1. Spermatogenesis The creation of sperm cells using mitosis, meiosis,
and
differentiation

2. Spermatogenesis Overview • • Germ cell Germ cells divide by mitosis
Meiosis review
Germ
cell 2n
Mitosis
Overview 1°
spermato cytes 2n •
Germ cells divide by mitosis
Diploid 1° spermatocytes divide by the first division of meiosis into haploid 2° spermatocytes
These divide by meiosis II into haploid spermatids
The spermatids mature into sperm cells (spermatozoa)
by the process of differentiation – nursed by Sertoli cells.
Meiosis I 2°
spermato
cytes n 2°
spermato
cytes n •
Meiosis II
Spermatid n
Spermatid n
Spermatid n
Spermatid n
Sperm
cell
Sperm
cell
Sperm
cell
Sperm
cell

3. Cross section showing the different stages

4. Oogenesis The creation of female gametes - using mitosis, meiosis, and
differentiation

5. Oogenesis Germ cells (oogonia) in the ovary divide by mitosis.
Outline
Germ cells (oogonia) in the ovary divide by mitosis.
1° oocytes produced begin meiosis I – in a structure
called the 1° follicle.
Meiosis I is completed before ovulation and a 2° oocyte is formed (in a 2° follicle) – the polar body usually degenerates.
Only after fertilisation will meiosis II be completed and a mature ovum formed by differentiation.
The second polar body will
degenerate

6. Stages of Oogenesis