Ovary and oogenesis Flashcards
Female gamete is called ……….., and the process of it’s production is ……………..
The female gamete is called ova, and the process of its production is oogenesis
Gametes are derived from …………
PGCs, primordial germ cells
The PGCs are formed in the …………….
Epiblast
The PGCs are formed in the epiblast during ……………. week
Second week
Formed PGCs move to …………..
The wall of the yolk sac
During ……… week PGCs begin to migrate from yolk sac to the gonads and arrive at …………… week
During 4th week PGCs begin to migrate from yolk sac to the gonads and arrive at 5th week
Ova are derived from ………..
Oogonia
………… is the female gonad
The ovary
All the oogonia to be used throughout fertile life of a female are produced before her birth. True or false
True
The oogonia undergo mitotic divisions, by the end of the …………. month, are arranged in clusters at the ovarian cortex.
Third month
The many rounded large cells called oogonia are contained in the …………… part of the ovary
The cortex
The oogonia arranged in clusters at the ovarian cortex are surrounded by ………. epithelial cells
Squamous/flat
All the oogonia in one cluster are from a single follicular cell. True or false
True
The total number of oogonia in the ovary reaches its maximum by the …………. month
5th month
What is the maximum number of oogonia in the ovary?
7 million
All surviving primary oocytes enters prophase of meiosis I, and are individually surrounded by a layer of ………….
Follicular cells
A primary oocyte, with its surrounding flat epithelial cells, is called a …………..
Primordial follicle
What is the state of all primary oocytes just before birth?
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.
Primary oocytes remain in prophase and do not finish their 1st meiotic division before puberty is reached. True or false
True
Why do primary oocytes remain in prophase and not finish their 1st meiotic division before puberty is reached?
Oocyte maturation inhibitor (OMI), secreted by follicular cells.
…………. Secrete OMI
Follicular cells
The total number of primary oocytes at birth is about …………..
700,000 to 2 million.
During childhood most oocytes become atretic and about how many are present by the beginning of puberty?
400 000
About how many of the surviving oocytes are ovulated throughout the life of a female?
Less than 500
The risk of having children with chromosomal abnormalities increases with maternal age indicates that primary oocytes …………………
are vulnerable to damage as they age.
Each month, 15 to 20 follicles begin to mature, passing through 3 stages namely;
-Primary or preantral
- Secondary or antral (vesicular or Graafian)
- Preovulatory.
Preovulatory stage is about ……… hours before ovulation
37
……. Is the longest stage in the development of follicles
Antral
When is the second meiotic division of the secondary oocyte completed?
After fertilisation occurs
Outline the stages of oogenesis
- 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
What happens to the secondary oocyte if fertilisation doesn’t occur?
If fertilization does not occur, the secondary oocyte fails to complete the 2nd meiotic division and degenerates within 24 hours after ovulation
What is the diameter of the Graafian follicle?
23 - 28mm
The heartbeat is first detected on the ………. Week
6th week
When does the gonad of an embryo start developing?
2nd week
