1. Embryonic Development
Exercise 46
Embryonic Development

2. Developmental stages of humans
Fertilization
Zygote
It is a fertilized egg
Diploid (2n)
Female pronuclei
Male pronuclei
Amphimixis

3. Developmental stages of humans
Zona pellucida
Surrounds the zygote
Disappears when the blastocyst reaches the uterine cavity
Corona radiata
Granulosa cells surrounding the zona pellucicda
Disappears after fertilization

4. Fertilization

5. Developmental stages of humans
Cleavage
Stages of the Cleavage
Blastomere
Early cleavage
4-cells stage…
Morula
16-32 cells stage

6. Developmental stages of humans
Blastocyst
Central cavity appears – blastocystic cavity
Inner cell mass (ICM) – forms the embryo
Trophoblast – nourishes the developing embryo
Final product of cleavage

7. Developmental stages of humans
Implantation
From day 7 to day 10 after the ovulation
The blastocyst will go from a floating stage to a complete implanted stage in the uterus
DISIDIUA BEISEILIS

8. Developmental stages of humans
Gastrulation
The ICM will develop into three primary germ layers
Ectoderm
Forms the epithelia and nervous system

9. Developmental stages of humans
Mesoderm
Forms everything between the ectoderm and the endoderm
Endoderm
Forms the mucosa of the digestive and respiratory tract, etc

10. Endometrium will form the deciduas
Deciduas basalis-part of the endometrium beneath the ICM. It will form the maternal portion of the placenta
Deciduas capsularis – it is the rest of the endometrium surrounding the blastocyst.

11. Developmental stages

12. Developmental stages of humans
Embryo
Until the 8th week
Fetus
From 8th week to birth
Trophoblast
Will develop villi
Will differentiate into the chorion that will form the fetal portion of the placenta

13. Developmental stages of humans
Placenta
Chorionic villi + decidua basalis
Embryonic membranes (from the ICM)
Amnion
Encases the embryo
Amniotic cavity
Amniotic fluid

14. Developmental stages

15. Developmental stages of humans
Yolk sac
Originates the embryo’s first blood cells
Allantois
Body stalk and later umbilical cord
Umbilical cord attaches the embryo to the placenta

16. In uterus development Placenta Fetal side Shine and smooth
Presence of large blood vessels
Maternal side
Spongy, torn-looking, rough