Spermatogenesis is the process by which sperm are produced in the seminiferous tubules of the testes over 65-70 days. It begins with spermatogonia that undergo mitosis and meiosis to form haploid spermatids from diploid spermatocytes. Sertoli cells secrete fluid to nourish spermatids and protect them, while interstitial cells secrete testosterone. Oogenesis similarly occurs in the ovaries, forming oocytes or eggs over a woman's lifetime from primary oocytes present at birth that undergo meiosis to become haploid secondary oocytes if fertilized.

1. Spermatogenesis
Occurs in the seminiferous tubules of the testes
the formation of sperm
Takes 65 to 70 days

2. Spermatogenesis Overview
Begins with one cell
 Which becomes two
 Finally four

3. Primary Spermatocytes
These are the basic cells, where process begins
 Diploid spermatogonia divide mitotically to produce primary
spermatocytes which divide meiotically to form haploid
secondary spermatocytes
 Secondary spermatocytes develop into spermatids which
eventually form mature sperm

4. SOME OTHER CELLS
SERTOLI CELLS
They secrete fluid which
nourish spermatids &
protect them from
immune system.
INTERSTITIAL CELLS
They secrete male hormone
testosterone

5. Oogenesis
Occurs in the ovaries
Formation of oocytes, eggs
Begins prior to birth!

6. Oogenesis Overview
Begins with one cell
 Which becomes two
 Then finally, four

7. Primary Oocyte
These are present at birth ( stop at prophase I)
Stay dormant until sometime after puberty
Diploid (2n)
 46 chromosomes
 Germinal epithelium divides to form primary oocytes and
follicle cells

8. First Polar Body
 Results from meiosis I
Smaller (has less cytoplasm)

9. Secondary Oocyte
Released by ovulation
 Happens roughly every 28 days

10. At puberty
Every month only one follicle called graafian follicle
matures
Primary oocyte divides meiotically to form secondary
oocyte and small polar body
Fluid filled spaces formed by follicle cells
Graafian follicle migrate to ovary surface

11. Ovulation
Follicle bursts and
secondary oocyte
released
After that remaining
follicle cells develop to
form corpus luteum
(secrete progesterone)
Second meiotic
division will occur
only if sperm
penetrates secondary
oocyte