26. Primordial germ cell in embryo
Mitotic divisions
Spermatogonial
stem cell
Mitotic divisions
Spermatogonium
Mitotic divisions
Primary spermatocyte
Meiosis I
Secondary spermatocyte
Meiosis II
Early
spermatid
Differentiation (Sertoli
cells provide nutrients)
Sperm
2n
2n
2n
n n
n n n n
n n n n
SPERMATO
-
GENESIS
30. Fig. 46-12g
Primordial germ cell
Mitotic divisions
Oogonium
Mitotic divisions
Primary oocyte
(present at birth), arrested
in prophase of meiosis I
Completion of meiosis I
and onset of meiosis II
Secondary oocyte,
arrested at metaphase of
meiosis II
First
polar
body
Ovulation, sperm entry
Completion of meiosis II
Second
polar
body
Fertilized egg
2n
2n
n
n
n
n
In embryo
OOGENISIS
49. Ovary
Uterus
Endometrium(a) From ovulation to implantation
(b) Implantation of blastocyst
Cleavage
Fertilization
Ovulation
Cleavage
continues
The blastocyst
implants
Trophoblast
Inner cell mass
Cavity
Blastocyst
Endo-
metrium
1
2
3
4
5
Formation of the zygote and early
post-fertilization events
60. Fig. 46-18
Estradiol Oxytocin
from
ovaries
Induces oxytocin
receptors on uterus
from fetus
and mother’s
posterior pituitary
Stimulates uterus
to contract
Stimulates
placenta to make
Prostaglandins
Stimulate more
contractions
of uterus
Positivefeedback
+
+
A model for the induction of
labour