Skeleton - Movement and Locomotion - Detailed Study Notes

Functions of Human Skeleton

The human skeleton serves multiple vital functions that are essential for survival and daily activities.

1. Support and Framework

• Structural Support: Provides rigid framework that maintains body shape and posture
• Body Architecture: Acts as scaffolding for attachment of muscles, organs, and tissues
• Weight Distribution: Distributes body weight evenly to prevent collapse
• Examples: Vertebral column supports upper body weight, leg bones support entire body weight

2. Protection of Internal Organs

• Cranium: Protects brain from physical damage
• Rib Cage: Shields heart, lungs, and major blood vessels
• Vertebral Column: Protects spinal cord
• Pelvic Girdle: Protects reproductive organs, bladder, and lower digestive organs
• Importance: Prevents damage from external impacts and mechanical stress

3. Movement and Locomotion

• Muscle Attachment: Provides anchor points for skeletal muscles
• Lever System: Bones act as levers, joints as fulcrums, muscles provide force
• Locomotion: Enables walking, running, jumping, and all forms of movement
• Fine Motor Skills: Allows precise movements like writing, typing, grasping

4. Blood Cell Production (Hematopoiesis)

• Red Bone Marrow: Produces red blood cells, white blood cells, and platelets
• Location: Found in flat bones (sternum, ribs, hip bones) and ends of long bones
• Continuous Process: Replaces old blood cells throughout life
• Importance: Maintains oxygen transport, immune function, and blood clotting

5. Mineral Storage and Homeostasis

• Calcium Storage: 99% of body's calcium stored in bones
• Phosphorus Storage: Major reservoir of phosphate ions
• Mineral Release: Releases minerals into bloodstream when needed
• pH Balance: Helps maintain acid-base balance in blood
• Bone Remodeling: Constant breakdown and rebuilding maintains mineral homeostasis

6. Fat Storage

• Yellow Bone Marrow: Stores fat (adipose tissue) in medullary cavities
• Energy Reserve: Provides energy during times of nutritional stress
• Location: Primarily in long bones of arms and legs in adults

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Division of Human Skeleton

The human skeleton is anatomically divided into two main parts based on location and function.

Axial Skeleton

The axial skeleton forms the central axis of the body and includes bones along the midline.

Components and Functions:

1. Skull (Cranium and Facial Bones)

• Cranium: 8 bones protecting the brain
  • Frontal bone, parietal bones (2), temporal bones (2), occipital bone, sphenoid bone, ethmoid bone
• Facial Bones: 14 bones forming face structure
  • Maxilla (2), mandible, nasal bones (2), zygomatic bones (2), lacrimal bones (2), palatine bones (2), vomer, inferior nasal conchae (2)
• Functions: Brain protection, sensory organ housing, digestive system beginning

2. Vertebral Column (Spine)

• Cervical Vertebrae: 7 bones in neck region (C1-C7)
  • C1 (Atlas): Supports skull, allows nodding
  • C2 (Axis): Allows head rotation
• Thoracic Vertebrae: 12 bones in chest region (T1-T12)
  • Attach to ribs, larger and stronger
• Lumbar Vertebrae: 5 bones in lower back (L1-L5)
  • Largest vertebrae, bear most body weight
• Sacrum: 5 fused vertebrae forming back of pelvis
• Coccyx: 4 fused vertebrae forming tailbone
• Functions: Spinal cord protection, body support, movement flexibility

3. Rib Cage (Thoracic Cage)

• Ribs: 12 pairs of curved bones
  • True ribs (1-7): Directly attached to sternum
  • False ribs (8-12): Indirectly attached or floating
• Sternum: Breastbone with three parts
  • Manubrium (upper), body (middle), xiphoid process (lower)
• Functions: Heart and lung protection, breathing assistance

Total Bones in Axial Skeleton: 80 bones

Appendicular Skeleton

The appendicular skeleton includes bones of the appendages (arms and legs) and their attachments to the axial skeleton.

