Body Movements

Body Movements: Complete Guide for CBSE Class 6 Science

Introduction to Body Movements

Body movements are essential activities that enable humans and animals to perform daily tasks and move from one place to another. From the simple act of chewing food to the complex coordination required for walking, our bodies execute countless movements through the intricate interplay of bones, muscles, and joints.

Locomotion is the ability of an organism to move its entire body from one location to another. This fundamental biological capability is observed across both higher organisms (like humans, animals, and plants) and lower organisms (such as bacteria and fungi).

Human Skeletal System: The Framework of Movement

Structure and Composition

The human skeletal system comprises 206 bones in adults, forming the body's structural framework. Interestingly, newborn babies possess approximately 300 bones, but as they grow, some bones fuse together, reducing the total count to 206 by adulthood.

Functions of the Skeleton

1. Structural Support: Holds the body together and provides definitive shape
2. Protection: Shields delicate internal organs (brain, heart, lungs, liver, spinal cord) from external damage
3. Attachment Points: Provides numerous sites for muscle attachment
4. Movement Facilitation: Works with muscles to enable body part movement and locomotion

Major Parts of the Skeletal System

1. Skull (Cranium)

The skull, called 'khopri' or 'kapli' in Hindi, consists of the hardest bones in the human body.

Components:

• Cranium: Box-like structure encasing and protecting the brain
• Facial Bones: Give shape to the face and form protective sockets for eyes

Functions:

• Protects the brain from injury
• Safeguards facial sense organs (eyes, ears, nose)
• Provides structural shape to the head
• Only the lower jaw is movable, enabling eating and speaking

2. Backbone (Vertebral Column/Spine)

The backbone extends from the skull base to the hip region, serving as the body's central support structure.

Structure:

• Composed of 33 separate bones called vertebrae
• First 24 vertebrae are connected serially by cartilage
• Forms a hollow, tube-like structure housing the spinal cord
• Last 9 vertebrae are fused and immobile

Functions:

• Provides primary body support
• Supports the head at its top
• Serves as attachment point for shoulder bones, ribs, and hip bones
• Protects the delicate spinal cord

3. Rib Cage

A protective cage structure centered around the breastbone (sternum).

Structure:

• Consists of 24 bones arranged in 12 pairs
• All ribs connect to the backbone
• Curved, flexible bones forming a protective enclosure

Functions:

• Protects vital internal organs (heart, lungs, liver)
• Participates in breathing movements

4. Shoulder Bones

The shoulder structure consists of two primary bones:

Components:

• Collar Bone (Clavicle): Keeps shoulders apart
• Shoulder Blade (Scapula): Connects arms to the body through ball-and-socket joints

Functions:

• Maintains shoulder separation
• Attaches arms to the skeletal framework
• Provides attachment sites for muscles controlling arms, neck, and upper body

5. Hip Bone (Pelvic Bone/Pelvis)

A large, basin-shaped structure at the backbone's lower end.

Structure:

• Forms the pelvic girdle
• Connects to thigh bones via ball-and-socket joints

Functions:

• Supports and protects lower abdominal organs (intestines, urinary bladder, reproductive organs)
• Attaches legs to the body
• Provides muscle attachment sites for leg, hip, and trunk movement

6. Bones of the Hand

Three Main Sections:

Part	Bones	Quantity	Function
Wrist	Carpals	8 small bones	Provides flexibility, forms movable joints with forearm
Palm	Metacarpals	5 longer bones	Connects wrist to fingers, enables grasping
Fingers	Phalanges	14 bones (3 per finger, 2 in thumb)	Enables precise manipulation and gripping

Types of Human Body Movements

Major Categories of Body Movements

1. Flexion: Bending movement that decreases the angle between body parts (e.g., bending elbow, knee)
2. Extension: Straightening movement that increases the angle between body parts (e.g., straightening leg)
3. Abduction: Moving a body part away from the body's midline (e.g., lifting arm sideways)
4. Adduction: Moving a body part toward the body's midline (e.g., bringing arm back to side)
5. Rotation: Circular movement around a fixed axis (e.g., turning head side to side)
6. Circumduction: Circular movement combining flexion, extension, abduction, and adduction

Movements in Anatomical Planes

1. Sagittal Plane (Divides body into left and right)

• Flexion: Bending forward at hip, knee, or elbow
• Extension: Straightening or bending backward
• Example: Walking, running, bicep curls

2. Coronal (Frontal) Plane (Divides body into front and back)

• Abduction: Moving limbs away from midline
• Adduction: Moving limbs toward midline
• Example: Jumping jacks, lateral arm raises

3. Transverse (Horizontal) Plane (Divides body into upper and lower)

• Rotation: Twisting movements around vertical axis
• Example: Turning head, twisting torso

