GENERAL EMBRYOLOGY

1. Bones of the Pelvic Girdle
And Lower Extremity
Prof. Mohamed A. Autifi
Lecture 2

2. Prof. Mohamed A. Autifi

3. Prof. Mohamed A. Autifi

4. First weekFirst week
Prof. Mohamed A. Autifi
1
2
3
1. Fertilization
2.Segmentation (Cleavage)
3.Implantation

8. Second weekSecond week
Prof. Mohamed A. Autifi
1. Completion of implantation
2. Differentiation of trophoplast
3. Formation of bilaminar germ disc
4. Appearance of extraembryonic
mesoderm
5. Appearance of 3 cavities: Amnion-
yolk sac-extraembryonic celom

10. 3rd week3rd week
Prof. Mohamed A. Autifi
1. Development of trilaminar germ disc
(gastrulation)
2. Development of trophoblast
3. Development of intraembryonic mesoderm
4. Folding of the embryo

11. 44thth
weekweek
Prof. Mohamed A. Autifi
The embryo is about 14 inch
1.Pharyngeal arches appear: 1st
appear by 21 day
2.Limb buds appear: UL:26 days, LL: 28 days
3.Otic and lens placode appear
4.Embryo has human characters
5.The heart has tubular form and begins to beat
6.The neural tube has formed

12. 5th week5th week
Prof. Mohamed A. Autifi
1. Head grows more
than other region
2. Upper limbs
showed hand plate
3. Blood formation
starts in the liver

13. 6th week6th week
Prof. Mohamed A. Autifi
The embryo is about 12
inch
1.Head is much larger
2.Upper limb shows elbow
and wrist region and the
shows digital rays
3.Swelling of ear auricle
appear
4.The heart has 4
chambers
5.The vertebral column is
developed and visible but
is composed of cartilage

14. 7th week7th week
Prof. Mohamed A. Autifi
1. Yolk sac forms
small duct
2. Physiological
umbilical hernia is
apparent

15. 8th week8th week
Prof. Mohamed A. Autifi
The embryo is about 1.5
inch
The embryo now is called
fetus
1.The fetus now has distinct
human appearance
2.Digits appeared in hand and
feet
3.The eyelids are formed
4.Scalp vascular plexus
5.Tail disappears by the end
of the week

16. 99thth
weekweek
Prof. Mohamed A. Autifi
1. Liver is the major site of
erythropoiesis
2. Urine is formed
3. The head is about half the
size of the fetus
(50% of crown-rump length)

17. 1010thth
weekweek
Prof. Mohamed A. Autifi
The fetus is about 2.5
inches
1.Physiological umbilical hernia
is reduced
2.Finger nails are developed
3.Eyelids fused together
4.All major body organs are
formed although they are not
able to function outside the
uterus

18. 1111thth
- 12- 12thth
weeksweeks
Prof. Mohamed A. Autifi
1. Primary ossification
centers appear in long
bones and skull
2. External genitalia are
differentiated
3. Erythropoiesis starts in
spleen
4. Face has more human
looking, eyes move ventrally
and the ears are close to
the sides of the head
5. Limbs are more developed

19. 13 - 16 weeks (413 - 16 weeks (4thth
month)month)
Prof. Mohamed A. Autifi
The fetus is about 3.5 – 6 inches
1.Rapid increase in the length of the
fetus
2.Lanugo hair cover the fetus
3.Ovaries are differentiated
4.The fetus is able to swallow and
the kidneys are able to make urine.
5.Blood begins to form in the bone
marrow
6.The fetus now sleeps and awakens
7.Movement of arms, legs, head and
neck
8.The mouth is able to open and
close

20. 17-20 weeks (517-20 weeks (5thth
month)month)
Prof. Mohamed A. Autifi
The fetus is about 6.5 – 9
inches
1.It is possible to distinguish
the sex of the fetus
2.Growth of fetus slows
3.Eye brows and head hairs are
visible
4.Quickening (movement of
fetus) starts
5.Uterus is formed and vagina
begins canalization
6.The lower limb are fully
formed
7.The fetus has the reflex
ability to suck and grasp

21. 21 - 25 weeks (621 - 25 weeks (6thth
month)month)
Prof. Mohamed A. Autifi
The fetus is about 12-13 inches
1.Increase weight gain
2.The skin is wrinkled and pink to red in
color
3.The eyelids open and closed
4.Formation of surfactant to maintain
patency of the alveoli but the respiratory
system still immature
(if the fetus born it dies)

22. 26-29 weeks (726-29 weeks (7thth
month)month)
Prof. Mohamed A. Autifi
The fetus is about 13.5-14
inches
1.Eyes reopen
2.Eye lashes and eye brows are
present
3.Toe nails are visible
4.Smoothing of skin wrinkles by
subcutaneous fat
5.The skin is covered by white
cheese-like substance called vernix
caseosa
6.Erythropoiesis by spleen ends by
28 weeks then bone marrow

23. 30-34 weeks (830-34 weeks (8thth
month)month)
Prof. Mohamed A. Autifi
The fetus is about 16-19 inches
1.Pupillary light reflex developed
2.Vernix caseosa is continuous to
form a thick coat on the skin
3.Toe nails are fully formed
4.The skin is pink and smooth
5.Lanugo hair disappears from the
face but remains on the head
6.The muscle tone is developed
and the fetus can turn and left its
head

24. 35-38 weeks (935-38 weeks (9thth
month)month)
Prof. Mohamed A. Autifi
The fetus is about 19.5-20
inches
1.Circumference of head and
abdomen are equal
2.Prominent chest and the
breast protrude in both
sexes
3.Growth is slow
4.Testes are in scrotum
5.Finger nails extend beyond
the finger tips

25. At birthAt birth
- Normal weight: 3500 gm
- Normal length: 50 cm (crown-heel)
Head circumference = 12 crown-rump
length in the 3rd
month, 13 crown-rump
length in the 5rd
month and 14 crown-rump
length at birth
- Premature infant:Premature infant: born more
than 2 weeks earlier than the
expected date (1000-2500 gm)
- Postmature infantPostmature infant: born more
than 2 weeks after the expected
date
- Immature infant:Immature infant: 500-1000 gm
- Abortion means delivery of fetus
before 22 weeks
Prof. Mohamed A. Autifi

26. The End
Prof. Mohamed A. Autifi

27. Prof. Mohamed A. Autifi