

700,000 to 2 million.

23
Q

During childhood most oocytes become atretic and about how many are present by the beginning of puberty?

A

400 000

24
Q

About how many of the surviving oocytes are ovulated throughout the life of a female?

A

Less than 500

25
Q

The risk of having children with chromosomal abnormalities increases with maternal age indicates that primary oocytes …………………

A

are vulnerable to damage as they age.

26
Q

Each month, 15 to 20 follicles begin to mature, passing through 3 stages namely;

A

-Primary or preantral
- Secondary or antral (vesicular or Graafian)
- Preovulatory.

27
Q

Preovulatory stage is about ……… hours before ovulation

A

37

28
Q

……. Is the longest stage in the development of follicles

A

Antral

29
Q

When is the second meiotic division of the secondary oocyte completed?

A

After fertilisation occurs

30
Q

Outline the stages of oogenesis

A
  • With each menstrual cycle, a few primary oocytes (PO) begin to mature and one completes the first meiotic division shortly before ovulation.
  • The first meiotic division of a primary oocyte produces 2 unequal daughter cell, each with haploid number of chromosome.
  • The large cell receives most cytoplasm and is called the secondary oocyte, the small cell is called the first polar body.
  • The secondary oocyte enters second meiotic division
  • Ovulation takes place while the oocyte is in the metaphase
  • The secondary oocyte remains arrested in metaphase till fertilization occurs
  • The second meiotic division is completed only if fertilization occurs.
  • This results in another 2 unequal daughter cells.

The smaller one becomes second polar body, while the larger one is the ovum

31
Q

What happens to the secondary oocyte if fertilisation doesn’t occur?

A

If fertilization does not occur, the secondary oocyte fails to complete the 2nd meiotic division and degenerates within 24 hours after ovulation

32
Q

What is the diameter of the Graafian follicle?

A

23 - 28mm

33
Q

The heartbeat is first detected on the ………. Week

A

6th week

34
Q

When does the gonad of an embryo start developing?

A

2nd week

Embryology (13 decks)

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