MUSCLE

MUSCLE

1. is one of the four primary tissue types.There are three types of muscle tissue:

   • Skeletal muscle
     • fuction
       • Is to contract and cause movement.
         • Constant small contractions of the skeletal muscle are needed to hold a body upright in any position, even at rest.
           • Skeletal muscle is located throughout the body at the openings of internal tracts to control the movement of various substances.
             • Also protect internal organs (particularly the abdominal organs).
               • Contribute to the generation of heat, primarily by shivering or intense bursts of movement.
     • Structure
       • Is an organ that consists of various integrated tissues.
         • These tissues include the skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue
           • Each skeletal muscle has three levels of connective tissue that enclose it.
             • Provide structure to the muscle as a whole, and also compartmentalize the muscle fibers within the muscle in to groups.
               • The epimysium also allows the muscle to move independently from other muscle groups and other types of tissue
   • Cardiac muscle
     • Features
       • Cardiac muscle tissue is only found in the heart, specifically the myocardium.
         • Contractions of cardiac muscle pump blood into the vessels of the circulatory system such as the aorta and pulmonary artery.
           • Cardiac muscle is striated and organized into sarcomeres
             • An intercalated disc allows the cardiac muscle cells to contract in a coordinated fashion so that the heart can work as a pump.
               • Intercalated discs are part of the sarcolemma and contain two structures important in cardiac muscle contraction: gap junctions and desmosomes.
   • Smooth muscle
     • Features
       • Is present in the walls of organs that contain a lumen like the urinary bladder, uterus, stomach, intestines, and in the walls of large vascular tubes.
         • Also present in the eye, where it functions to change the size of the pupil and in the skin where it causes hair to stand erect in response to low temperatures or fear.
           • Smooth muscle is referred to as an involuntary muscle since is not under voluntary control.
             • Contraction relies on the presence of Ca++ ions similar to skeletal and cardiac muscle.
               • Smooth muscle fibers have a limited calcium-storing sarcoplasmic.

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