A&P Exam 3- Joints & Articulations (Ch.8)F

Functions of Joints/Articulations(4)

1. Connect 2 bones

2. enable movement

3. provide stability

4. allow long bones to lengthen

How do joints enable movement

• surrounding muscles and tendons exert necesary amount of force across joint to enable movement

How do joints provide stability

• joints that do not allow movement or don’t have a lot of mobility are very stable, important for the structures that protect underlying strcutures like the skull

How do joints allow long bones to lengthen

• epiphyseal plate is a temporary joint in long bones that allow growth during skeletal development

How to classfity joints (2 ways)

1. functional classification: amount of movement they allow

2. strucutral classification: based on anatomical features, type of connective tissue taht links bones and whether or not there is space between the bones

3 functional classes of joints

1. synarthrosis: no movement between articulating bones, gives most stability

2. amphiarthrosis: small amount of movement between bones; gives a good amount of stability

3. diathrosis: freely moveable with wide variety of movements but least amount of stability

(MORE MOVEMENT = LESS STABILITY)

3 structural classes of joints

1. fibrous joints

2. cartilaginous joints

3. synovial joints

Fibrous joints & 3 classes

• united by dense regular collagenous connective tissue; no joint space; functionally synathroses or amphiarthroses. collage fiber gives stability but not a lot of motion

1. sutures

2. gomphoses

3. syndesmoses

Sutures

• type of fibrous joint between bones of skull

• after skull development, edges have finger-like projections that intervweave adn are held tgt by short collagen fibers

• stable synathroses

Synostosis

• When bones of skull fuse together during 4th or 5th decade of life

gomphoses

• type of fibrous joint between tooth and alveolus in mandible or maxilla

• stable synarthroses

• each tooth is attached to bone fibers called periodontal ligament

Syndesmoses

• type of fiborus joint

• bones are jointed by a long interosseous membrane or ligament; composed of dense irregular tissue

• example: between radius and ulan in forearm or fibula and tibia. Ampiarthroses since there’s a little movement

Cartilagenous Joints& 2 classes

• lack a joint cavity and have very little motion. Cartilage between articulating bones; no joint space; functionally synathroses or amphiathroses

1. synchrondoses

2. symphyses

Synchondroses

• type of cartiagenous joint where bones are united by hyaline cartilage (synarthroses) bc tough and flexible

• examples: epiphyseal plate between diaphysis and epiphysis of growing long bone. When cartiagle in plate is replaced by bone, synotosis is formed

• example 2: first sternocostal joint: first rib to manubrium and costochondral joint: rib to costal cartilage

Symphyses

• type of cartilagenous joint where bones are united by a fibrocartilage pad (amphiarthroses)

• resist compression and tension while moving a little

• example: intervertebral joints or discs between bodies

• example 2: pubic symphysis between 2 pubic bones & flexible during childbirth

Synovial Joint

• have a joint cavity, filled with fluid between articulating bones, functionally diarthroses

Joint (Synovial) Cavity & 3 features

• presence of space between synovial joints/ 2 bones

• 3 features:

1. articular capsule

2. synovial fluid

3. articular cartilage

Articular Capsule

• double layered strucutre of synovial joint: outer fibrous layer and inner synovial membrane

• outer fibrous layer: dense irregula tissue to hold bones tgt and keep out blood supply

• synovial membrane: loose CT with cels to secrete synovial fluid

What would happen if blood vessels entered the synovial joint cavity?

• vessels would be damaged as the bones between the synovial joint move freely

• diseases from blood could enter

Synovial Fluid (3 functions)

1. lubrication: reduces friction and protects articulating ends of bone

2. metabolic functions: supplies nutrients, like glucose to cells in joint cavity and removes metabolic waste

3. shock absorption: evenly distributes force and stress on articular surfaces of bone during movement

Synovial Fluid + What happens when there’s too little/ too much

• fluid continuously replenished, circiulated and removed in synovial joints that’s thick and clear in synovial joint cavities

• if there’s too little, joint damage

• needs to also be removed as quickly as it is secreted because too much can cause pain or impair joint mobiliy

Articular Cartilage

• part of synovial joint cavity. Hyaline cartilgae that covres all exposed articulating bone surfaces within the joint cavity

• smoot surface reduces friction and absorbs shock

• avascula and needs circulation of synovial fluid since damage is probably permanent

3 other components of synovial joint cavity

1. adipose tissue for padding

2. blood vessels to surround articular capsule

3. nerves to transmit painful stimuli to brain and stimuli relating to position of joint for proper body movement/posture

