2. Morula
After fertilization 2 blastomeres are formed 30 after
They divide geometrically forming a morula
The volume of cells remain intact and zona pellucida remains for
3 days as the ball of cells enter uterine cavity
3. Blastocyst
• Morula remains free in uterus on 4th and 5th day.
• It's covered by a film of mucus.
• The fluid seperates the cells forming a blastocyst
• Zona pellucida becomes stretch and thins and
disappears (zona hatching)
4. Cont
• Cells on outer side blastocyst become
trophectoderm.
• The inner side has active sites for Catherin e
protein
• Trophoctoderm or trophoblast differntiate into
chorion (placenta) and inner mass of embryo
(embryonic stem cells)
• The embryonic stem cells become ectoderm,
mesoderm, endoderm
5.
6. Implantation /nidation
• Occurs on day six on anterior or posterior wall of
body near fundus
• Changes in blayocyst :trophoblast cells adjacent to
inner cell mass enables adhesion to endometrial
cells. It's enabled by integrins and trophonin
• Endometrium at implantation site:microvilli on
surface of trophoectoderm intercept with decidual
cells forming juctional complexies. Mediated by
COX -2
7. Cont
• Apposition -microvilli (pinopods) absorb endometrial
fluid from endometrial fluid from endometrial Glands
which enriched Blastocyst intially. Ashesion happens.
Mediated by integrin, selectins and catherins
• Penetration -At day 10,There is erosion of maternal
blood vessels forming lacunae and decidial cells. This
enables the blastocyst to get nutrition. This enables
blastocyst penetrate until it's stopped by maternal
immunological factors
8.
9.
10. trophoblast
• The tropheectodem differentiate into
synchitiotrophoblast (outer layer) and
cytotrophoblast (inner layer)
• Synchitiotrophoblast enables the blastocyst
invertion into endetrium to enable placental
formation while cytotrophoblast forms embryonic
layers
11. DECIDUA
• Increased secreatory activity due to increase in
progesterone especially at implantation site
• Fibrous connective tissues of stroma change into
epithilliod cells called decidual cells
• Glands swell due to increase in secreatory activity
• Has 3 layers
• 1.superficial compact layer-decidual cells, gland
duct, dilated capillaries
12. Cont
• 2.intermediate spongy layer -dilated uterine glands,
decidual cells, blood vessels
• 3.basal layer -uterine muscle, basal portion of glands
After implantation the layers are renamed
1.Decidua basalis /serotina -decidua in contact with the
base of blastocyst
2.decidua Capularis/reflexia -layer covering blastocyst
3.Decidua Vera/parietalis -decidua outside site of
implantation
13. Cont
• Function
• 1.Enables blastocyst
• 2.supplies nutrition
• 3.enable deeper penetration of trophoblast
• 4.decidua basalis form basal plate of placenta
14. Chorion and chorionic villi
• At beginning of 3rd week synchitiotrophoblast produce
finger like projection called primary stem villi.
• Lacuna spaces that surround it later form inteevillous
spaces
• After apperance of primitive mesenchyme and
development of chorion, primary stem villi
• Primary mesoderm is insinuated into primary mesoderm
into central core of villi structures to form secondary villi
• The mesodermal cells form blood vessels Forming tertiary
villi
