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Lecture Notes: Unit II: Principles of Support and Movement
Chapter Nine – Joints (Articulations) / "A Quick Reference"
I. Two Criteria for Classification of Joints:
1. Structural - based upon the histologic structures that are present
2. Functional - based upon the amount of movement
II. Structural Classes of Joints:
1. Fibrous (collagenous connective tissue; lacks a cavity)
2. Cartilagenous (bones tightly connected by cartilage conn. tiss.; lacks cavity)
3. Synovial (joint cavity present; lined by a synovial membrane)
III. Functional Classes of Joints:
1. Synarthrosis (immoveable joint)
2. Amphiarthrosis (slightly moveable joint)
3. Diarthrosis (freely moveable joint)
Examples of each of these (Match the structural classes with the functional classes; there is a
one-to-one correlation; that is, 1-1; 2-2; and 3-3):
1. Fibrous Synarthroses (Note: arthroses is the plural form of arthrosis)
a. Suture: skull sutures; immoveable, collagenous conn. tiss., (ie. Sagittal, Coronal, Lambdoidal, )
b. Syndesmosis: very little movement, collagenous c.t., (i.e., distal tibiofibular joint)
c. Gomphosis: cone-shaped peg in socket, periodontal ligament" which is collagenous c.t.,(ie
roots of teeth in their sockets (maxillae and mandible)
2. Cartilagenous Amphiarthroses
a. Synchondrosis: hyaline cartilage conn. tiss., no movement, considered a temporary joint
since it is replaced by a boney synostosis, i.e., epiphyseal plate, where it joins the diaphysis
b. Symphysis: slight movement possible, fibrocartilage conn. tiss. pad between adjoining
bones, ie., the pubic symphysis, and all the intervertebral discs
3. Synovial Diarthroses
a. Summary of the structure of synovial joints:
1) Joint with a space between articulating bones - this space is called the synovial
joint – allows the union to be freely moveable
2) Characterized by articular cartilage (hyaline cartilage conn. tiss.) covering the
ends of adjoining bones
3) Joint is surrounded by a sleeve-like articular capsule which encloses the bones
- there are two layers to this sleeve-like capsule:
a) Outer layer: "fibrous capsule" is dense collagenous c.t. which attaches to
the periosteum. Sometimes called "ligaments" (very strong)
b) Inner layer: "synovial membrane" is loose c.t. with lots of elastic fibers
and adipose tissue. It secretes synovial fluid which lubricates the joint and
noursishes the articular cartilage. * It also contains phagocytic cells that
remove microbes, debris, and wastes which result from wear and tear on
the joint.
c) Note: Synovial fluid is made of hyaluronic acid and interstitial fluid from
the blood plasma. Movement of the joint decreases the viscosity of the
hyaluronic acid. Sometimes there is a fibrocartilage pad called an
articular disc within the joint, ie., within the knee-joint and in the TMJ,
which help the two articulating bones to fit more snugly together when
they are of different size and shape.
b. There are 6 types of synovial joints (based upon shape of the articulating surfaces):
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1) Ball-and-Socket (also called spheroid)
a) Rounded head in socket-like fossa, ie, head of femur in acetabulum of hip
b) Allows for the most amount of movement (greatest range of motion)
c) Examples: hip, shoulder, 1st finger (metacarpal-1st phalangeal joint)
2) Hinge (also called ginglymus)
a) Convex surface of one bone fits into concave surface of another bone
b) Motion stops at a certain point, ie., just like a hinged-door
c) Examples: elbow, knee, TMJ
3) Gliding
a) Articulating surfaces of bones are quite flat
b) Only side-to-side or back-and-forth motion are possible (referred to as
non-axial, as movement is NOT around a single axis)
c) Examples: between the carpals and between the tarsals; also, the
sternoclavicular joint and claviculoscapular joint
4) Pivot (also called trochoid)
a) Rounded, pointed or conical surface of one bone articulates within a ring
formed by another bone and its ligament
b) The movement permitted is rotation
c) Examples: Atlantoaxial joint; also, proximal ends of the radius and ulna
5) Ellipsoidal (also called condyloid)
a) An oval-shaped condyle of one bone fits into an elliptical cavity of
another bone
b) Movements include side-to-side and back-and-forth movements
c) Examples: joint at wrist (formed between the radius and ulna (together)
superior to the carpals)
6) Saddle (also called sellaris)
a) Both articulating bones have saddle-shaped surfaces (are concave in one
direction and convex in the other). Saddle joints are modified ellipsoidal
joints in which movement is freer
b) Movements are side-to-side and back-and-forth, but with greater range of
motion
c) Example: Metacarpal of the thumb which articulates with trapezium
carpal bone.
OTHER TERMS:
1. Bursitis: A bursa is a fluid-filled sac found where bone is close to the skin, ie., in the knees, hips
and shoulder. These bursa act as a cushion. Bursitis is an inflammation of this bursa sac, usually
caused by over-use of the joint resulting in undue strain on the bursa
2. Tendonitis: Inflammation of the tendons and sheaths. A dense fibrous c.t. ribbon which attaches
muscle to bone. Very painful. Needs to be treated with cortisone to reduce the inflammation.
3. Dislocations: A condition in which the bone is displaced from its normal position in the joint
4. Sprain: A "twisted joint". Injury to blood vessels, tendons, ligaments are usually included. A
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sprain can be slow to heal and more painful than a break.
5. Scoliosis: Abnormal lateral curvature of any region of the vertebral column. Can be congenital or
position related.
6. Lordosis: Abnormal anterior curvature of the lumbar region of the vertebral column. Also called
"sway-back". Usually congenital.
7. Kyphosis: Abnormal posterior curvature of the thoracic region of the vertebral column. Also
called "hunch-back". Usually congenital; but can be a part of the aging process as one loses muscle
tone to hold self erect; thus losing the ability to hold all the vertebrae in place. Kyphosis is
exacerbated by osteoporosis. Also, osteoporosis can, and often does, lead to kyphosis.
8. Fontanels: Know these 6 fontanels: (See Pages 210 - 211 of textbook)
a. Anterior (unpaired): Largest fontanel; midline between the two parietal
bones and the frontal bone; closes at age 18 - 24 months.
b. Posterior (unpaired): Midline between the two parietal bones and the
occipital bone; closes at age 2 months.
c. Anterolateral (paired): Bilateral between the frontal, parietal, temporal,
and sphenoid bones; close at age 3 months.
d. Posterolateral (paired): Bilateral between the parietal, temporal, and
occipital bones; closure begins at age 1-2 months but not complete until
age 1 year.