The first week of human development begins with fertilization of the
egg by sperm forming the zygote, followed by early cell division forming the
blastocyst. These notes also cover events before fertilization formation of both the
egg and sperm, gametogenesis.
Initially, there is a halving of
choromosomal content in the gametes, which
is restored by fertilization, allowing
genetic recombination to occur. This is
then followed by a series of cell
divisions without cytoplasmic growth.
During this first week the egg, then
zygote, then the blastula is moving along
the uterine horn into the uterus for
implantation in the uterine wall.
Implantation also begins in this first
week, but will be covered in Week
2 notes, as the implantation process
is completed by the end of the second
week.
Eppig et al., (2002) has shown that in the ovary, it is the oocyte (egg)
that regulates the development of the ovarian follicle (the surrounding cells).
Eppig et al., 2002
Reading
Human Embryology (2nd ed.) Larson Ch1
p1-32
The Developing Human: Clinically Oriented
Embryology (6th ed.) Moore and Persaud
Before we Are Born (5th ed.) Moore and
Persaud Ch 2 p14-33
Essentials of Human Embryology Larson Ch1
p1-16
Human Embryology Fitzgerald and Fitzgerald Ch2 p8-14
BBC series The Human Body, Episode 2 available commercially as a
book
by Anthony Smith, video,
or CD Rom , short sample
video available from ABC (needs realvideo)
In Anatomy Department: "Ancient" Japanese video on fertilization.
Development Overview
Mature Human Egg: large egg in comparison to surrounding granulosa cells.
Fertilized Human Zygote: male and female nuclei fusing in centre of cell, 2 polar bodies on right.
4 Cell Human Embryo: during each mitotic division the embryo does not increased in size and divides the existing cytoplasm.
acrosome- the packet of enzymes in a
sperm's head that allows the sperm to dissolve a
hole in the coating around the egg, which allows
the sperm to penetrate and fertilize the
egg.
atresia- the process of follicle
degeneration. At any one time the majority of
follicles are destined not to complete
maturation and at any stage (from type 4-7)
degeneration of the follicle can occur.
blastocyst- [Greek, blastos =
sprout + cystos = cavity] early stage in
development before implantation, consists of
outer trophoblast and inner cell mass.
cortical reaction-
capacitation- the process of
activation of the sperm so that fertilization of
the egg can occur.
fertilization- The penetration of the
egg by the sperm and the resulting combining of
genetic material that develops into an embryo.
The union of two haploid gametes to form a
diploid cell or zygote.
flagella-
gametes- Greek gamos = marriage]
A specialized reproductive cell through which
sexually reproducing parents pass chromosomes to
their offspring; a sperm or an egg.
gonad- the male or female site of
gametogenesis and also sex hormone source.
Graafian follicle- the preovulatory
follicle, the final stage in follicle
development in the ovary, type 8 (>1000
cells)
I have also included in the Week 1 notes information about male sex determination and X inactivation, which are not really specific to the first week of development.
An easier introduction to this first week of development is given in K12 Week 1.
Note the introduction page has additional week 1 links listed on the lefthand menu "Internal Links Week 1" and "related pages" .
Please email Dr Mark Hill if you wish to make a comment about this current project.
Folliculogenesis and Ovulation (986Kb)
Sperm Penetration
(706Kb)
Pronuclear Fusion (264Kb)
Cell Cleavage (527Kb)
