Articulations



Articulations



LANGUAGE OF SCIENCE


imageBefore reading the chapter, say each of these terms out loud. This will help you avoid stumbling over them as you read.



abduction


(ab-DUK-shun)


[ab- away, -duct- lead, -tion process]


adduction


(ad-DUK-shun)


[ad- toward, -duct- lead, -tion process]


amphiarthrosis


(am-fee-ar-THROH-sis)


[amphi- both sides, -arthr- joint, -osis condition] pl., amphiarthroses


angular movement


articular cartilage


(ar-TIK-yoo-lar KAR-ti-lij)


[artic- joint, -ul- little, -ar relating to, cartilag cartilage]


articulation


(ar-tik-yoo-LAY-shun)


[artic- joint, -ul- little, -ation state]


biaxial joint


(bye-AK-see-al)


[bi- two, -axi- axle, -al relating to]


bursa


(BER-sah)


[bursa purse] pl., bursae


carpometacarpal joint


(kar-po-met-ah-KAR-pal)


[carpo- wrist, -meta- beyond, -carp- wrist, -al relating to]


circular movement


circumduction


(ser-kum-DUK-shun)


[circum- around, -duct lead]


depression


[de- down, -press- press, -sion process]


diarthrosis


(dye-ar-THROH-sis)


[dia- between, -arthr- joint, –osis condition] pl., diarthroses


distal interphalangeal (DIP)


(DIS-tal inter-fah-LAN-gee-al)


[dist- distance, -al relating to, inter- between, -phalang- finger bones (ref. from rows of soldiers), -al relating to]


dorsiflexion


(dor-si-FLEK-shun)


[dorsi- back, -flex- bend, -ion process]


elevation


[e(x)- up, -lev- raise, -at- perform, -tion process]


eversion


(ee-VER-shun)


[e(x)- outward, -ver- turn, -sion process]


extension


[ex- outward, -tens- stretch, -sion process]


flexion


(FLEK-shun)


[flex- bend, -ion process]


gliding joint


gliding movement


gomphosis


(gom-FOH-sis)


[gomphos- bolt, -osis condition] pl., gomphoses


goniometer


(gon-ee-OM-eh-ter)


[gonio- angle, -meter measure]


hyperextension


(hye-per-ek-STEN-shun)


[hyper- excessive, -ex- out, -ten- stretch, -sion process]


intercarpal joint


(in-ter-KAR-pal)


[inter- between, -carp- wrist, -al relating to]


interphalangeal joint


(in-ter-fah-LAN-jee-al)


[inter- between, -phalang- finger bones (ref. from rows of soldiers), -al relating to]


inversion


(in-VER-shun)


[in- inward, -ver- turn, -sion process]


joint capsule


joint cavity


ligament


(LIG-ah-ment)


[liga- bind, -ment result of action]


meniscus


(meh-NIS-kus)


[meniscus crescent] pl., menisci


metacarpophalangeal joint


(met-ah-KAR-poh-fah-LAN-jee-al)


[meta- beyond, -carpo- wrist, -phalang- finger bones (ref. from rows of soldiers), -al relating to]


multiaxial joint


(mul-tee-AK-see-al)


[multi- many, -axon axle]


nonsteroidal antiinflammatory drug (NSAID)


(nahn-STAYR-oyd-al an-ti-in-FLAM-ah-toh-ree)


[non- not, -stero- solid, -oid like, -al relating to, anti- against, –inflam- set afire, -ory relating to]


olecranon bursa


(oh-LEK-rah-non BER-sah)


[olecranon elbow, bursa purse] pl., bursae


plantar flexion


(PLAN-tar FLEK-shun)


[planta- sole, -ar relating to, flex- bend, -ion process]


pronation


(proh-NAY- shun)


[pronat- bend forward, -tion process]


protraction


(proh-TRAK- shun)


[pro- forward, -tract- drag, -tion process]


proximal interphalangeal (PIP)


(PROK-si-mal in-ter-fah-LAN-gee-al)


[proxima- near, -al relating to, inter- between, -phalang- finger bones (ref. from rows of soldiers), -al relating to]


radiocarpal joint


(RAY-dee-oh-KAR-pal)


[radio- ray, -carp- wrist, -al relating to]


radioulnar joint


(RAY-dee-oh-UL-nur)


