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 is also known as a myocyte when referring to either a cardiac muscle cell (cardiomyocyte), or a smooth muscle cell as these are both small cells. A skeletal muscle cell is long and threadlike with many nuclei and is called a mus ...
.
It also contains
capillaries and
nerves. It overlies the muscle fiber's
cell membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...
: 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
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...
,
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
, and
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
, 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, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...
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 found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...
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
Type may refer to:
Science and technology Computing
* Typing, producing text via a keyboard, typewriter, etc.
* Data type, collection of values used for computations.
* File type
* TYPE (DOS command), a command to display contents of a file.
* ...
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 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 ...
, 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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