Under sufficient stress, the collagen fibers of the perimysium begin to orient parallel to the stress direction. The stretching and reorientation of the perimysium makes it much stiffer and able to transmit tensile force. Scanning electron microscope images have shown that the perimysium has an organized crimped structure. The crimped structure of the perimysium makes it very compliant in tension under normal physiological conditions allowing the muscle to change shape, thus rendering it unfeasible for tensile force transmission.
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Although strong efforts have been made to demonstrate the mechanical role of the perimysium as a force transmission pathway during active contraction of the muscle, an accepted model has yet to be derived. It can also be suggested that the perimysium could transmit force generated in fascicles to neighboring fascicles by shear, similar to the endomysium described above. The perimysium is significantly thicker than the endomysium. Even if the shear modulus of the perimysium were within an order of magnitude of the endomysium, the perimysium would still be a lot more compliant in shear than the endomysium, also making it an inefficient force transmission pathway.
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The collagen fibers in the perimysium usually orient between 45 and 60 degrees to the long axis of the muscle fibers in their relaxed state. Well defined contact regions between the endomysium and perimysium were observed and coined the perimysial junctional plate (PJP).Passerieux, E., Rossignol, R., Chopard, A., Carnino, A., Marini, J.F., Letellier, T., Delage, J.P. (2006). Structural organization of the perimysium in bovine skeletal muscle: Junctional plates and associated intracellular subdomains, J Struct Biol, 154 (2), 206-216.
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Sarcomeres are marked by Z lines which show the beginning and the end of a sarcomere. Individual myocytes are surrounded by endomysium. Myocytes are bound together by perimysium into bundles called fascicles; the bundles are then grouped together to form muscle tissue, which is enclosed in a sheath of epimysium. The perimysium contains blood vessels and nerves which provide for the muscle fibers.
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These sites were hypothesized to be a focal region for delivery of tension during muscle contraction. To test the possibility of tensile force transmission via the perimysium, it was experimentally shown that cutting of the aponeurosis in a pennate muscle did not prevent tension generation further along towards the tendon. Also, in a separate study it was clearly demonstrated that the perimysium could transmit force if tendons normally transmitting force from distinct parts of the extensor digitorum longus muscle were cut. Although a lot of evidence may seem to point to lateral force transmission via the perimysium in tension, the experiments were conducted at very high loads.
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It also protects muscles from friction against other muscles and bones. Within the epimysium are multiple bundles called fascicles, each of which contains 10 to 100 or more muscle fibers collectively sheathed by a perimysium. Besides surrounding each fascicle, the perimysium is a pathway for nerves and the flow of blood within the muscle. The threadlike muscle fibers are the individual muscle cells (myocytes), and each cell is encased within its own endomysium of collagen fibers.
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Unlike the endomysium, the perimysium has large variations in quantity and organization from one muscle group to another.Borg and Caulfield (1980). Morphology of connective tissue in skeletal muscle, Tissue Cell, 12 (1), 197-207. Muscles contain far more perimysial than endomysial connective tissue, and it has also been observed that the ratio of the dry mass of perimysium to that of endomysium ranges between 2.8-1 and 64-1.Light, N., Champion, A. E., Voyle, C. and Bailey, A. J. (1985).
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Connective tissue is present in all muscles as fascia. Enclosing each muscle is a layer of connective tissue known as the epimysium; enclosing each fascicle is a layer called the perimysium, and enclosing each muscle fiber is a layer of connective tissue called the endomysium.
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Bundles of muscle fibers, called fascicles, are covered by the perimysium. Muscle fibers are covered by the endomysium. The gross anatomy of a muscle is the most important indicator of its role in the body. There is an important distinction seen between pennate muscles and other muscles.
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Skeletal muscle includes skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue. Skeletal muscle is wrapped in epimysium, allowing structural integrity of the muscle despite contractions. The perimysium organizes the muscle fibers, which are encased in collagen and endomysium, into fascicles. Each muscle fiber contains sarcolemma, sarcoplasm, and sarcoplasmic reticulum.