[radio- ray, -ulna- elbow or arm, -ar relating to]


range of motion (ROM)


retraction


[re- back, -tract- drag, -tion process]


rotation


(roh-TAY-shun)


[rot- turn, -ation process]


special movement


supination


(soo-pi-NAY-shun)


[supin- lying on the back, -ation process]


suture


(SOO-chur)


[suture- seam]


symphysis


(SIM-fi-sis)


[sym- together, -physis growth] pl., symphyses


synarthrosis


(sin-ar-THROH-sis)


[syn- together, –arthr- joint, -osis condition] pl., synarthroses


synchondrosis


(SIN-kon-DROH-sis)


[syn- together, -chondr- cartilage, -osis condition] pl., synchondroses


syndesmosis


(SIN-dez-MO-sis)


[syn- together, -desmo- bond, -osis condition] pl., syndesmoses


synovial membrane


(si-NO-vee-all)


[syn- together, -ovi- egg (white), -al relating to, membran- thin skin]


uniaxial joint


(yoo-nee-AK-see-al)


[uni- one, -axi- axle, -al relating to]


LANGUAGE OF MEDICINE



arthritis


(ar-THRY-tis)


[arthr- joint, -itis inflammation]


Bouchard node


(boo-SHAR)


[Charles J. Bouchard French physician, nod- knot]


bursitis


(ber-SYE-tiss)


[bursa- purse, -itis inflammation]


chondral fracture


(KON-dral)


[condr- cartilage, -al relating to, fracture a breaking]


dislocation


[dis- apart, -locat- to place, -tion process]


gouty arthritis


(gow-TEE ar-THRY-tis)


[gout- drop, -y of or like, arthr- joint, -itis inflammation]


Heberden node


(HEB-er-den)


[William Heberden English physician, nod- knot]


herniated disk


(HER-nee-ayt-ed)


[hernia- rupture, –ate act of]


inflammatory joint disease


(in-FLAM-ah-toh-ree)


[inflam- set afire, -ory relating to]


juvenile rheumatoid arthritis (JRA)


(JOO-veh-neyel ROO-mah-toyd ar-THRY-tis)


[juven- youth, -ile of or like, rheuma- flow, -oid like, arthr- joint, -itis inflammation]


noninflammatory joint disease


(nahn-in-FLAM-ah-toh-ree)


[non- not, – inflam- set afire, -ory relating to]


olecranon bursitis


(oh-LEK-rah-nohn ber-SYE-tis)


[olecranon elbow, burs- purse, -itis inflammation]


osteoarthritis


(os-tee-oh-ar-THRY-tis)


[osteo- bone, -arthr- joint, -itis inflammation]


pannus


(PAN-us)


[pannus tattered cloth]


prepatellar bursitis


(pree-pah-TEL-er ber-SYE-tis)


[pre- in front of, -pat- dish, -ella small, -ar relating to, bursa- purse, -itis inflammation]


prosthesis


(pros-THEE-sis)


[prosthesis addition] pl., prostheses


rheumatoid arthritis (RA)


(ROO-mah-toyd ar-THRY-tis)


[rheuma- flow, -oid like, arthr- joint, -itis inflammation]


sprain


sprained ankle


TNF (tumor necrosis factor) blocker


tophus


(TOH-fus)


[tophus porous rock] pl., tophi


ulnar deviation


(UL-nur dee-vee-AY-shun)


[ulna- elbow, -ar relating to, deout of, –viaroad or path, -ation process]




An articulation, or joint, is a point of contact between bones. Although most joints in the body allow considerable movement, some are completely immovable or permit only limited motion or motion in only one plane or direction. In the case of immovable joints, such as the sutures of the skull, adjacent bones are bound together into a strong and rigid protective plate. In other joints, movement is possible but highly restricted. For example, joints between the bodies of the spinal vertebrae perform two seemingly contradictory functions. They help firmly bind the components of the spine to each other and yet permit normal, but restricted movement to occur. Most joints in the body allow considerable movement to occur as a result of skeletal muscle contractions. It is the existence of such joints that permits us to execute complex, highly coordinated, and purposeful movements. Functional articulations between bones in the extremities, such as the shoulder, elbow, hip, and knee, contribute to controlled and graceful movement and provide a large measure of our enjoyment of life. This chapter begins by classifying joints and describing their identifying features. Coverage of joint classification and structure is followed by a discussion of body movements and a description of selected major joints. The chapter concludes by describing life cycle changes and some common joint diseases.


