Muscular System Human A & P

There are 3 types of muscle tissue: ◦A. Skeletal ◦B. Smooth ◦C. Cardiac ◦The essential function of a muscle is contraction, or shortening, and are responsible for essentially all of the body’s ability to move.

Skeletal Muscle Description They attach to bones. They are huge, cigar-shaped, multinucleated cells. The largest type (up to 30 cm). Striated (stripes in the fibers) Voluntary (conscious control—except reflexes) Contract rapidly and with great force, but also tire easily and require reset after short periods of activity.

Skeletal Muscle Structure Thousands of skeletal muscle fibers are bundled together by connective tissue, which provides strength and structure to the muscle as a whole. Each individual fiber is enclosed in an endomysium. Several fibers are bundled together into a fascicle and covered with a coarse perimysium. Several fasciles are bound together and covered by an epimysium, which covers the entire muscle.

Tendons and Aponeuroses Skeletal muscle fibers blend or taper into tendons or aponeuroses. Aponeuroses attach indirectly to bones, carilage, or connective tissue coverings. Tendons anchor muscle to bone, but also provide durability and conserve space. They are tough collagenic fibers, so they can cross rough bony projections without tearing like muscles would.

Tendon pictures and diagrams

Apopneuroses

Smooth Muscle Description Smooth muscle has no striations. It is involuntary (cannot consciously control it). They are found mainly in the walls of hollow visceral (internal) organs, such as the stomach, urinary bladder, and repertory passages. They propel substances along a definite tract or pathway within the body, such as moving food through the digestive tract and emptying bowels and bladder.

Smooth Muscle Structure Smooth muscle is spindle shaped with a single nucleus and are surrounded by a small endomysium. They are arranged in layers, usually 2, one is circular, the other longitudinal. The 2 layers alternately contract and relax as they change the size and shape of the organ. The movement is slow and sustained.

Smooth Muscle

Cardiac Muscle Cardiac muscle is found only in the heart. It forms the bulk of the heart walls. It is striated and involuntary. The cardiac fibers are cushioned by small amounts of soft connective tissue (endomysium) and arranged in spiral bundles (figure 8 shaped). Cardiac fibers are branching cells joined by special junctions called intercalated discs.

Cardiac Muscle Fibers

How the heart muscle works When the heart contracts, its internal chambers become smaller, forcing the blood into the large arteries leaving the heart. Cardiac muscle usually contracts at a fairly steady rate set by the heart’s “in- house” pacemaker.

Muscle Functions 1. Produce Movement 2. Maintaining Posture 3. Stabilizing Joints 4. Generating Heat

Microscopic Anatomy of Skeletal Muscle