Myofiber Length and Myofiber Arrangement in the Antebrachial and Leg Muscles of Sheep

Abstract

Summary: The myofibers of the skeletal muscle vary in length in muscle and from muscle to muscle. Information about myofiber length and myofiber arrangement is necessary to understand the architecture of muscles and differences in myofiber length in muscles. The purpose of the present study was to determine myofiber lengths, ratio of myofiber length to muscle length, and myofiber arrangement of the antebrachial and leg muscles in the sheep. The myofibers of the antebrachial muscles ranged from 7.3 mm (m. extensor carpi ulneris, bipennate muscle) to 39.6 mm (m. flexor digitorum profundus caput radiale, unipennate muscle) in length. The myofibers of the leg muscles ranged from 10.0 mm (m. flexor digitorum superficialis, multipennate muscle) to 119.2 mm (m. soleus, fusiform muscle) in length. The ratio of myofiber length to muscle length in the fusiform muscle was higher than that in the uni-, bi-, and multipennate muscles. The unipennate muscles tended to have a higher ratio of myofibers length to muscle length than did the bi-and multipennate muscles. No difference in the ratio of myofiber length to muscle length existed between the bipennate muscles and multipennate muscles.The myofibers of the skeletal muscle extend across the entire length of muscle or are shorter than the muscle length. In the human, the myofibers of the m. sartorius range from 1.5 to 30 cm in length, whereas the myofiber lengths of the m. biceps femoris, m. semimembranosus, and m. semitendinosus range from 6 to 11 cm (Barrett, 1962). The myofibers vary in length in muscle and from muscle to muscle.The myofiber length of the distal portion of the m. extensor carpi radialis of the horse is 3.1 cm and of the proximal portion 9.2 cm (Hermanson, 1997). The myofiber lengths of the muscle belly of the digit II, digit III, digit IV, and digit V in the m. extensor digitorum longus of the mouse are about 0.5, 0.5, 0.55, and 0.6 cm, respectively (Chleboun et al., 1997).The elbow extensor muscles of the monkey tend to have shorter myofibers (3.05-4.08 cm) than do the elbow flexor muscles (3.20-6.65 cm) (Roy et al., 1984). The knee extensor muscles of the cat tend to have shorter myofibers (1.92-2.73 cm) than do the knee flexor muscles (2.12-8.45 cm) (Sacks & Roy, 1982). The myofibers of muscle of horse (Hermanson, 1997), mouse (Chleboun et aL, 1997), monkey (Roy et al. , 1984), and cat (Sacks & Roy, 1982) are shorter than the muscle length. The facts imply that the variation in ratio of myofiber length to muscle length is related with the myofiber arrangement.Information about myofiber length and myofiber arrangement is necessary to understand the relation between the architecture of muscles and myofiber length. The purpose of the present study was to determine myofiber lengths, ratio of myofiber length to muscle length, and myofiber arrangement of the antebrachial and leg muscles and to examine correlation between ratio of myofiber length to muscle length and myofiber arrangement in the sheep. Materials and MethodsSix adult sheep were used in this stu...

Myoblast replication is reduced in the IUGR fetus despite maintained proliferative capacity in vitro

“…Fetal lower extremity limb length was measured from the femoral head to the top edge of the hoof. In a subset of fetuses, muscles of the fetal hindlimb were collected to include a variety of oxidative and glycolytic muscles (biceps femoris, soleus, tibialis anterior, and gastrocnemius) (Finkelstein, et al 1992; Konno and Suzuki 2000; Suzuki and Tamate 1988) and were weighed within 15 min post-mortem. Muscle mid-bellies from the biceps femoris, tibialis anterior, and soleus muscles were placed on corkboard thinly coated with optimal cutting temperature media, frozen in liquid nitrogen-cooled isopentane for 60 s, and stored at −70 C.…”

Distribution of myofiber types in the crural musculature of sheep

“…In sheep, however, the tibialis cranialis muscle was found to possess a large population of type I myofibers, suggesting that a tension generated by craniolateral crural muscles may participate in maintaining a standing posture of unguligrade animals. The tibialis cranialis muscle is a flat shaped unipennate muscle with a relatively long myofiber length, and its architecture is therefore suitable for a rapid contraction rather than a generation of large and constant tension 14) . While keeping a standing posture, plantar antigravity muscles of crus extend the tarsal joint.…”

“…In sheep, the soleus muscle consisted of 100% type I myofibers. However, the soleus muscle of sheep is a thin and filamentous muscle with long myofiber length, indicating that the tension from this muscle during posture maintenance is small 14) .…”

Morpho-functional relationship between muscular architecture and proportion of myofiber types in ovine antebrachial musculature

“…Myofiber length of antebrachial muscles was utilized from our previous report (Konno and Suzuki, 2000).…”

“…Therefore, the type I myofibers are efficiently distributed to antigravity muscles to support a standing posture in the ovine antebrachial musculature. Also, their architectural characteristics having a small myofiber length/muscle length ratio indicate that these muscles seem to be capable to generate large tension (Konno and Suzuki, 2000). However, the actual force generated by the antigravity muscles in antebrachium for posture maintenance is unknown.…”