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. Author manuscript; available in PMC: 2018 Jan 1.
Published in final edited form as: J Mech Behav Biomed Mater. 2016 Aug 15;65:383–397. doi: 10.1016/j.jmbbm.2016.08.010

Figure 1.

Figure 1

Forebrain development in chick embryo. (A–C) Bright-field images of extracted embryos. (A) At HH11 (dorsal view), the brain tube (BT) is divided into three primary vesicles: forebrain (F), midbrain (M) and hindbrain (H). Optic vesicles (OVs) protrude bilaterally from the forebrain. (B) By HH13, the forebrain has further divided into diencephalon (D) and the telencephalon-hypothalamus complex (T). On each side the optic stalk (OS) has also constricted to separate OVs from T. (C) By HH20, a 90 degree rotation at the level of the spinal cord (not shown) results in a lateral instead of dorsal view of the BT. All sulci persist as the BT bends and expands. Scale bars: 500 µm. (D) Schematic of forebrain development (lateral view). The notochord (nt) and caudal-rostral axis (blue-to-green gradient) of the BT are relatively straight initially. As the BT grows, the notochord and BT bend ventrally, maintaining dorsal-ventral signaling (black-to-gray gradient) along the new curvature. Together the OVs, telencephalon (tel), and hypothalamus (hy) comprise the secondary prosencephalon (SP). DMB, diencephalon-midbrain boundary sulcus (blue dashed line); AIS, anterior intraencephalic sulcus (green dashed line).