Oogenesis (4)

Question 1

What is oogenesis?

Answer 1

The production of haploid, mature eggs in the follicles of the ovaries is known as oogenesis.

Question 2

What are the differences between oogenesis and spermatogenesis?

Answer 2

• The number of eggs is determined before birth. Oogonia were produced by mitosis and growth from the germ cells of the germinal epithelium before birth. • The mature eggs, unlike sperm, are not formed continuously throughout life. This process starts at puberty and stops at menopause. • Oogenesis occurs in a monthly cycle, or menstrual cycle, where an egg reaches maturity approximately every 28 days while sperm are produced daily.

Question 3

What does the multiplying phase entail?

Answer 3

Before birth, germ cells from the germinal epithelium which surrounds the ovary, sink in and divide by mitosis to form the primary follicles. Each follicle has a large central cell, the oogonium (2n) surrounded by a single layer of cells, the theca.

Question 4

What does the growth phase entail?

Answer 4

• From puberty onwards, the primary follicles start periodically growing and developing to form Graafian follicles. • Within each Graafian follicle the oogonium grows into a primary oocyte (2n).

Question 5

What do the reduction and maturity phases entail?

Answer 5

• The primary oocyte (2n) undergoes meiosis resulting in an egg (n). • There is no splitting of the cell during this meiosis. Of the four haploid nuclei one will form the nucleus of the egg. The other three will degenerate. See the diagram. • Mature Graafian follicles move periodically to the surface of the ovary, where they burst, releasing the mature egg and surrounding follicle cells. A process called ovulation.

Question 6

What is the ovulation?

Answer 6

Ovulation is the release of a mature egg from a Graafian follicle in the ovary every 28 days. The egg survives for 24 hours after ovulation.

Question 7

Diagram of an egg.

Answer 7