Joints of the Body

functions of the skeleton

-protection of internal organs and structures -support for body -movement of body--serve as attachment points for muscles -primary storage site for calcium, phosphorus, magnesium -site of blood cell formation (red bone marrow) -energy storage (adipose tissue of yellow bone marrow)

ligaments

-strong connective tissue structures that provide joint support and hold bones of joint together -ligaments do not restrict normal joint movement, but do limit movement at extreme extent of normal range and also prevent movement in abnormal directions types of joint ligaments: -extrinsic ligament, intrinsic ligament, intracapsular ligament some joints are poorly supported by ligaments--instead, surrounding muscles provide primary support for the joint. 1) muscles act as dynamic ligaments (provide dynamic limitation)--degree of muscle contraction constantly adjusted to level needed for joint support 2) example: rotator cuff muscles for glenohumeral joint: subclavius muscle for sternoclavicular joint

Bone tissue

-type of connective tissue -heavily mineralized for weight-bearing support -rich blood supply--very dynamic tissue and heals well if damaged 1) constantly remodels Itself to accommodate to changes in stress 2) increases or decreases bone thickness and strength with changes in weight bearing or degree of muscle pull

cartilage

1. a solid but slightly flexible (pliable) type of connective tissue 2. avascular-- all nutrients must reach cells by diffusion from outside the cartilage a) heals poorly if damaged 3) hyaline cartilage 4) fibrocartilage

joint classifications

a joint (articulation) is where 2 or more bones come together joints are divided into different types based on their structural features and function (movement ability)

Articular capsule

a) dense fibrous connective tissue structure that completely surrounds joint cavity b) capsule is attached to bones immediately above/below joint (usually near the outer margins of the articular cartilages of each bone) c) synovial membrane

cartilaginous joint

adjacent bones are united by cartilage (hyaline cartilage or fibrocartilage) a) synchondrosis b) symphysis

uniaxial joints

allow for only single axis of movement ex. elbow, C1/C2 joint --> atlantoaxial joint -hinge joints and pivot joints

multiaxial (triaxial) joints

allows 3 axes of movement; movement in 2 directions, plus rotation -plane joints and ball and socket joints

biaxial joints

allows for 2 axes of movement, at right angles to each other -ex. fingers/digits -condylar joints and saddle joints

fat pad

area of fibrous adipose (fat) tissue located inside the articular capsule 1) fat pad is located between the fibrous articular capsule and the synovial membrane (fat pad is covered by synovial membrane and therefore is not within space of joint cavity) 2) provides padding ex. olecranon fossa fat pad at elbow joint; infrapatellar fat pad of knee joint

movement limited by muscles

ball and socket joints: actions available to joint are defined by the muscles that cross the joint and the moment-to-moment degree of muscle activity (contraction) 1) joint movement determined by which muscles are active (or inactive) and by their strength of contraction --changes in contractile activity alters joint movement and joint position ex. at the shoulder joint, latissimus dorsi produces adduction, full extension, and medial rotation of the arm when acting alone. In combination, with pectoralis major, the actions of adduction and medial rotation are reinforced, but the range of extension produced by latissimus dorsi is limited by pectoralis major.

functional classifications of synovial joints

based on the range and type of motions available at the joint -uniaxial, biaxial, multiaxial joints

Bones of the body

bones of the body (the skeleton) consist of multiple tissues-bone tissue, articular (hyaline) cartilage, blood vessels, nerves, and bone marrow

synostosis

bony joints -bones that are fused together (united by bone tissue) a) since the bones of synostosis are fused together, they are also classified as immobile joints (synarthrosis) b) synarthrosis examples: --sutures of skull: in middle/old age, bone replaces fibrous connective tissue between bones of skull (suture line disappears as bones fuse together) --epiphyseal line: marks line of fusion between epiphysis and diaphysis of long bone of an adult (after disappearance of the epiphyseal plate cartilage) --sacrum: 5 sacral vertebrae fused together to form single adult sacrum; fusion of vertebrae begins at age 16-18 and is usually completed by age 34 --hipbone: single adult bone formed by fusion of individual ilium, ischium, and pubis bones; fusion completed between ages of 20-25

