3th Week-GastrulationPrimitive Node and Streak

(16 DAY)• Ectoderm• Mesoderm• Endoderm

• Prochordal plate,Notochord,Primitive NodeNeuroctoderm

EMBRYONIC PERIODORGANOGENESIS

SOHRABI

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Neurolation,Ectoderm

• Central Nervous System• Peripheral Nervous System• Neuroepithelium(Eyes.Ears,Nose)• Epidermis,Hair,Nail• Glands(Mammary G.Sweat G.Hypophysis)• Enamel• Derivities of NCC

Neurolation,Ectodermm• Derivities of NCC:• Ganglions(Cranial,Spinal,Autonome)• Medula of Adrenal G.• Melanocytes• Odontoblasts• Smooth muscles in vessels of face and forebrain• Meninges of forebrain• Glial cells,Schwan cells• C cells of thyroid G.• Connective tissue(Dermis) of face and neck• Heart(trunco conus cuhsion)

04/19/236

Neurulation

The Events of Neurulation • Neural ectoderm

thickens • Neural folds form

producing Neural Groove

• Neural folds contact

• Cells rearrange forming Neural Tube with overlying Ectoderm

Cell Lineages At Neurula Stage

Hensen’s Node Induces Neural Axis

• this special region of tissue has been shown to establish the vertebrate body plan in everything from frogs to zebra fish to mice

• the node is an embryonic organizer in mammals– the mammalian node is not a classic organizer

because it can't act alone to induce the embryonic axis but requires other anterior germ tissues to be fully effective

• Thus progressive cellular interactions are more important rather than a single inductive event

3th,4thWeek-Neurolation

• Neural Folds(20 DAY)• Neural Groove(20 DAY)• Neural Crest,BMP4• Neural Tube(27 day)• Cranial and Caudal Neuropores(25 day,27 day)• Brain Vesicles,Spinal Cord• Otic Placodes(28 day)• Otic Vesicles• Lens Placodes

3th Week-NeurolationNeural Plate(19 DAY)

• Neuroctoderm(Forebrain,Midbrain), FGF Chordin,Noggin,Folistatin BMP4

• Neuroctoderm(Hindbrain), FGF,WNT-3a

• Ectoderm,Epiderm,BMP4• Ventral Mesoderm(Intermediate and Latral),BMP4• Dorsal

Mesoderm(Paraxial),Chordin,Noggin ,Folistatin

4th week,Mesoderm

• Paraxial Mesoderm(17 DAY)• Latral Plate: (19 DAY) Intermediate M.(20 DAY) Latral M. : (21 DAY)• Somatic or Parietal M.• Splanchnic or Visceral M.

4th week,Intermediate M. Latral M.

Intermediate M. :• Nephrotome• Nephrogenic Cord Urogenital System(kidneys,gonads, urinary

bladder)+Spleen,Cortex of Adrenal G.• Somatic M. +Ectoderm Latral and Ventral Wall• Splanchnic M. + Endoderm Digestive tube

4th ,5th week,Paraxial M.• WNT,Notch Cyclic genes Forming Gens(FGF8-,

RA+)• Somitomers• Somites: (20 DAY to 35 DAY)• 4 ,postcranial• 8,neck• 12 thoracic• 5,lumbar• 5,sacral• 8-10,coxygeal

4th week,Paraxial M.Somite:Cartilage,Bone,Muscle,C. T. of DermSclerotome,Noggin,SHH PAX1Myotome,WNT PAX3 MYF5WNT+BMP4,FGF MYODDermatome,WNT PAX3 NT-3

3th WeekBlood & Blood Vessels

• VEGF • Splanchnic M.(Yolk Sac)+ Intermediate M.(AGM)

(Liver,Bone Marrow) (HOXB5 FLK1)• Hemangioblasts, Blood Islets:Hematopoietic Stem Cells(Blood)Angioblasts, VEGF(Endothelium)Vasculogenesis, VEGF,PDGF,TGFbAngiogenesis, VEGF Arteris,Veins, Lymphatics

3th WeekBlood & Blood Vessels

• Arteris,Veins, Lymphatics:• Notochord,SHH VEGF(Notch) Ephrin

b2(EPH) Artery,Vein

• Notochord,SHH VEGF(Notch) Eephrin b4(EPH) Vein

• PROX1 Lymphatics

Capillary Hemangioma

• Infants• 10%• Focal.Diffuse• IGF2• VEGF?

3th WeekBlood & Blood Vessels

• VEGF • Splanchnic M.(Yolk Sac)+ Intermediate M.(AGM)

(Liver,Bone Marrow) (HOXB5 FLK1)• Hemangioblasts, Blood Islets:Hematopoietic Stem Cells(Blood)Angioblasts, VEGF(Endothelium)Vasculogenesis, VEGF,PDGF,TGFbAngiogenesis, VEGF Arteris,Veins, Lymphatics

3th WeekBlood & Blood Vessels

• Arteris,Veins, Lymphatics:• Notochord,SHH VEGF(Notch) Ephrin

b2(EPH) Artery,Vein

• Notochord,SHH VEGF(Notch) Eephrin b4(EPH) Vein

• PROX1 Lymphatics

Capillary Hemangioma

• Infants• 10%• Focal.Diffuse• IGF2• VEGF?

Embryo consists of all primary germ layers Development continues to form tissues & organs As the neural tube is forming,the somites are forming & the embryo is elongating & flexing

4th Week, Endoderm

Brain Vesicle growth• Craniocaudal Folding (Cranial folding, Caudal

Folding)• Foregut• Hindgut• Midgut+Vitelline duct• Buccopharyngeal rupture(4th week)• Cloacal rupture(7th week)

4th Week, Endoderm

Somites formation• Latral Folding• Latral and Ventral Wall• Vitelline Duct(2nd Month in chorion cavity,3rd

Month,Close)• Cloaca

4th Week, Endoderm

• Endoderm Epithelium:• Primary gut• Vitteline duct• Allantois• Auditory duct,Tympanic cavity,Respiratory duct,

urinary bladder,urethra,Thyroid,Parathyroid,Liver and Pancreas paranchyma,Thymus and Tonsils stroma

Folding of the germinal disk (4th week)

Characteristic signs:

External acoustic meatus

The circumference of the head increases

The trunk lengthens

Fusion of the 6 auricular hillocks

Atrophy of the embryonic tail

Formation of the interdigital zones

Stage 17Approx. 41rst day

11 - 14 mm

THE END