Introduction
Locomotion and movement are essential for performing daily activities and interacting with the environment. Movement in humans is possible due to the musculoskeletal system, which includes bones, muscles, and joints. In this post, we’ll cover the structure of bones, types of joints, muscle physiology, and types of human movements.
1. Skeletal System
The human skeleton provides support, protection, and shape to the body. It also serves as the framework for movement.
a) Types of Bones
- Long bones: Femur, humerus; support weight and movement.
- Short bones: Carpals, tarsals; provide stability and support.
- Flat bones: Skull, ribs; protect internal organs.
- Irregular bones: Vertebrae; support complex functions.
b) Bone Structure
- Compact bone: Dense and strong; provides strength.
- Spongy bone: Porous; contains red bone marrow for blood cell formation.
- Bone Marrow:
- Red marrow: Produces RBCs, WBCs, platelets.
- Yellow marrow: Stores fat.
2. Joints
Joints are points where two or more bones meet. They allow movement and flexibility.
Types of Joints:
- Fibrous Joints: Immovable (skull sutures).
- Cartilaginous Joints: Slightly movable (vertebrae).
- Synovial Joints: Freely movable; contain synovial fluid.
Examples of Synovial Joints:
- Hinge Joint: Elbow, knee (flexion and extension).
- Ball-and-Socket Joint: Shoulder, hip (rotation, flexion, extension).
- Pivot Joint: Neck (rotation).
- Saddle Joint: Thumb (movement in two planes).
3. Muscular System
Muscles are contractile tissues that work with bones to produce movement.
Types of Muscles:
- Skeletal Muscle: Voluntary, striated, attached to bones.
- Smooth Muscle: Involuntary, found in internal organs.
- Cardiac Muscle: Involuntary, found in heart.
Structure of Skeletal Muscle:
- Made of muscle fibers → myofibrils → sarcomeres.
- Sarcomere: Functional unit; contains actin (thin) and myosin (thick) filaments.
Mechanism of Muscle Contraction (Sliding Filament Theory):
- Myosin heads attach to actin filaments forming cross-bridges.
- Actin filaments slide over myosin filaments.
- Muscle shortens, producing contraction.
4. Types of Human Movement
- Flexion: Decreasing angle between bones (bending elbow).
- Extension: Increasing angle between bones (straightening elbow).
- Abduction: Movement away from midline (raising arm sideways).
- Adduction: Movement toward midline (lowering arm).
- Rotation: Turning around an axis (neck rotation).
- Circumduction: Circular movement (arm in circle).
- Supination & Pronation: Rotation of forearm (palm up/down).
5. Disorders of Musculoskeletal System
- Osteoporosis: Loss of bone density.
- Arthritis: Inflammation of joints causing pain and stiffness.
- Muscular Dystrophy: Genetic disorder causing muscle weakness.
- Tendonitis: Inflammation of tendons.
MCQs for Exam Preparation
- The functional unit of a muscle is:
- A) Myofibril
- B) Sarcomere
- C) Actin
- D) Myosin
- Answer: B) Sarcomere
- Which type of joint allows rotation of the head?
- A) Hinge
- B) Pivot
- C) Ball-and-socket
- D) Saddle
- Answer: B) Pivot
- Which bone is an example of a long bone?
- A) Femur
- B) Vertebra
- C) Skull
- D) Tarsal
- Answer: A) Femur
- Which type of muscle is voluntary and striated?
- A) Cardiac
- B) Smooth
- C) Skeletal
- D) None
- Answer: C) Skeletal
- Flexion decreases the angle between bones. Which of these is an example?
- A) Straightening the knee
- B) Bending the elbow
- C) Turning the head
- D) Raising the arm sideways
- Answer: B) Bending the elbow
- Ball-and-socket joint is found in:
- A) Knee
- B) Elbow
- C) Shoulder
- D) Skull sutures
- Answer: C) Shoulder
- Synovial fluid is present in:
- A) Cartilaginous joint
- B) Fibrous joint
- C) Synovial joint
- D) None of the above
- Answer: C) Synovial joint
- Actin and myosin are found in:
- A) Bones
- B) Sarcomeres
- C) Cartilage
- D) Ligaments
- Answer: B) Sarcomeres
- Which disorder is caused by loss of bone density?
- A) Arthritis
- B) Osteoporosis
- C) Muscular dystrophy
- D) Tendonitis
- Answer: B) Osteoporosis
- Abduction refers to:
- A) Movement towards midline
- B) Circular movement
- C) Movement away from midline
- D) Rotation
- Answer: C) Movement away from midline