Joints
மூட்டுகள்
The joint between atlas and axis is a pivot joint — and pivot joints are synovial. Students who answer 'fibrous' or 'cartilaginous' have mixed up the type with the sub-type.
The idea
Joints are points of contact between bones, or between bones and cartilages. Force generated by the muscles is used to carry out movement through joints, where the joint acts as a fulcrum. The movability at these joints varies depending on different factors. Joints are classified into three major structural forms — fibrous, cartilaginous and synovial. Fibrous joints do not allow any movement; this type is shown by the flat skull bones, which fuse end-to-end with the help of dense fibrous connective tissue in the form of sutures to form the cranium. In cartilaginous joints the bones involved are joined together with the help of cartilages; the joint between adjacent vertebrae in the vertebral column is of this pattern and permits limited movements. Synovial joints are characterised by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones; such an arrangement allows considerable movement and these joints help in locomotion and many other movements. Examples: ball and socket joint (between humerus and pectoral girdle), hinge joint (knee joint), pivot joint (between atlas and axis), gliding joint (between the carpals) and saddle joint (between the carpal and metacarpal of the thumb).
Why it matters
Some places need rigid protection (skull), some need slight flexibility (spine), and limbs need wide movement — three joint types match these needs.
NEET lens
Pairs NEET asks: fibrous — sutures of skull bones (no movement); cartilaginous — between adjacent vertebrae (limited movement); synovial — ball and socket (humerus and pectoral girdle), hinge (knee), pivot (atlas and axis), gliding (between carpals), saddle (carpal and metacarpal of thumb). Pivot joint between atlas and axis is a synovial joint.
Clinical significance
Synovial joints such as the knee and hip are where arthritis strikes; when cartilage wears away, joint replacement surgery may be needed. A baby's skull sutures are not yet fused, allowing the head to change shape during birth.
Introduction
Joints are points of contact between bones (or bone and cartilage). They act as fulcrums for the force produced by muscles.
Core concept
Fibrous joints: no movement; flat skull bones joined by dense fibrous connective tissue as sutures (cranium). Cartilaginous joints: bones joined by cartilage; between adjacent vertebrae; limited movement. Synovial joints: fluid-filled synovial cavity between articulating surfaces; considerable movement. Types: ball and socket — humerus and pectoral girdle; hinge — knee joint; pivot — atlas and axis; gliding — between carpals; saddle — between carpal and metacarpal of thumb.
Go deeper
Pubic symphysis (fibrous cartilage) is a cartilaginous joint. Synovial fluid lubricates the joint and nourishes the articular cartilage.
From Class 10
You have seen hinge joints (elbow, knee) and ball-and-socket joints (shoulder, hip). NEET adds the structural classes and the exact example locations.