Muscle spindle
Perimysium is a slightly thicker layer of connective tissue consisting mainly of type I and III collagen and surrounds a group of fibers. It is made up of a delicate layer of reticular fibers and permits only small-diameter nerve fibers and capillaries, thus acting as a site of metabolic exchange. Endomysium surrounds individual muscle fibers. There are three types of connective tissue sheaths named for their location. Skeletal muscle tissue is made up of a collection of muscle fibers wrapped in connective tissue sheaths. They have a small amount of cytoplasm and because of their locations can sometimes be mistaken for skeletal muscle cell nuclei. Satellite cells are precursors to skeletal muscle cells and are responsible for the ability of muscle tissue to regenerate. They are accompanied by satellite cells between the external lamina and sarcolemma. Nuclei of skeletal muscle tissue are oval-shaped and located at the periphery of the cell. Because the cells are fused and multinucleated, they form a structural syncytium. This fusion results in a characteristic multinucleated structure. Skeletal muscle tissue develops through the fusion of individual myoblasts, or early muscle cells. Under a microscope, sarcomeres give skeletal muscle a striated appearance. The actin and myosin filaments making up the myofibrils are organized into sarcomeres. Myofibrils are rod shaped subunits of muscle cells. In contrast, muscle fibers making up the stapedius, a small muscle of the inner ear, are only a few millimeters in length. In the anterior thigh, a muscle fiber may be a meter long. The length of a skeletal muscle fiber varies by location. Individually, skeletal muscles cells are referred to as muscle fibers. A muscle fiber may also be referred to as a myofiber. The plasma membrane is called the sarcolemma and the endoplasmic reticulum is called the sarcoplasmic reticulum. The cytoplasm of a muscle cells is referred to as sarcoplasm. Muscle tissue terms often begin with myo-, mys-, or sarco. Special terms are used to describe structures associated with skeletal muscle tissue. Muscular dystrophy, actin aggregate myopathy, myotubular myopathies Place on the sarcolemma where motor fiber synapses with muscle in order to deliver contraction command Neurotransmitter is acetylcholine Perimysium - around multiple muscle fibers -> arranges them in fascicles Type IIb - get energy from anaerobic glicolysis, appear pink, fast-twitch and prone to fatigue Type IIa - get energy from oxidative glicolysis have high amount of glycogen, birhgter than type I, they are fast-twitch and resistant to fatigue Type I - use aerobic metabolysm to function they appear red because of the high amount of myoglobin they are slow-twitch and resestant to fatigue Sarcomere - functional unit (made of actin and myosin)Īccessory proteins - titin, tropomodulin, alpha-actinin, desmin, nebulin, dystrophin, myomesin Sarcomplasmic reticulum - modified endoplasmic reticulum T-tubules - invaginations of sarcolemma that transfer action potentials to the inside of the muscle cell Terminal cisterna - extension of sarcolemma that stores calcium Key facts about the skeletal muscle Function This article will discuss the histology of the skeletal muscle. Extensible tissue can be stretched and elastic tissue is able to return to its original shape following distortion. Skeletal muscle tissue is also extensible and elastic. Contractile tissue is able to generate tension of force. Excitable tissue responds to stimuli through electrical signals. It attaches to bones and the orbits through tendons. Skeletal muscle is an excitable, contractile tissue responsible for maintaining posture and moving the orbits, together with the appendicular and axial skeletons. Striated skeletal muscle, Textus muscularis striatus skeletalis
