skeletal muscle

Examples of skeletal muscle in the following topics:

• Blood Flow in Skeletal Muscle

  • Skeletal muscles are important in maintaining posture and controlling locomotion through contraction.
  • Blood vessels are closely intertwined with skeletal muscle tissues lying between the fascicles, or bundles of muscle fibers.
  • Skeletal muscles also play a key role in the movement of blood around the body.
  • The skeletal muscles of the legs are particularly important skeletal muscle pumps as they prevent pooling of the blood in the feet and calves due to gravity.
  • Skeletal muscle: 1] Bone, 2] Perimysium, 3] Blood vessel, 4] Muscle fiber, 5] Fascicle, 6] Endomysium, and 7] Epimysium Tendon.

• Types of Muscle Tissue

  • There are three kinds of muscle tissue: skeletal, smooth, and cardiac.
  • Skeletal muscles are highly organized with cells lying parallel to each other.
  • Skeletal muscle fibers are the longest muscle fibers and have stripes on their surface.
  • Skeletal muscle is striated, multinucleate, and involuntary.
  • Cardiac muscle is striated, similar to skeletal muscle, but beats involuntarily.

• Characteristics of Muscle Tissue

  • The three types of muscle tissue are skeletal, smooth, and cardiac.
  • Some skeletal muscle can attach directly to other muscles or the skin, as seen in the face where numerous muscles control facial expression.
  • As with skeletal muscle cardiac muscle is striated, however it is not consciously controlled and so is involuntary.
  • Cardiac and skeletal muscle are both striated in appearance, while smooth muscle is not.
  • Both cardiac and smooth muscle are involuntary while skeletal muscle is voluntary.

• Arrangement of Fascicles

  • Skeletal muscles are grouped into fascicles, which are bunches of muscle fibers surrounded by a perimysium.
  • Skeletal muscle tissue is composed of numerous muscle fibers which are separated from adjacent muscles and other tissues by a layer of dense, elastic connective tissue termed the fascia.
  • Beneath the fascia in skeletal muscle is another layer of connective tissue termed the epimysium which is closely associated with the fascia.
  • Whilst both cardiac and smooth muscles are also wrapped in connective tissue, they are not differentiated in the same way as skeletal muscles.
  • Skeletal muscle is surrounded by a thick outer layer of connective tissue termed the fascia.

• Interactions of Skeletal Muscles

  • Skeletal muscles interact to produce movements by way of anatomical positioning and the coordinated summation of innervation signals.
  • Skeletal muscle contractions can be grouped based on the length and frequency of contraction.
  • If an additional action potential were to stimulate a muscle contraction before a previous muscle twitch had completely relaxed then it would sum onto this previous twitch increasing the total amount of tension produced in the muscle.
  • For skeletal muscles, the force exerted by the muscle can be controlled by varying the frequency at which action potentials are sent to muscle fibers.
  • Explain the summation interactions of skeletal muscles and how they affect movement

• How Skeletal Muscles Are Named

  • The anatomical arrangement of skeletal muscle fascicles can be described as parallel, convergent, pennate, or sphincter.
  • Skeletal muscle can be categorised into four groups based on its anatomical arrangement.
  • Most skeletal muscles in the body are parallel muscles; although they can be seen in a variety of shapes such as flat bands, spindle shaped, and some can have large protrusions in their middle known as the belly of the muscle.
  • In Pennate muscles, the tendon runs through the length of the muscle.
  • Skeletal circular muscles are different from smooth muscle equivalents due to their structure and because they are under voluntary control

• Abnormal Contractions of Skeletal Muscle

  • Involuntary muscle contractions are referred to as spasms, and can be due to abnormal activity of the nerve or the muscle.
  • In medicine, a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice .
  • Examples of spasms include muscle contractions due to abnormal nerve stimulation, or abnormal activity of the muscle itself.
  • In this case, the hypertonic muscle tone is excessive and the muscles are unable to relax.
  • Hypertonic muscle spasms is the state of chronic, excessive muscle tone, or tension in a resting muscle – the amount of contraction that remains when a muscle is not actively working.

• Microscopic Anatomy

  • Cardiac muscle, like skeletal muscle, appears striated due to the organization of muscle tissue into sarcomeres.
  • While similar to skeletal muscle, cardiac muscle is different in a few ways.
  • Cardiac muscles are composed of tubular cardiomyocytes, or cardiac muscle cells.
  • A sarcomere is the basic unit of muscle tissue in both cardiac and skeletal muscle.
  • Skeletal muscle contracts following activation by an action potential.

• Muscle Attachment Sites

  • Most skeletal muscle attaches to bone in order to produce movement.
  • However, some skeletal muscle attaches directly to other muscles, fascia, or tissues such as the skin.
  • Not all muscle attaches via tendons.
  • The skeletal muscles involved in controlling expression attach directly onto the fascia of the skin.
  • Tendons are a common tissue that connect muscle to bone.

• Overview of the Musculoskeletal System

  • The bones of the skeletal system provide stability to the body analogous to a reinforcement bar in concrete construction.
  • The skeletal portion of the system serves as the main storage system for calcium and phosphorus.
  • Skeletal muscles are attached to bones and arranged in opposing groups around joints.
  • These are skeletal, smooth, and cardiac muscle.
  • Only skeletal and smooth muscles are considered part of the musculoskeletal system.