Gametes (germ cells)
Haploid reproductive cells
-1 copy of every chromosome/genes (1n)
Male Gametes
spermatozoa (sperm)
Female Gametes
ova (egg)
Diploid
2 copies of every chromosome/genes (2n)
46 chromosomes
44 autosomes = non sex chromosomes
22 pairs of genes
2 sex chromosomes
X & Y
- not always paired
X: essential genes for both M & F
Y: only in M
XX
F
XY
M
1n * 1n = 2n
Fertilization
Zygote
2n (Spermatoza + Ova)
Gametogenesis
production of gametes from undifferentiated germ cells
Gametogenesis : Mitosis
normal cell division ( 2n > 2n )
- 2 identical cells
- DNA replicated 1x
- divides 1x
Gametogenesis :
Meiosis
produce gametes ( 2n > 1n , 1n > 1n ) 4n total
- DNA replicated 1x
- divides 2x
Testes
site of sperm production @ seminiferous tubules
Epididymus
site of sperm maturation
Hormone Regulation
Hypothalamus >
GnRH > AP : FSH & LH
FSH
stimulate gametogenesis
-made up of Sertoli cells in seminiferous tubules > “babysitters of sperm”
LH
stimulate androgen secretion
-Leydig cells release testosterone
FSH for M
stimulate gametogenesis
-made up of Sertoli cells in seminiferous tubules > “babysitters of sperm”
LH for M
stimulate androgen secretion
-Leydig cells release testosterone > further stimulate Sertoli cells
lumen
contain sperm
Process of Sperm
1) Spermatogonium 2n
2) Mitosis
3) Primary Spermatocyte 2n & Spermatogonium 4) Meiosis I
5) Secondary Spermatocyte 1n
6) Meiosis II
7) Spermatid 1n
Process of Sperm
1) Spermatogonium 2n
2) Mitosis
3) Primary Spermatocyte 2n & Spermatogonium 4) Meiosis I
5) Secondary Spermatocyte 1n
6) Meiosis II
7) Spermatid 1n
8) Differentiation
9) Spermatozoa
Head of sperm
- contains chromosomes in nucleus
- acrosome cap: fertilization
Midpiece of sperm
mitochondria
energy
Tail of sperm
flagella: whip like motion for motility
Spermatozoa
released into lumen
- immotile, cannot swim for 20 days
- moves to epididymis = motility
Oogenesis
limited gamete production
- number of oogonia fixed (not replenished)
- meiosis starts at fetal and end after fertilization
Oogenesis process
1) Oogonium 2n
2) Mitosis
3) Primary oocytes 2n
4) Meiosis I > Meiotic arrest
5) Ovulation > Meiosis I
6) Secondary Oocyte 1n
7) Fertilization > Meiosis II
8) Ovum/zygote 2n
Polar bodies
remaining daughter cells containing little cytoplasm
cell unevenly divides