1. Elaine Frances Corpuz

2. Prenatal Development
Embryonic period
Fetal Period
Fertilization – 8
weeks
9 weeks - birth

3. Embryonic Development in
Days

5. Third Week of Development: Trilaminar
Germ Disc
Gastrulation - process that establishes all three germ layers
(ectoderm, mesoderm, and endoderm) in the embryo.

6. GERM LAYER DERIVATIVES
• Embryonic ectoderm
• Epidermis, hairs and nails
• Central and Peripheral
nervous systems
• Sensory epithelia of eye,
ears, nose
• Neural crest cells (spinal,
cranial, autonomic
ganglia)
• Many connective tissues
of the head
• Mammary glands
• Pituitary gland
• Subcutaneous glands
• Enamel of teeth

7. GERM LAYER DERIVATIVES
• Embryonic endoderm
• Epithelial lining of the gastrointestinal and
respiratory tracts
• Parenchyma of the tonsils, thyroid and
parathyroid glands, thymus, liver, and
pancreas
• Epithelial lining of the urinary bladder and
most of the urethra
• Epithelial lining of the tympanic cavity,
tympanic antrum, and pharyngotympanic
(auditory) tube

8. GERM LAYER DERIVATIVES
• Embryonic mesoderm
• Skeletal muscles
• Blood cells and the lining of blood vessels
• All visceral smooth muscular coats
• Serosal linings of all body cavities
• Ducts and organs of the reproductive and
excretory systems, and most of the
cardiovascular system.
• Connective tissues, including cartilage, bones,
tendons, ligaments, dermis, and stroma of
internal organs.

10. Gastrulation

12. 16 days old

14. Establishment of Body Axes
• Fibroblast growth factor 8 (FGF8) – control cell
migration and specification
• Anterior visceral endoderm (AVE) – expresses genes
essential for head formation (TFs: OTX2, LIM1, and
HESX1)
• Cerberus and Lefty – inhibit nodal activity in the cranial
end of the embryo

15. • Nodal [transforming growth factor-β (TGF-β)] – upregulates
genes responsible for formation of dorsal and ventral
mesoderm and head and tail structures; initiate and
maintain primitive streak
• Bone morphogenetic protein 4 (BMP4) – in the presence of
this protein and FGF, the mesoderm will be ventralized to
contribute to kidneys (intermediate mesoderm), blood, and
body wall mesoderm (lateral plate mesoderm).

16. • HNF-3b – maintains the node and later induces regional
specificity in the forebrain and midbrain areas; without it,
embryos fail to gastrulate properly and lack forebrain and
midbrain structures.
• Brachyury (T) gene – controls regulation of dorsal
mesoderm formation in middle and caudal regions of the
embryo

18. Clinical correlates
• Holoprosencephaly

19. Clinical correlates
• Caudal dysgenesis (sirenomelia)

20. Clinical correlates
• Situs inversus

21. Clinical correlates
• Sacrococcygeal teratoma

22. Organogenetic Period: Fourth to
Eighth Weeks
• All major external and internal structures are established
during the fourth to eighth weeks.
• The main organ systems have begun to develop; however,
the function of most of them is minimal except for the
cardiovascular system.
• By the eighth week, it has a distinctly human appearance.

23. Phases of Embryonic
Development
• Growth – cell division
• Morphogenesis – development of shape, size or features
of particular organ or part or whole of the body
• Differentiation – maturation of physiologic processes

25. Folding of the Embryo

26. Carnegie Stages of Human
Development

27. Carnegie Stages of Human
Development
Carnegie Stage
Week
1-4
5-6
7-9
10 - 13
14 - 15
16 - 17
18 - 19
20 - 23
1
2
3
4
5
6
7
8

28. Carnegie Stages
Stage 1
Stage 2
Stage 3

29. Stage 4
Stage 5
Stage 6
Stage 7

30. Stage 8
Age (days) – 17- 19
days
Length – 1 – 1.5 mm
Characteristic signs:
• Mesoblast
immigration
• Chordal process
• Neural plate
• Genesis of the
blood vessel
system and
formation of
blood
Age (days) – 19 – 21 days
Length – 1.5 – 2.5 mm
Characteristic signs:
• Flat embryonic disc. Deep neural groove and
prominent neural folds. One to three pairs of
somites present. Head fold evident.
Stage
9

31. Carnegie Stage 10 (Fourth Week)
Age (days) – 22- 23
No. of Somites – 4 – 12
Length – 1 – 3.5 mm
Main External Characteristics
• Embryo straight or slightly
curved.
• Neural tube forming or
formed opposite somites
• First and second pairs of
pharyngeal arches visible.

32. Carnegie Stage 11 (Fourth Week)
Age (days) – 24 - 25
No. of Somites – 13 - 20
Length – 2.5 - 4.5 mm
Main External Characteristics
• Embryo curved owing to
head and tail folds.
• Rostral neuropore closing.
• Otic placodes present.
• Optic vesicles formed.

33. Carnegie Stage 12 (Fourth Week)
Age (days) – 26 - 27
No. of Somites – 21 - 29
Length – 3 - 5 mm
Main External Characteristics
• Upper limb buds appear.
• Rostral neuropore closed.
• Caudal neuropore closing.
• Three pairs of pharyngeal
arches visible.
• Heart prominence distinct.
• Otic pits present.

