The correct answer is option 3. Explanation & Key Takeaways: • The joint where the neck joins the head is called a pivotal joint. Hence, option 3 is correct. • This joint allows rotation of the head from side to side (left-right movement). • It is located between the first cervical vertebra (atlas) and the second cervical vertebra (axis) in the neck. Related Concepts: • Saddle joint: Found in the thumb (between the metacarpal and carpal bones), allowing movement in two directions. • Hinge joint: Found in the knee and elbow, allowing movement in only one direction (like a door hinge). • Ball and socket joint: Found in the shoulder and hip, allowing movement in all directions. • Types of Joints: • Fibrous Joints → Immovable (e.g., skull sutures) • Cartilaginous Joints → Slightly movable (e.g., vertebrae) • Synovial Joints → Freely movable (main joints for movement) • Examples of Synovial Joints: • Ball and Socket Joint → Shoulder, Hip → movement in all directions • Hinge Joint → Elbow, Knee → bending and straightening • Pivot Joint → Neck (atlas-axis) → rotation • Saddle Joint → Thumb → back-and-forth, side-to-side movement • Gliding Joint → Wrist, ankle → sliding movements • Condyloid Joint → Fingers → up/down and side/side movement • Key Features of Synovial Joints: • Synovial cavity filled with synovial fluid → reduces friction • Articular cartilage → smooth surfaces at bone ends • Ligaments → connect bones and provide stability • Muscles and tendons → enable movement