31. Reproductive tissue. Oogenesis. Oocytes.

The reproductive organs that produce gametes are called __________.

gonads

In females, the gametes produced are __________, while in males they are __________.

eggs; sperm

Gamete formation occurs via __________.

meiosis

Highly differentiated germ cells include progenitor and __________ cells.

satellite

Follicular cells are present in the __________ reproductive system.

female

Sertoli cells are present in the __________ reproductive system.

male

Satellite cells are derived from __________ germ cells.

primordial

Primordial germ cells develop in the __________ embryonal week.

3rd

Primordial germ cells are large cells with __________ cytoplasm.

light

Primordial germ cells are PAS reaction __________.

positive

Primordial germ cells migrate to the __________ sex cords.

primitive

At the early development stage, the gonad is __________.

indifferent

The formation of an ovum occurs during __________.

oogenesis

Oogenesis takes place in the __________.

ovaries

Oogenesis has three phases: proliferative phase, growing phase, and __________ phase.

maturation

Oogenesis ends after the __________ of an oocyte.

fertilisation

Oogenesis begins during the __________ embryonal week.

3rd

The main germ cell in oogenesis is called __________.

oogonia

After the primary oocyte, the next stage in oogenesis is the __________ oocyte.

secondary

Oogenesis consists of both __________ and meiosis.

mitosis

The first meiotic division in oogenesis ends after __________.

ovulation

The secondary oocyte must undergo the second meiotic division to produce __________.

haploids

Each oocyte is surrounded by a number of __________ cells.

follicle

The stages of growth of oocytes during the menstrual cycle include primordial follicle, primary follicle, __________, tertiary follicle, and graafian follicle.

secondary

At birth, the primary oocytes are surrounded by a thin single layer of __________ follicles.

primordial

Oogenesis is regulated by three hormones: FSH, LH, and __________.

oestrogen

FSH and LH are produced by the __________ gland.

pituitary

ovum formation

occurs durin googenesis, takes place in the ovaries had 3 phases : proliferative, growing and maturation

ends after the fertilisation of an oocyte

oogenesis

• begins during 3rd embryonal weel during fetal period but interrupted and continues when menstruation begins, making it a cycle every 28 days

oogenesis process

1. start with germ cell giving rise to oogonia

2. oogonia give rise to primary oocyte developing into secondary oocyte

3. secondary oocyte to ovum

4. it consists of mitosis and meisosis, 1st meiosis ends after ovulation and 2nd meiosis after fertilisation

begins ½ months before a baby girl is born, by this time most of her oogonia die and the remaining oogonia enter meiosis I becoming primary oocytes, they are stuck here till the girl begins her first menstrual cycle

When the primary oocyte finally completes its first meiotic division, it divides the chromosomes evenly, however, it does not divide its cytoplasm equally. Almost all of the cytoplasm goes to one of the two daughter cells, which becomes a secondary oocyte

The secondary oocyte still has two copies of each chromosome, it must undergo the second meiotic division in order to produce haploids. This division is also uneven. Ovum achieves its haploid state.

stages of growth of oocyte during menstrual cycle

 primordial follicle, primary follicle, secondary follicle, tertiary follicle and graafian follicle

At the time of birth, all surviving primary oocytes are surrounded by thin single layer of primordial follicles. They give rise to the primary follicles. When primary follicles survive, secondary follicles are created. Growing follicle contains the primary oocyte surrounded by zona pellucida, theca interna, theca granulosa and theca externa

If the secondary follicles survive, tertiary follicles are produced. If the tertiary follicle survive, graafian follicles are produced.

3 hormones regulating oogenesis

FSH and LH by pituitary gland

oestrogen by ovaries

explain oogenesis stages in detail

a fetus girls entire egg supply is made whilst in the womb, but inactive, called oogenesis

1. oogonia undergo several mitotic divisions, at the 7th month of development they stop producing and are left with around 2-4 mil

2. all the oogonia that have been produced develop into primary oocytes

3. primary oocytes begin meiosis I but are in meiotic arrest until puberty

4. some destined to be ovulated get past meiotic arrest, other die off

5. at puberty 1 primary oocyte attempts to split but 1 is a regular secondary oocyte whilst the other has the DNA but little cytoplasm, this is called a polar body and generally withers and dies

6. secondary oocyte stays in the uterine tubule till a sperm comes and meiosis II can begin, where it halves the number of chromosomes, and a second polar body is made

7. the secondary oocyte becomes and ovum, but after fertilisation quickly becomes a zygote

8. if the sperm doesn’t come to fertilise the secondary oocyte then meiosis II doesn’t happen and the secondary oocyte is released during menstruation doesn’t become an ovum