Chapter 5: How The Skeleton is Joined Together

joints/articulations

Where 2 bones meet

-they hold the skeleton together & allow for body mobility

How are bones classified by function?

The movement of the joint

How are bones classified by structure?

The tissue that joints bones together

What are the functional classification of joints?

synarthroses, amphiarthroses, diarthroses

Synarthroses

Immovable joints

Prefix: Syn-

Together

Prefix: Arthro-

Of a joint, relating to a joint

Amphiarthroses

Slightly movable joints

Prefix: Amphi-

Both, two; on both sides

Diathroses

Freely movable joints

Prefix: Dia-

Passing through

Prefix: Di-

Two, double

What are fibrous joints?

Bones are joined by dense connective tissue.

Most are immovable or slightly movable, depending onfiber length

What are the 3 types of fibrous joints?

sutures, syndesmoses, gomphoses

Fibrous Joint: Sutures

Rigid, interlocking joints of skull

Short connective tissue fibers that do not move

Ex: between skull bones

"short stitch by doctors"

Fibrous Joint: Gomphoses

Peg-in-socket joints

Fibrous connection is the periodontal ligament

Ex: teeth in alveolar sockets

"gom sounds like gum; chew gum in mouth"

syndesmosis

Bones connected by ligaments, bands of fibrous tissue

Fiber length varies, so movement varies

Ex: holds the tibia and fibula + radius and ulna together

"Together; Dense connective tissue"

What are cartilaginous joints?

Bones united by cartilage.

Movement is variable

cartilaginous joints

synchondroses and symphyses

Synchondroses

Hyaline Cartilage that unites bones

Can be immovable or slightly moveable

Ex: epiphyseal plate joints + cartilage of 1st rib with manubrium of sternum

"think of this when you see 'chon' (cartilage) in the word"

Symphyses

Fibrocartilage unites bones in symphysis joint

Strong, slightly moveable joint

Ex: pubic symphysis & intervertebral discs

"think of 'physis' - to grow - just like how bones grow at the diaphysis"

What are synovial joints?

Bones separated by a synovial or fluid-filled cavity

Are diarthroses

Ex: shoulder, elbow, wrist, hip, knee, ankle

distinct features of all synovial joints

1. synovial cavity

2. articular cartilage

3. articular capsule

4. reinforcing ligaments

synovial cavity

Fluid-filled cavity between two bones

Filled with viscous, slippery fluid, synovial fluid that lubricates the joint

What is articular cartilage?

Hyaline cartilage covering the ends of the bones

Helps increase the fitbetween the articulating bones

What is the articular capsule?

Encloses both bones' ends on all sides creates the synovial cavity

-external fibrous layer made of dense CT

-inner synovial membrane that makes the synovial fluid

-capsule is continuous with periosteum

What are reinforcing ligaments?

Helps stabilize joints

What may synovial joints also have?

1. menisci

2. bursae

3. tendon sheath

Menisci

Fibrocartilage discs that improve the fit between bones

Minimize wear and tear on joint surfaces

Bursae

Sacs of synovial fluid located between ligaments, muscles, bones, or tendons to reduce friction.

Tendon sheath

Bursa that wraps around a tendon to reduce friction.

-dense CT that goes from a muscle to a bone

What plays a role in the stability and mobility of a joint?

1. muscle tone keeps tendon tight as they cross joints - this is most important feature for strengthening a joint

2. ligament number and location have a limited role

3. the shape of the articular (joint) surface has a minor role

-more mobile something is the less stable and vice versa

Uniaxial Synovial Joints: Pivot Joint

Movements in one plane or a single direction

ex: joints between atlas (C1) and axis (C2) + humerus and radius

Performs rotation: bone turning around its long axis, toward the midline, or away from it

Supination

Turning the palms anterior or ventral

"Holding soup"

Pronation

Turning the palms posterior or dorsal

"Proposal"

Uniaxial Synovial Joints: Hinge Joint

Movements in one planeor a single direction

ex: joint between the humerus and ulna

Performs flexion & extension

Flexion

Decreases the angle between bones

Extension

Increasing the angle between bones

Biaxial Synovial Joints: Condylar & Saddle Joints

Movements in two planes or directions

ex: wrist joint or between palm and fingers

Performs flexion/extension + abduction/adduction

Abduction

Movement away from the midline of the body

Adduction

Movement toward the midline of the body

Multiaxial Synovial Joints: Ball-&-Socket Joints

Movements in many planes or directions.

ex: hip joint & shoulder joint

Performs many actions (flexion/extension, abduction/adduction, protraction/retraction, elevation/depression, etc.)

Protraction

Moving a part forward laterally

Retraction

Moving a part backward laterally

Elevation

Moving a body part superiorly

Depression

Moving a body part inferiorly

Dorsiflexion

Bending of the foot or the toes upward

Plantar Flexion

Bends the foot downward at the ankle or toes down

Inversion

Turning the sole of the foot inward

Eversion

Turning the sole of the foot outward