3th Week-Gastrulation Primitive Node and Streak (16 DAY) Ectoderm Mesoderm Endoderm Prochordal plate,Notochord,Primitive Node Neuroctoderm

EMBRYONIC PERIOD ORGANOGENESIS SOHRABI 17/آوريل/23

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)

Neurulation 4/23/2017

The Events of Neurulation Neural ectoderm thickens Neural folds form producing Neural Groove Neural folds contact Cells rearrange forming Neural Tube with overlying Ectoderm While the neural tube is forming, other embryonic tissues are undergoing changes too as the embryo itself is elongating. The following gives an idea of some of these changes and, more importantly, sets the stage for some of the developmental processes (e.g., limb formation) that we will cover in future lectures. . Note that as the neural tube is forming, many other events are occuring as well. The somites are forming and the embryo is elongating and flexing.

Cell Lineages At Neurula Stage In the previous lecture on gastrulation, the role of the node (Hensen's Node) in organizing the overall body plan was discussed briefly. Historically, this special region of tissue has been shown to establish the vertebrate body plan in everything from frogs to zebra fish to mice (Nieto, 1999. Cell 98:417-425).  Experimentally this organizing ability is shown by the ability of transplanted nodal tissue to induce a second embryonic axis as revealed in the next diagram.

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 In the previous lecture on gastrulation, the role of the node (Hensen's Node) in organizing the overall body plan was discussed briefly. Historically, this special region of tissue has been shown to establish the vertebrate body plan in everything from frogs to zebra fish to mice (Nieto, 1999. Cell 98:417-425).  Experimentally this organizing ability is shown by the ability of transplanted nodal tissue to induce a second embryonic axis as revealed in the next diagram.

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-Neurolation Neural 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. 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 Derm Sclerotome,Noggin,SHH PAX1 Myotome,WNT PAX3 MYF5 WNT+BMP4,FGF MYOD Dermatome,WNT PAX3 NT-3

3th Week Blood & 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,TGFb Angiogenesis, VEGF Arteris,Veins, Lymphatics

3th Week Blood & 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 Week Blood & 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,TGFb Angiogenesis, VEGF Arteris,Veins, Lymphatics

3th Week Blood & 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?

As the neural tube is forming, the somites are forming 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)

Stage 7 Approx. 19th day: Dorsal view 0.4 mm Characteristic signs: Mesoblast immigration Notochordal process Neural plate Genesis of the blood vessel system and formation of blood

Stage 8 Approx. 23th day 0.5 - 1.5 mm Characteristic signs: Pear shaped embryo Axial process Neurenteric canal

Characteristic signs: Embryo with somites (1-3 somites) Pharyngeal membrane Neural groove Caudal eminence Intraembryonic coelom Cardiac primordium, septum transversum Placode and auditory pit Stage 9 Approx. 25th day 1.5 - 2.5 mm

2 - 3.5 mm Approx. 28th day Stage 10a, 10b Characteristic signs: Lateral folding Closure of the neural groove into a neural tube The 2 first pharyngeal arches appear Ophthalmic vesicle Rupture of the pharyngeal membrane 4 - 12 somites Stage 10a, 10b Approx. 28th day 2 - 3.5 mm

Characteristic signs: Closure of the rostral neuropore Nasal placode Ophthalmic vesicle Auditory pit 13 – 20 somites Stage 11 Approx. 29th day 2.5 - 4.5 mm

Stage 12 Approx. 30th day 3 - 5 mm Characteristic signs: Closure of the caudal neuropore Third pharyngeal arch Buds of the upper extremities Cervical sinus 21–29 somites

Characteristic signs: Buds of the lower extremities Lens placode Auditory pit Fourth pharyngeal arch More than 30 somites Stage 13 Approx. 32th day 4 - 6 mm

Characteristic signs: Opthalmic vesicle Genesis of the endolymphatic canal Augmented cephalo-cervical flexure Cerebellar primordium Visible ocular primordium Sixth pharyngeal arch Stage 14 Approx. 33th day 5 - 7 mm

Stage 15 Approx. 36th day 7 - 9 mm Characteristic signs: Lens vesicle covered with the ectoderm Auditory primordium Genesis of the hand plate

Characteristic signs: Deep, ventrally lying nasal pit Pigmentation of the eye Genesis of the foot plate Physiologic umbilical hernia Stage 16 Approx. 39th day 8 - 11 mm

Stage 17 Approx. 41rst day 11 - 14 mm 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

Characteristic signs: Toe primordium Nasal primordium The elbow joint forms Gonadal gender can be determined in male embryos Stage 18 Approx. 44th day 13 - 17 mm

Characteristic signs: Lengthening and straightening of the torso Appearance of the external acoustic meatus Genesis of the hip and knee joints Atrophied embryonic tail Rupture of the cloacal membrane Stage 19 Approx. 46th day 16 - 18 mm

Characteristic signs: Arms in pronation Separated fingers Gonadal gender determinable in female embryos Stage 20 Approx. 49th day 18 - 22 mm

Stage 21 Approx. 51rst day 22 - 24 mm Characteristic signs: Subcutaneous vessel network of the head spreads out Hands and feet come closer and touch each other

Characteristic signs: Development of the eyelids and the external ear canal Tragus and antitragus Nasal septum Stage 22 Approx. 53rd day 23 - 28 mm

Characteristic signs: Angle between the head and trunk amounts to 30° The head makes 50% of the embryo's size The head is rounded, the extremities lengthened and stand out from the body Chin Nasal pit Development of the external genital primordium Stage 23 Approx. 56th day 27 - 31 mm

THE END