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G6: Rathke's pouch. Floor of pharynx with foramen caecum (remains of thyroglossal duct), and caudally to it, the hypopharyngeal eminence. Aortic sac ventral to H-P eminence. Caudal pharynx (extending laterally, ventral to dorsal aorta - cf B4). L lungbud caudal to L atrium with attachment of pulmonary mesenchyme to septum transversum. Stomach, mesentery.
DEVELOPMENT OF THE GUT
G7: Stomach and lesser sac in mesentery. Triangular flange of mesentery with triangular hole and intervitelline anastomosis. Hindgut (without lumen) seen at caudal end of mesentery.
DEVELOPMENT OF THE MUSCULOSKELETAL SYSTEM
G7: Cervical region: dark masses of dorsal root ganglia. Lumbar region: dorsal aorta with its dorsal segmental arterial branches. Between each dorsal segmental artery is a darker-staining mass of mesenchyme (the dark part of a sclerotome) which is the anlage of the intervertebral disc. The dorsal segmenta lartery itself marks the location of the centre of the light-staining part of the sclerotome, which is the future vertebral body. The dark band dorsal to the sclerotomes is the basal lamina of the wall of the neural tube.