Examples of Muscles Responsible for Key Movements

Movement	Primary Muscles	Location	Example Action
Flexion	Biceps brachii	Front of upper arm	Bending elbow
Flexion	Hamstrings	Back of thigh	Bending knee
Extension	Triceps brachii	Back of upper arm	Straightening elbow
Extension	Quadriceps	Front of thigh	Straightening knee
Abduction	Deltoids	Shoulder	Lifting arm sideways
Adduction	Pectoralis major	Chest	Bringing arm to body
Rotation	Sternocleidomastoid	Neck	Turning head

Specialized Movements: Pronation, Supination, and Rotation

Pronation:

• Rotational movement of the forearm causing the palm to face downward
• Example: Turning a doorknob counterclockwise with right hand

Supination:

• Rotational movement of the forearm causing the palm to face upward
• Example: Holding a bowl of soup

Rotation:

• Circular movement around a bone's longitudinal axis
• Internal Rotation: Turning toward body's center
• External Rotation: Turning away from body's center
• Example: Rotating shoulder joint when throwing a ball

Differences:

Aspect	Pronation/Supination	Rotation
Location	Primarily forearm	Various joints throughout body
Axis	Longitudinal axis of radius/ulna	Longitudinal axis of any long bone
Direction	Palm down (pronation) / Palm up (supination)	Inward (internal) / Outward (external)
Example	Turning screwdriver	Rotating shoulder, hip, or head

Cartilage: The Body's Shock Absorber

Cartilage is a specialized connective tissue that is softer and more flexible than bone, yet provides essential support and cushioning.

Characteristics:

• Softer than bone but firm enough to maintain structure
• Can bend without breaking
• Elastic and somewhat flexible
• Acts as a shock absorber between bones

Locations of Cartilage:

1. Pinnae (Upper part of ears): Provides flexible structure
2. Nose tip: Allows nose to bend without breaking
3. Joint surfaces: Cushions bone ends where they meet
4. Intervertebral discs: Acts as cushion between vertebrae in backbone

Joints: Where Movement Happens

A joint is the point where two or more bones meet. Bones are connected at joints by tough, flexible bands of elastic tissue called ligaments.

Types of Joints

1. Fixed Joints (Immovable)

Joints that allow no movement between bones.

Examples:

• Cranial sutures (between skull bones)
• Joints between teeth and jawbone
• Joints between hip bones

Function: Primarily protective, maintaining rigid structure

2. Ball and Socket Joints

The most mobile joints allowing movement in all directions.

Structure:

• Rounded head of one bone fits into cup-shaped socket of another
• Permits circular, rotational, and multidirectional movement

Examples:

• Shoulder Joint: Where upper arm (humerus) meets shoulder blade (scapula)
• Hip Joint: Where thigh bone (femur) meets pelvic bone

Movement Capabilities:

• Flexion and extension
• Abduction and adduction
• Rotation and circumduction

3. Hinge Joints

Joints that work like a door hinge, allowing movement in only one direction.

Structure:

• Convex surface of one bone fits into concave surface of another
• Permits bending and straightening only

Examples:

• Elbow Joint: Allows forearm to bend and straighten
• Knee Joint: Enables leg to bend and straighten
• Finger Joints: Allow fingers to curl and extend

Limitation: Cannot bend backward or sideways

4. Pivot Joints

Joints where a bony ring rotates around an axis, enabling twisting movements.

Structure:

• One bone rotates around another stick-like bone
• Allows rotational movement only

Example:

• Atlas-Axis Joint: At the top of spine, allows head to turn side to side

Movement: Twisting and rotating

5. Gliding Joints

Joints that allow limited sliding movements between bones.

Structure:

• Flat or slightly curved surfaces slide over each other
• Cartilage between bones permits small movements

Examples:

• Between vertebrae in the backbone
• Between wrist bones (carpals)
• Between ankle bones (tarsals)

Movement: Small sliding and gliding motions

Common Clinical Tests to Assess Joint Range of Motion

Healthcare professionals use various methods to evaluate joint flexibility and movement:

1. Goniometry

• Uses a goniometer (protractor-like device) to measure joint angles
• Assesses flexion, extension, abduction, and adduction
• Provides precise angular measurements in degrees

2. Visual Assessment

• Healthcare provider observes joint movement through normal range
• Identifies limitations, asymmetry, or pain during movement
• Quick screening method

3. Active Range of Motion (AROM) Testing

• Patient moves joint independently without assistance
• Assesses muscle strength and joint function together
• Example: "Bend your elbow as far as you can"

4. Passive Range of Motion (PROM) Testing

• Healthcare provider moves the joint while patient remains relaxed
• Isolates joint flexibility from muscle strength
• Identifies joint stiffness or structural limitations

5. Functional Movement Screening

• Evaluates movement patterns in real-life activities
• Assesses multiple joints working together
• Examples: Squatting, reaching overhead, walking

