Download JOINTS (Ch. 8)

Crafton Hills College
Human Anatomy & Physiology 150
JOINTS (Ch. 8)
A. General Characteristics of Joints
1. Weakest parts of the skeleton
2. Site of Articulation: Where two or more bones meet
3. Functions
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Give skeleton mobility & hold skeleton together
B. Classification of Joints: An OVERVIEW
1. Structural classification
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Joint classified according to the material binding bones together; regardless of whether or not
a joint cavity is present
a. Fibrous, Cartilaginous, Synovial
2. Functional classification
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Amount of movement allowed by joint
a. Three functional classes
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Synarthroses - immovable, Amphiarthroses - slightly movable, Diarthroses - freely
movable
C. Structural Classification (of Joints)
1. Fibrous Joints
a. General Characteristics
i. Immovable with no joint cavity
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Sutures, syndesmoses, and gomphoses
b. Sutures
i. Bones joined by fibrous tissues (e.g. bones of skull)
ii. Comprised of interlocking junctions completely filled with connective tissue fibers
iii. Middle age: Skull bones fuse
c. Syndesmoses
i. Bones connected by fibrous tissue ligament
ii. Movement varies: Immovable to slightly variable
iii. Examples: Connection between tibia & fibula, radius & ulna
d. Gomphoses
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Peg-in-socket fibrous joint between a tooth and its alveolar socket
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Fibrous connection is periodontal ligament
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2. Cartilaginous Joints
a. General Characteristics
i. Articulating bones are united by cartilage
ii. Lack a joint cavity
iii. Two types: Synchondroses and Symphyses
b. Synchondroses
i. Bar or plate of hyaline cartilage unites bones
ii All synchondroses are synarthrotic
iii. Examples
1) Epiphyseal plates of children
2) Joint between the costal cartilage of the first rib and the sternum
c. Symphyses
i. Hyaline cartilage covers articulating bone surface; fused to intervening fibrocartilage pad
ii. Amphiarthrotic joints designed for strength and flexibility
iii. Examples: Intervertebral joints & Pubic symphysis
3. Synovial Joints
a. General Characteristics
i. Joints in which articulating bones are separated by a fluid-containing joint cavity
ii. All are freely movable diarthroses
iii. Examples: All limb joints, most joints of body
b. Structure
i. Articular cartilage:
Covers articulating bone surfaces
ii. Joint (synovial) cavity:
Encapsulated by "sac" consisting of Synovial membrane &
Articular cartilage
iii. Articular capsule:
Combo of synovial membrane & fibrous capsule
iv. Synovial fluid:
Liquid contents of joint capsule
Reinforcing ligaments:
Overlays fibrous capsule, binds bone on either side
c. Associated structures
i. Bursae - Flattened, fibrous sacs lined w/ synovial membranes & containing synovial fluid
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Common where ligaments, muscles, skin, tendons, or bones rub together
ii. Tendon sheath - Elongated bursa that wraps completely around a tendon
d. Stability factors
i. Articular surfaces: Shape determines possible movements
ii. Ligaments: Unite bones and prevent excessive or undesirable motion
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iii. Muscle tone:
1) Muscle tendons across joints act as stabilizing factors (kept tight at all times by
muscle tone)
D. Synovial Joint Movement
1. Range of Motion ( R.O.M.)
a. Nonaxial - slipping movements only
b. Uniaxial - movement in one plane
c. Biaxial - movement in two planes
d. Multiaxial - movement in or around all three planes
2. Movement Types
a. Gliding
i. One flat bone surface glides or slips over another similar surface
ii. Examples - intercarpal & intertarsal joints, & between flat articular processes of vertebrae
b. Angular
i. Flexion - bending movement that decreases the angle of the joint
ii. Extension - reverse of flexion; joint angle is increased
iii. Abduction - movement away from the midline
iv. Adduction - movement toward the midline
v. Circumduction - movement describes a cone in space
c. Rotation
i. Bone turns around its own long axis
ii. Examples
1) Between 1st two vertebrae
&
2) Hip & shoulder joints
E. Synovial Joints Types
1. Plane joints
a. Flat articular surfaces allow only slipping/ gliding movements
b. Only examples of nonaxial joints
2. Hinge joints
i. Cylindrical projections of one bone fits into a trough-shaped surface on another
ii. Motion along a single plane
iii. Uniaxial joints permit flexion and extension only
iv. Examples: elbow and interphalangeal joints
3. Pivot Joints
a. Rounded end of one bone protrudes into a "sleeve," or ring, composed of bone (and possibly
