A muscle fascicle is a bundle of
skeletal muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...
fibers surrounded by
perimysium, a type of
connective tissue
Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
.
Structure
Muscle cells are grouped into muscle fascicles by enveloping
perimysium connective tissue
Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
.
Fascicles are bundled together by
epimysium connective tissue.
Muscle fascicles typically only contain one type of muscle cell (either
type I fibres or
type II fibres), but can contain a mixture of both types.
Function
In the
heart
The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
specialized
cardiac muscle cells transmit
electrical impulses from the
atrioventricular node (AV node) to the
Purkinje fibers – fascicles, also referred to as bundle branches. These start as a single fascicle of fibers at the AV node called the
bundle of His that then splits into three bundle branches: the right fascicular branch, left anterior fascicular branch, and left posterior fascicular branch.
Clinical significance
Myositis may cause
thickening of the muscle fascicles.
This may be detected with
ultrasound scans.
Muscle fascicle structure is a useful diagnostic tool for
dermatomyositis
Dermatomyositis (DM) is a long-term inflammatory disorder which affects skin and the muscles. Its symptoms are generally a skin rash and worsening muscle weakness over time. These may occur suddenly or develop over months. Other symptoms may inc ...
. Myocytes towards the edges of the muscle fascicle are typically narrower, while those at the centre of the muscle fascicle are a normal thickness.
Muscle fascicles may be involved in
myokymia, although commonly only individual myocytes are involved.
See also
*
Connective tissue in skeletal muscle
*
Endomysium
The endomysium, meaning ''within the muscle'', is a wispy layer of areolar connective tissue that ensheaths each individual muscle fiber, or muscle cell. It also contains capillaries and nerves. It overlies the muscle fiber's cell membrane: th ...
*
Epimysium
References
External links
* – "Slide 77
skeletal muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...
"
* – "Smooth Muscle"
Diagram at kctcs.edu
Muscular system
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