4 supportive strucutres of a synovial joint

1. ligaments (intrinsic and extrinsic)

2. tendons

3. bursae

4. tendon sheaths

Ligaments

• strand of dense regular collagenous connective tissue to connect one bone to another bone

• give strength for joints (synovial usually)

2 types of ligaments to help synovial joints

1. intrinsic ligament: thickened regions of articular capsule found within the capsule

2. extrinsic ligament: not part of articular capsule that may be inside or outside joint cavity

Tendons

• Dense regular collagenous connective tissue strucutre to connect muscle to bone or another strucutre

• typically cross over or are around a joint to transmit force, and can pull on the bone it attaches to during contraction

Muscle Tone

• small contractions for muscles to keep tendons tight and pulled

• allows tendons to be around or cross over properly another joint & ends of articulating bones near one another

Bursae

• strucuctural support for synovial joints

• synovial fluid-filled strcuture lined with a synovial membrane that can be attached or seperate from the articualr capsule to minimize friction

• found in regions of high stress where bones and skin interact in small spaces for less friction

Tendon Sheaths

• support of synovial joints

• long bursae that surround some tendons in high-stress regions

• protect long tendons as they course over and around synovial joints

Bursaitis

• inflammation of bursa usually in the shoulder, elbow, hip and knee that cause pain at rest and with movmeent

• can result from a. single traumatic event like a fall or repetitive movements, even arthritis

• important to rest and ice, also give anti-inflammatory injections into bursa to remove fluid

Arthritis & 3 types

• inflammation of one or more joints causing pain, joint stiffness and less ROM

• results from breakdown of articular cartilage

Types:

1. Osteoarthritis

2. Rheumatoid arthritis

3. Gout

Osteoarthritis

• most common type of arthritis

• occurs from wear and tear (cartiagle gradually breaks down)

• increased age increases likelihood

Rheumatoid Arthritis

• autoimmune disease taht results in joint destruction from an indiviual’s own immune system

• immune system attacks tissues around synovial joints, damaging articular cartialge

Gouty Arthritis (GOUT)

• excess uric acid (waste product) crystalizes and forms in connective tissue around the joint

Functional Classes of Synovial Joints

• Bones in synovial joint travel through a plane around an axis. Each plane has an axis perpendicular to its surface

• grouped based on number of axes around which a bone can move

4 Functional Classes of Synovial Joints

1. Nonaxial Joints: smooth gliding movement can occur in one or more planes but doesn’t move around an axis

2. Uniaxial joints: allow movement only one axis

3. biaxial joint: allow movement around 2 axes

4. multiaxila/triaxial joint: allow motion around 3 axes

Elbow joint (waht axis moving joint)

• uniaxial joint that only has one axis and acts like a hinge

• allows motion in one plane perpendicular to axis

• forearm and hand can move toward the shoulder or move in opposite direction

metacarpophalangeal joint (waht axis moving joint)

• biaxial joint that can move around axis one to allow phalanges to move away or toward palm

• also can move around axis two for figners to squeeze tgt or fan apart

Shoulder Joint (what axis movemnet joint)

• example of triaxial joint

• moves forward and backward (axis one)

• moves away from and toward body (axis 2)

• moves in a circular pattern (axis 3)

4 types of movements at synovial joints

1. gliding movements

2. angular movements

3. rotational movements

4. special movements

Gliding Movements

• nonaxial movements as articulating surfaces of bones slide past each other in single plane but not around axis

• no rotation

• example: intertarsal joints

Angular Movements & 7 examples

• increase or decrease angle between articulating bones

1. flexion

2. extension/ hyperextension

3. abduction

4. adduction

5. circumduction

6. rotation (internal and external)

7. circumduction

Flexion

• type of angular movement

• decreases angle between articulating bones by bringing thme together

Lateral flexion

• sideways movements that decrease angles (specific angular movement)

• example: tilt head to one side, bend trunk sideways

Extension

• type of angular movement that increases angle between articulating bones

• example: arm and forearm move away from each other or move arm or thigh behind the rest of the body

Hyper extension

• angular movement where there is extension beyond the anatomical position of the joint

Abduction

• type of angular movement where the motion of a body part is moving away from midline of body or reference point

• example: moving away from midline of hand or foot

Adduction

• type of angular movment where the motion of a body part moves toward the midline of the body or other reference point

Circumduction

• type of angular movement where a freely moveable distal bone moves around a proximal bone in a cone shaped motion

