The endomysium, meaning ''within the muscle'', is a wispy layer of
areolar connective tissue that ensheaths each individual
muscle fiber, or
muscle cell
A muscle cell, also known as a myocyte, is a mature contractile Cell (biology), cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal muscle, skeletal, smooth muscle, smooth, and Cardiac muscle, cardiac ...
.
It also contains
capillaries and
nerves. It overlies the muscle fiber's
cell membrane
The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...
: the
sarcolemma. Endomysium is the deepest and smallest component of
muscle connective tissue. This thin layer helps provide an appropriate chemical environment for the exchange of
calcium,
sodium
Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
, and
potassium
Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
, which is essential for the excitation and subsequent contraction of a muscle fiber.
Endomysium combines with
perimysium and
epimysium to create the collagen fibers of
tendon
A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...
s, providing the tissue connection between muscles and bones by indirect attachment. It connects with perimysium using intermittent perimysial junction plates.
Collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
is the major protein that composes connective tissues like endomysium. Endomysium has been shown to contain mainly
type I and
type III collagen components, and
type IV and
type V in very minor amounts. Others have found type IV and type V more common.
The term
cardiac skeleton is sometimes considered synonymous with endomysium in the
heart
The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...
, but cardiac skeleton also refers to the combination of the endomysium and
perimysium.
Clinical significance
Anti-endomysial antibodies (EMA) are present in
celiac disease. They do not cause any direct symptoms to muscles, but detection of EMA is useful in the diagnosis of the disease.
See also
*
Connective tissue in skeletal muscle
*
Epimysium
*
Perimysium
References
External links
*
Illustration at wku.edu*
*
Soft tissue
Muscular system
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