Human Frontalis Muscle Innervation and Morphology.

Unlabelled: Due to its clinical importance and due to a suggestion regarding the afferent innervation, the microscopic appearance of the frontalis muscle was investigated.

Methods: From seven human cadavers, serial sections of the frontalis muscle were studied using light microscopy. Immunhistochemistry was performed using antibodies against collagen XXII and neurofilament.

Muscle spindles in the rhesus monkey platysma.

The platysma of the rhesus monkey consists of two parts: a platysma myoides located similar to the human platysma, and a platysma cervicale passing the dorsal cervical region and being in contact with the cheek pouch. Our investigation showed that the muscle fiber morphology was comparable in both parts. Muscle spindles were only present in regions connected to the cheek pouch and contained only nuclear chain fibers.

In the human, true myocutaneous junctions of skeletal muscle fibers are limited to the face.

Within the panniculus carnosus-associated skeletal muscles in the human, the palmaris brevis and the platysma showed myotendinous/myofascial junctions with clear distance to the corium and the specific connection collagen type XXII. The orbicularis oris muscle, in contrast, contained bundles of striated muscle fibers reaching the corium at two distinct levels: the predominant inner ending was connected to the elastic network of the inner corium and the outer ending was within the more superficial collagen network. At both locations, the striated muscle fibers showed brush-like cytoplasmic protrusions connecting a network which was not oriented toward the muscle fibers.