Rotation

• type of angular movment where it’s a nonangular pivoting motion

• one bone rotates or twists on an imaginary line running down the middle (logitudinal axis)

• bone turns around itself

2 specific types of rotation

1. internal (medial) rotation: rotates body part toward midline

2. external (lateral) rotation: rotates body part away from midline

Circumduction

• type of angular movement

• bone can move in a circle around something else

Special Movements (6 types with an opposite)

• movements that only pertain to one or a few synovial joints

1. opposition & Reposition

2. depression & elevation

3. protaction & retraction

4. inversion & eversion

5. dorsiflexion & plantarflexion

6. supination & pronation

Opposition & Reposition

• types of spexialized movements that occr at the thumb

• opposition: movement of the thumb across plamar suface of hand

• reposition: return of thumb to anatomical position

Depresion and elevation

• types of spexialized movements

• depression: movement of body part in inferior direction (opening mouth depresses mandible moving inferiorly to maxilla)

• elevation: movement of body part in superior direction/opposite of depression. (closing motuh elevates mandible moving towards maxilla)

Protraction and retraction

• types of special movements

• protraction: move body part anteriorly (mandible moves forward so bottom teeth stick out)

• retraction: moves body part posteriorly (return of mandible position)

Inversion & Eversion

• special movements

• inversion: rotational movement of foot where sole of food rotates medially toward body’s midlein

• eversion: plantar surface of foot rotates laterally away from midline

Dorsiflexion & Plantarflexion

• types of special movements

• dorsiflexion: angle between foot and tibia decreases (toes pull toward leg)

• plantarflexion: angle between foot and tibia increases. toes point toward ground

Supination and pronation

• types of special movement

• supination: palm face anteriorly with thumb pointing laterally (anatomical position)

• pronation: turn palmar surface medially until faces posteriorly with thumb pointing medially

Range of motion (which joint has most and least)

• amount of movement a joint is able to do normally

• nonaxial joints (intercarpal) have smallest ROM

• multiaxial joints (shoulder) have greatest ROM

Structural Classes of Synovial Joints

• based on amount of motion joint allows is determiined by shape of surfaces of bones and number of axes it can move

6 structural classes of synovial joints

1. plane joint

2. hinge joint

3. pivot joint

4. condylar (ellipsoid) joint

5. saddle joint

6. ball-and-socket joint

Plane Joint

• strucutral classification of synovial joint; nonaxial

• two bones whose flat surfaces sit next to each other and perform a gliding movement

• example: intercarpal joint of wrist or intertarsal joint of ankle

Hinge joint

• strucutral classification of synovial joint; uniaxial

• convex surface of one bone fits into concave depression of another

• example: elbow, knee, and interphalangeal joitn

Pivot joint

• strucutral classification of synovial joint; uniaxial

• rounded surface of one bone fits into groove on surface of another

• example: atlantoaxial joint between atlas and axis cervical vertebrae

Condylar (ellipsoid) Joint

• strucutral classification of synovial joint; biaxial

• oval, convex surface of one bone fits into shallow concave surface of another

• allows flexion and extension, or abudction and adduction

• example: knuckels of fingers

Saddle Joint

• strucutral classification of synovial joint; biaxial

• sufrace of each articulating bone has both convex and concave regions to complement each other

• allows more motion than condylar joints

• example: carpometacarpal joint between first metacarpal of thumb and trapezium for thumb opposition and reposition

Ball-and-Socket Joint

• structural classification of synovial joint; multiaxial but unstable lowk

• articulating surface of one bone is ball shaped or spherical and fits into a cup or socket formed by other articulating surface of bone

• example: shoulder and hip joints

What are the elbow and knee examples of?

• specific hinge joints often injured bc of instability

• primary motions are flexion and extension.

2 articulations of the elbow

1. humeroulner joint: between trochlea of humerus and trochlear notch of unla

2. humeroradial joint: between capitulum of humerus and head of radius

• both of these articulations make up the hinge joint of elbow

3 extrinsic ligaments to support articular capsule & stabilize elbow joint

1. radial (lateral) collateral ligament: support lateral side of joint

2. ulnar (medial) collateral ligament: support medial side of joint

3. anular ligamet: stabilizes radial head by binding it to neck of ulna

The Knee

• largest diarthrosis in the body; hinge joint to allow some degree of rotation and lateral gliding and cal lock out in extension without causing muscle fatige

