The Joints�A&P-I�Unit-V

Objectives

By the end of this session, the students will be able to:

• Define the term joint and other key terms.
• List three types of joints i.e.

Fibrous , Cartilaginous, and Synovial

• Describe the common characteristic features of a synovial joint.
• List the types of synovial joints.
• Discuss different types of movements at synovial joints.

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Terms

• Joint: is a point of contact between two bones, between bone and cartilage, or between bone and teeth.
• Joint is also known as articulation or arthrosis.
• Arthrology: The scientific study of joints.

Classification of Joints

• Structural Classification: is based on their anatomical characteristics.
• Functional Classification: is based on the type of movement.
• The structural classification of joints is based on two criteria:
• the presence or absence of a space between the joints, called synovial cavity, and
• the type of connective tissue that binds the bones together.

Classification of Joints cont….

Structural Classification includes:

• Fibrous Joints:
• No synovial cavity.
• Bones are held together by dense irregular connective tissue rich in collagen fibers.
• Cartilaginous Joints:
• No synovial cavity.
• Bones are held together by cartilage.
• Synovial Joints:
• They have synovial cavity.
• Bones are united by a capsule of dense irregular connective tissue and often accessory ligaments.

�Functional Classification�

• Relates to the degree of movement they permit. They are:
• Synarthrosis (syn= together): Immovable joints.
• Amphiarthrosis (amphi= on both sides): Slightly movable joints.
• Diarhrosis: (=movable joints): Freely movable joints.

Immovable Joints (synarthrosis)

Slightly Movable Joint (amphiarthrosis)

(diarthrosis)- freely moveable

Structure of Synovial Joints

Distinguishing Characteristics of synovial joints are:

• Synovial Cavity: A space between the articulating bones.
• All synovial joints are functionally diarthroses.
• Articular cartilage: Covers the tips of the articulating bones
• Articular capsule: Surrounds synovial joint and encloses the synovial cavity. It unites the articulating bones. It is composed of two layers—the outer fibrous membrane and an inner synovial membrane. The fibrous membrane is flexible and has great tensile strength to allow free movement and prevent dislocation of the bones.

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Structure of Synovial Joints Cont…

• Synovial Fluid (oval= egg): named for its appearance like egg white. It is Secreted by synovial membrane.
• It consists of albumin, Hyaluronic acid, and phagocytic cells.
• It functions as lubricating, absorbing shocks, supplying oxygen and nutrients to the chondrocytes of the articular cartilage.

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Types of Synovial Joints

Six types of Synovial Joints are:

1. Pivote Joint:

• The rounded or pointed surface of one bone articulates with a ring formed by another bone.
• Pivote is monoaxial joint as it allows motion around a single axis.
• Examples: atlanto-axial joint, radioalnar joints.

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Types of Synovial Joints

2. Hinge Joints:

• In a hinge joint, the convex surface of one bone fits into the concave surface of another bone.
• They are monoaxial
• Examples: Knee, Elbow, and interphalangeal joints.

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Types of Synovial Joints cont…

3. Gliding or Planar Joints:

• The articulating bones are flat or slightly curved.
• They are biaxial as they allow back-and-forth and side-to-side movement.
• Examples: Intercarpal, intertarsal, sternoclavicular, acromioclavicular, and vertebrocostal joints.

4. Condyloid Joints:

• It is formed by the convex oval-shaped projection of one bone and the oval-shaped depression of another bone.
• Condyle joints are biaxial.
• Example: Metacarpophalageal joints

Types of Synovial Joints cont…

5. Saddle Joints:

• One bone of the articular surface is saddle-shaped, and the other one fits into the saddle.
• Saddle joint is a modified condyloid in which the movement is somewhat freer.
• It is triaxial.
• Example: Carpometacarpal joint b/w the trapezium of the carpus and metacarpal of the thumb.

Types of Synovial Joints cont…

6. Ball and Socket Joints:

• It consists of ball-like surface of one bone fitting into a cuplike depression of another bone.
• It is triaxial.
• Examples: shoulder and hip joints.

Types of Movements at Synovial Joints

Types of synovial joint movements are Four:

• Gliding: is a simple movement of relatively flat bone surfaces back-and-forth and side-to-side.
• Example: Intercarpal and intertarsal joints.
• Angular movements: are concerned with an increase or a decrease in the angle between the articulating bones. Such major movements are flexion, lateral flexion, extension, hyperextension, abduction, adduction, rotation, and circumduction.

Types of Movements at Synovial Joints cont…

• Rotation: Movement of a bone around its longitudinal axis. In the limb, it may be medial or lateral.
• Special Movements: Occur only at specific or certain joints. They include depression, elevation, protraction, retraction (at TMJ), inversion, eversion, dorsiflexion, planter flexion, supination, pronation, and opposition (pinching).

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Abduction

Extension

Rotation

Flexion

Adduction

Synovial Joint Movement