Skeletal System 4

Honors Anatomyto be copied

Joints & Homeostasis• Joints contribute to homeostasis

by holding bones together in ways that allow movement & flexibility

Joints • aka: “articulation” or “arthrosis”• a point of contact between 2

bones, a bone & cartilage, or between a bone & tooth

Joint Classification• 1. structural classification– based on anatomical characteristics• Fibrous joints• Cartilagenous joints• Synovial joints

• 2. functional classification– based on type of movement they permit• Synarthrosis• Amphiarthrosis• Diarthrosis

Fibrous Joints• Articulating bones held very

closely together by fibrous CT• 3 types:1. Sutures– skull bones

2. Syndesmoses– interosseous membrane

3. Gomphoses – dentoalveolar joint

Gomphoses

Cartilagenous Joints• allows little or no movement• bones are tightly connected by either

hyaline cartilage or fibrocartilage• 2 types:1. Synchondoses– hyaline cartilage connects bones– epiphyseal plate

2. Symphyses – fibrocartilage connects bone– pubic symphysis

Symphyses

Synovial Joints• distinguishing characteristics:– synovial joint cavity• filled with synovial fluid

– bones covered by articular cartilage• reduces friction

Synovial Fluid• secreted by synovial membrane• viscous, clear, pale yellow fluid• forms film over surfaces w/in

articular capsule• functions:1. reduce friction2. absorbing shocks3. supporting chondrocytes in w/in

articular cartilage

By the way….

• cracking sounds heard as joints move or popping sounds people make when the “crack” their knuckles explanation:–When synovial cavity expands

creates partial vacuum suction from that draws CO2 & O2 out of blood vessels in synovial membrane form bubbles in synovial fluid bubbles pop

Sprains • a forcible wrenching or twisting

of a joint that stretches or tears ligaments but does not dislocate the bones

• occurs when ligaments are stressed beyond their capacity

• may have associated damage to surrounding blood vessels, muscles, tendons, or nerves

Strains • stretched or partially torn

muscle• often due to muscle contracting

suddenly & powerfully

Bursae • saclike structures situated to

alleviate friction in some joints• filled with fluid similar to

synovial fluid• located between: – skin & bones – tendons & bones –muscles & bones – ligaments & bones

Bursitis • inflammation of a bursa• usually caused by irritation from

repeated, excessive exertion of a joint

• or by: trauma, infection (syphilis or TB), RA

• symptoms: pain, swelling, tenderness, limited movement

Types of Movements @

Synovial Joints• 1. Gliding• relatively flat surfaces move

back-and-forth & side-to-side

Types of Movements @

Synovial Joints• 2. flexion/extension/

hyperextension:• opposite movements– flexion: decrease in angle between

articulating bones– extension: increase in angle between

articulating bones– hyperextension: continuation of

extension beyond the anatomical position

Types of Movements @

Synovial Joints• 3. abduction/adduction/

circumduction– abduction: movement of bone away

from midline– adduction: movement of bone toward

midline– circumduction: movement of distal

end of a body part in a circle

Types of Movements @

Synovial Joints• 4. elevation/depression:• elevation: upward movement of

part of body (closing mouth, shrugging shoulders)

• depression: downward movement of part of body (opening mouth, returning elevated shrugged shoulders to anatomical position)

Types of Movements @

Synovial Joints• 5. protraction/retraction• protraction: movement of part of

body anteriorly in transverse plane

• retraction: returning a protracted part of body to anatomical position

Types of Movements @

Synovial Joints• 6. inversion/ eversion• inversion: movement of soles

medially @ intertarsal joints (soles face each other)

• eversion: movement of soles laterally @ intertarsal joints

Types of Movements @

Synovial Joints• 7. dorsiflexion/ plantar flexion• dorsiflexion: bending foot @

ankle in direction of dorsum (superior surface)

• plantar flexion: bending foot @ ankle in direction of plantar surface

Types of Movements @

Synovial Joints• 8. supination/pronation• supination: movement of forearm

in which palm is turned anteriorly

• pronation: movement of forearm in which distal end of radius crosses over distal end ulna & palm is turned posteriorly

Types of Movements @

Synovial Joints• 9. opposition• movement of thumb in which

thumb moves across palm to touch tips of the fingers on same hand

Ball - & - Socket Joint• ball-like surface of one bone fits into

a cuplike depression of another bone

• permits movement around 3 axis + all directions in between– flexion– extension– abduction– adduction– circumduction– rotation

Homeostatic Imbalances• Rheumatoid Arthritis (RA)• autoimmune disease: immune

system attacks joint linings• characterized by: – inflammation of joint swelling,

pain, loss of function– usually bilateral joints involved but

may not be to same degree

Medical Terminology• arthralgia: pain in a joint• subluxation: partial or

incomplete dislocation of a joint