Components and Functions:

1. Upper Extremities

• Shoulder Girdle (Pectoral Girdle):
  • Clavicle (collarbone) - 2 bones
  • Scapula (shoulder blade) - 2 bones
• Arms:
  • Humerus (upper arm) - 2 bones
  • Radius and Ulna (forearm) - 4 bones
  • Hand bones - 54 bones total
    • Carpals (wrist): 16 bones (8 per hand)
    • Metacarpals (palm): 10 bones (5 per hand)
    • Phalanges (fingers): 28 bones (14 per hand)

2. Lower Extremities

• Pelvic Girdle (Hip Bones):
  • Hip bones (coxal bones) - 2 bones
  • Each hip bone formed by fusion of ilium, ischium, and pubis
• Legs:
  • Femur (thigh bone) - 2 bones (longest bone in body)
  • Patella (kneecap) - 2 bones
  • Tibia and Fibula (lower leg) - 4 bones
  • Foot bones - 52 bones total
    • Tarsals (ankle): 14 bones (7 per foot)
    • Metatarsals (arch): 10 bones (5 per foot)
    • Phalanges (toes): 28 bones (14 per foot)

Total Bones in Appendicular Skeleton: 126 bones

Total Bones in Human Body: 206 bones (adult)

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Types of Joints

Joints are points where two or more bones meet. They are classified based on the degree of movement they allow.

Classification by Movement

1. Immovable Joints (Synarthroses)

Joints that allow no movement between bones.

Characteristics:

• Bones are tightly fitted together
• Connected by fibrous connective tissue
• Provide maximum stability and protection
• No joint cavity present

Types and Locations:

Sutures:

• Location: Between skull bones (cranial sutures)
• Examples:
  • Coronal suture (between frontal and parietal bones)
  • Sagittal suture (between parietal bones)
  • Lambdoid suture (between parietal and occipital bones)
• Function: Protect brain, allow skull growth during childhood

Gomphoses:

• Location: Between teeth and jaw bones
• Example: Tooth roots in dental sockets (alveoli)
• Function: Secure teeth firmly in jaw for effective chewing

Functions:

• Maximum protection of vital organs
• Structural stability
• Force distribution across bones

2. Slightly Movable Joints (Amphiarthroses)

Joints that allow limited movement between bones.

Characteristics:

• Connected by cartilage or fibrous tissue
• Allow slight flexibility while maintaining stability
• Absorb shock and distribute forces
• Limited joint cavity or no cavity

Types and Locations:

Cartilaginous Joints:

• Location: Between vertebrae (intervertebral discs)
• Structure: Fibrocartilage discs between vertebral bodies
• Movement: Slight bending and twisting of spine
• Function: Shock absorption, spinal flexibility

Symphyses:

• Location: Pubic symphysis (between hip bones)
• Structure: Fibrocartilage pad between bones
• Movement: Slight separation during childbirth
• Function: Stability with limited flexibility

Syndesmoses:

• Location: Between tibia and fibula (lower leg)
• Structure: Dense fibrous connective tissue
• Movement: Slight spreading during ankle movement
• Function: Maintains bone alignment while allowing flexibility

Functions:

• Shock absorption
• Limited flexibility for specific functions
• Structural stability with some movement

3. Freely Movable Joints (Diarthroses/Synovial Joints)

Joints that allow considerable movement in one or more directions.

General Characteristics:

• Joint Cavity: Fluid-filled space between bones
• Synovial Membrane: Lines joint cavity, secretes synovial fluid
• Synovial Fluid: Lubricates joint, reduces friction
• Articular Cartilage: Smooth cartilage covering bone ends
• Joint Capsule: Fibrous capsule surrounding joint
• Ligaments: Connect bones, provide stability

Types of Synovial Joints:

A. Hinge Joint

Structure and Movement:

• Allows movement in one plane only (flexion and extension)
• Resembles door hinge mechanism
• Strong ligaments on sides prevent lateral movement

Locations and Examples:

