Gametogenesis''

1
Gametogenesis..
Geoffrey T. Meyer Room 217, School of Anatomy and
Human Biology Coordinator of Human Organs and
Systems 214 Semester 2
2
(No Transcript)
3
(No Transcript)
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
6
(No Transcript)
7
Testis Seminiferous epithelium
Spermatogonia Diploid spermatogenic
cells Location? Destiny? Derived
from? Implications for male fertility
8
Primary spermatocyte
Undergoes 1st meiotic division Secondary
spermatocytes Spermatids
9
Testis Seminiferous epithelium
Spermatogonia Diploid Primary spermatocytes (meio
sis I) Secondary spermatocytes (meiosis
II) Spermatids Haploid
10
(No Transcript)
11
Meiosis in the male
Spermatogonia stem cell
Puberty
until death
12
(No Transcript)
13
(No Transcript)
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)
400-500 ovulate
Atretic follicles
17
Gametes dont 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)
19
(No Transcript)
20
Leydig cells
Location
Secrete Testosterone (LH) requiring Prolactin (LH
receptor)
21
Corpus luteum formation
Theca lutein
Theca interna
Theca interna
Granulosa cells
Granulosa cells
Granulosa lutein
22
Theca interna
Ovulation
Androstenedione (LH)
Corpus luteum
Granulosa cells
Progesterone Estradiol
Testosterone
Granulosa lutein cells (FSH) Theca lutein cells
(LH)
Estradiol (FSH)
Acquire LH receptors