34. Carnegie Stage 13 (Fourth Week)
Age (days) – 28 - 30
No. of Somites – 30 - 35
Length – 4 - 6 mm
Main External Characteristics
•
•
•
•
•
•
•
•
Embryo has C-shaped curve.
Caudal neuropore closed.
Upper limb buds are flipper-like.
Four pairs of pharyngeal arches
visible.
Lower limb buds appear.
Otic vesicles present.
Lens placodes distinct.
Tail-like caudal eminence present.

35. Carnegie Stage 14 (Fifth Week)
Age (days) – 31 - 32
Length – 5 - 7 mm
Main External Characteristics
• Upper limbs are paddle
shaped.
• Lens pits and nasal pits
visible.
• Optic cups present.

36. Carnegie Stage 15 (Fifth Week)
Age (days) – 31 - 32
Length – 5 - 7 mm
Main External Characteristics
• Handplates formed; digital
rays visible.
• Lens vesicles present.
• Nasal pits prominent.
• Lower limbs are paddle
shaped.
• Cervical sinuses visible.

37. Carnegie Stage 16 (Sixth Week)
Age (days) – 37 - 40
Length – 8 - 11 mm
Main External Characteristics
• Footplates formed.
• Pigment visible in retina.
• Auricular hillocks
developing.

38. Carnegie Stage 17 (Sixth Week)
Age (days) – 41 - 43
Length – 11 - 14 mm
Main External Characteristics
• Digital rays clearly visible in
handplates.
• Auricular hillocks outline
future auricle of external
ear.
• Trunk beginning to
straighten.
• Cerebral vesicles prominent.

39. Carnegie Stage 18 (Seventh Week)
Age (days) – 44 - 46
Length – 13 - 17 mm
Main External Characteristics
• Digital rays clearly visible
in footplates.
• Elbow region visible.
• Eyelids forming.
• Notches between the
digital rays in the hands.
• Nipples visible.

40. Carnegie Stage 19 (Seventh Week)
Age (days) – 47 - 48
Length – 16 - 18 mm
Main External Characteristics
• Limbs extend ventrally.
• Trunk elongating and
straightening.
• Midgut herniation
prominent.

41. Carnegie Stage 20 (Eighth Week)
Age (days) – 49 - 51
Length – 18 – 22 mm
Main External Characteristics
• Upper limbs longer and
bent at elbows.
• Fingers distinct but
webbed.
• Notches between the
digital rays in the feet.
• Scalp vascular plexus
appears.

42. Carnegie Stage 21 (Eighth Week)
Age (days) – 54 - 55
Length – 23 – 28 mm
Main External Characteristics
• Hands and feet approach
each other.
• Fingers are free and
longer.
• Toes distinct but webbed.

43. Carnegie Stage 22 (Eighth Week)
Age (days) – 52 - 53
Length – 22 – 24 mm
Main External Characteristics
• Toes free and longer.
• Eyelids and auricles of
external ears more
developed.

44. Carnegie Stage 23 (Eighth Week)
Age (days) – 56
Length – 27 – 31 mm
Main External Characteristics
• Head more rounded and
shows human
characteristics.
• External genitalia still
have sexless appearance.
• Distinct bulge still present
in umbilical cord
• Caudal eminence ("tail")
has disappeared.

47. Estimation of Embryonic Age
Crown-rump length (CRL) – sitting height
Crown-heel length (CHL) – standing height

48. Fetal Period: Third Month to Birth

49. Fetal Period: Third Month to Birth

50. Fetal Period: Third Month to Birth

51. Fetal Period: Third Month to Birth
Third Month
•
•
•
•
Face become more human looking
Eyes move to the ventral aspect of face
Eyes come to lie at the side of the head
Upper limbs reach relative length but lower limbs are still not
so developed
• Primary ossification centers appear in the skeleteon (cranium
and long bones)
• Intestines have returned to the abdomen

52. Fetal Period: Third Month to Birth
Fourth and Fifth Month
• Lengthens rapidly (CRL is about half the total length)
• Covered with fine hair (lanugo hair); eyebrows and head hair are
visible
• Slow eye movements occur (14 weeks)
• Movements of the fetus can be felt by the mother
• Sex of the fetus can be recognized (12 – 14 weeks)
• Ovaries are differentiated and contain primordial follicles (16wks)

53. Fetal Period: Third Month to Birth
4 months baby

54. Fetal Period: Third Month to Birth
Sixth and Seventh Month
•
•
•
•
•
The skin becomes reddish and has wrinkled appearance
Rapid eye movements begin and blink-startle responses
Fingernails are present and toenails become visible
Eyelids are open at 26 weeks and lanugo hair are well-developed
Subcutaneous fat is present under the skin, smoothing out
wrinkles
• Lungs and pulmonary vasculature have developed sufficiently to
provide adequate gas exchange; CNS has matured

55. Fetal Period: Third Month to Birth
Sixth months baby

56. Fetal Period: Third Month to Birth
Eighth and Ninth Month
•
•
•
•
•
•
•
•
Pupillary light reflex of the eyes can be elicited
Skin is pink and smooth; limbs have chubby appearance
Quantity of white fat is approximately 8% of body weight
Have firm grasp and spontaneous orientation to light
Nervous system is sufficiently mature
Most fetus are plump
Fetal foot is slightly larger than femoral length
There is slowing of growth as the time of birth approaches

57. Birth
• The date of birth is most accurately indicated as 266
days, or 38 weeks, after fertilization.

58. From Conception to
Birth...