Anatomy Session 9: Muscular System

Muscular System

• Muscle tissue is specialized for contraction and makes up about 40% of a person's body weight.
• There are over 650 skeletal muscles in the human body.

Types of Muscle

• There are three types of muscular tissue: skeletal muscle, cardiac muscle, and smooth muscle.
• Skeletal muscle:
  • Found attached to bones of the skeleton
  • Voluntary, striated
  • Attached to bone and causes movement of the body
  • Known as voluntary muscle because it can be contracted at will
  • Appears markedly striated when examined with a microscope
• Cardiac muscle:
  • Found in the heart
  • Involuntary, striated, branching
• Smooth muscle:
  • Found in organs
  • Involuntary, non-striated

Functions of Muscle

• Produce body movements
• Maintain posture/body position
• Heat production

Microscopic Anatomy of Skeletal Muscles

• Skeletal muscle structure consists of bundles of tiny fibers that run the length of the muscle.
• Most fibers are about 3 cm long and 0.05 mm wide.
• Three connective tissue sheaths: epimysium, perimysium, and endomysium.
  • Epimysium: surrounds the entire muscle, dense irregular connective tissue
  • Perimysium: surrounds fascicles, dense irregular connective tissue
  • Endomysium: surrounds individual muscle fibers, reticular connective tissue
• Nerves and blood vessels enter, exit, and branch throughout connective tissue.

Organization of Skeletal Muscle

• A skeletal muscle cell is called a muscle fiber.
• A muscle fiber contains organelles called myofibrils.
• Myofibrils are groups of contractile proteins, actin and myosin, arranged in a sarcomere.
• Sarcomere arrangement creates the “stripes” seen in skeletal muscle.
• Muscle fibers are grouped in bundles called fascicles.
• Perimysium layer encases the fascicles.
• Epimysium layer surrounds the muscle as a whole and binds all the muscle fibers together.
• Connective tissue called fascia surrounds the muscle outside the epimysium.

This quiz covers the basics of the muscular system, including the types of muscles, their functions, and the microscopic anatomy of skeletal muscle.