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Renin Angiotensin Mechanism.

Joints in Human Body (Short).

  Joints in Human Body (Short).

Introduction:

  • A joint is the place in the body where bones of the skeleton meet.

  • It is also called “Articulation.”

  • Joints allow locomotion.

Classification of Joints:

  • Joints can be classified as structurally or functionally. 

  • The structural classification of joints depends on the manner in which the bones connect to each other. 

  • The functional classification of joints depends on the nature of the movement the joints allow.

  • Arthrology is the branch of science that deals with the study of joints it is also called “Synosteology”.

Structural Classification of Joints:

  • The structural classification of joints is based on the type of tissue that binds the bones to each other at the joint. 

  • There are three types of joints in the structural classification.

    • Fibrous,

    • Cartilaginous,

    • Synovial joints.

  1. Fibrous Joints:

  • These are joints in which bones are joined by dense connective tissue that is rich in collagen fibers. 

  • These joints are also called sutures. 

  • The joints between bones of the cranium are fibrous joints.

  1. Cartilaginous Joints:

  • Cartilaginous joints are joints in which bones are joined by cartilage. 

  • The joints between most of the vertebrae in the spine are cartilaginous joints.

  1. Synovial joints:

  • Synovial joints are characterized by a fluid-filled space, called a synovial cavity, between the bones of the joints. 

  • The cavity is enclosed by a membrane and filled with a fluid, called the synovial fluid, which provides extra cushioning to the ends of the bones. 

  • Cartilage covers the articulating surfaces of the two bones, but the bones are actually held together by ligaments. 

  • E.g. Knee joint.

Types of Synovial Joints:

  • There are different types of synovial joints that offer different kinds of movements and articulations.

    1. Gliding joint.

    2. Hinge Joint.

    3. Pivot Joint.

    4. Condyloid Joint.

    5. Saddle Joint.

    6. Ball & Socket Joint.

  1. Gliding joint:

  • Also called “Planar Joints”.

  • The articulating surfaces are flat or slightly curved.

  • This joint allows side to side and back and forth movements between the flat surfaces of the bones.

  • e.g 

    • Intercarpal joints.

    • Intertarsal joints.

    • Sternoclavicular joints.

  1. Hinge Joint:

  • This joint allows an angular opening and closing motion.

  • One bone remains stationary while the other bone moves in an axis.

  • The convex surface of one bone fits in the concave surface of another bone.

  • They are monoaxial; they allow movement in only one direction.

  • e.g. 

    • Knee joint.

    • Elbow joint.

    • Ankle joint.

  1. Pivot Joint:

  • The rounded or pointed surface of one bone articulates with the ring formed by another bone.

  • This monoaxial allows movement in only the longitudinal axis.

  • e.g 

    • Atlanto-axial joint: Between Atlas and axis which permits side to side rotation of the head.

    • Radioulnar joints which permit anterior and posterior movements of the palms.

  1. Condyloid Joint:

  • Also called “ellipsoidal Joint”.

  • Here in this joint convex- oval shaped projection of one bone fits in the oval shaped depression of another bone.

  • Biaxial joint; movement is permitted in around two axis.

  • e.g. 

    • Wrist joint.

    • Metacarpo-phalangeal joints.

  1. Saddle Joint:

  • As the name indicates, the articulating surface of one bone is saddle shaped and the articular surface of another bone fifties in the saddle.

  • It is a modified condyloid joint.

  • Triaxial; allows movements in three axes.

  • e.g Carpometacarpal joint between Carpal bone: Trapezium and metacarpal of the thumb.

  1. Ball & Socket Joint:

  • Here in this joint the ball-like articulating surface of one bone fits in a cup like depression of another articulating bone.

  • Triaxial; allows movements in three axes.

  • e.g. 

    • Shoulder Joint. (The head of Humerus fits in the glenoid cavity of the scapula.)

    • Hip Joint (head of femur fits in the acetabulum cavity of the hip bone.)

Commonly Asked Questions:

  1. Define and classify joints.

  2. Describe the structure of a typical synovial joint.

  3. Classify and describe different types of joints.

  4. Write a note on,

    1. Fibrous joints.

    2. Ball and socket joints.

    3. Pivot Joints.

    4. Gliding Joints.

    5. Synovial joints.

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