• Elbow Joint: Between humerus and ulna
  • Flexion: Bending arm (biceps contraction)
  • Extension: Straightening arm (triceps contraction)
• Knee Joint: Between femur and tibia
  • Flexion: Bending leg backward
  • Extension: Straightening leg
• Ankle Joint: Between tibia/fibula and talus
  • Dorsiflexion: Lifting foot upward
  • Plantarflexion: Pointing foot downward
• Finger Joints: Between phalanges
  • Enables gripping and fine motor control

Functions:

• Powerful lever actions
• Precise directional movement
• Essential for locomotion and manipulation

B. Ball and Socket Joint

Structure and Movement:

• Rounded head of one bone fits into cup-shaped cavity of another
• Allows movement in all planes and rotation
• Most mobile type of joint

Locations and Examples:

• Shoulder Joint: Between humerus and scapula
  • Flexion/Extension: Moving arm forward/backward
  • Abduction/Adduction: Moving arm away/toward body
  • Rotation: Circular arm movements
  • Circumduction: Circular motion combining all movements
• Hip Joint: Between femur and hip bone
  • Similar movements but more restricted than shoulder
  • Weight-bearing function limits range of motion

Functions:

• Maximum range of motion
• Multi-directional movement capability
• Essential for complex movements like throwing, swimming

C. Gliding Joint (Plane Joint)

Structure and Movement:

• Flat or slightly curved bone surfaces
• Bones slide past each other
• Limited movement in multiple directions

Locations and Examples:

• Wrist Joints: Between carpal bones
  • Allows complex hand movements
  • Enables wrist bending and turning
• Ankle Joints: Between tarsal bones
  • Provides foot flexibility
  • Aids in walking on uneven surfaces
• Vertebral Joints: Between vertebral processes
  • Allows slight spinal twisting and bending
  • Contributes to overall spinal flexibility
• Sternoclavicular Joint: Between sternum and clavicle
  • Allows shoulder girdle movement

Functions:

• Fine adjustment of position
• Distribution of forces across multiple bones
• Enhanced flexibility in complex structures

D. Pivot Joint

Structure and Movement:

• One bone rotates around another
• Cylindrical or ring-like structure
• Allows rotation only

Locations and Examples:

• Atlantoaxial Joint: Between C1 (atlas) and C2 (axis) vertebrae
  • Allows head rotation (saying "no")
  • Atlas rotates around odontoid process of axis
• Radioulnar Joint: Between radius and ulna in forearm
  • Pronation: Turning palm downward
  • Supination: Turning palm upward
  • Essential for hand positioning

Functions:

• Rotational movements
• Important for orientation and positioning
• Enables complex manipulative tasks

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Summary of Joint Types and Movements

Movement Classification Table

Key Movement Terms

• Flexion: Decreasing joint angle (bending)
• Extension: Increasing joint angle (straightening)
• Abduction: Moving away from body midline
• Adduction: Moving toward body midline
• Rotation: Turning around bone's axis
• Circumduction: Circular movement combining flexion, extension, abduction, adduction
• Pronation: Turning palm downward
• Supination: Turning palm upward

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Question-Answer Section

1 Mark Questions

Q1. Name two functions of the human skeleton. A1. Support and protection of internal organs.

Q2. What is the total number of bones in an adult human skeleton? A2. 206 bones.

Q3. Give one example of an immovable joint. A3. Skull sutures.

Q4. Name the joint between the atlas and axis vertebrae. A4. Pivot joint.

Q5. Which type of joint is present at the elbow? A5. Hinge joint.

Q6. What is the function of synovial fluid? A6. To lubricate joints and reduce friction.

Q7. Name the longest bone in the human body. A7. Femur (thigh bone).

Q8. How many cervical vertebrae are present in humans? A8. 7 cervical vertebrae.

Q9. Give one example of a ball and socket joint. A9. Shoulder joint or hip joint.

Q10. What type of joint allows rotation around an axis? A10. Pivot joint.