saddle joints

both bones have concave and convex articulating surfaces (both are shaped like a saddle)- opposing bones fit together like a rider sitting on a saddle -allows flexion/extension, adduction/abduction, and circumduction ex. carpometacarpal joint of thumb (trapezium-1st metacarpal); sternoclavicular joint

synchondrosis

cartilaginous joint in which the bones are united by hyaline cartilage 1) epiphyseal plate 2) manubriosternal joint 3) 1st sternocostal joint 4) all synchondriosis joints are classified as synarthrosis (immobile joints)

symphysis

cartilaginous joint where bones are united by fibrocartilage 1) fibrocartilage fills gap between adjacent bones and strongly unites them 2) gap between bones can be narrow or wide: a) narrow: pubic symphysis: unites right and left pubic bones of pelvis b) wide: intervertebral discs: thick fibrocartilage pads between adjacent vertebrae 3) symphysis joints allow for limited movement between the adjacent bones and thus are classified as amphiarthrosis (slightly moveable joints) a) wider symphysis of intervertebral disc allows for greater movement between bones, compared to narrow pubic symphysis with very limited movement.

blood supply to joints

collateral circulation--formed by the anastomosis (joining together) of several arteries around --a joint-enables multiple arteries to supply blood to the joint and surrounding structures -anastomoses between arteries ensure adequate blood supply if some arteries are pinched off during some joint movement --also ensures good blood supply to synovial membrane lining inside of articular capsule

joint crungruency

congruency- a measure of how well the shape of the articulating bone surfaces match congruent joint, incongruent joint

epiphysis

enlarged ends of a long bone 1) has thin outer wall of compact bone 2) interior filled with spongy bone 3) marrow cavity (spaces between strands of spongy bone) filled with red bone marrow

articular disc

fibrocartilage pad found at incongruent articulations--increases congruency of joint articular disc may be attached to only one of the bones or may attach to both bones 1) when attached to both bones, articular disc also serves as a strong ligament that holds the bones together (ex. sternoclavicular joint; distal radioulnar joint) 2) disc may also completely separate bones of joint and thus divide the joint into two individual joint cavities--this produces separate articulations between the disc and each bone (ex. temporomandibular joint)

labrum

fibrocartilage ring that encircles outer margin of socket portion of a ball and socket joint 1) labrum forms a lip around margin of socket-- serves to deepen socket ex. only examples: glenoid labrum of shoulder joint and acetabular labrum of hip joint

suture

fibrous joint where connective unites bones of the skull; most are classified as a synarthrosis (immobile joint) a) in infant, bones joined by broad areas of connective tissue (fontanelles)--form soft areas of an infant's head--connective tissue allows for movements between bones during childbirth and allow for growth of the skull and brain after birth b) fontanelles disappear by 18 months--remaining thin layer of connective tissue between adjacent bones allows for continued skull growth up to age 20 (when skull growth stops) c) with increasing age, sutures between adjacent bones can fuse together (fibrous connective tissue of suture gradually replaced by bone, converting suture to synostosis joint) 1) original sutures found between right and left frontal bones or right and left halves of mandible disappear entirely during early childhood 2) starting in late middle age, other sutures slowly begin to disappear- some skull sutures can disappear entirely in elderly individuals

structural classifications of joints

fibrous joints: bones united by fibrous connective tissue (CT) cartilaginous joints: bones joined together by cartilage synovial joints: bony articulation is within a joint cavity, surrounded by an articular capsule

plane joints

flat or slightly curved bony surfaces that permit simple gliding movements and rotation -however, ligaments and a tight fibrous articular capsule usually limit plane joint movement to only 1 or 2 axis of motions ex. upper limb examples: carpal-carpal joints, carpometacarpal joints, acromioclavicular joints

diarthrosis

freely moveable joints 1. synovial joints

synarthrosis

immobile joints 1. suture (a fibrous joint) 2. gomphosis (a fibrous joint) 3. synchondrosis (a cartilaginous joint) 4. synostosis (a bony joint)

