Types of Muscle Tissue

Skeletal Muscle

Skeletal muscle tissue is organized into skeletal muscles, which are organs attached to bones and skin. These muscles are responsible for voluntary movements and are under conscious control.

• Skeletal muscle fibers are the longest muscle cells and have striations (striped appearance).

• Also called voluntary muscle because it can be consciously controlled.

Cardiac Muscle

Cardiac muscle tissue is found only in the heart and forms the bulk of the heart walls.

• Striated appearance.

• Involuntary: cannot be consciously controlled.

Smooth Muscle

Smooth muscle tissue is located in the walls of hollow organs such as the stomach, urinary bladder, and airways.

• Not striated.

• Involuntary: cannot be consciously controlled.

Characteristics & Functions of Muscle Tissue

Main Characteristics

All muscle tissues share four key characteristics:

• Excitability (Responsiveness): Ability to receive and respond to stimuli.

• Contractility: Ability to shorten forcibly when stimulated.

• Extensibility: Ability to be stretched.

• Elasticity: Ability to recoil to resting length after being stretched.

Functions of Muscle Tissue

• Produce movement: Responsible for locomotion and manipulation (e.g., walking, digesting, pumping blood).

• Maintain posture and body position

• Stabilize joints

• Generate heat as they contract

Skeletal Muscle Anatomy

Structural Features

Skeletal muscle is an organ composed of various tissues and has three main features: nerve and blood supply, connective tissue sheaths, and attachments.

• Each muscle receives a nerve, artery, and veins.

• Every muscle fiber is supplied by nerves for conscious control.

• Contracting muscle fibers require large amounts of oxygen and nutrients, and waste products must be removed quickly.

Connective Tissue Sheaths

Connective tissue sheaths support and reinforce the whole muscle. They are organized from external to internal:

• Epimysium: Dense irregular connective tissue surrounding the entire muscle; may blend with fascia.

• Perimysium: Fibrous connective tissue surrounding fascicles (groups of muscle fibers).

• Endomysium: Fine areolar connective tissue surrounding each muscle fiber.

Table: Connective Tissue Sheaths of Skeletal Muscle

Muscle Attachments

Attachment Sites

Muscles span joints and attach to bones at two main sites:

• Insertion: Attachment to the movable bone.

• Origin: Attachment to the immovable or less movable bone.

Types of Attachments

• Direct (fleshy) attachment: Epimysium fused to periosteum of bone or perichondrium of cartilage.

• Indirect attachment: Connective tissue wrappings extend beyond muscle as ropelike tendon or sheetlike aponeurosis.

Summary Table: Types of Muscle Tissue

Example

When you walk, skeletal muscles contract to move your limbs, cardiac muscle pumps blood to supply oxygen, and smooth muscle in your digestive tract moves food along.