Structure of Muscle (and associated connective tissues)
Skeletal muscles consist of 100,000s of muscle cells that are also known as 'muscle fibres'.
These cells act together to perform the functions
of the specific muscle of which they are a part.
This is possible due to the integration
of the muscle with the other tissues and structures
of other associated body systems - especially
the bones (skeletal
system) or, in the cases of facial
muscles, the skin
(integumentary system), and also the nerves (nervous
system).
A general example of the structure of muscle and associated tissues
is shown below.
Above: Diagram of the Structure of Muscle
(and associated connective tissue)
Tissue Type |
Description of Tissue Type |
Periosteum
|
Periosteum is the outer layer of bone (as illustrated below).
It is to this layer that ligaments and tendons are attached. |
|
Tendon |
Tendons attach muscle to bone.
They are tough pale coloured (whitish) cords formed
from many parallel bundles of collagen fibres.
Tendons are flexible (they bend around other tissues,
changing position as they move), yet inelastic. |
Tendon sheath
(not illustrated above) |
Some tendons are surrounded by tubular double-layered
sacs that are lined with synovial membrane and
contain synovial fluid. These structures are called
'tendon sheaths'. Their purpose is to
minimise friction associated with movement at
the join, and to facilitate movement of the joint. |
|
Fascia |
The word 'fascia' means
bandage - a fitting analogy as the tissue called fascia takes the form of sheets or broad
bands of fibrous connective tissue that cover
muscles or organs, forming an outer-wrapping.
There are two types of fascia:
- Superficial
Fascia, and
- Deep Fascia.
Superficial fascia consists of areolar
connective tissue and adipose tissue, and may
also be referred to as the 'subcutaneous
layer' of the skin. Deep Fascia is more relevant to the study of muscle structures
because it is deep fascia that holds the muscles
together. It consists of dense fibrous connective
tissue. |
Skeletal Muscle
(="Voluntary" Muscle) |
The type of muscle that causes movement of
the skeletal system (especially limbs), and of
skin in the cases of the muscles of facial expression
in the head and neck area has many names. These
include "skeletal muscle" (because it
moves bones), "voluntary muscle" (because
it is usually under conscious control), and "striated
muscle" (because they have a striped appearance). |
Perimysium |
Perimysium is a fibrous sheath that surrounds
and protects bundles of muscle fibres.
(It is shown as thin pale grey lines in the cross-section
of skeletal muscle illustrated above.) |
Epimysium |
Epimysium is fibrous elastic tissue that surrounds
muscle.
There are usually many muscle fascicles
that form a single muscle.
Epimysium surrounds the total bundle of many fascicles - as compared with perimysium (the fibrous sheath that surrounds and protects
individual fascicles, filling the spaces between
the fascicles within the bundle of fascicles
that forms the muscle itself), and endomysium (the fine connective tissue that surrounds and
protects each individual muscle fibre - also known
as a 'muscle cell', hence filling the
spaces between muscle fibres within each
muscle fascicle). |
Fascicle |
The word fascicle (sometimes expressed as a
'fasciculus'), refers to a 'bundle',
such as a bundle of muscle fibres e.g. as illustrated
above, or alternatively a bundle of nerve fibres. |
|
Endomysium |
Endomysium is the name of the fine connective
tissue sheath that surrounds/covers each single/individual
muscle fibre. |
Muscle Fibre
(="Muscle Fiber"
=
"Muscle Cell") |
Muscle fibres, also known as 'muscle fibers'
(American spelling) and 'muscle cells',
are special cells that are able to contract, thereby
causing movement - of other tissues/parts of the
body.
There are three types of muscle:
- Striated / skeletal
muscle (causing the movement of bones/limbs)
- Smooth muscle (surrounding organs and blood vessels),
and
- Cardiac muscle (forming the walls of the heart).
|
Myofibril |
Myofibrils are small contractile filaments
located within the cytoplasm of striated muscle
cells. These filaments cause the distinctive appearance
of skeletal = voluntary = striated muscle because
they consist of bands of alternating high and
low refractive index, which gives the muscles their striped appearance |
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|
For more about the structure of muscle, see the more detailed page about the structure of a muscle cell.