Joints Intro/Types of Joints

Joints 1. With one exception (the hyoid bone in the neck) every bone forms a joint with at least one other bone. 2. Joints, also called articulations, are the sites were two or more bones meet.

Function 3. Joints have two functions: – A. Hold bones together securely – B. Give the rigid skeleton mobility

Classification 4. Joints are classified in two ways: A. Functional classification (focuses on the amount of movement a joint allows) Immovable joints (synarthroses), ex: axial skeleton (SKULL sutures) Slightly immovable joints (amphiarthroses), ex: axial skeleton (VERTEBRA) Freely movable joints (diarthroses), ex: appendicular skeleton ….limbs (SHOULDERS, HIPS, etc) Protects organs Movement is MOST important

Classification Continues B. Structural Classification These classifications are based on whether fibrous tissue, cartilage, or a joint cavity separates the bony regions at the joint. 1.Fibrous Joints: 2.Cartilaginous Joints: 3.Synovial Joints:

Types of Joints: Fibrous Joints Connected by Fibrous Tissue (made of collagen) usually immovable Three Types: 1)Sutures – bound tightly allowing no movement, ex: sutures of the skull

Types of Joints: Fibrous Joints 2) Syndesmoses – longer fibers, have more “give”, ex: distal ends of tibia and fibula

Types of Joints: Fibrous Joints 3) Gomphosis – Periodontal ligaments immobile Ex) tooth in mandible

Types of Joints: Cartilaginous Joints Bone ends/parts are united by fibrocartilage Two Types: 1.Sychondrosis - immobile hyaline cartilage 2.Symphysis – slightly movable fibrocartilage

What’s the difference between types of cartilage? Hyaline cartilage, elastic cartilage, and fibrocartilage are all similar in that they are mostly made of collagen proteins with some additional compounds. The difference is in the way they are arranged. Hyaline cartilage consists of rounded collagen which makes it hard and like marble. It is usually found in movable joints. Elastic cartilage is made of elastin fibers and collagen in a wavy pattern that makes it flexible like rubber. It is found in your ears and nose. Fibrocartilage contains both type I and type II arranged in bundles. This makes it strong and slightly flexible and well suited for its main job as interbvertebral discs in your spine.

Types of Joints: Cartilaginous Joints Look at the next few images of cartilaginous joints : 1.Decide if it is movable or immovable. 2.Decide if the cartilaginous joint is made of fibrocartilage or hyaline cartilage. 3.Decide if the cartilaginous joint is an example of a synchondrosis or symphysis joint.

Types of Joints: Cartilaginous Joints

Types of Joints: Synovial Joints Freely movable Joints in which the articulating bones are separated by a joint cavity containing synovial fluid.

Types of Joints: Synovial Joints Have four distinguishing features: 1.Articular cartilage 2.Articlular capsule 3.Joint cavity Filled with fluid 4.Reinforcing ligaments

Parts of Synovial Joints 1.Articular Cartilage: covers ends of the bone forming the joint 2. Articular Capsule: joint surfaces are enclosed by a sleeve/layer of fibrous connective tissue 3. Joint Cavity: articular capsule encloses a cavity which contains lubrication, i.e. synovial fluid 4. Reinforcement Ligaments: fibrous layer of the capsule is usually reinforced with ligaments

Types of Joints: Synovial Joints Six types based on shape: Movements can be 1)Nonaxial 2)Uniaxial 3)Biaxial 4)multiaxial

Types of Joints: Synovial Joints 1.Plane Joint : articular surfaces are flat, movements are nonaxial, i.e. gliding does not involve rotation Ex: inter carpal joints of the wrist

Types of Joints: Synovial Joints 2.Hinge Joint: cylindrical end of bone fits into trough-shaped surface of another bone. Hinge joints are uniaxial (allows movement around one axis) Ex: elbow joint Ex: ankle joint Ex: phalanges of fingers

Types of Joints: Synovial Joints 3.Pivot Joint: rounded end of one bone fits into sleeve, or ring, of another bone, it is uniaxial Ex: joint between the atlas and the dens of the axis Ex: joint between radius and ulna

Types of Joints: Synovial Joints 4. Saddle Joint: each articular surface has both convex and concave areas (like a saddle), it is biaxial Ex: between carpals & metacarpals: thumb, twiddle your thumbs

Types of Joints: Synovial Joints 5.Condylar Joint: the egg shaped articular surface of one bone fits into the oval concavity in another Bone can move side- to-side and back-and- forth but can not rotate around an axis

Types of Joints: Synovial Joints 6.Ball-and-Socket Joint: spherical head of one bone fits into round socket in another multi-axial (allows rotations) Ex: shoulder Ex: hip