ARTICULATIONS

HUMAN ANATOMY AND PHYSIOLOGY SUMMER, 2002

ARTICULATIONS ‑ contact points between bones or cartilage and bones; closer fit at contact point ‑ stronger joint.

TYPES

I FUNCTIONAL ‑ based on degree of movement permitted

A. SYNARTHROSES ‑ immovable

B. AMPHIARTHROSES ‑ slightly movable

C. DIARTHROSES ‑ freely movable

II STRUCTURAL ‑ based on presence or absence of joint cavity

A. FIBROUS ‑ no joint cavity; bone held together by fibrous C.T.;

1) SUTURES ‑ between skull bones; unite bones with dense fibrous C.T.;

SYNOSTOSES ‑ when suture is replaced with bone

2) SYNDESMOSIS ‑ greater dense fibrous C.T. ‑ interosseous membrane or ligament therefore slight movement (eg. art. of tibia/fibula & art.of radius/ulna)

3) GOMPHOSIS ‑ cone shaped peg which fits into socket (eg. art. of tooth roots with sockets (alveoli)

B. CARTILAGINOUS ‑ no joint cavity; bones held together by cartilage

1) SYNCHONDROSES ‑ connecting material: hyaline cartilage (eg. epiphyseal plate; joint between 1st rib and sternum)

2) SYMPHYSIS ‑ connecting material: broad flat disc of fibrocartilage (eg. Between vertebrae bodies)

C. SYNOVIAL ‑ has joint cavity; articular capsule surrounding bones of joint + accessory ligaments.

1) SYNOVIAL CAVITY ‑ space between articulating bones within joint

2) ARTICULAR CARTILAGE ‑ cover bone surface; hyaline cartilage

3) ARTICULAR CAPSULE ‑ encloses cavity; unites articular bones

FIBROUS CAPSULE ‑ outer; dense C.T.; attached to periosteum; some fibers arranged in parallel bundles =LIGAMENTS

SYNOVIAL MEMBRANE ‑ inner; loose C.T. with elastic fibers & adipose tissue; secretes SYNOVIAL FLUID ‑ lubricates/nourishes joints, has phagocytic cells, has hyaluronic acid + intestinal fluid made from blood plasma, greater movement the less viscous, up to .1oz

4) ACCESSORY LIGAMENTS

a) EXTRACAPSULAR ‑ outside art. capsule (eg. fibular collateral ligament of knee)

b) INTRACAPSULAR ‑ within art. capsule but excluded from synovial cavity by reflections of synovial membrane (eg. cruciate ligament of knee)

5) ARTICULAR DISC (MENISCI) ‑ pads of fibrocartilage between art. surface and attached to fibrous capsule by their margins; increase fit of joint, maintains stability

6) BURSAE ‑ sac‑like structures within body tissue; acts as cushion to reduce friction between moving parts; filled with synovial‑like fluid; found where excessive rubbing (skin over bone, tendons and bone, muscles and bone)

D. SYNOVIAL JOINT TYPES

1) GLIDING (ARTHRODIA) ‑ ant. surface flat; non‑axial movement (eg. intercarpal/intertarsal joints)

2) HINGE (GINGLYMUS) ‑ spool like surface fits into concave surface; mono‑axial (flex/extend) (eg. elbow/ankle, interphalangeal)

3) PIVOT (TROCHOID) ‑ rounded, pointed or concave surface fits into ring formed by part bone/ligament; mono‑axial (rotational) (eg.atlantoaxial joint)

4) ELLIPSOIDAL (CONDYLOID) ‑ oval shaped condyle fits into elliptical cavity; biaxial (flex/extend, adduct/abduct) (eg. radiocarpal joint)

5) SADDLE (SELLARIS) ‑ articular surface concave in 1 direction, convex in other; biaxial(flex/extend, adduct/abduct) (eg. carpometacarpal joint of thumb)

6) BALL & SOCKET (SPHEROID) ‑ ball into cup‑like depression; tri‑axial (flex/extend, adduct/abduct/rotational) (eg.shoulders/hips)

III JOINT MOVEMENT ‑ influenced by apposition of soft parts, tension of ligaments (more tense in certain positions), muscular tension, and structure of art. bones

A. GLIDING ‑ back and forth/side to side; no angular or rotary motion (eg. between tarsals and carpals)

B. ANGULAR ‑ changes angles between bones

C. FLEXION ‑ decrease angle between anterior surface of art. bones (except for toe & knee) (eg. bend head forward)

D. EXTENSION ‑ increase angle between anterior surface of art. bones (eg. resumes anatomical position)

E. ABDUCTION ‑ movement away from body midline (eg. raise arm/leg to the side)

F. ADDUCTION ‑ movement towards body midline (eg. resume anatomical position)

G. ROTATION ‑ around it's own axis

MEDIAL ‑ ant. surface of bone or extremity towards midline (eg. rotate palm inward)

LATERAL ‑ ant. surface of bone or extremity away from

midline (eg. rotate palm outward)

H. CIRCUMDUCTION ‑ distal end of bone moves in circle while proximal end is stable (eg. rotate outstretched arm)

I.. SPECIAL ‑

· INVERSION ‑ movement of foot/sole medially at ankle joint

· EVERSION ‑ movement of foot/sole laterally at ankle joint

· DORSIFLEXION ‑ flex foot at ankle joint

· PLANTAR FLEXION ‑ extend foot at ankle joint

· PROTRACTION ‑ move mandible/clavicle forward parallel to ground

· RETRACTION ‑ move mandible/clavicle backward parallel to ground

· SUPINATION ‑ forearm movement where in palm is turned ant. or sup. with flexed arm

· PRONATION ‑ forearm movement where in palm is turned post. or inf. with flexed arm

· ELEVATION ‑ upward body movement (eg. close mouth)

· DEPRESSION ‑ downward body movement (eg. open mouth)