joint cavity

interior space of joint-- defined by articular capsule, synovial membrane, & articular cartilages filled with synovial fluid

marrow cavity

interior spaces of a bone

syndesmosis

joint in which parallel bones are separated by a gap, but united by connective tissue a) connective tissue forms a sheet called an INTEROSSEOUS MEMBRANE ex. tibia/fibula--interosseous membrane prevents separation between the bones --anterior & posterior distal tibiofibular ligaments that unite distal ends of theses bones also contribute to the tibia-fibula syndesmosis ex. radius/ulna-- interosseous membrane prevents separation between the bones, but is flexible enough to allow for pronation-supination of forearm b) a syndesmosis is classified as an amphiarthrosis (provides limited movement)

intrinsic ligament

ligament that is fused to wall of the articular capsule or is formed by a localized thickening of the articular capsule wall ex. shoulder

intracapsular ligament

ligament that is located inside the articular capsule ex. ACL, PCL

extrinsic ligament

ligament that is located outside of the fibrous articular capsule ex. LCL, MCL, UCL

Movement limited by ligaments

ligaments restrict or limit actions of joint--allow joint movement within normal range of motion but prevent excessive or abnormal movements ex. range of extension at hip joint or extension at knee joint are limited by ligaments

epiphyseal line

line seen on adult bones that marks location of fusion between epiphysis and diaphysis (indicates former site of epiphyseal plate) ex. anatomical neck of humerus

parts of a long bone

long bones have elongated shape include: clavicle, humerus, radius, ulna, metacarpals, femur, tibia, fibula, metatarsals, phalanges a) diaphysis b) epiphysis c) articular cartilage d) periosteum e) epiphyseal plate f) marrow cavity

hyaline cartilage

most common type of cartilage -take friction load -resists friction and compression (very good at weight bearing) locations: 1) articular cartilage of joints (covers articulating surfaces of bones) 2) costal cartilages (between end of bony rib and sternum) 3) anterior part of nasal septum 4) most cartilages of larynx 5) cartilage rings of tracheal wall 6) forms embryonic precursor of long bones and epiphyseal plate in growing long bones

fibrous joints

opposing bones are strongly united by fibrous connective tissue three types: syndesmoses, sutures, gomphoses

Synovial joints

presence of a joint cavity-- contains articulation between bones -all synovial joints provide for free movement between articulating bones--classified as diarthrosis (mobile joints) features of synovial joints: 1) articular cartilage 2) articular capsule 3) joint cavity 4) ligaments 5) joint congruency

ball and socket joints

provides greatest range of motion of all body joints -large, rounded end (head) of one bone fits into socket on second bone -allows flexion/extension, adduction/abduction, circumduction, and medial/lateral rotation -only ball and socket joints in body: glenohumeral joint and hip joint

nerve supply to joints

rich afferent (sensory) nerve supply from joint capsule, ligaments, and surrounding structures (such as muscles and muscle tendons) provides proprioception (joint position sense)--somatic afferent information sent to CNS afferent nerve endings responsible for: 1) mediation of spinal reflex responses (stretch reflex with changes in muscle length, or withdrawal reflex if limb is injured) 2) feedback to motor centers in cerebellum/cerebrum of brain--for control of voluntary (conscious) movements and postural (unconscious) movements of body 3) pain sensations--twisting, stretching, tearing injuries of joint capsule, ligaments, articular disc, or muscle tendons in general: the nerve that innervates a joint is the same nerve that also supplies cutaneous sensory innervation to the skin over that joint.

condylar joints

rounded end (condyle) of one bone sits in slight depression on second bone- both articulating surfaces have an oval shape -allows for flexion/extension (larger movement) and adduction/abduction (lesser movement) -also permits circumduction (combination of flexion/extension and adduction/abduction movements)-rotation not permitted

diaphysis

shaft portion of a long bone 1) has thick wall of compact bone 2) marrow cavity filled with yellow bone marrow

congruent joint

shape of bony articulating surfaces form good match for each other ex. trochlea of humerus and trochlear notch of ulna

incongruent joint

shape of two bony surfaces match poorly a) an incongruent joint usually has an articular disc between the bones--serves to fill in between adjacent bones and thus increases joint congruency ex. sternoclavicular joint ex. knee joint--each rounded femoral condyle rests on flattened tibial condyle with an articular disc (meniscus) located between the bones

