Fig. 7.

(A,B) Human embryo GI-4 (26.5 mm CR; O'Rahilly's stage 22). Frontal sections. (C) Diagrammatic sketch of the arrangement of the structures in O'Rahilly's stage 22. The anlage of the stapedial base (SB) is enclosed by the otic capsule (OC). The medial surface of the stapedial base (SB) is adjacent to the mesenchymal layer (ML), which is continuous with the otic capsule. The stapedial muscle (SM) is attached to the vertex of the angulation of the interhyale (I). The cranial end of Reichert's cartilage (R) is continuous with the otic capsule (OC). Incus (IN). Facial nerve (F). Stapes (ST).