Q11. Name the process of blood cell formation in bones. A11. Hematopoiesis.

Q12. Which skeleton includes the skull and vertebral column? A12. Axial skeleton.

Q13. Give one example of a gliding joint. A13. Wrist joints (between carpal bones).

Q14. How many ribs are present in the human rib cage? A14. 12 pairs (24 ribs total).

Q15. What movement does a hinge joint allow? A15. Flexion and extension.

2 Mark Questions

Q1. Differentiate between axial and appendicular skeleton. A1.

• Axial skeleton: Forms central axis, includes skull, vertebral column, and rib cage
• Appendicular skeleton: Includes bones of arms, legs, and their attachments to axial skeleton

Q2. List four functions of the human skeleton. A2.

• Support and framework for the body
• Protection of internal organs
• Movement and locomotion
• Blood cell production (hematopoiesis)

Q3. Name two examples each of immovable and freely movable joints. A3.

• Immovable joints: Skull sutures, tooth sockets
• Freely movable joints: Shoulder joint, knee joint

Q4. State two characteristics of synovial joints. A4.

• Presence of joint cavity filled with synovial fluid
• Bones covered with smooth articular cartilage

Q5. Differentiate between hinge joint and ball and socket joint. A5.

• Hinge joint: Allows movement in one plane only (flexion/extension), e.g., elbow
• Ball and socket joint: Allows movement in all planes including rotation, e.g., shoulder

Q6. Name the three types of vertebrae with their numbers. A6.

• Cervical vertebrae: 7
• Thoracic vertebrae: 12
• Lumbar vertebrae: 5

Q7. List two functions of red bone marrow. A7.

• Production of red blood cells
• Production of white blood cells and platelets

Q8. State two examples of pivot joints with their locations. A8.

• Atlantoaxial joint (between atlas and axis vertebrae)
• Radioulnar joint (between radius and ulna in forearm)

Q9. Name four bones of the appendicular skeleton. A9.

• Humerus (upper arm)
• Femur (thigh)
• Radius (forearm)
• Tibia (lower leg)

Q10. Differentiate between flexion and extension movements. A10.

• Flexion: Decreasing the angle between bones (bending movement)
• Extension: Increasing the angle between bones (straightening movement)

Q11. List two components each of axial and appendicular skeleton. A11.

• Axial skeleton: Skull, vertebral column
• Appendicular skeleton: Arms and hands, legs and feet

Q12. State two characteristics of slightly movable joints. A12.

• Allow limited movement between bones
• Connected by cartilage or fibrous tissue

Q13. Name two movements possible at ball and socket joints. A13.

• Rotation around the bone's axis
• Circumduction (circular movement)

Q14. List two functions of the vertebral column. A14.

• Protection of the spinal cord
• Support of the upper body weight

Q15. State two locations where gliding joints are found. A15.

• Between carpal bones in the wrist
• Between tarsal bones in the ankle

3 Mark Questions

Q1. Explain the structure and functions of axial skeleton. A1. Structure: Includes skull (cranium and facial bones), vertebral column (cervical, thoracic, lumbar vertebrae, sacrum, coccyx), and rib cage (12 pairs of ribs and sternum) Functions:

• Forms central axis and framework of body
• Protects vital organs (brain, spinal cord, heart, lungs)
• Provides attachment sites for muscles involved in posture and breathing

Q2. Describe three types of joints based on degree of movement. A2.

• Immovable joints: No movement, bones connected by fibrous tissue, e.g., skull sutures
• Slightly movable joints: Limited movement, connected by cartilage, e.g., intervertebral joints
• Freely movable joints: Considerable movement, synovial joints with joint cavity, e.g., shoulder, knee

Q3. Explain the structure and function of a hinge joint with examples. A3. Structure: Cylindrical end of one bone fits into corresponding depression of another, strong lateral ligaments prevent sideways movement Function: Allows flexion and extension in one plane only, like a door hinge Examples: Elbow joint (humerus-ulna), knee joint (femur-tibia), ankle joint

Q4. Describe five important functions of the human skeleton. A4.

