including all stages and events of fertilization and formation of embryo

1. TRANSPORTATION OF
GAMETES

2. Oocyte Transport
 The secondary oocyte is expelled at ovulation from the
ovarian follicle with the escaping follicular fluid
 During ovulation, the fimbriated end of the uterine tube
becomes closely applied to the ovary.
 The fingerlike processes of the tube, fimbriae, move back
and forth over the ovary. The sweeping action of the
fimbriae and fluid currents produced by the cilia of the
mucosal cells of the fimbriae "sweep" the secondary
oocyte into the funnel-shaped infundibulum of the uterine
tube.
 The oocyte passes into the ampulla of the tube, mainly as
the result of peristalsis-movements of the wall of the tube
characterized by alternate contraction and relaxation-
that pass toward the uterus.

4. Sperm Transport
 From their storage site in the epididymis,
the sperms are rapidly transported to the
urethra by peristaltic contractions of the
thick muscular coat of the ductus
deferens.
 The accessory sex glands-seminal glands
(vesicles), prostate, and bulbourethral
glands-produce secretions that are added
to the sperm-containing fluid in the ductus
deferens and urethra

5.  From 200 to 600 million sperms are deposited
around the external os of the uterus and in the
fornix of the vagina during sexual intercourse.
 The sperms pass slowly through the cervical canal
by movements of their tails. The enzyme
vesiculase, produced by the seminal glands,
coagulates some of the semen and forms a
vaginal plug that may prevent the backflow of
semen into the vagina.
 When ovulation occurs, the cervical mucus
increases in amount and becomes less viscid,
making it more favorable for sperm transport.

6.  The volume of sperm or ejaculate averages 2
to 6 mL.
 The sperms move 2 to 3 mm/minute, but the
speed varies with the pH of the environment.
They are nonmotile during storage in the
epididymis, but become motile in the
ejaculate. They move slowly in the acid
environment of the vagina, but move more
rapidly in the alkaline environment of the
uterus.
 It is not known how long it takes sperms to
reach the fertilization site
 Only approximately 200 sperms reach the
fertilization site. Most sperms degenerate and
are resorbed by the female genital tract.

7. MATURATION OF
SPERMS

8.  to fertilize an oocytes, sperms must undergo a
period of conditioning-capacitation-lasting
approximately 7 hours.
 During this period, a glycoprotein coat and
seminal proteins are removed from the surface of
the sperm's acrosome.
 The membrane components of the sperms are
extensively altered. Capacitated sperms show
no morphologic changes, but they are more
active.
 Sperms are usually capacitated in the uterus or
uterine tubes by substances secreted by these
parts of the female genital tract.

9.  THE ACROSOME REACTION:
 The intact acrosome of the sperm binds to a glycoprotein
(ZP3) on the zona pellucida.
 Capacitated sperms come in contact with the corona
radiata surrounding a secondary oocyte
 Undergo complex molecular changes that result in the
development of perforations in the acrosome.
 Multiple point fusions of the plasma membrane of the
sperm and the external acrosomal membrane occur.
Breakdown of the membranes at these sites produces
apertures.
 The changes induced by the acrosome reaction are
associated with the release of enzymes, including
hyaluronidase and acrosin, from the acrosome that
facilitate fertilization

10. VIABILITY OF GAMETES

11.  human oocytes are usually fertilized within
12 hours after ovulation.
 In vitro observations have shown that the
oocyte cannot be fertilized after 24 hours
and that it degenerates shortly thereafter.
 Most human sperms probably do not
survive for more than 48 hours in the female
genital tract.
 Sperms and oocytes can be stored frozen
for many years to be used in assisted
reproduction.

12. FERTILIZATION

13.  Site of fertilization: the ampulla of the
uterine tube
 If the oocyte is not fertilized here, it slowly
passes along the tube to the uterus,
where it degenerates and is resorbed.
Although fertilization may occur in other
parts of the tube, it does not occur in the
uterus.
 Chemical signals (attractants), secreted
by the oocyte and surrounding follicular
cells, guide the capacitated sperms
(sperm chemotaxis) to the oocyte.

14.  DEFINATION: Fertilization is a complex
sequence of coordinated molecular
events that begins with contact between
a sperm and an oocyte and ends with the
intermingling of maternal and paternal
chromosomes at metaphase of the first
mitotic division of the zygote, a unicellular
embryo.
 The fertilization process takes
approximately 24 hours.

