JOINTS

Learning Objectives

• To know the different joint types

• To understand how to classify joint types

• To be able to discuss the importance of the structure and function of a synovial joint

Joints The human skeleton is jointed to

allow movement.

Muscular contraction causes the bones to move about the joints.

A joint is where two or more bones meet and

muscles act together to cause movement.

There are 3 main types of joint found in the body.

Types of Joints

1. Fibrous/ immovable joints The bones at an immoveable joint cannot move -

they overlap or interlock, and are held together by

a tough fibre, e.g. the skull.

2. Cartilaginous/slightly moveable jointsThe bones at a slightly moveable joint can only move a little - they are held together by strong straps called ligaments and are joined by protective pads

known as cartilage, e.g. the ribs.

3. Synovial joint/freely moveableAt a freely moveable joint the bones move freely.They are also known as synovial joints, andare the largest group of joints found in the body,

e.g. the hips, shoulders and knees.

Freely Moveable joints are also known as Synovial Joints.

They are freely moving and occur where 2 or more bones meet.

There are about 70 freely moveable joints in the human skeleton.

These interest us the most because they allow the greatest range of movement and are found in the appendicualr skeleton

Freely Moveable Joints

Cartilage

1. Hyaline or Articular cartilage- found on the surface of bone

2. Yellow Elastic cartilage- elastic and found in the external ear

3. White Fibrocartilage- tough, dense tissue that acts as a shock absorber. Found between the vertebrae

1. Articular/hyaline Cartilage – A material which covers the end of each bone, and which helps prevent friction between the joint.

• Absorbs compression placed on the joint, protects the joint.

2. Joint Capsule – The outer layer is a tough fibrous layer called the fibrous capsule.

• Increases stability• The inner layer is called the synovial

membrane• Secretes synovial fluid, strengthens the joint

3. Synovial Membrane– Thin membrane which lines the inside of the joint capsule.

• It produces synovial fluid

4. Synovial Fluid – The fluid which surrounds the joint and is contained in the joint cavity.

• Reduce friction between the cartilage• Nourish the cartilage• Get rid of any waste debris

5. Tendons– Strong connective tissue that attached muscle to bone.

• Connect muscle to muscle

6. Bursa- pad of fat provide cushioning between the fibrous capsule and a bone or muscle.

• Cushion the joint and act as shock absorbers

4. Ligaments – A band of strong fibrous tissue, helps prevent dislocation.

• Connect bone to bone

The Synovial Joint of the Knee

The knee is a hinge joint.

Cruciate Ligaments

TendonsTibia/Fibula

FemurArticular(hyaline)Cartilage

Synovial Fluid

Synovial Membrane

Patella

Joint cavity

Joint capsule

The Hip is a ball and socket joint.

Ligaments

Synovial Fluid

Tendons

SynovialMembrane

Pelvis

Cartilage

Femur

The Synovial Joint of the Hip

TASK

1.Label the diagram of a synovial joint using a colour code system

YOU MAY BE ASKED TO LABEL A SYNOVIAL JOINT IN EXAM OR EXPLAIN THE STRUCTURE AND FUCTION

2. List two features that increase joint stability and give their specific function?

Examples of Synovial Joints

Types of Synovial Joints

KEY

Ball & Socket JointHinge Joint

Pivot Joint

Gliding Joint

Saddle Joint

Condyloid Joint

Synovial joints are classifed according to the shape of the articulating surface.

KEY TERM

ARTICULATION-

The different bones that form to make the joint

EXAMPLE

Joint Joint type Articulating bones Movement

Elbow Hinge joint Humerus, radius, ulna

Write down another example

1. Ball and Socket Joints

The ball has a head shaped of one bone which articulates with a cuplike socket.Allows the greatest range of movement

Examples

HIP

SHOULDER

2. Hinge Joints

They are cylindrical shaped of 1 bone articulates with a depression of an adjacent boneMovement is restricted to bending and straightening

EXAMPLES

ELBOW

KNEE

3. Pivot Joints

These are rounded, pointed or concave of one bone which articulates which a ring shaped bone.

Movement is restricted to 1 bone rotating around the longitudinal axis.

EXAMPLE

VERTEBRAE OFTHE NECK

4. Gliding Joints

The articulating surfaces are flat.

It allows limited movement

EXAMPLES

HAND BETWEEN THE CARPELS

5. Saddle Joints

The articulating surfaces are shaped like a saddle

It allows very limited movement

EXAMPLE

THUMB JOINT

6. Condyloid Joints

The surfaces are flatter and oval forming a shallow joint

It allows the second greatest range of movement.

EXAMPLE

WRIST JOINT

Structure and function

Hyaline/Articular cartilageStructure: Smooth, spongy cartilage that covers end of bone.Function: prevent friction between bones absorb compression placed on the joint protect bone from getting crushed

Joint capsule:Structure: Outer layer is a tough fibrous layer- fibrous membrane.

The inner layer- synovial membrane

Function:strengthen the joint secrete synovial fluid

Synovial FluidStructure; slippery fluid, contained in the joint cavityFunction; reduce friction between cartilage nourish the articular cartilage get rid of waste debris in joint

LigamentStructure; band of strong fibrous tissueFunction; connect bone to bone

Meniscus (cartilage)

Structure: white fibrocartilageFunction: improves the fit between bone ends increases joint stability reduces wear and tear at joint

BursaStructure:fluid filled sacs

Function: prevent friction where bones, ligaments and muscles may rub together

PLENARYIdentify the bones that articulate at the shoulder joint? (2 marks)

Identify the bones that articulate at the elbow joint? (3 marks)

Ball and Socket JointsThe ball has a head shaped

of one bone which articulates

with a cuplike socket.

Allows the greatest range of movement

Examples

HIP

SHOULDER

Hinge JointsThey are cylindrical shaped of 1 bone articulates with a depression of an adjacent boneMovement is restricted to bending and straightening

EXAMPLES

ELBOW

KNEE

Pivot JointsThese are rounded, pointed or concave of one bone which articulates which a ring shaped bone.Movement is restricted to 1 bone rotating around the longitudinal axis.

VERTEBRAE OFTHE NECK

Gliding Joints

The articulating surfaces are flat.

It allows limited movement

HAND BETWEEN THE CARPELS

Saddle Joints

The articulating surfaces are shaped like a saddle

It allows very limited movement

EXAMPLE

THUMB JOINT

Condyloid Joints

The surfaces are flatter and oval forming a shallow joint

It allows the second greatest range of movement.

EXAMPLE

WRIST JOINT