ligaments) of another
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b. Only uniaxial movement allowed
c. Examples: Atlas & dens, Proximal radioulnar joint
4. Condyloid
a. Oval articular surface of one bone fits into a complementary Oval depression in another
b. Biaxial joints: Permits angular motions
c. Examples: Radiocarpal (wrist) joints & Metacarpophalangeal (knuckle) joints
5. Saddle
a. Each articular surface has both concave and convex surface (more movement than condyloid)
Example: Carpometacarpal joint of the thumb
6. Ball-and-Socket
a. Spherical or hemispherical head articulates with cuplike socket
b. Multiaxial joints: Permits most freely moving of synovial joints
c. Examples: Shoulder & Hip joints
F. Selected Synovial Joints
1. Knee
a. Tendon of quadriceps femoris muscle
b. Lateral & medial patellar retinacula
c. Fibular and tibial collateral ligaments
d. Patellar ligament
e. Anterior cruciate ligament
f. Posterior cruciate ligament
g. Medial meniscus (semilunar cartilage)
h. Lateral meniscus
2. Shoulder (Glenohumeral)
a. Ball-and-socket joint
b. Greater freedom of movement by sacrificing stability
c. Head of humerus articulates with the glenoid fossa of the scapula
d. Weak stability is maintained by:
i. Ligaments - Coracohumeral, and three Glenohumeral
ii. Tendon of long head of biceps: Travels through intertubercular groove & secures
humerus to glenoid cavity
iii. Rotator cuff (four tendons): Encircles shoulder joint and blends with articular capsule
3. Elbow
a. Hinge joint: allows flexion & extension only
b. Radius & ulna articulate with the humerus
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c. Ligaments
i. Annular ligament
ii. Ulnar collateral ligament
iii. Radial collateral ligament
G. Common Joint Injuries
1. Sprains
a. Ligaments (reinforcing a joint) are stretched or torn
i. Partially tare: Heal/repair themselves slowly
ii. Complete tare: Requires prompt surgical repair
2. Cartilage Injuries
i. The snap and pop of overstressed cartilage
ii. Common aerobics injury
iii. Repaired with arthroscopic surgery
3. Dislocations
a. Occur when bones are forced out of alignment
b. Usually accompanied by sprains, inflammation, and joint immobilization
c. Caused by serious falls and are common sports injuries
H. Inflammatory and Degenerative Conditions
1. Bursitis
a. An inflammation of a bursa, usually caused by a blow or friction
b. Symptoms are pain and swelling
c. Treated with anti-inflammatory drugs; excessive fluid may be aspirated
2. Tendonitis
a. Inflammation of tendon sheaths typically caused by overuse
b. Symptoms and treatment are similar to bursitis
3. Arithritis
a. General Characteristics
i. Most widespread crippling disease in the U.S.
ii. Symptoms: Pain, stiffness & swelling of joint
iii. Acute forms: Caused by bacteria - treated with antibiotics
iv. Chronic forms: Osteoarthritis, rheumatoid arthritis, and gouty arthritis
b. Osteoarthritis (OA)
i. General Characteristics
1) Affects women more than men; Aged more than young
2) 85% of Americans develop OA
3) Slow, irreversible
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ii. Coarse
1) Years of abrasion/compression cause:
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Increase in metalloproteinase enzymes (break down cartilage faster than replaced)
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Bone ends enlarge, form bone spurs, and restrict movement
2) Most affected joints:
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Cervical and Lumbar spine, Fingers, Knuckles, Knees, and Hips
iii. Treatments
1) Mild pain relievers with moderate activity
2) Glucosamine sulfate: Decreases pain & inflammation
c. Rheumatoid Arthritis (RA)
i. Chronic, inflammatory, autoimmune disease
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Cause unknown; Sudden/severe onset
ii. Onset ages of 40 to 50 (any age possible)
iii. Signs and symptoms:
1) Joint tenderness, anemia, osteoporosis, muscle atrophy, and cardiovascular problems
2) Exacerbations (flare-ups) and remissions
iv. Course
1) Inflammatory chemicals wrongly released
2) Inflamed synovial membrane eventually erodes, leaving articulating bone ends in
direct contact (painful; Ankylosis-bent, fingers)
v. Treatment
1) Conservative therapy - aspirin, long-term use of antibiotics, and physical therapy
2) Progressive treatment - anti-inflammatory drugs or immunosuppressants
3) The drug Enbrel, a biological response modifier, neutralizes the harmful properties of
inflammatory chemicals
4. Synovial Joints: Hip (Coxal) Joint
a. Ball-and-socket joint
b. Head of the femur articulates with the acetabulum
c. Good range of motion, but limited by the deep socket and strong ligaments
d. Hip Stability
i. Acetabular labrum
ii. Iliofemoral ligament
iii. Pubofemoral ligament
iv. Ischiofemoral ligament
v. Synovial Joints: Hip Stability
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