UNSW Embryology

B1: Developing diencephalon. Rathke's pouch. Lens pit (arrowed, derived from lens placode).

B2: Optic cup with optic ventricle. Note unequal thickness of walls of optic cup (inner wall; sensory retina: outer wall; pigment epithelium). Lens pit. Note position of eye with respect to maxillary arch. Hyaloid vessels near ventral margin of optic cup.

B2: Optic ventricle inner wall; sensory retina: outer wall; pigment epithelium

B4: Junction of optic stalk to wall of prosencephalon (diencephalon). Note small branches of hyaloid blood vessels in region between lens pit and optic stalk.

B5: Continuity of optic ventricle and single forebrain ventricle via optic stalk. Note proximity of eye to nasal placode (R).

B6: Hyaloid vessels ventral to optic stalk. Optic mesenchyme (mesectoderm) arising directly from epithelium of dorsal surface of optic cup. Nasal placodes.

B7: Tangential section through optic cup, with surrounding optic mesenchyme. Nasal placode Interorbital ligament. Bridge of nose.

Al: Thin caudolateral walls of rhombencephalon.

A2: Otocyst (R). Apex of otocyst (primordium of L endolymphatic sac).

A3: Otocyst; surrounding mesenchyme = otic capsule. Note proximity of otocyst to wall of rhombencephalon. Superior glossopharyngeal ganglion. Vestibulo-cochlear-facial ganglion complex (R). Trigeminal ganglion (not in image excerpt).

A4: Indentation in rostral margin of otocyst = primordium of utriculosaccular canal. Note alignment of superior cardinal vein (LS) in relation to the nerve trunks (XS). Trigeminal ganglion (not in image excerpt). Note variation in height of cells of L otocyst wall. Dorsal end of 1st pharyngeal arch and groove (not in image excerpt).

A5: Facial ganglion (R). "Floor" of L otocyst. Note on R, the former position of the otocyst in relation to the 2nd pharyngeal arch.

A6: 1st, 2nd arches, grooves and pouches on R. Inferior glossopharyngeal and facial ganglia on left.

A7: 1st pharyngeal pouch opening into pharynx.

B1: 1st pharyngeal pouch opening into pharynx.

B5: Nasal placode, note its proximity to the eye. Note the large number of blood vessels lying in the mesenchyme directly beneath the placode.

(due to the slightly oblique sectioning R/L levels do not correspond)

B6: Nasal placodes. Note the lateral and medial portions of a single placode. At this stage of development the placodes are mainly on the lateral aspect of the head region.

B7: Nasal placode (arrowed) compare the thickness of the placode region with the other regions of the embryo ectoderm.

C1-C7: Nasal placodes (nasal pit forming on one side).

Forebrain. note proximity of nasal pit to prosencephalon (future site of olfactory nerve).

C2-C4: Identify the medial and lateral nasal swellings.

See Movie of Nose (sections B5-C4, 220 Kb)