Changes in the collagen fibre orientation and stiffness of the connective tissues surrounding individual muscle fibres with muscle length

The M. pectoralis (pars thoracicus) of pigeons ( Columba livia ) is comprised of short muscle fibres that do not extend from muscle origin to insertion but overlap ‘in-series’. Individual pectoralis motor units are limited in territory to a portion of muscle length and are comprised of either fast twitch, oxidative and glycolytic fibres (FOG) or fast twitch and glycolytic fibres (FG). FOG fibres make up 88 to 90% of the total muscle population and have a mean diameter one-half of that of the relatively large FG fibres. Here we report on the organization of individual fibres identified in six muscle units depleted of glycogen, three comprised of FOG fibres and three comprised of FG fibres. For each motor unit, fibre counts revealed unequal numbers of depleted fibres in different unit cross-sections. We traced individual fibres in one unit comprised of FOG fibres and a second comprised of FG fibres. Six fibres from a FOG unit (total length 15.45 mm) ranged from 10.11 to 11.82 mm in length and averaged (±s.d.) 10.74±0.79 mm. All originated bluntly (en mass) from a fascicle near the proximal end of the muscle unit and all terminated intramuscularly. Five of these ended in a taper and one ended bluntly. Fibres coursed on average for 70% of the muscle unit length. Six fibres from a FG unit (total length 34.76 mm) ranged from 8.97 to 18.38 mm in length and averaged 15.32 ±3.75 mm. All originated bluntly and terminated intramuscularly; one of these ended in a taper and five ended bluntly. Fibres coursed on average for 44% of the muscle unit length. Because fibres of individual muscle units do not extend the whole muscle unit territory, the effective cross-sectional area changes along the motor unit length. These non-uniformities in the distribution of fibres within a muscle unit emphasize that the functional interactions within and between motor units are complex.

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Histology of allometric growth in hindlimb muscles of pigs

The Journal of Agricultural Science ◽

10.1017/s0021859600054423 ◽

1982 ◽

Vol 98 (3) ◽

pp. 629-632

Author(s):

H. J. Swatland

Keyword(s):

Cross Sections ◽

Muscle Length ◽

Biceps Femoris ◽

Longitudinal Growth ◽

Muscle Fibres ◽

Allometric Growth ◽

Cross Sectional ◽

Relative Growth ◽

Limb Bones ◽

Hindlimb Muscles

SUMMARYHindlimbs of pigs were dissected at 4-week intervals from 9 to 29 weeks after birth. Allometric growth ratios of the gluteal muscles, biceps femoris and semitendinosus were calculated relative to gastrocnemius. Relative growth in weight of the proximal limb muscles was greater than that of the distal muscle, gastrocnemius. The greater relative growth of proximal muscles was not due to greater relative growth of muscle fibre diameters, nor to greater relative growth of muscle cross-sectional areas. In biceps femoris and gluteal muscles, growth in the area of musole cross sections did not keep pace with the radial growth of muscle fibres. The relative longitudinal growth of proximal limb bones exceeded that of distal bones, and the relative longitudinal growth of biceps femoris and semitendinosus exceeded that of any of the limb bones. New sarcomeres were added to muscle length at a faster rate in biceps femoris and semitendinosus than in the peroneus longus located distally in the limb.

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Peripheral neurosecretory cells in some Lepidoptera

Canadian Journal of Zoology ◽

10.1139/z75-119 ◽

1975 ◽

Vol 53 (8) ◽

pp. 1035-1038 ◽

Cited By ~ 15

Author(s):

C. F. Hinks

Keyword(s):

Single Cell ◽

Neurosecretory Cells ◽

Muscle Fibres ◽

Individual Muscle ◽

The Individual

A segmental series of peripheral neurosecretory cells was found in larvae of some Lepidoptera. They occur in the thoracic segments and in the first eight abdominal segments, towards the distal end of the transverse nerves. In the thorax, and in abdominal segments 1, 2, and 8 there is usually a single cell, but in abdominal segments 3–7 there are 2–14 cells. The latter have the appearance of small ganglia and lie on the aliform muscles where the transverse nerve divides to innervate the individual muscle fibres. All of the peripheral neurosecretory cells appear to produce the same secretion, some of which is discharged through the transverse nerves and released at the proximal neurohaemal dilations. Other fibers extend distad from the cell bodies and may supply the aliform muscles.

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