Craniofacial Muscles

14 I. Harel and E. Tzahor
Fig. 2.2 Pharyngeal mesoderm cells give rise to parts of the heart and the pharyngeal muscles.
( a – d ) Schematic illustration of the anatomy of the pharyngeal mesoderm in a 1.5–3-day-old chick
embryo is shown. Pharyngeal mesoderm cells ( green ) in the anterior part of the embryo surround
the pharynx. Later, these cells fi ll the mesoderm core of the pharyngeal arches, and are incorporated
into the arterial pole of the heart (e.g., out fl ow tract). The fi rst heart fi eld ( red ) is restricted to
the lateral splanchnic mesoderm that later contributes to the linear heart tube. Second heart fi eld
cells ( green ) are PM cells that contribute to the arterial pole of the heart. PM cells interact and
migrate together with cranial neural crest cells. Cardiac neural crest cells are part of the cranial
neural crest population, migrating into the out fl ow tract via the posterior arches (arches 3–6)
which is contiguous with the PM, differentiates earlier, and eventually populates the
left ventricle (reviewed in Buckingham et al. 2005 ; Dyer and Kirby 2009 ; Evans
et al. 2010 ; Tzahor and Evans 2011 ; Tzahor and Lassar 2001 ; Vincent and
Buckingham 2010 ) .
2.4 Head Muscle Satellite Cells
Recent studies have begun to uncover an unexpected heterogeneity in head muscles
with respect to their origins, genetic lineages, and transcriptional programs, as well
as their proliferative, differentiative, and regenerative properties (Harel et al. 2009 ;