Articulations

Chapter 9

I. Classification of Joints

A. Synarthroses (Immovable)1. Bony edges are close together or may

interlock

2. Extremely strong, prevents movement

3. 4 types:a. Sutures

i. Located between skull bones

ii. Bound together by dense connective tissue

b. Gomphosesi. Binds teeth to sockets in

maxillary bone and mandible

ii. Teeth are connected to

sockets by periodontal ligaments

c. Synchondrosesi. Rigid, cartilaginous bridge between 2

articulating bones

ii. Ex. epiphyseal plate

(diaphysis +

epiphysis)

& vertebrosternal

ribs + sternum

d. Synostosesi. Totally rigid, immovable

ii. 2 separate bones fuse so that no boundary exists

iii. Ex. epiphyseal line & suture of frontal bones

B. Amphiarthroses (Slightly Moveable)1. More movement than a synarthrosis, but

much stronger than a diarthrosis

2. May be connected by collagen fibers or cartilage

3. 2 major types:a. Syndesmosis

i. Bones are connected by a ligament

ii. Ex. Distal articulation between tibia & fibula

b. Symphysisi. Articulating bones are separated by a pad

of fibrocartilage.

ii. Ex. intervertebral discs & pubic symphysis

C. Diarthroses (Freely Moveable)1. AKA Synovial Joint

2. Permits a wide range of motion

3. Surrounded by an articular capsule & lined by a synovial membrane

4. Typically found at the ends of long bones

5. Articular Cartilage

a. Similar to hyaline cartilage with more water in the matrix

b. Reduces friction during joint movement

c. Cartilages don’t touch each other b/c of a thin film of synovial fluid

6. Synovial Fluida. Like interstitial fluid

b. Very viscous (like heavy molasses)

c. 3 functions:i. Lubrication

Articular cartilages are like sponges filled w/ SF

ii. Nutrient Distribution WHY????

iii. Shock Absorption Like those gel shoe inserts

7. Accessory Structuresa. Menisci

b. Fat Pads

c. Ligaments

d. (Tendons)

e. Bursae

Comprehension Check:

Answer the 3 questions on page 258 with someone near you.

Q. What common characteristics are found in typical synarthrotic and amphiarthrotic joints?

A. Except for synostosis, they all consist of bony regions separated by fibrous or cartilaginous connective tissue.

Q. In a newborn infant, the large bones of the skull are joined by fibrous connective tissue. What type of joints are these? These bones later grow, interlock, and form immovable joints. What type of joints are these?

A. Syndesmosis; Sutural Joints

Q. Why would improper circulation of synovial fluid lead to degeneration of articular cartilages in the affected joint?

A.Nutrients would not be delivered and waste would accumulate.

II. Articulation Form & Function

A. Describing Dynamic Motion (3 possibilities):

1. Linear Motiona. Forward / backward

b. Left / right

c. Diagonally

2. Angular Motiona. Changing angle between shaft & art. surfaceb. Circumduction (complete circular

movement)

3. Rotationa. Monaxial- movement along 1 axisb. Biaxial- movement along 2 axesc. Triaxial- combo of angular movement and

rotation

B. Types of Movements

1. Glidinga. 2 opposing surfaces slide past one another.

b. Allows slight movement in any direction

c. Ex. carpals; tarsals; clavicle & sternum

Gliding Motion

2. Angular Motion

a. Flexion and Extension

i. Flexion- movement in the anterior/posterior plane that reduces the angle between the articulating elements.

ii. Extension- same, but increases the angle between the articulating elements.

iii. Hyperextension- extension past the anatomical position

b. Abduction and Adductioni. Abduction- movement away from the

longitudinal axis of the body in the frontal plane

ii. Adduction- movement back to anatomical position (back to the body)

iii. These 2 terms always apply to the appendicular skeleton, not the axial skeleton.

c. Rotationi. Left / Right Rotation- head

ii. Medial (internal / inward) / Lateral Rotation (external / outward)- whole limbs

iii. Pronation (palm down) / Supination (palm up)- hands

d. Special Movementsi. Inversion- twisting motion that turns the foot

sole-inward

ii. Eversion- twisting motion that turns foot sole-outward

iii. Dorsiflexion- flexing the ankle to elevate the

toes

iv. Plantar Flexion- extending the ankle to elevate heel (standing on toes)

v. Opposition- moving the thumb towards the palm or towards the fingertips

vi. Protraction- moving part of the body anteriorly in a horizontal plane

vii. Retraction- moving part of the body posteriorly in a horizontal plane

viii.Elevation- moving part of the body in a superior direction

ix. Depression- moving part of the body in an inferior direction

x. Lateral Flexion- bending the vertebral column to the side (laterally)

C. Structural Classification of Synovial Joints

1. Gliding Joints (Plantar Joints)a. Flattened, slightly curved faces

b. Surfaces slide across each other

c. Movement is slight

2. Hinge Jointsa. Permit angular movement in a single

plane

b. Like opening a door

3. Pivot Jointsa. Monaxial movement

b. Permit only rotation

4. Ellipsoidal Joints (Condyloid Joints)a. Articular surfaces are convex/concave

b. Biaxial movement

5. Saddle Joint (Sellaris Joints)a. Saddle-shaped articular surfaces

b. Permits angular movement, including circumduction

c. Prevents rotation

6. Ball-and-Socket Joint

a. Permits all combos of angular & rotational movement, including circumduction & rotation

III. Representative Articulations

A. Intervertebral Articulations

B. The Shoulder Joint

C. The Elbow Joint

D. The Hip Joint

E. The Knee Joint

YOU DO THE WORK! TEACH ME!!

IV. Aging & Articulations

V. Bones & Muscles