Muscle Histology Overview

The smallest contractile unit of striated muscle. Composed of thick and thin filaments, arranged in a specific pattern that creates alternating light and dark bands seen under a microscope.

The light-staining band in a sarcomere, containing mainly thin filaments.

The dark-staining band in a sarcomere, primarily composed of thick filaments.

The process by which myosin heads attach to and move actin filaments, resulting in muscle contraction.

Specialized skeletal muscle stem cells that help repair damaged muscle fibers. Located beneath the basal lamina of muscle fibers.

A type of muscle tissue found in the heart. It is striated, but unlike skeletal muscle, it is not under voluntary control.

Individual cells that make up cardiac muscle tissue.

Specialized junctions between cardiac myocytes that allow for coordinated contraction of the heart.

The ability of muscle cells to increase in size due to increased demand.

The inability of heart muscle to regenerate once damaged, resulting in scar tissue formation.

Smooth muscle cells are elongated, spindle-shaped cells with tapered ends, lacking striations due to the absence of sarcomeres. They are characterized by slow, sustained contractions triggered by various stimuli, including mechanical, electrical, and chemical signals.

Smooth muscle plays a crucial role in regulating blood pressure by controlling the diameter of small arteries (arterioles).

Smooth muscle's rhythmic contractions in the digestive tract, known as peristalsis, propel food along the digestive system.

Skeletal muscle fibers, the largest cells in the body, are multinucleated due to the fusion of multiple myoblasts during development. They exhibit a striated appearance resulting from the arrangement of sarcomeres in series.

The functional unit of a skeletal muscle fiber is the sarcomere, which is composed of myosin (thick) and actin (thin) filaments arranged in a precise pattern.

The nuclei of skeletal muscle fibers are located at the cell periphery, with approximately one nucleus every 3μm along the fiber length.

Smooth muscle cells have a remarkable capacity for regeneration, as they can divide and increase in number. Pericytes, cells lining small blood vessels, contribute to this regeneration by dividing and generating new smooth muscle cells.

Smooth muscle cells can also undergo hypertrophy, increasing in size without dividing. This allows for increased contractile force.

Skeletal muscle fibers are formed by the fusion of multiple myoblasts during development. These myoblasts are mononucleated cells that combine to form a single, multinucleated muscle fiber.

Skeletal muscle fibers have a striated appearance due to the arrangement of sarcomeres, which are repeating units containing myosin and actin filaments.

A layer of connective tissue surrounding individual muscle fibers, providing support and structure.

Connective tissue that surrounds a bundle of muscle fibers, called a fascicle.

The outermost connective tissue layer that encloses the entire muscle, providing strength and protection.

A dense connective tissue sheath surrounding a tendon, acting as a protective layer.

Divisions within the tendon, formed by connective tissue, separating tendon fascicles.

Loose connective tissue surrounding individual tendon fibers, containing fibroblasts and minimal collagen.

Muscle fibers rich in mitochondria, myoglobin, and capillaries, giving the muscle a red appearance. They contract slowly but sustain activity for long periods.

Muscle fibers with low mitochondria, myoglobin, and capillary density, giving the muscle a pale color. They contract quickly but fatigue rapidly.

A dense connective tissue sheet that wraps, supports, and separates muscles, blood vessels, and nerves.

A fluid-filled sac lined by synovial membrane, reducing friction between tendons and bony prominences.