ANAT - all 3 parts of 3.2 [Articular system and joints]

Why Do We Even Need Joints?

Bones are very rigid & don’t bend easily - If they try to bend, they could get damaged.

To prevent this the body connects bones together at joints/articulations so movement can happen safely.

Hence a join/articulation is the point of contact between bones/between teeth and bone.

What are the 2 structural classifications of joints?

1) Presence/absence of space between articulating bones: how closely the bones fit together

2) Type of connective tissue that binds bones together: either fibrous tissue or cartilage

This divides joints into synovial joints, fibrous joints & cartilaginous joints.

Cartilage

It’s a resilient, semi-rigid form of connective tissue made of collagen fibre and elastin fibres.Cartilage forms parts of the skeleton where flexibility is needed. (ex// costal cartilage attaches the ribs to the sternum)

• cartilage is avascular (meaning blood vessels do NOT enter cartilage). Instead, it gets oxygen and nutrients through diffusion from surrounding tissues.

  • Because cartilage has poor blood supply, injuries heal slowly.

• Young people have more cartilage

What are the 3 types of cartilage?

• Hyaline cartilage: the MOST abundant cartilage in the body.

  • helps form articulations and creates smooth joint surfaces.

• Elastic cartilage:

  • provides strength, elasticity and shapes maintenance

  • is found in ear & epiglottis (epi helps separate windpipe & esophagus)

• Fibrocartilage: strongest type of cartilage.

  • found in intervertebral discs (sit between vertebrae) & pubic symphysis (joins the two hip bones anteriorly)

  • imp for strength and shock absorption

The 3 Classes of Joints

1. Synovial joints

   • movable - allow the greatest movement.

   • In synovial joints, bones are joined by an articular capsule

   • the bone ends are covered with hyaline cartilage

2. Fibrous joints

   • solid

   • minimal movement - movement depends on length of the fibrous fibers

   • Fibrous joints unite bones using fibrous tissues

3. Cartilaginous joints

   • solid

   • minimal movement

What are the 3 types of fibrous joints?

1) Sutures: These are the joints in skull.

• are made of dense irregular connective tissue

• occur ONLY between bones of the cranium

2) Gomphoses: joint between teeth and alveolar sockets

• tooth is connected using a periodontal ligament made of dense irregular connective tissue

• technically a specialized syndesmosis because it also uses a ligament.

3) Syndesmoses:

• joins bones using a ligament or a membrane

• An example: the interosseous membrane between the radius and ulna

What are the 2 types of cartilaginous joints?

1) Synchondroses:

• is a primary cartilaginous joint.

• Bones are united by hyaline cartilage (these are usually temporary)

  • Example: epiphyseal plate in a growing bone

  • Another example: first rib joining the sternum

When adulthood happens:

• the epiphyseal plate becomes an epiphyseal line

2) Symphyses:

• is a secondary cartilaginous joint

• Bones are united by fibrocartilage

• These joints are strong & slightly movable

  • Examples: pubic symphysis & intervertebral discs

What makes synovial joints different?