Embryology

Absence of part of a limb

Absence of one or more limbs

Extra digits

Webbing between digits

Short, poorly formed limb

Axial skelton (Schlerotome), skeletal muscles (Myotome), dermis (Dermatome)

Urogenital system

Somatic = lining of body cavities, long bones, connective tissue of body wall
Splanchnic = smooth muscle of G.I. system and serosa lining on organs

Hypomere

Epimere

Apical Ectodermal Ridge

Shunt near arch of aorta to keep blood away from lungs; eventually becomes ligamentum arteriosum

Begins week 3

Beginning of Week 4

Splanchnic mesoderm

Endocardial heart tubes

Transverse (Lateral) folding

Brings heart into region of thorax

Creates intraembryonic coelom

Future pericardial cavity

Myocardial (outer muscle layer) and cardiac jelly (thick, inner gelatinous matrix)

Sinus venosus, Atrium, Ventricle, Bulbis cordis, Truncus arteriosus, aortic arches

Inflow region from:
Common Cardinal veins (body)
Umbilical veins (placenta)
Vitelline veins (Yolk sac)
Right sinus venosus persists as sinus venarum (smooth part of right atrium)
Left sinus venosus persists as coronary sinus

Outflow region:
Dorsal aortae

Bulbus cordis and ventricle enlarge and move down and to the right, which brings atrium and sinus venous up

Heart abnormally positioned on right side of thorax and is associated with other severe cardiac anomalies (transposition of great arteries) because the heart loops to the left instead of the right when folding

Organs on wrong side of body

Endocardial cushions close the atrioventricular canal

Partial partition before birth; functionally complete at birth

Grows from roof of atrium down toward endocardial cushions; ostium primum is opening between septum primum and cushions

Grows from roof of atrium immediately to the right of septum primum; gradually overlaps septum primum

Shunts blood from right atrium to left atrium before birth

Embryological remnant of heart development; closed foramen ovale; adherence of septum primum to septum secundum

Incomplete fusion of septum primum and septum secundum

Forms pericardial, pleural, and peritoneal cavities

Mostly maintained; Persists as greater omentum and mesentery proper of jejunum and ileum; Provides route for BV, nerves, lymphatics to reach gut

Mostly regresses making peritoneal cavity a continuous space; Persists as lesser omentum; Persists as falciform ligament

Pleuroperitoneal folds and pleuropericardial folds

Sheet of somatic mesoderm that separates pericardial and pleural cavities; forms fibrous pericardium

Forms from somatic mesoderm; forms part of diaphragm

Septum transversum (central tendon); Pleuroperitoneal folds; Dorsal mesentary of esophagus (crura); Body wall myoblasts (muscle around central tendon)

Formed from paraxial mesoderm; several of more rostral (occipital) somites and large # of coccygeal disappear; most caudal occipital somite contributes to first cervical vertebra

Failure of posterior neuropore to close; oculta and cystica

Absence of portion of vertebral body, covered by skin

Meninges and/or spinal cord protrude through skin

Undifferentiated connective tissue

Apical ectodermal ridge

Meninges (not dura)
C cells of thyroid
Pigment cells of skin
Medulla of adrenal gland
Conotruncal region of heart
Connective tissue, some bone, dermis of head and neck
Schwann cells
Glial cells
Spinal, autonomic, and cranial nerve ganglia

Inner cell mass

Outer cell mass

HCG

Amniotic cavity

Primitive yolk sac (exocoelomic membrane); then secondary (definitive) yolk sac

Layer formed between exocoelomic membrane and cytotrophoblast layer

Extraembryonic mesoderm