Skeletal muscles


Skeletal muscles by design are set to influence their assigned body part through the process of contraction. Their attached connective tissue is in effect the function unit of the system, providing the conductor for the force behind the skeletal muscles. Skeletal muscles line the bone, which are secured at each end with tendons. Tendons are strong and dense regular connective tissue that secure the muscle to the periosteum of the bone. Muscle contraction causes a shortening of the muscle length, which in turn creates a pressurized tension on the tendon, creating movement of the structure involved. Movement of the structure occurs at the synovial joint, which allows the muscle tissue to contract and readily move the bone that is designed to swing back and forth or side to side in its place, not altogether different from a pendulum. The bony attachments are considered either easily moveable or experience discouraged motion. Muscle contraction creates movement of the easily moveable bone, which is often referred to as the insertion, toward the discouraged motion bone, often referred to as the origin.

If a muscle attachment experiences a more complex design, such as girdles and appendages, the proximal attachment is considered the origin while the distal attachment is then considered the insertion.

The belly of the muscle is thick, somewhat fleshy, and usually runs along the center. It can also be determined as the gaster of the muscle. Aponeuroses are the flatter, almost sheet-like tendons. The top and sides of the muscles and tendons within the skull are an excellent illustration of this design, known as the galea aponeurotica. Areas such as the wrist, ankle, and other short or susceptible area, the tendons are first covered with protective sheaths, and then as a group of tendons, they are additionally protected by connective tissue comprised of thin and strong bands of tissue known as retinaculum. Retinacula are attached to the articulating bones and are designed to protect against strenuous movements such as bending, bowing, or over exerting during normal muscular contractions.


Skeletal muscle
Image: Skeletal Muscle

Isolating muscle fibers as solitary contracting units creates an ineffectual design. Thus, fibers as individuals are bound together with other fibers, which are then bound together with other groups of fibers, creating a core of fiber that leads to unification. This binding process not only allows the muscle fibers to work cohesively with the fibers they are located right next to, but with fibers that are on the opposite side of the muscle structure, creating a single unit. The fibers are held together with associated loose connective tissue.

Connective tissue is purposefully designed to provide many various functions. Protection, securing muscle fibers to each other and to the necessary structures, strengthening, and binding large groups of bundles all fall within the responsibilities of the muscle fibers. Endomysium is a highly specific associated muscle fiber that is designed to wrap around the individual muscle fibers in a protective manner. The endomysium is also multi-functional, binding the various muscle fibers together while simultaneously providing structural support for the nerve ending and the blood vessels the muscle tissue needs to survive. The perimysium is a secondary connective tissue that is primarily responsible for creating fasciculi, bound groups of muscle tissue fibers. The necessary blood vessels and nerve endings that is required for the fasciculi’s survival is structurally supported by the perimysium. Tendons are continuous with the connective tissue which covers the entire muscle, the epimysium.

There is an additional fibrous connective tissue. The fascia is design to not only cover the entire muscular organ, but it also attaches to the skin, giving the muscle an additional grounding point. Invariable, the thickness of the fascia is often determined by several factors, including how far from the under-surface of the skin the muscle is located. The skin is then adhered to most of the structures which lie under the skin by superficial fascia. Under the skin of the buttocks and under the skin of the abdominal wall, the superficial fascia is given an additional layer of interwoven adipose connective tissue. Areas such as the face, the back of the hand, and the elbow have remarkably thin underlying superficial fascia. When superficial fascia has an additional extension that reaches inward toward the viscera, this is known as deep fascia. It is devoid of adipose connective tissue and simply blends into the epimysium. Most often deep fascia can be found in muscles which are nearly adjacent to or actually all but connect to each other. It is able to keep the muscle fibers connected and working cohesively with appropriate muscle group while segregating it from the touching muscle fibers. In between the deep fascia and the serous membrane, the subserous fascia can be located. The subserous fascia serves as a guide post and structural support for the blood vessels nerve pathways that are dedicated to the associated serous membranes.
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