Muscle Tissues Quiz

Muscular Tissues

• Muscles function in movement, posture maintenance, joint stabilization, and heat generation.
• Three types of muscle tissue exist: smooth, striated (skeletal), and cardiac.
• All three types originate from the mesoderm.

Smooth Muscle

• Found in hollow viscera, blood vessels, respiratory passages, and glands.
• Spindle-shaped cells with a single, centrally located nucleus.
• Cytoplasm contains actin, myosin, and intermediate filaments.
• Contractions are involuntary, slow, sustained, and resistant to fatigue.
• Muscle fibers are smaller than skeletal muscle fibers.
• Fibers are densely packed, often with the narrower portion of one fiber next to the wider portion of a neighboring fiber.
• Size: Length (18-200 μm), Diameter (3-8 μm).
• Cells are rounded or polygonal in shape and may or may not contain nuclei.

Smooth Muscle Functions

• Regulates lumen size of hollow viscera.
• Produces peristaltic movements in the digestive tract.
• Maintains muscle tonus in blood vessels.
• Synthesizes collagen and elastin.

Skeletal Muscle

• Composed of long, cylindrical, multinucleated cells with striations.
• Makes up 40% of body weight.
• Contractions are voluntary, fast, and forceful.
• Cells contain myofibrils which consist of overlapping actin and myosin filaments
• The sarcomere is the basic unit of contraction within a myofibril.
• The plasma membrane is called sarcolemma.
• Size: Length (1-40 mm), Diameter (10-100 μm).
• Surrounded by connective tissues; epimysium (enclosing the entire muscle), perimysium (enclosing bundles of muscle fibers), and endomysium (enclosing individual muscle fibers).

Cardiac Muscle

• Found only in the heart.
• Cells are branched, striated, and have a single, centrally located nucleus.
• Cells connect via intercalated disks at branching points.
• This creates a network, which facilitates rapid and coordinated contraction.
• Contractions are involuntary, rhythmic, and sustained.
• Cardiac muscle cells are self-excitable, beating without external nervous stimulation.
• Fibers have diameters from 9 to 22 μm. .

Skeletal Muscle Structure

• LM (light microscopy): Fibers are cylindrical, nuclei are peripheral, sarcoplasm (cytoplasm) contains myofibrils, and cross-striations are present.
• EM (electron microscopy): Sarcoplasm contains sarcoplasmic reticulum (SER), mitochondria, glycogen, lipid droplets, and myofibrils.

Myofibrils

• Myofibrils show alternating light (I-bands) and dark (A-bands) striations.
• A band contains an H-zone (pale area) bisected by an M-line.
• Each I-band is bisected by a Z-line.
• Sarcomeres lie between the successive Z-lines.

Sarcomere

• A sarcomere is the contractile unit of skeletal muscle.
• It extends from one Z-line to the next.
• Contains thin (actin) and thick (myosin) myofilaments.

Cardiac Muscle Cells

• Branch and interconnect to form a network (syncytium).
• Intercalated discs connect adjacent cells, ensuring rapid conduction of impulses.
• Cells are striated and have one central nucleus.
• Cells are self-excitable.

Test your knowledge on muscular tissues, focusing primarily on smooth muscle. This quiz covers the functions, structure, and characteristics of smooth muscle, as well as its role in the body. Perfect for biology students learning about human anatomy.