2 articulations of the knee

1. tibiofemoral joint: between femoral and tibial condyles

2. patellofemoral joint: between patella and patellar surface of femur

• articular capsule covers all but anterior surface of knee joint which is covered by patella, tendon of quadriceps femoris muscle group and patellar ligament

Menisci of knee joints

• medial and lateral menisci

• C-shaped fibrocartilage pads on tibial condyles to improve fit between bones and shock absoprtion and cushioning for more stabilization

2 extrinsic collateral ligaments of knee joint

1. tibial (medial) collateral ligament: links femur with tibai and attaches to medial meniscus. prevents tibia from moving too far laterally

2. fibular (lateral) collateral ligament: links femur with fibula but does not attach to lateral mensicus. prevents tibia from moving too far away medially

• collateral: found on side of joint to control side-to-side motion

2 cruciate ligaments of knee (cross-shaped) on the inside

1. anterior cruciate ligament (ACL): runs from anterior insertion site on tibia to posterior part of femur. prevents tibia from moving too far anteriorly. tightens when knee joint is extended

2. posterior curciate ligament (PCL): runs form posterior position on tibia to anterior femur. prevents tibia from moving too far posteriorly. tigthens during knee flexion

• controls anterior to posterior movements

Knee injuries

• any activity that involves quick changes in direction can injure knee

• common in contact sports especially if knee is struck from the side or from behind

The unhappy triad

• common knee injury where lateral blows can rupture tibial collateral ligament and put pressure on lateral meniscus. lateral meniscus can tear

• force of blow can also rupture ACL forming the unhappy triad

• (tibial collateral ligament, lateral mensicus, and ACL)

glenohumeral joint

• example of ball-and-socket joint; multiaxial

• ball shaped humeral head and glenoid cavity on lateral scapula connect

• most freely moveable joint but also most unstable (glenoid cavity is very shallow)

5 General structures that reinforce the articular capsule of glenohumeral joint

1. tendons

2. coracohumeral ligament

3. 3 glenohumeral ligaments (may or may not be present)

4. 2 bursae

5. glenoid labrum

Tendon of glenohumeral joint

• supports articular capsule

• tendon of long head of biceps brachii muscle passes through capsule towards scapula

Coroacohumeral ligament

• specific ligament that supports articular capsule of glenohumeral joint

• thickening of superior aspect of articular capsule between humeral head and coracoid process of scapula

2 bursae around glenohumeral joint’s capsule

1. subacromial bursa

2. subscapular bursa

• minimize friction as shoulder moves

Rotator Cuff

• 4 tendons of other muscles that surrounds shoulder joints to provide strength and stability

• rotator cuff tears are common injuries

4 muscles of rotator cuff

• SItS muscles

• subscapularis (anteriorly)

• supraspinaturs muscle (most superior on posterior side)

• infraspinatus muscle (middle on posterior side)

• teres minor muscle (inferior on posterior side)

Glenoid Labrum

• deep to rotator cuff and articular capsule

• fibrocartilaginous ring that sits on the rim of the glenoid cavity

Dislocated shoulder

• involves glenohumeral joint with traumatic dispalcement of head of humerus from glenoid cavity

• 90% of disolactions are because inferior part of anterior capsule is damage, it’s the weakest part with least amount of structures

• usually because of falls and contact sports but minor ones can “pop” back into place

Seperated Shoulder

• involves acromioclavicular joint, which is not a component of the shoulder

The Hip (Coxal joint)

• example of ball-and-socket joint; multiaxial and more stable than shoulder

• articulation between acetabulum and ball-shaped head of femur

Acetabular Labrum

• fibrocartiagle ring that strengthens the fit between the bones at the hip joint (acetabulum and femur head)

What are the 3 main strucutres that support the hip joint?

1. strong articula capsule

2. many large, powerful muscle groups

3. many ligaments

4 extrinsic ligaments of hip joint

1. iliofemorla ligament: reinforces anterior side

2. Ischiofemoral ligament: supports posterior side

3. Pubofemoral ligament: traingular thickening of inferior portion of articular capsule

4. ligament of head of the femur: links center of head of femur with acetabulum, pathway for small artery

Hip joint replacement surgery

• replaces damaged joint with artificial prosthetic device

• common reasons are arthritis, trauma, fractures and bone tumors

• after surgery, patients beghin physical therapy and may return to normal activities within 2-8 weeks

Total hip replacement

• when needing to do hip joint replacement surgery

• removes and repalces head of femur and reconstructs acetabulum

partial hip replacement

• when needing to do hip joint replacement surgery

• removes only head of femur and leaves acetabulum intact