i want 25 multiple choice question swith their model answer below each question that covers differnet aspects of all of the following : General EmbryologyObjectives
By the end of this lecture student should be able to:
Study the first week of development
(Fertilization)Contents
- Corpus Luteum & Albicans
- FertilizationCorpus luteum
Fallopian tube
OvaryCorpus luteum
Wall of
Oocyte
Ovary
Corpus
luteum
the follicleCorpus luteum
-Following ovulation under
the effect of LH hormone the
cells in the wall of the
Graafian follicle form a
yellow body called corpus
luteum (Lutenization).
-It secretes estrogen and
progesterone hormone,
which prepares the uterine
mucosa for implantation of
the embryo (Secretory stage).Corpus luteum
- If the oocyte is fertilized
the corpus luteum grows and
forms the corpus luteum of
pregnancy.
- It secretes progesterone
hormone until the end of the
4th month as secretion of
progesterone by the placenta
becomes adequate to
maintain the pregnancy.Corpus albicans
- If fertilization does not occur;
the corpus luteum (L) reaches
maximum development 9 days
after ovulation.
-It shrinks and forms a mass of
fibrotic tissue, the Corpus
albicans (A).
-Progesterone hormone
decreases and the menstrual
bleeding starts.
A
LFertilization46
Primary oocyte
Meiosis I
23
Secondary oocyte
First polar body
Meiosis II
23
Definitive
oocyte
Second
polar
body
Polar bodiesDefinition
Fertilization
Fertilization is
the process by
which male and
female gametes
(sperm and ovum)
fuse.Definition
Fertilization
Fertilization is
the process by
which male and
female gametes
(sperm and ovum) fuse.Site
Fertilization
In the ampullary
part of the
uterine tube
(the widest part
of the tube)Mature sperm
Fertilization
Middle piece
Mitochondrial
sheathSecondary oocyte
Zona Pellucida
Fertilization
Corona radiata
Oocyte membraneFertilization
- For the spermatozoon
to fertilize the oocyte it
must undergo:
(1) Capacitation
(2) Acrosome reaction
(In the female genital tract)Capacitation
Fertilization
-It occurs in the female
reproductive tract (Uterine tube).
-It lasts for 7 hours.
-The glycoprotein coat and
seminal plasma proteins are
removed from the plasma
membrane of the acrosomal
region of the spermatozoon.Capacitation
Fertilization
-It occurs in the female
reproductive tract (Uterine tube).
-It lasts for 7 hours.
-The glycoprotein coat and
seminal plasma proteins are
removed from the plasma
membrane of the acrosomal
region of the spermatozoa.Acrosome reaction
The acrosome reaction
occurs after binding to
the zona pellucida (1)
Fertilization
ZP
Release of enzymes
(acrosin & trypsin) (2)
needed to penetrate the
zona pellucida (3)Phases
Fertilization
- Phase 1:penetration of the corona radiata.
- Phase 2:penetration of the zona pellucida.
- Phase 3:fusion of the oocyte and sperm cell
membranes.
1
2
3Phase I
Fertilization
Penetration of
the corona radiata
The capacitated sperm
can pass freely through
the corona cellsPhase I
Penetration of
the corona radiata
The capacitated
sperm can pass
freely through
the corona cells
FertilizationPhase II
Fertilization
Penetration of the Zona Pellucida
The zona (ZP) is a glycoprotein
membrane surrounding the ovum
(It induces the acrosomal reaction).
The release of acrosomal
enzymes (2) allows the sperm to
penetrate the zona pellucida (3).
ZPPhase III
Fusion of the oocyte and
sperm cell membranes
Adhesion occurs between
the head of the sperm and
the plasma membrane of
the oocyte (1)
The plasma membranes of the
sperm and oocyte fuse (2)
Plasma membrane
of the sperm
Plasma membrane
of the oocyte
FertilizationPhase III
Fertilization
Fusion of the oocyte and
sperm cell membranesPhase III
The head and the tail of
the sperm enter the
cytoplasm of the oocyte,
(The plasma membrane
is left behind on the
oocyte surface)
FertilizationPhase III
Fertilization
When the spermatozoon enters the oocyte,
the egg responds in three ways:
1. Cortical and
zona reactions
2. The oocyte
finishes its second
meiotic division
3. Metabolic
activation of
the egg.Phase III
Fertilization
Cortical and zona reactions:
Release of cortical granules lining
the plasma membrane of the oocyte,
which contain lysosomal enzymes
causes:
The oocyte membrane and the zona
pellucida becomes impenetrable to
other spermatozoa
(No sperm binding or penetration)Phase III
Cortical and zona reactions
Fertilization
Prevent the polyspermy
FertilizationPhase III
The oocyte finishes the
second meiotic division
Second
polar body
Fertilization
The tail of spermatozoon degenerates
and the male pronucleus is formed
Definitive oocyte
(23 chromosomes)
(female pronucleus)Phase III
Fertilization
The male and female pronuclei lose
their nuclear membranes and fuse
together forming the zygotePhase III
Fertilization
The male and female pronuclei lose
their nuclear membranes and fuse
together forming the zygoteResults 1. Zygote
formation and
restoration of the diploid number of chromosomes.
Fertilization
2. Determination of the sex. female (XX) embryo, or male (XY) embryo
3. Initiation of cleavage