ARTICULATIONS

I.   CLASSIFICATION OF JOINTS

articulations = joints

* def: a place where two or more bones meet

-- Two ways to classify joints:

1) structure

a) Fibrous Joints (fig 9.2):

* dense regular CT (fibrous CT) connects bones

b) Cartilaginous Joints (fig 9.3):

* cartilage binds the bone

c) Synovial Joints (fig 9.4):

* ligaments support articulating bones

* bone ends separated by a joint cavity

2. Movement

a) Synarthrosis: immovable joint

b) Amphiarthrosis: slightly moveable

c) Diarthrosis: freely moveable

-- in joints, there’s an inverse relationship between mobility and stability (the more mobile a joint, the less stable it is)

II.  FIBROUS JOINTS (fig 9.2)

A. Suture: dense regular CT binds bones

* immovable joint (synarthrosis)

B. Syndesmosis:  bones held together by interosseous ligaments

* slight movement (amphiarthrosis)

C. Gomphosis: root of tooth attached to jaw by periodontal ligaments

* synarthrosis

III. CARTILAGINOUS JOINTS (fig 9.3)

A. Synchondrosis: bones connected by hyaline cartilage

            * synarthrosis

B. Symphysis: bones connected by fibrocartilage

* amphiarthrosis

IV.  SYNOVIAL JOINTS (fig 9.4, 9.5)

–  diarthroses

A.  Structure

--  ligaments

            --  articular (joint) capsule

--  synovial membrane

* makes synovial fluid

-- joint cavity

-- ends of bones lined w/articular cartilage

B.  Kinds of Synovial Joints (fig 9.6)

1) Planar (Gliding):

* side-to-side movements

2) Hinge:

* permits bending in only one plane

* most common kind of synovial joint

3) Pivot:

* permits rotational movement about a longitudinal axis

4) Condyloid (Ellipsoidal):

* biaxial movements (movements in 2 planes)

5) Saddle:

*  wide range of movement

6) Ball-and-Socket:

* provides greatest range of movement

V.   MOVEMENTS AT SYNOVIAL JOINTS

(figs 9.7-9.11)

      A. Flexion: decreases joint angle in A-P plane

* special kinds of flexion at ankle joint:

1) dorsiflexion: dorsum (top) of foot is elevated

2) plantar flexion: bringing foot and toes closer to back of leg

B. Extension: increases joint angle in A-P plane

C. Abduction: body part moved away from midline of the body, in a lateral direction

D. Adduction: body part moved toward the midline of the body, in a medial direction

E. Rotation: movement of a body part around its own axis

* special kinds of rotation of forearm:

1) supination: palm of hand facing anteriorly

2) pronation: palm facing posteriorly

F. Circumduction: circular, conelike movement of a body segment

G.  Inversion: movement of the sole of the foot inward or medially

H.  Eversion: movement of the sole of the foot outward or laterally

I.  Depression: inferior movement of a body part

J.   Elevation: superior movement of body part

K. Protraction: movement of a body part anteriorly, in a horizontal plane

L.  Retraction: movement of a body part posteriorly, in a horizontal plane