Fiber architecture and histochemistry in the cat neck muscle, biventer cervicis

Abstract

1. Biventer cervicis (BC) is an anatomically complex muscle that is divided by tendinous inscriptions into five in-series compartments of motor units. We have analyzed the fiber architecture and fiber-type composition of these different compartments using microdissection and histochemical methods. 2. BC narrows as it runs rostrally, but its in-series compartments have similar cross-sectional areas. The tapered shape of BC comes about because tendinous inscriptions and the tendon of insertion are oriented obliquely and muscle fibers attach in a progressively offset fashion from the medial to the lateral muscle edge. 3. Individual compartments of BC differ from one another in their architecture. The rostral two compartments (1 and 2) contain fibers of similar length that run between two plates of tendinous tissue. Compartments 3 and 4 are divided into two or three in-parallel subvolumes whose fiber bundles differ in their lengths and sites of attachment. Compartment 5 is the most variable in its structure. In some cats it is separated from compartment 4 by a tendinous inscription, but in other cats, it blends with a dorsomedial part of compartment 4 to form a single subvolume. 4. The relative lengths of fibers in different compartments were analyzed when the head and neck were held in different postures. Fibers in rostromedial regions were stretched more effectively when the head was flexed at suboccipital joints, and appeared to be less sensitive to movements at lower cervical joints. Movements across lower cervical joints produced substantial length changes in caudolateral parts of BC. 5. Muscle fibers of different histochemical types were not distributed evenly within each muscle compartment. Slow, oxidative (SO) fibers accounted for the majority of fibers near the nuchal midline but for only 30%-45% of fibers in lateral muscle regions. Proportions of fast, glycolytic (FG) fibers were greatest in lateral regions. Fast, oxidative-glycolytic (FOG) fibers were distributed quite uniformly throughout each compartment. 6. The specialized architecture of BC may shape its physiological capabilities. The complex internal structures of different compartments may alter the length-tension properties of BC.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphology of the Lumbar Transversospinal Muscles Examined in a Mouse Bearing a Muscle Fiber‐Specific Nuclear Marker

“…Thus, it seemed likely that the longer fascicles of the TSP muscles might be constructed of fibers from multiple segments arranged in an end-to-end series. The results presented here show this is not the case, but rather that the mouse TSP muscles have a simple parallel-fibered arrangement consistent with that seen in most other small mammalian muscles, rather than the in-series arrangement seen in many larger mammalian muscles (Richmond and Armstrong, 1988;Gans and Gaunt, 1991;Paul et al, 2004).…”

In vivo and in vitro Examination of the Tendinous Inscription of the Human Semitendinosus Muscle

“…Although there is not enough information on the mechanical role of the TI for human ST muscle function, evidence from other muscles of the human body underlies the importance of compartmentalization for muscle function [Krogh and Towns, 1984;Richmond and Armstrong, 1988;Hijikata et al, 1992;Herring et al, 1993;Kamibayahsi and Richmond, 1998;Brown and McGill, 2009]. Particularly, some neck and trunk muscles display multiple long regions with in-series fibers which display multiple attachments to vertebrae or ribs, each innervated by a different bundle of motor axons [Krogh and Towns, 1984;Richmond and Armstrong, 1988;Hijikata et al, 1992;Herring et al, 1993].…”

“…Particularly, some neck and trunk muscles display multiple long regions with in-series fibers which display multiple attachments to vertebrae or ribs, each innervated by a different bundle of motor axons [Krogh and Towns, 1984;Richmond and Armstrong, 1988;Hijikata et al, 1992;Herring et al, 1993]. This arrangement may allow integration of forces exerted by multiple regions as the muscles contract.…”

Neuromuscular compartments and fiber‐type regionalization in the human inferior pharyngeal constrictor muscle

“…Anatomically, separate intramuscular nerve branches can be seen to innervate distinct regions in a compartmentalized muscle (English and Ledbetter, 1982a;English and Weeks, 1987;Windhorst et al, 1989;Chanaud et al, 1991a;Sanders et al, 1994;Sanders, 1998b, 2000). Histochemically, the compartmentalized muscle is often characterized by uneven muscle fiber-type distribution (English and Ledbetter, 1982b;Richmond and Armstrong, 1988;Chanaud et al, 1991b;Sanders, 1998b, 2000, in press), which is termed muscle fiber-type regionalization (Chanaud et al, 1991a, b). Based on these criteria, the human IPC is composed of at least two NMCs: rostral and caudal.…”