Muscular System: Structure, Function, and Major Muscles

Overview of the Muscular System

Properties of Muscles

The muscular system consists of muscles and their associated tendons. Muscles are specialized tissues that produce movement by contracting and relaxing. Tendons are bands of connective tissue that attach muscle to bone.

• Contractility: The ability of muscle tissue to shorten forcefully when stimulated, producing movement. Example: Biceps muscle contracts to bend the elbow.

• Extensibility: The ability of muscle tissue to be stretched or extended without being damaged. Example: Triceps muscle extends as the arm straightens.

• Elasticity: The ability of muscle tissue to return to its original length after being stretched or contracted. Example: Muscles regain their shape after movement.

• Excitability: The ability of muscle tissue to respond to nerve impulses or stimulation. Example: Muscles respond to signals from the nervous system to initiate contraction.

Additional info: Muscles also generate heat and help maintain posture.

Types of Muscles

Classification of Muscle Tissue

There are three main types of muscle tissue in the human body, each with distinct structure and function:

Type	Location	Control	Striation	Contraction Speed
Skeletal	Attached to bones	Voluntary	Striated	Rapid
Cardiac	Heart	Involuntary	Striated	Rapid
Smooth	Hollow organs & blood vessels	Involuntary	Non-striated	Slow

• Striated appearance: Skeletal and cardiac muscles have a striped appearance due to highly organized contractile units.

• Voluntary vs. Involuntary: Skeletal muscle is under conscious control, while cardiac and smooth muscle contract automatically.

Major Skeletal Muscles: Anterior View

Key Muscles and Locations

The major skeletal muscles of the body are named based on their location, function, or shape. The following are important anterior (front) muscles:

• Deltoid: Shoulder

• Biceps brachii: Front of upper arm

• Pectoralis major: Chest

• Rectus abdominis: Abdomen

• Sartorius: Thigh (runs diagonally across the thigh)

• Tibialis anterior: Front of lower leg

Example: The biceps brachii flexes the elbow, while the rectus abdominis helps flex the trunk.

Major Skeletal Muscles: Posterior View

Key Muscles and Locations

The major skeletal muscles of the posterior (back) body include:

• Trapezius: Upper back and neck

• Latissimus dorsi: Middle and lower back

• Triceps brachii: Back of upper arm

• Gluteus maximus: Buttocks

• Gastrocnemius: Calf

• Soleus: Lower calf, beneath gastrocnemius

• Achilles tendon: Attaches calf muscles to heel bone

Example: The gluteus maximus extends the hip, while the gastrocnemius and soleus muscles are involved in plantar flexion of the foot.

Muscle Matching and Application

Examples and Practice Questions

• Muscle properties such as contractility are directly related to movement production.

• Cardiac muscle is not under voluntary control, unlike skeletal muscle.

• Muscle matching exercises help reinforce the anatomical location and function of major muscles.

Description	Muscle Name
Proximal lateral side of arm	Deltoid
Superior anterior side of arm	Biceps brachii
Superior anterior side of chest	Pectoralis major
Anterior side of lower leg	Tibialis anterior

Additional info: Understanding muscle location and function is essential for clinical practice, physical therapy, and sports medicine.