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The role of epimysial, perimysial and endomysial collagen in determining texture in six bovine muscles, Meat Sci, 13, 137-149. The anatomical arrangement of the connective tissue at each level of organization influences the function of the muscle. Attachment of the perimysium to the endomysium at the perimysial junctional plates (PJPs).
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Purslow, P.P. (2010). Muscle fascia and force transmission, J Bodyw Mov Ther, 14 (4), 411-7. There are alternate theories on the role of the perimysium being strictly for distributing passive forces imposed on the muscle and that the perimysial network's main purpose is to prevent over-stretching of the muscle fascicles.Purslow, P.P. (1989).
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Muscle tissue is a soft tissue that composes muscles in animal bodies, and gives rise to muscles' ability to contract. This is opposed to other components or tissues in muscle such as tendons or perimysium. It is formed during embryonic development through a process known as myogenesis. Muscle tissue consists of elongated cells also called as muscle fibers.
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Figure 1 Pennate muscle fiber arrangements: A, unipennate; B, bipennate; C, multipennate In muscle tissue, 10-100 endomysium- sheathed muscle fibers are organized into perimysium-wrapped bundles known as fascicles. Each muscle is composed of a number of fascicles grouped together by a sleeve of connective tissue, known as an epimysium. In a pennate muscle, aponeuroses run along each side of the muscle and attach to the tendon. The fascicles attach to the aponeuroses and form an angle (the pennation angle) to the load axis of the muscle.
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In the peripheral nervous system, the myelin sheath of each axon in a nerve is wrapped in a delicate protective sheath known as the endoneurium. Within the nerve, axons targeting the same anatomical location are bundled together into groups known as fascicles, each surrounded by another protective sheath known as the perineurium. Several fascicles may be in turn bundled together with a blood supply and fatty tissue within yet another sheath, the epineurium. This grouping structure is analogous to the muscular organization system of epimysium, perimysium and endomysium.
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A muscle fascicle is a bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue. (There is also a nerve fascicle of axons.) Specialized muscle fibers in the heart that transmit electrical impulses from the atrioventricular node (AV Node) to the Purkinje fibers are 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.
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Deep fascia (or investing fascia) is a fascia, a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments. This fibrous connective tissue interpenetrates and surrounds the muscles, bones, nerves, and blood vessels of the body. It provides connection and communication in the form of aponeuroses, ligaments, tendons, retinacula, joint capsules, and septa. The deep fasciae envelop all bone (periosteum and endosteum); cartilage (perichondrium), and blood vessels (tunica externa) and become specialized in muscles (epimysium, perimysium, and endomysium) and nerves (epineurium, perineurium, and endoneurium).
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Structure of a skeletal muscle. A key component in lateral force transmission in skeletal muscle is the extracellular matrix (ECM). Skeletal muscle is a complex biological material that is composed of muscle fibers and an ECM consisting of the epimysium, perimysium, and endomysium. It can be described as a collagen fiber-reinforced composite. The ECM has at least three functions: (1) to provide a framework binding muscle fibers together and ensure their proper alignment, (2) to transmit the forces, either from active muscle contraction or ones passively imposed on it, and (3) providing lubricated surfaces between muscle fibers and bundles enabling the muscle to change shape.
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Functionally, the external ear is served by three (3) ear muscles, the auricularis posterior muscle (rear ear-muscle), the auricularis superior muscle (upper ear-muscle), and the auricularis anterior muscle (front ear-muscle), the most notable of which is the auricularis posterior muscle, which functions to pull the ear backwards, because it is superficially attached to the ponticulus (bridge) of the conchal cartilage, and to the posterior auricular ligament (rear ligament of the ear). The posterior muscle of the ear is composed of 2–3 fascicles (skeletal-muscle fibers contained in perimysium connective tissue), originates from the mastoid process of the temporal bone and is inserted to the lower part of the cranial surface of the concha, where it is surrounded by fibroareolar tissue deep within the temporal fascia. The posterior auricular artery irrigates the ear tissues with small, branch-artery blood vessels (rami). Likewise, the rear muscle of the ear is innervated with fine rami of the posterior auricular nerve, which is a branch of the facial nerve.
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