This document summarizes the stages of human embryo and fetal development from conception through birth. It is divided into three sections: embryo development, fetal development by trimester, and specific weeks of development. The key stages of embryo development include fertilization, cleavage, gastrulation and cellular differentiation. Fetal development is broken down by the three trimesters, with the first establishing organs and the second focusing on growth and the third preparing for birth. Each week of development outlines the changes, growth and milestones occurring with the fetus.

1. EMBRYO DEVELOPMENT
BY
FARUK HOSEN
DEPT. OF FTNS, MBSTU

2. EMBRYO DEVELOPMENT
Embryo-
the stage in human development from the
first division of the zygote until about nine weeks
after fertilization.
Stages
• Fertilization
• Cleavage
• Gastrulation
• CELLULAR DIFFERENTIATION

3. HUMAN DEVELOPMENT FROM
CONCEPTION TO BIRTH IS
DIVIDED INTO THREE
TRIMESTERS
• First trimesters,
• Second trimesters,
• Third trimesters.

4. FIRST TRIMESTERS
• It’s period weeks 1-12.
• Fertilization
• Placenta & all organs begin to formed
1. Heart
2. Brain
3. Lungs
4. Eye
5. Ears
6. bone

5. FERTILIZATION
• Sperm penetrates an egg and creates a single set of 46
chromosomes called a zygote.
• The fertilized egg traveling through the fallopian tube toward
the uterus, dividing into cells ; it is called a morula. The
morula becomes a blastocyst.

6. CLEAVAGE
The term used to describe the early cell division associated with
embryonic development.
• During this time period, the number of cells increase tremendously.
• The fertilized egg traveling through the fallopian tube toward the uterus,
dividing into cells ; it is called a morula. The morula becomes a
blastocyst.

7. GASTRULATION
• Three layers
• Each layer will eventually
• form the different organ systems

8. CELLULAR DIFFERENTIATION
Due to gene expression, cells undergo
cellular differentiation, in which the
cells become increasingly specialized
in structure & function.

9. FETAL DEVELOPMENT : WEEK 1,2&3
• Heart is now beating at a steady rhythm.
• Placenta has begun to form
• Movement of rudimentary blood through the
main vessels.
• Eyes and ears are forming.
• Embryo is ¼ inch long.

10. FETAL DEVELOPMENT – WEEK 4
• Formation of the lungs, jaw,
nose, and palate begin now.
• Hand and feet buds have
webbed structures that will
become the fingers and toes.
• The brain is continuing to form.
• Detect audible heartbeat.
• Embryo is about ½ inch in length.

11. FETAL DEVELOPMENT – WEEK 5
• Every essential organ has begun to form.
• Hair and nipple follicles are forming.
• Eyelids and tongue have begun formation.
• Elbows and toes are more visible
• Trunk begins to straighten out.

12. FETAL DEVELOPMENT – WEEK 6
• Ears are continuing to form externally and internally.
• bones are beginning to form
• muscles can contract.
• Embryo is about 1 inch long.

13. FETAL DEVELOPMENT – WEEKS 7 TO 12
• At 10 weeks, the embryo is at the end of the embryonic
period and begins the fetal period.
• Fetus has grown to about 3 inches in length and weighs
about an ounce.
• Genitalia clearly formed
into male or female
• Buds for baby teeth appear.

14. SECOND TRIMESTERS
 Time 14 to 24 week
 Skin cover fetus body
 Develop sweat gland, liver, pancreas,
nervous system, heartbeat.
 Hair begin to formed
 Develop sleeping & waking cycle

15. FETALAGE – WEEKS 12 TO 14
• Fetus’s skin is transparent.
• Fine hair begins to form on the
head.
• Fingerprints developed on
fingers of the fetus.
• Sweat glands have developed,
and the liver and pancreas
produce fluid secretions.
• The fetus has reached 6
inches in length and
weighs about 4 ounces.

16. FETALAGE – WEEKS 15 TO 18
• Movements are being felt more often
by the mother.
• Eyebrows and eyelashes grow &tiny
nails have begun to grow on the
fingers and toes.
• A fetal heartbeat can be heard by a
stethoscope.
• Fetus has reached a length
of 8 inches and weighs
about 12 ounces.

17. FETALAGE – WEEKS 19 TO 21
• Skin covers the fetus’s entire body.
• Transparent while fat begins to
develop.
• All the components of the eyes are
developed.
• Liver and pancreas are working
hard to develop completely.
• Fetus has reached about 10-11
inches in length and weighs
about 1 – 1 ¼ pounds

18. FETALAGE – WEEKS 22 TO 24- BEGINNING
THE THIRD TRIMESTER
• Fetus has developed sleeping and
waking cycles.
• The fetus has a startle reflex, and the
air sacs in the lungs have begun
formation.
• The nervous system has
developed enough to
control some functions.
• Fetus has reached about
14 inches in length and
weighs about 2 ¼ pounds.

19. THIRD TRIMESTER
• Time 27 to 40 week
• Gain weight rapidly
• Bones fully developed
• Eyelids open
• Notice fetal movement
• Lanugo hair disappear from skin
• Descend head down position for
preparing birth

20. FETAL AGE – WEEKS 25 TO 30
• store fat on the body, reach about 15-17 inches long and
weigh about 4-4 ½ lbs.
• rhythmic breathing movements in lungs occur.
• Bones are fully developed, but are still soft and pliable.
• The fetus is storing its own calcium, iron and phosphorus.
• The eyelids open after being closed, since the end of
the first trimester.

21. FETALAGE – WEEKS 31 TO 34
• Fetus will descend into the head down position preparing
for birth.
• Gain weight more rapidly.
• Lanugo hair disappear from the skin, and become less
red and wrinkled.
• Fetus is 16-19 inches and weigh from 5 ¾ lbs to 6 ¾ lbs.

22. FETAL AGE – WEEKS 35 TO 38
• Fetus becomes bigger, notice a change in fetal movement.
• The fingernails have grown
• Small breast buds are present on both sexes.
• All organs are developed.
• Fetus is about 19 – 21 inches in length and weighs
anywhere from 6 ¾ lbs to 10 lbs.

23. FETAL CIRCULATION
• Umbilical Cord
• Fetal Heart Rate-
110-160 BPM
• Ductus venosus
• Ductus arteriosus
• Foramen ovale
•