• Support: Provides structural framework maintaining body shape and posture
• Protection: Shields internal organs (skull protects brain, ribs protect heart/lungs)
• Movement: Serves as attachment points for muscles enabling locomotion
• Blood cell production: Red bone marrow produces blood cells through hematopoiesis
• Mineral storage: Stores calcium and phosphorus, releases them when needed

Q5. Compare ball and socket joint with pivot joint. A5. Ball and Socket Joint:

• Structure: Round head fits into cup-shaped cavity
• Movement: All directions plus rotation
• Examples: Shoulder, hip joints

Pivot Joint:

• Structure: One bone rotates around another
• Movement: Rotation only
• Examples: Atlas-axis joint, radioulnar joint

Q6. Explain the components and functions of appendicular skeleton. A6. Components: Upper extremities (shoulder girdle, arms, hands), lower extremities (pelvic girdle, legs, feet) Functions:

• Enables locomotion and movement through attachment of limb muscles
• Provides manipulation capability through arm and hand bones
• Supports body weight and enables upright posture through leg bones

Q7. Describe the structure and characteristics of synovial joints. A7. Structure:

• Joint cavity filled with synovial fluid
• Articular cartilage covers bone ends
• Synovial membrane lines joint cavity
• Joint capsule surrounds entire joint

Characteristics: Allow free movement, lubricated for smooth motion, most mobile joint type

Q8. Explain three types of freely movable joints with their movements. A8.

• Hinge joint: Flexion and extension in one plane (elbow, knee)
• Ball and socket joint: Movement in all planes including rotation (shoulder, hip)
• Gliding joint: Sliding movements in multiple directions (wrist, ankle bones)

Q9. Describe the vertebral column structure and its functions. A9. Structure:

• 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused)
• Natural curves for shock absorption
• Intervertebral discs between vertebrae

Functions: Spinal cord protection, body support, movement flexibility, shock absorption

Q10. Explain how bones contribute to mineral homeostasis. A10. Calcium storage: Bones store 99% of body's calcium in calcium phosphate crystals Mineral release: When blood calcium drops, bones release calcium; when excess, bones store it Regulation: Controlled by hormones (parathyroid hormone, calcitonin) maintaining proper blood mineral levels

Q11. Describe the differences between red and yellow bone marrow. A11. Red Bone Marrow:

• Function: Produces blood cells (hematopoiesis)
• Location: Flat bones, ends of long bones
• Active throughout life

Yellow Bone Marrow:

• Function: Stores fat as energy reserve
• Location: Medullary cavities of long bones
• Can convert to red marrow when needed

Q12. Explain the joint classification based on structural features. A12.

• Fibrous joints: Connected by dense fibrous tissue, immovable (skull sutures)
• Cartilaginous joints: Connected by cartilage, slightly movable (vertebral joints)
• Synovial joints: Have joint cavity with synovial fluid, freely movable (knee, shoulder)

Q13. Describe the protective functions of different parts of axial skeleton. A13.

• Skull: Cranium protects brain from trauma and impact
• Rib cage: Ribs and sternum shield heart, lungs, and major blood vessels
• Vertebral column: Vertebrae protect spinal cord and nerve roots from damage

Q14. Explain the movements possible at different synovial joints. A14.

• Flexion/Extension: Decreasing/increasing joint angles (hinge joints)
• Abduction/Adduction: Moving away/toward midline (ball and socket)
• Rotation: Turning around bone axis (pivot joints)
• Gliding: Sliding movements (plane joints)
• Circumduction: Circular combination movement

Q15. Describe how the skeleton enables movement and locomotion. A15. Lever system: Bones act as levers, joints as fulcrums, muscles provide force Muscle attachment: Bones provide anchor points for skeletal muscle attachment Movement coordination: Different joint types allow specific movements - hinge for walking, ball-socket for arm swinging, enabling complex locomotor patterns like running, jumping