Ectoderm, Endoderm, Mesoderm Derivatives

Organogenesis

Establishment of organ systems

Ectoderm

Derivatives of this maintain contact with the outside world; central nervous system, peripheral nervous system, sensory epithelium of ear/nose/eye, epidermis/hair/nails, mammary/pituitary/subcutaneous glands

Neural Crest Cells

Migratory cell populations from neural folds (neuroectoderm)

Treacher Collins Syndrome, DiGeorge Anomaly, Robin Sequence, Hemifacial Macrosomia

Cranio-Facial Defects from neural crest errors

Neuralation

Results from notochord formation Days 16-28

Neural Plate

Structure induced by notochord and prechordal mesoderm

BMP4 (Bone Morphogenic Protein 4)

Ventralizing protein; high results in epidermis, medium results in neural crest, low results in neural plate

Neural Fold

Elevation of lateral proteins of the neural plate around Day 20

Forebrain, Midbrain, Hindbrain (Proencephalon, Mesencephalon, Rhombencephalon)

Parts of brain formed in development

Somites

Form from paraxial mesoderm - will become vertebrae

Anencephaly

Failure of cranial neuropore closing; missing brain elements

Spina Bifida

Failure of caudal neuropore closing; neural tissue/meninges protrusions

Folic Acid

Prevents Spina Bifida/neuropore closure defects during pregnancy

Hox Genes

Patterns the body plan along anteroposterior axis

Retinoic acid

Modulates Hox gene expression

Endoderm

Derivatives of which result in GI Tract, Respiratory Tract, Urinary Bladder, Auditory Tube, Liver, Pancreas, Cloaca

Cephalocaudal folding

Promotes endoderm-lined cavity in embryo body around Day 17-22

Allantois

Invagination of the hindgut surrounded by mesoderm of the connecting stalk

Somatic mesoderm

Encloses embryo

Splanchic mesoderm

Encloses gut/yolk sac

Vitelline duct

Midgut connection with yolk sac; intestines develop here until 10 weeks

Ectopia Cardis

Outside heart from not closing ventral body wall

Bladder Extrophy

Failure of pelvic region to close

Gastroschisis

Herniation of intestines through abdominal wall

Respiratory diverticulum

Lungs develop from these; outgrowth from ventral wall of foregut at ~4 weeks

Tracheoesophageal septum

Divides foregut into dorsal esophagus and ventral trachea, lung bud

Paraxial mesoderm

Medial thickened portion of mesoderm; becomes the somite

Somitomeres

Organized structure of paraxial mesodermal cells arranged in concentric whorls, craniocaudal

Sclerotome

Somite - Forms ribs, vertebrae, rib cartilage

Myotome

Somite - Forms muscles of back/body wall

Dermatome

Somite - Forms dermis of back

Ventrolateral cells

Somite - Forms musculature for body wall and limbs

Epithelialization

Balls of somatic mesoderm undergo this process of forming circular shape around small lumen in each somite

Pharyngeal Arches

Derived from paraxial mesoderm and neural crest cells - associated with aortic arches, contribute to face, neck, mouth, laryx, pharynx

Pharyngeal clefts/grooves

Derived from ectoderm, found between arches externally

Pharyngeal pouches

Endodermal, outpocketings of the pharyngeal gut

Intermediate mesoderm

Mesoderm that develops into the urogenital system

1 - pronephric, 2 - mesonephric, 3 - metanephric; 3

Name the three overlapping kidney systems. Which one is permanent?

Lateral Plate

Mesodermal structure that becomes heart, blood vessels, body wall

Primordial germ cells

Made from epiblast, move into yolk sac wall for genital system, then into genital ridges

Intraembryonic coelom

Lateral plate cavities

Somatic (parietal) mesoderm

Mesoderm that lines the intraembryonic cavity - some blood vessels, core of villi, chorionic plate

Splanchnic (visceral) mesoderm

Mesoderm for heart formation

Endocardium

Originating blood vessel that contributes to heart formation

Myocardium

Mesoderm outside of endocardium

Cardiac jelly

Substance surrounding endocardial tube

Pericardial cavity

Space surrounding endocardial tube

Angiogenic cell clusters

Form blood vessels ~ 3 weeks

Vasculogenesis

De novo formation of endothelial tubes

Hemangioblasts

Mesodermal cell subpopulations of blood cell/endothelial cell precursors

FGF2

Signals proliferation of hemangioblasts from mesoderm

VEGF; VEGFR2

Differentiate and center hematopoietic cells and outside angioblasts to blood islands

VEGFR1

Forms blood and endothelial cells

Angiogenesis

Sprouting of tubes off of existing blood vessels

Capillary hemangiomas

Incorrect blood vessel formation

Bone marrow

Definitive blood cell originating site ~7 mo

Aorta-gonad-mesonephros region

Early developmental blood cell originating site week 3-~2 mos; colonizes liver

Crown-rump length

After 1st mo, development indicator

Limb buds

Outpocketings from ventrolateral body wall with mesenchymal core and a covering of cuboidal ectoderm

Apoptosis

Allows for cell death and digit formation at apical ectodermal ridge

Syndactyly

Fusion of digits