6. Special Tests for Specific Joints

• Shoulder: Apley scratch test, empty can test
• Knee: McMurray test, drawer test
• Spine: Schober's test for lumbar flexibility

Animal Locomotion: Diverse Movement Strategies

Earthworm Movement

Structure:

• No bones or legs
• Two types of muscles: circular and longitudinal
• Tiny bristles (setae) on underside of each segment

Mechanism:

1. Circular muscles contract: Body segments become long and thin
2. Longitudinal muscles contract: Long segments become short and fat
3. Bristles grip ground: Anchor segments during movement
4. Alternating contractions: Create wave-like movement forward

Result: Moves by lengthening and shortening body segments alternately

Snail Movement

Structure:

• Body covered by protective hard shell
• Shell does not aid movement but provides protection
• Muscular foot projects from shell opening

Mechanism:

• Foot muscles contract and relax alternately
• Creates gliding motion over surfaces
• Secretes mucus to reduce friction

Characteristics: Slow, continuous gliding movement

Cockroach Movement

Capabilities: Walking, climbing, and flying

Structure:

• Three pairs of legs: Enable walking and climbing
• Hard outer skeleton: Made of connected units allowing flexibility
• Two pairs of wings: Attached to back segment

Muscles:

• Leg muscles: Facilitate walking movements
• Back muscles: Power wing movements for flight

Movement: Versatile locomotion on ground and in air

Bird Flight

Adaptations for Flying:

1. Streamlined body shape: Reduces air resistance
2. Hollow, light bones: Minimize body weight
3. Modified forelimbs: Wings with extended surface area
4. Strong shoulder and breast bones: Anchor powerful flight muscles
5. Air sacs in lungs: Provide double breathing (air passes through lungs twice)
6. Feathers: Reinforce wings and tail, increase lift

Flight Mechanism:

• Wing shape creates differential air pressure
• Higher pressure below wings creates lift
• Flight muscles move wings up and down
• Tail and various wing feathers control direction

Additional Movement: Hindlimbs adapted for walking and perching

Fish Swimming

Body Adaptations:

1. Streamlined shape: Allows easy water flow around body
2. Various fins: Aid swimming and stability
3. Strong muscles: Cover skeleton, power swimming movements
4. Flexible body: Enables side-to-side movement

Swimming Mechanism:

1. Muscles make front body curve to one side
2. Tail swings toward opposite side, forming a curve
3. Body and tail quickly curve to other side
4. Jerk motion pushes body forward
5. Fins maintain balance and direction

Result: Forward movement through water via side-to-side body and tail motion

Snake Locomotion

Structural Advantages:

1. Long backbone: Many vertebrae provide exceptional flexibility
2. Numerous ribs: Extend along body length
3. Thin interconnected muscles: Link backbone, ribs, and skin
4. Elongated body: Forms multiple loops simultaneously

Movement Mechanism:

• Body curves into many loops
• Each loop pushes against ground
• Multiple simultaneous pushes create fast forward movement
• Does not move in straight line

Movement Patterns:

• Concertina: Accordion-like bunching and stretching
• Serpentine: S-shaped lateral undulation (most common)
• Sidewinding: Diagonal movement across loose surfaces

Formula

While body movements primarily involve qualitative understanding, here are important quantitative concepts:

Concept	Formula/Relationship	Explanation
Range of Motion (ROM)	ROM = Maximum angle - Minimum angle	Measures joint flexibility in degrees
Lever System	Effort × Effort Arm = Load × Load Arm	Bones act as levers; joints as fulcrums
Muscle Force	Force = Mass × Acceleration	Muscles generate force to move body parts
Mechanical Advantage	MA = Load Arm ÷ Effort Arm	Efficiency of body's lever systems
Bone Count (Adult)	Total Bones = 206	Standard adult human skeleton
Bone Count (Newborn)	Total Bones ≈ 300	Fuse during growth to reach 206
Vertebrae Count	Total Vertebrae = 33	24 movable + 9 fused
Rib Pairs	Rib Pairs = 12 (24 total ribs)	Form the protective rib cage

Conclusion

Understanding body movements is fundamental to appreciating how humans and animals interact with their environment. The skeletal system, with its 206 bones, provides the framework for movement, while joints enable flexibility and range of motion. Muscles work in coordination with bones to produce controlled, purposeful movements.

From the protective fixed joints of the skull to the highly mobile ball-and-socket joints of the shoulder and hip, each joint type serves specific functional needs. Similarly, different animals have evolved diverse locomotion strategies—whether the muscular contractions of earthworms, the streamlined swimming of fish, or the powered flight of birds.

By studying body movements, students gain insights into anatomy, biomechanics, and the remarkable adaptations that enable life's diverse forms to thrive. This knowledge forms the foundation for understanding more advanced topics in biology, physiology, and health sciences.