Unit 14 

The Muscular System 


Q. Explain the Muscular System. Describe the types, structure, and functions of muscles in detail.

Answer:

The muscular system is an organ system that is mainly responsible for movement of the body. It consists of nearly 700 muscles connected to the bones of the skeletal system. Muscles make up about half of the total body weight. Each muscle is an organ made up of muscle tissue, blood vessels, nerves, and tendons.

The muscular system helps in body movement, maintenance of posture, production of heat, circulation of blood, and movement of substances within internal organs.

Types of Muscles

There are three main types of muscle tissues:

  • Skeletal Muscle
  • Cardiac Muscle
  • Visceral (Smooth) Muscle


1. Skeletal Muscle

Definition : Skeletal muscles are voluntary muscles attached to bones and are responsible for body movements.

Features : 

Voluntary in action

Cylindrical and long fibres

Multinucleated cells

Striated appearance

Attached to bones by tendons


Functions : 

Helps in movement

Maintains posture

Produces heat

Supports joints


Examples : Biceps, Triceps , Quadriceps


2. Cardiac Muscle

Definition : Cardiac muscles are muscles present only in the heart.

Features : 

Involuntary in action

Branched fibers

Striated appearance

Uninucleated cells

Rhythmic contraction


Functions : 

> Pumps blood throughout the body

> Maintains blood circulation


Location : Wall of the heart


3. Visceral (Smooth) Muscle

Definition : Visceral muscles are involuntary muscles found in internal organs.

Features : 

Smooth appearance

Spindle-shaped cells

Uninucleated

Non-striated

Involuntary action


Functions :

Helps movement of food in the digestive tract

Controls blood vessel diameter

Helps in urination and childbirth

 

Location :

Stomach

intestines

Blood vessels

Urinary bladder


Structure of Muscle : 

     Each muscle consists of:

Muscle fibers

Blood vessels

Nerves

Connective tissue

Tendons

Muscle fibers  contain proteins called actin and myosin that help in muscle contraction.

Mechanism of Muscle Contraction

Muscle contraction occurs by the sliding movement of actin and myosin filaments. This is explained by the:

Sliding Filament Theory

 

According to this theory:

> Actin filaments slide over myosin filaments.

> Muscle fibers shorten and produce contraction.

> Energy for contraction is supplied by ATP.


Functions of the Muscular System

Movement – Helps in walking, running, writing, and other body movements.

Posture Maintenance – Maintains the shape and posture of the body.

Joint Stability – Supports and stabilizes the joints.

Heat Production – Produces heat during muscle contraction to maintain body temperature.

Blood Circulation – Cardiac muscles pump blood throughout the body.

Movement of Food – Smooth muscles help move food through the digestive tract.

Breathing – Muscles like the diaphragm help in respiration.

Protection of Internal Organs – Muscles protect delicate internal organs.

Support to Soft Tissues – Supports organs and soft tissues of the body.

Control of Body Openings – Muscles control openings like the mouth, anus, and urethra.




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