Morphometry, histochemistry, and innervation of cervical shoulder muscles in the cat

Morphometric and histochemical methods were used to estimate the force-deve loping capabilities and fiber-type contents of four muscle complexes (rhomb oideus, levator scapulae, trapezius, and sternomastoideus) that link the sh oulder girdle to the skull and cervical vertebrae. Each complex contained a t least two member muscles that were distinctive architecturally and often had specialized innervation patterns. Trapezius and sternocleido-mastoideus were innervated by both cranial nerve XI and cervical spinal nerves. Glyco gen depletion of trapezius suggested that the nerves derived from cervical roots might be entirely sensory. Muscles within each complex varied in phys iological cross-sectional area from less than 0.1 cm(2) to greater than 1 c m(2). They showed differences in fiber-type composition that suggested spec ialized roles for different behaviors. The morphometric features of the cer vical shoulder muscles suggest that they have considerable potential to pro duce head movements and should be incorporated into feline head-movement mo dels. (C) 1999 Wiley-Liss, Inc.