15. PHASES OF
FERTILIZATION

16. 1ST PHASE:
Passage of a sperm through the
corona radiata.
Dispersal of the follicular cells of the corona
radiata surrounding the oocyte and zona
pellucida
enzyme hyaluronidase released from the
acrosome of the sperm, tubal mucosal
enzymes and movements of the tail of the
sperm are important in its penetration of the
corona radiata.

18.  2ND PHASE:
 Penetration of the zona pellucida. Passage
of a sperm through the zona pellucida.
 The enzymes esterases, acrosin, and neuraminidase
appear to cause lysis of the zona pellucida, thereby
forming a path for the sperm to follow to the oocyte.
 Once the sperm penetrates the zona pellucida, a
zona reaction-a change in the properties of the
zona pellucida-occurs making it impermeable to
other sperms. The zona reaction is believed to result
from the action of lysosomal enzymes released by
cortical granules near the plasma membrane of the
oocyte. They cause changes in the plasma
membrane that make it impermeable to other
sperms.

19.  3RD PHASE:
 Fusion of plasma membranes of the
oocyte and sperm.
 The plasma or cell membranes of the
oocyte and sperm fuse and break down
at the area of fusion.
 The head and tail of the sperm enter the
cytoplasm of the oocyte, but the sperm's
plasma membrane remains behind

20.  4th PHASE:
 Completion of the second meiotic division
of oocyte and formation of female
pronucleus. Penetration of the oocyte by a
sperm activates the oocyte into
completing the second meiotic division
and forming a mature oocyte and a
second polar body
 Following decondensation of the maternal
chromosomes, the nucleus of the mature
oocyte becomes the female pronucleus.

21.  5TH PHASE:
 Formation of the male pronucleus. Within
the cytoplasm of the oocyte, the nucleus
of the sperm enlarges to form the male
pronucleus and the tail of the sperm
degenerates
 Morphologically, the male and female
pronuclei are indistinguishable. During
growth of the pronuclei, they replicate
their DNA-1 n (haploid), 2 c (two
chromatids). The oocyte containing two
haploid pronuclei is called an ootid.

22.  6TH PHASE
 As the pronuclei fuse into a single
diploid aggregation of
chromosomes, the ootid becomes a
zygote. The chromosomes in the
zygote become arranged on a
cleavage spindle in preparation for
cleavage of the zygote

23.  7TH PHASE:
 As the pronuclei fuse into a single
diploid aggregation of chromosomes,
the ootid becomes a zygote. The
chromosomes in the zygote become
arranged on a cleavage spindle in
preparation for cleavage of the
zygote

25. CLEAVAGE OF THE
ZYGOTE

26.  Cleavage consists of repeated mitotic
divisions of the zygote, resulting in a rapid
increase in the number of cells. These embryonic
cells-blastomeres-become smaller with each
successive cleavage division.
 Division of the zygote into blastomeres begins
approximately 30 hours after fertilization. After the
nine-cell stage, the blastomeres change their shape
and tightly align themselves against each other to
form a compact ball of cells. This phenomenon,
COMPACTION, is probably mediated by cell surface
adhesion glycoproteins.
 When there are 12 to 32 blastomeres, the developing
human is called a MORULA. Internal cells of the
morula are surrounded by a layer of cells that form
the outer cell layer. The spherical morula forms
approximately 3 days after fertilization and enters the
uterus.

28. FORMATION OF THE
BLASTOCYST

29.  Shortly after the morula enters the uterus
(approximately 4 days after fertilization), a
fluid-filled space called the blastocystic
cavity appears inside the morula. The fluid
passes from the uterine cavity through the
zona pellucida to form this space. As fluid
increases in the blastocystic cavity, it
separates the blastomeres into two parts:
 A thin, outer cell layer, the trophoblast, which
gives rise to the embryonic part of the
placenta
 A group of centrally located blastomeres, the
inner cell mass, which gives rise to the
embryo; because it is the primordium of the
embryo, the inner cell mass is called the
embryoblast

31. TOPICS FOR 1ST CLASS TEST ON 7TH NOVEMBER
2012:
 DEFINATIONS IN GENERAL EMBRYOLOGY
 MALE AND FEMALE REPRODUCTION
 GAMETOGENESIS
 MATURATION AND TRANSPORT OF
GAMETES
 FERTILIZATION, CLEAVAGE, BLASTOCYST
FORMATION