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  1. 1. Elaine Frances Corpuz
  2. 2. Prenatal Development Embryonic period Fetal Period Fertilization – 8 weeks 9 weeks - birth
  3. 3. Embryonic Development in Days
  4. 4. Third Week of Development: Trilaminar Germ Disc Gastrulation - process that establishes all three germ layers (ectoderm, mesoderm, and endoderm) in the embryo.
  5. 5. 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
  6. 6. 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
  7. 7. 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.
  8. 8. Gastrulation
  9. 9. 16 days old
  10. 10. 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
  11. 11. • 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).
  12. 12. • 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
  13. 13. Clinical correlates • Holoprosencephaly
  14. 14. Clinical correlates • Caudal dysgenesis (sirenomelia)
  15. 15. Clinical correlates • Situs inversus
  16. 16. Clinical correlates • Sacrococcygeal teratoma
  17. 17. 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.
  18. 18. 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
  19. 19. Folding of the Embryo
  20. 20. Carnegie Stages of Human Development
  21. 21. 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
  22. 22. Carnegie Stages Stage 1 Stage 2 Stage 3
  23. 23. Stage 4 Stage 5 Stage 6 Stage 7
  24. 24. 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
  25. 25. 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.
  26. 26. 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.
  27. 27. 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.
  28. 28. 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.
  29. 29. 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.
  30. 30. 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.
  31. 31. 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.
  32. 32. 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.
  33. 33. 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.
  34. 34. 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.
  35. 35. 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.
  36. 36. 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.
  37. 37. 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.
  38. 38. 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.
  39. 39. Estimation of Embryonic Age Crown-rump length (CRL) – sitting height Crown-heel length (CHL) – standing height
  40. 40. Fetal Period: Third Month to Birth
  41. 41. Fetal Period: Third Month to Birth
  42. 42. Fetal Period: Third Month to Birth
  43. 43. 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
  44. 44. 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)
  45. 45. Fetal Period: Third Month to Birth 4 months baby
  46. 46. 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
  47. 47. Fetal Period: Third Month to Birth Sixth months baby
  48. 48. 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
  49. 49. Birth • The date of birth is most accurately indicated as 266 days, or 38 weeks, after fertilization.
  50. 50. From Conception to Birth...

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