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Bones & Joints

Access Human Biology.

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Introduction

Bones are connected to each other by connective tissue.

A joint is where two or more bones meet together.

Without joints the skeleton would not be able to move or have very limited movement.

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Cancellous (spongy) bone.

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Types of Joints.

There are three main types of joints. Immovable joints (fibrous or fixed): Fibrous

connective tissue is used for immovable joints such is the cranium (sutures).

Semi-movable joints (cartilaginous or slightly movable): Cartilage is used for semi-moveable joints such as the vertebrae.

Synovial joints are the most common types of joints.

Synovial joints are freely moveable joints that are held together by ligaments.

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Synovial joints

Synovial joints have a fibrous capsule that is lined with the synovial membrane.

The synovial membrane secretes synovial fluid. Synovial fluid;

– Lubricates the joint.– Provides nutrients to joint.– Helps to maintain stability of joint.– Helps to keep ends of bones in line.

Articular cartilage coats the ends of the bones to protect against wear and tear by reducing friction at the joint.

Extra ligaments may surround the outside of the joint to provide extra strength and some also contain discs of cartilage to maintain stability.

The main support to the joints is provided by muscles.

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Synovial Joints.

Synovial joints are subdivided according to movements possible.

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Ball and socket

Location Movement

The hip joint.Shoulder joints.

The ball and socket joint is one of the most mobile joints.It allows movement in three planes.

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The Three Planes of Movement.

Flexion (forwards and backwards). Extension (straightening). Abduction (away from body). Adduction (towards the body). Rotation (around). Circumduction (combination).

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Hinge joint Location Movement

Elbow.Phalanges in fingers and toes.

The hinge joint allows movement in one plane; flexion. extension.

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Pivot joint Location MovementPivot joints are located at the joint between the radius and ulna.In-between the atlas and axis at the base of the skull.

The pivot joint also allows movement in one plane; rotation (round).Pronation (crossing over eg palm downwards).Supination (crossing over eg palm upwards).

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Saddle joint Location MovementThe saddle joint is only found at the site where the carpal bone meets the metacarpal bone of the thumb.

Saddle joint allows two planes of motion;Flexion.Extension.Abduction.Adduction.Small amount of rotation.

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Gliding joint Location MovementThe carpals of the hand, the tarsals of the feet are where gliding joints are found.

Movement at the gliding joint occurs as two flat surfaces slide over each other. In the hand, the carpals will slide over each to allow flexion, extension, and radial or ulnar deviation. Likewise, in the foot, the tarsals slide over each other during pronation & supination.

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Condyloid joint

Location Movement

Knee joint. Where the temporal and mandible bones meet.

Allows primary movement in mainly one plane; - flexion and extension with small amounts rotation also.