12.5 gastration notochord etc

What is unique about oropharyngeal & cloacal membranes?

No mesoderm between ectoderm and endoderm

What are the major neural crest derivatives?

PNS + pigment + face + adrenal medulla + conotruncal septum

Neural crest gives rise to which nervous structures

• Dorsal root ganglia

• Autonomic ganglia

• Schwann cells

• Enteric nervous system

Neural crest forms what pigment cells?

Melanocytes

Neural crest forms what craniofacial structures?

Bones, cartilage, connective tissue of face

Branchial cleft cyst characteristics

• Lateral neck mass

• Does NOT move with swallowing

Thyroglossal duct cyst characteristics

• Midline neck mass

• Moves with swallowing

Where does the thyroid originate?

Foramen cecum (base of tongue)

When does thyroglossal duct normally disappear?

10th week

DiGeorge syndrome is due to defects in which pouches?

3rd and 4th pharyngeal pouches

Classic triad of DiGeorge syndrome

• Thymic hypoplasia

• Hypocalcemia

• Cardiac defects

Main mesoderm subdivisions

• Paraxial

• Intermediate

• Lateral plate

Paraxial mesoderm forms what?

Somites

Somites give rise to what?

• Vertebrae

• Ribs

• Skeletal muscle

• Dermis

Paraxial mesoderm defects cause what?

Vertebral anomalies

Remaining somites contribute to what?

Axial skeleton

Sclerotome gives rise to?

Vertebrae and ribs

Myotome gives rise to?

Skeletal muscle

Dermatome gives rise to?

Dermis

What happens in week 4 to somites?

Ventromedial cells → sclerotome (surrounds neural tube + notochord)

Epimere forms what?

Intrinsic back muscles

Hypomere forms what?

Lateral + ventral body wall + limb muscles

Lateral plate mesoderm splits into what?

• Somatic (parietal)

• Splanchnic (visceral)

What forms between somatic and splanchnic layers?

Intraembryonic coelom (future body cavities)

Somatic mesoderm lines what?

Intraembryonic cavity

Somatic mesoderm forms what?

• Dermis of body wall and limbs

• Bones and connective tissue of limbs

• Sternum

Intermediate mesoderm forms what system?

Urogenital system

Intermediate mesoderm gives rise to?

• Kidneys

• Ureters

• Gonads

• Genital ducts

Intermediate mesoderm defects cause what?

• Renal agenesis

• Genital malformations

ZPA controls what axis?

Anterior–posterior (thumb → pinky)

AER controls what axis?

Proximal–distal (shoulder → fingers)