1. Dr. Ahmed Fathalla Ibrahim
GAMETOGENESIS
Dr. Ahmed Fathalla Ibrahim

2. MITOSIS

4. DIFFERENCE BETWEEN MITOSIS & MEIOSIS

5. DEFINITION The process of formation of mature male & female gametes.
Spermatogenesis: sequence of events by which the primitive germ cells (spermatogonia) are transformed into mature sperms or spermatozoa
Oogenesis: sequence of events by which the primitive germ cells (oogonia) are transformed into mature oocytes

6. SPERMATOGENESIS
AIM: formation of sperms with haploid number of chromosomes
SITE: in the seminefrous tubules of testis
DURATION: takes about two months
OCCURRENCE: starts at puberty & continues throughout life

7. SPERMATOGENESIS

8. SPERMATOGENESIS STAGES:
PROLIFERATION: each spermatogonium divides by mitosis into 2 daughter spermatogonia (with diploid number of chromosomes: 44 + XY)
GROWTH: spermatogonium enlarges to form a primary spermatocyte (with diploid number)
MATURATION (BY MEIOSIS):
1st meiotic division: a reduction division by which a primary spermatocyte divides into two secondary spermatocytes (haploid number of chromosomes: 22 + X or 22 + Y)
2nd meiotic divison: a process of mitosis without a normal interphase (without DNA replication) through which a secondary spermatocyte divides into two spermatids (with haploid number of chromosomes)
SPERMIOGENESIS: a process by which a spermatid is transformed into a mature sperm (with haploid number)

9. SPERMIOGENESIS

11. SPERM

12. SEMINAL FLUID
SOURCE: secretions from seminal vesicles, prostate gland & bulbourethral glands
VOLUME: 3 – 5 ml
SPERM COUNT: about 100 millions/ml
MOTILITY: about 3mm/min, at least 70% of sperms should be motile
ABNORML FORMS: should not exceed 10%

13. OOGENESIS
AIM: formation of secondary oocytes with haploid number of chromosomes
SITE: in the cortex of ovary
OCCURRENCE: starts during fetal life , becomes completed after puberty & continues till menopause

14. OOGENESIS

15. OOGENESIS STAGES: DURING FETAL LIFE:
Proliferation: each oogonium divides by mitosis into 2 daughter oogonia (with diploid number of chromosomes: 44 + XX)
Growth: oogonium enlarges to form primary oocyte (with diploid number). Primary oocytes begin 1st meiotic division & stop at prophase
DURING EACH OVARIAN CYCLE (AFTER PUBERTY):
1st meiotic division is completed: a reduction division by which a primary oocyte divides into one secondary oocyte (haploid number of chromosomes: 22 + X) & 1st polar body (degenerates)
2nd meiotic divison begins: begins at ovulation, progresses only to metaphase and becomes arrested
AFTER FERTILIZATION (IN THE FALLOPIAN TUBE)
2nd meiotic division is completed: 2ry oocyte divides into one mature ovum (haploid number) & 2nd polar body (degenerates)
N.B.: NO PRIMARY OOCYTES FORM AFTER BIRTH IN FEMALES

16. OVULATION