Amphiarthrosis

slightly movable joints 1. syndesmosis (a fibrous joint) 2. symphysis (a cartilaginous joint)

periosteum

specialized layer of fibrous connective tissue that covers outer surface of a bone (except at articular surfaces that are covered by hyaline cartilage) 1) contains cells which can differentiate into bone-producing cells as needed (during bone growth or healing)--adds layers of bone tissue to outer surface of the bone

functional classifications of joints

synarthrosis: immovable joint amphiarthrosis: slightly moveable joint diarthrosis: freely movable joint, uniaxial, biaxial, mulitiaxial

manubriosternal joint

synchondrosis between manubrium and body of sternum; forms the sternal angle

epiphyseal plate (growth plate)

synchondrosis formed by the layer of hyaline cartilage that unites the diaphysis and epiphysis in a growing long bone of children a) growth of epiphyseal cartilage produces increase in bone length 1) cartilage is replaced by bone--during childhood, rate of cartilage growth equals rate of bone replacement (ex. thickness of epiphyseal plate does not change) 2) at adult height, cartilage stops growing and is completely replaced by bone--bony diaphysis and epiphysis fuse together (form synostosis)

1st sternocostal joint

synchondrosis that forms the attachment between the sternum and costal cartilage of 1st rib. --all other sternocostal joints are movable synovial joints

fibrocartilage

takes compressive load -cartilage that contains numerous thick bundles of collagen fibers -strong, tough cartilage that resists both compression and pull -locations: articular disc and meniscus (knee), intervertebral discs of vertebral column, pubic symphysis of pelvis

movement limited by bones

the shape of the bony articulation defines the type of motion that are allowed at the joint ex. humeroulnar articulation of elbow joint (trochlea--trochlear notch) allows for flexion/extension movements only muscle placement around joint not important for limiting joint movement

epiphyseal plate

thin layer of growing hyaline cartilage (growth plate) that produces bone lengthening in growing long bones of children 1) located at junction between diaphysis and epiphysis (at both ends of a long bone) a) prominent bony landmarks may also have a separate epiphyseal plate ex. medial and lateral epicondyles of humerus, greater and lesser trochanters of femur 2) during childhood growth, epiphyseal cartilage grows at steady rate- pushes epiphysis away from diaphysis (produces bone lengthening) a) cartilage of plate is replaced by bone at same place--thickness of epiphyseal plate does not change 3) when adult height is reached, cartilage growth stops and epiphyseal plate disappears a) bony epiphysis and diaphysis fuse together, no additional bone lengthening is possible b) epiphyseal line

articular cartilage (synovial joints)

thin layer of hyaline cartilage that covers articulating surfaces of bones 1) cartilage maintains smoothness (reduces friction) of articulation and resists pressure (good at weight bearing) 2) cartilage lacks blood vessels (avascular)--regenerates poorly if damaged

articular cartilage

thin layer of hyaline cartilage that covers bone's articular surfaces 1) provides for smooth, friction-free movement between adjacent bones 2) good for weight-bearing (resists compression)

synovial membrane

thin tissue layer that lines inner walls of fibrous articular capsule and also covers non-articulating surfaces of the adjacent bones 1) secretes a thick synovial fluid--fills joint cavity a) provides lubrication between bones of joint b) also provides nutrients to articular cartilage of adjacent bones (cartilage is avascular and thus all nutrients get to the cartilage cells via diffusion)

hinge joints

type of uniaxial joints -allows for flexion/extension only -supported by collateral ligaments at outside margins of joint-these hold joints together without limiting normal range of movement -ex. elbow, knee, ankle, interphalangeal joints

pivot joints

type of uniaxial joints -allows for rotational movement only (rotation around long axis of bone) -bone rotates within ring composed of a bony fossa and a ligament -locations: head of radius at proximal radioulnar joint; dens of C2 (axis) vertebra and Its articulation with the C1 (atlas) vertebra