Anatomy chapter 8

Articulation

Joint- two or more bones meet

Joint classifications based on movement

synarthrosis, amphiarthrosis, diarthrosis

Joint classifications based on anatomy/tissue type

fibrous, cartilaginous, synovial

Synarthrosis

immovable

Amphiarthrosis

slight movement

Diarthrosis

freely moves

Fibrous joints

lack a synovial cavity, held together closely by fibrous connective tissue, little to no movement

Suture joint

fibrous joint that is synarthrotic- flat bones of the skull, suture ligament

Syndesmoses

fibrous joint that is amphiarthrotic with more connective tissue than suture

Examples of a syndesmoses joint

anterior tibiofibular joint and interosseous membrane

Synostosis joint

fibrous joint that is synarthrotic, fuses and ossifies

Example of a synostosis joint

epiphyseal plate to epiphyseal line

Gomphosis joint

fibrous joint that joins a cone-shaped bony process with a bony socket

Example of gomphosis joint

teeth in alveolar process

Cartilage joint

lacks a synovial cavity, allows little to no movement, connects bone through hyaline cartilage or fibrocartilage

Synchondrosis joint

cartilage joint that connects 2 bones via hyaline cartilage, immovable, before fusion occurs

Examples of a synchondrosis joint

epiphyseal plate and joint between ribs and sternum

Symphysis

cartilage joint that connects 2 bones via fibrocartilage attaching to hyaline cartilage at the end of the bones, amphiarthrotic

Examples of symphysis

Intervertebral discs and pubic symphysis

Synovial joint

Contains 2 bones separated by fluid-filled cavity and an articular (joint capsul) that has two layers

Synovial membrane

layer of joint capsul that produces synovial fluid

Articular cartilage

layer of joint capsul that acts as shock absorber and reduces friction

Synovial fluid functions

keeps cartilage healthy by lubricatiing joint surface, nourishing chondrocytes, and shock absorbing

Composition of synovial fluid

blood filtrate, hyaluronic acid, and glycoproteins

Accessory structures in a synovial joint

ligaments, articular discs, fat pads, bursae, tendo sheath, and labrum

Ligament

reinforces and strenghtns the joint capsul and is inelastic

Extrascapular ligament

outside of joint capsul

Examples of an extrascapular ligament

tibial and fibular collateral, stylomandibular, and sphenomandibular

Intrascapular ligament

inside of joint capsul

Examples of an intrascapular ligament

cruciates (ACL, etc.)

Articular disc

menisci- fibrocartilage pads that subdivide synovial cavity

Examples of articular disc

ulnoulnate joint and knee joint

Functions of articular discs

channel flow of synovial fluid, modifies articular surface, restricts movements at joints, help distribute body weight

Fat pads

around periphery of joint

Example of fat pad

tibiofemoral joint

Functions of fat pads

protect articular cartilage, packing material, fills space when joint changes shape

Bursae

fluid filled sacs containing synovial fluid

Locations of bursae

hypodermis, between tendons/ligaments and bones

Functions of bursae

cushions and aids movement of tendons

Tendon sheath

not part of articulation, surrounds tendons to reduce friction

Tendonitis

inflammation of tendon sheath

Labrum

lip or rim, extends rim of shoulder and hip joint

Gliding movements

Sliding at articulation in one direction (forward and backward)

Examples of gliding movements

tarsals and carpals

Angular movement

a change in angle between the shaft and the articular surface

Abduction

moving a part away from the midline

Adduction

moving a part towards from the midline

Flexion

bending parts of a joint so angle between them decreases

Extension

movement that increases the angle between parts of a joint

Hyperextension

extending joint beyond anatomical position

Circumduction

pivoting around the origin of a limb

Rotation

turning around its own axis

Pronation

turning hand so palm is downward

Supination

turning hand so palm is upward

Eversion

turning sole of foot outward

Inversion

turning sole of foot inward medially

Dorsiflexion

flexing foot at ankle

Plantar flexion

tipping toes downward

Lateral flexion

when vertebral column bends gto side

Protraction

movement anteriorly in the horizontal plane

Retraction

moving a part backward

Opposition

pad to pad contact of thumb with palm or other finger

Elevation

movement superiorly

Depression

lowering a part

Principle of synovial joints

there is always a trade-off between flexibility and stability as determined by shape of articulating surface that prevents movement in certain directions, tightness of ligaments, presence of accessory ligaments and collagen fibers, other muscles, fat pads or bones

Types of synovial joints

Plane, hinge, pivot, condylar, saddle, and ball-and-socket

Plane joint

articulating surfaces are flat or slightly curved, allows sliding in 1 or 2 planes

Examples of plane joint

intercarpal or intertarsal joints, sternoclavicular joints, vertebrocostal joints

Hinge joint

convex surface of one bone fits into concave surface of another, movement in 1 plane only (uniaxial)

Examples of hinge joint

knee, elbow, ankle, interphalangeal joints

Pivot joint

rounded surface of one bone articulates with shallow depression or foramen in another, movement around a central axis

Condylar joint

ovoid condyle of one bone fits into ellipsoidal depression in another, biaxial movement

Pivot joint examples

proximal radioulnar joint, atlanto-axial joint

Condylar joint examples

wrist and metacarpophalangeal 2-5

Saddle joint

articular surfaces are saddle shaped (one convex and one concave), biaxial movement but not rotational

Saddle joint example

trapezium of carpus and metacarpal of thumb

Ball-and-socket joint

ball shaped head on one bone fits into cup shaped socket on another, movement in all directions

Ball-and-socket joint examples

shoulder and hip joints

Temporomandibular joint (TMJ)

hinge joint between condylar process of the mandible and mandibular fossa of the temporal bone- gliding and rotational, 2 synovial joints

Intervertebral articulation

Plane joints separated by intervertebral discs

Movement of intervertebral articulation

lateral flexion, rotation, flexion, and extension

Annulus fibrosis

outer layer of disc with collagen fibers in this attach disc to bodies of adjacent vertebrae

Nucleus pulposes

inner layer of disc that allows the disc to work as a shock absorber

Composition of nucleus pulposes

water, hyularonic acid, reticular and elastic fibers

Herniated disc

Nucleus pulpous breaks through annulus fibrosus, movements of vertebral column compresses the nucleus

Shoulder joint

glenohumeral joint, head of humerus meets glenoid cavity, contains many musckes, ligaments, bursae

Why does the shoulder joint have lots of ligaments and muscles for reinforcements?

the joint capsul encloses the joint, but it is still loose

Glenohumeral ligament

stablizes joint when humerus reaches or extends limits of normal motion

Coracohumeral ligament

strengthens articular capsul and supports weight of limb

Acromialclavicular ligament

restricts clavicular movement at acromial end, dislocattions common here

Coracoclavicular ligament

limits motion between clavicle and scapula

Transverse humeral ligament

holds down tendon of long head of bicep brachii in intertubercular

Elbow joint

hinge joint involving humerus, radius, and ulna, allows for flexion and extension

Why is the elbow joint stable?

bony surface of radius and ulna interlock, thick articular capsule, and ligaments

Medial collateral ligament (ulnar colleteral)

stabalizes medial surface

Lateral collateral ligament (radial collateral)

stabilizes lateral surface

Annular ligament

helps keep radial head in contact with olecranon, blends with lateral collateral and joint capsule

Joints of the wrist

distal radioulnar, radiocarpal, and intercarpal joints

Distal radioulnar joint

pronation and supination

Radiocarpal joints

flexion/extension, abduction/adduction, and circumduction