1. Gametogenesis….. Geoffrey T. Meyer
Room 217, School of Anatomy and Human Biology
Coordinator of Human Organs and Systems 214
Semester 2

4. One Essential Question: Why is sexual reproduction necessary?
The main purpose of sexual reproduction is the formation of offspring who are
genetically different from one another and from their parents.
Meiosis is the fundamental process underlying sexual reproduction.
It involves two essential outcomes:
1. Reduction Division - the process in which each gamete receives a haploid set (n)
of chromosomes and genes. The diploid number (2n) is restored on fusion of
two gametes.
2. Rearrangement of genes on the maternal and paternal chromosomes.
This ensures that the offspring are genetically different from one another.

5. Consequences of meiosis Meiosis
Sperm and oocytes contain only
one representative of each
homologous pair of chromosomes
Maternal and paternal chromosomes
are randomly assorted
Crossing over increases
genetic variation

7. Seminiferous epithelium
Testis
Seminiferous epithelium
Spermatogonia
Diploid spermatogenic cells
Location?
Destiny?
Derived from?
Implications for male fertility

8. Undergoes 1st meiotic division Secondary spermatocytes
Primary spermatocyte
Undergoes 1st meiotic division
Secondary spermatocytes
Spermatids

9. Seminiferous epithelium
Testis
Seminiferous epithelium
Spermatogonia
Diploid
Primary spermatocytes
(meiosis I)
Secondary spermatocytes
(meiosis II)
Spermatids
Haploid

11. Spermatogonia stem cell
Meiosis in the male
Spermatogonia stem cell
Puberty
until death

14. Meiosis in the female

15. Oogonia Meiosis in the female Proliferation of oogonia
(equivalent of spermatogonia
in the male)
occurs in the fetal ovary
Birth
Ovulation
Fertilisation
Polar bodies arise from unequal cell division

16. 7 million primary oocytes
400,000 at birth
Several primary follicles
initiate maturation
1 completes its development
Remainder degenerate (atresia)
ovulate
Atretic follicles

17. Gametes don’t develop on their own
– they need supporting cells
So I wish to introduce the:
Sertoli cell (testis)
Interstitial cell of the testis (Leydig cell)
Granulosa cell (ovary)

18. Sertoli cells Location Junctional complexes
Divide the seminiferous tubule into a:
(a) basal compartment
(b) adluminal compartment
Support/protect/nourish
spermatogenic cells
Phagocytic
Release mature spermatids
Secrete ABP (FSH), Inhibin (-ve; FSH) and Activin (+ve; FSH)

20. Leydig cells
Location
Secrete Testosterone (LH) requiring Prolactin (LH receptor)

21. Corpus luteum formation
Theca interna
Theca interna
Theca lutein
Granulosa cells
Granulosa cells
Granulosa lutein

22. Granulosa lutein cells (FSH) Theca lutein cells (LH)
Theca interna
Ovulation
Androstenedione (LH)
Corpus luteum
Granulosa cells
Progesterone
Estradiol
Testosterone
Estradiol (FSH)
Granulosa lutein cells (FSH)
Theca lutein cells (LH)
Acquire LH receptors