PeriFIG 4: Hemicentin tracks in the head.

A. Graphic representation of the left lateral hemicentin tracks (tendons) (radial orange lines). During pharynx pumping, the relative tilt of these tracks can change.
B. Hemicentin accumulates in 15-20 thin, regularly spaced tracks (arrowheads) between the pharyngeal BL and the BL of the first column of muscle cells in all four quadrants when viewed by this GFP construct (Vogel and Hedgecock, 2001). These tracks persist in all postembryonic stages. This image is from a transgenic animal expressing the him-4::GFP reporter gene. Bar, 10 μm. (Image source: B. E. Vogel.)
C. Graphic representation of the hemicentin tracks (arrows). Cross section of the anterior head. (P) Pharynx; (IL) inner labial nerve; (OC) outer labial quadrant and cephalic nerves (outer labial nerves are omitted); (A) amphid nerve; (green ovals) bodywall muscle; (pink) sensory dendrites; (dark and light aqua) sheath cells; (rose) socket cells.
D. Hemicentin tracks (arrow) are about 0.2-0.3 μm thick and 7-9 μm long. They attach to the pharyngeal BL (black arrowhead) on the inside and the merged BL of the muscle and the hypodermis (white arrowhead) on the outside. Due to transverse oblique sectioning, only the inner half of this track is seen in this TEM image. Hemicentin tracks are flexible such that during foraging and feeding, they can shift from an acute angle to almost parallel relative to the pharynx. (P) Pharynx; (BWmu) body wall muscle Bar; 1 μm. (Image source: MRC anterior head 3811-3.)

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