016 - Skeletal Muscle Histology

7/31/2019 016 - Skeletal Muscle Histology

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Skeletal muscle, TS and LS - haematoxylin and eosin: mediumpower

Tongue

The tongue is the only organ that contains intermingling bundles of striatedmuscle running perpendicularly to one another

1. Striations in fibres cut in LS2. The position of the nuclei in fibres cut in LS3. The positon of the nuclei in fibres cut in TS4. The shape of the nucleus, in LS5. The nucleolus6. Connective tissue (endomysium) around individual fibres7. Connective tissue (perimysium) around fasciculi8. Blood vessels, predominantly capillaries. Where?

Note: the CT surrounding skeletal muscle is composed largely ofreticular fibres (collagen III).


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Skeletal muscle inserting into tendon: high power

There is a lot of muck in this image, which is an occupational hazard of theiron haematoxylin stain

Nearly all the nuclei in this image belong to fibroblasts. Skeletal musclenuclei tend not to reside close to the ends of the cell

Note:

1. The abrupt junction between the muscle fibres and the tendon2. The large number of fibroblasts in the junctional region

Skeletal muscle, motor end-plates: high power

Within the nerve, this stain (iron haematoxylin) picks out the nerve axonsbut not the myelin sheath.

Axons, or small bundles of axons, branch off from the main nervetrunk (NT).

The axons themselves branch (B), and terminate in a motor end-plate (MEP)

The actual nerve terminal resembles a bunch of grapes: each "grape"may be called a terminal bouton


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Together with the specialised area of sarcolemma opposite the nerveterminal, the MEP forms a neuromuscular junction. To be morespecific: a somatic neuromuscular junction

In mature skeletal muscle each muscle fibre (usually) has a singleMEP

A single nerve fibre will innervate from 6 to approximately 100muscle fibres. The nerve fibre plus the muscle cells that it innervatesis known as a motor unit. Muscles that require fine control, e.g.finger muscles, contain small motor units. Muscles not requiring finecontrol, e.g. postural muscles, have large motor units

There is a trailing ending (TE) present in this image, making contactwith a very narrow muscle cell. This is probably a muscle spindle

Note the vascular tree (BV)

Muscle spindle: medium power

Muscle spindles (MS) sit in parallel with ordinary muscle fibres. Theirfunction is to monitor changes in length of the muscle. Golgi tendon organsmonitor muscle tension.

Spindles are modified striated muscle fibres, much narrower than normalfibres, innervated by sensory as well as motor nerves.


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The muscle spindle (MS) has a diameter about one quarter of that of askeletal muscle fibre (SkM)

Note the difference in appearance between the motor end-plate on thespindle and those on muscle fibres.

The spindle itself is contractile. Birefringence of its contractile proteins isvisible.

016 - Skeletal Muscle Histology

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