CLASSIFICATION OF JOINTS


Joints may be classified into three major categories by using a structural or a functional scheme. If a structural classification is used, joints are named according to the type of connective tissue that joins the bones together (fibrous or cartilaginous joints) or by the presence of a fluid-filled joint capsule (synovial joints). If a functional classification scheme is used, joints are divided into three classes according to the degree of movement they permit: synarthroses (immovable), amphiarthroses (slightly movable), and diarthroses (freely movable). Table 10-1 classifies joints according to structure, function, and range of movement. Refer often to this Table and to the illustrations that follow as you read about each of the major joint types in this chapter.



Fibrous Joints (Synarthroses)


The articulating surfaces of bones that form fibrous joints fit closely together. The different types and amount of connective tissue joining bones in this group may permit very limited movement in some fibrous joints, but most are fixed. There are three subtypes of fibrous joints: syndesmoses, sutures, and gomphoses.


SYNDESMOSES


Syndesmoses (SIN-dez-MO-seez) are joints in which fibrous bands (ligaments) connect two bones. The joint between the distal ends of the radius and ulna is joined by the radioulnar interosseous ligament (Figure 10-1). Although this joint is classified as a fibrous joint, some movement is possible because of ligament flexibility.



SUTURES


Sutures are found only in the skull. In most sutures, teethlike projections jut out from adjacent bones and interlock with each other with only a thin layer of fibrous tissue between them. Sutures become ossified in older adults and form extremely strong lines of fusion between opposing skull bones (see Figure 10-1).


GOMPHOSES


Gomphoses (gom-FOH-seez) are unique joints that occur between the root of a tooth and the alveolar process of the mandible or maxilla (see Figure 10-1). The fibrous tissue between the tooth’s root and the alveolar process is a sheet made up of tiny ligaments and called the periodontal membrane.


Cartilaginous Joints (Amphiarthroses)


The bones that articulate to form cartilaginous joints are joined together by either hyaline cartilage or fibrocartilage. Joints characterized by the presence of hyaline cartilage between articulating bones are called synchondroses, and those joined by fibrocartilage are called symphyses. Cartilaginous joints permit only very limited movement between articulating bones in certain circumstances. During childbirth, for example, slight movement at the pubic symphysis facilitates the baby’s passage through the pelvis.


SYNCHONDROSES


Note that joints identified as synchondroses (SIN-kon-DROH-seez) have hyaline cartilage between articulating bones. One example of a synchondrosis is the joint between the sphenoid bone and the occipital bone (see Figure 9-4 on p. 229). Another commonly cited example is the articulation between the first rib and sternum (a costosternal synchondrosis; Figure 10-2). Some anatomists, however, prefer to classify this joint as a special kind of synarthrosis. All other sternocostal joints are synovial joints, even though they often lack joint capsules.



The best example of a synchondrosis is the joint present during the growth years between the epiphyses of a long bone and its diaphysis (see Figure 10-2). The epiphyseal plate between the epiphysis and diaphyses of a long bone is a temporary synchondrosis that normally does not move. The plate of hyaline cartilage is totally replaced by bone at skeletal maturity. Most synchondroses are present only in the immature skeleton as epiphyseal plates—they eventually disappear as the bones fuse together.


SYMPHYSES


A symphysis (SIM-fi-sis) is a joint in which a pad or disk of fibrocartilage connects two bones. The tough fibrocartilage disks in these joints may permit slight movement when pressure is applied between the bones.


Most symphyses are located in the midline of the body. Examples of symphyses include the pubic symphysis and the articulation between the bodies of adjacent vertebrae (see Figure 10-2). The intervertebral disk in these joints is composed of tough and resilient fibrocartilage that absorbs shock and permits limited movement. The bones of the vertebral column have numerous points of articulation between them. Collectively, these joints permit limited motion of the spine in a very restricted range. The articulation between the bodies of adjacent vertebrae is classified as a cartilaginous joint. The points of contact between the articular facets of adjacent vertebrae are, however, considered synovial joints and are described later in the chapter.


Table 10-2 summarizes the different kinds of fibrous and cartilaginous joints.




Synovial Joints (Diarthroses)


Synovial joints are freely movable joints. They are not only the body’s most mobile but also its most numerous and anatomically most complex joints. A majority of the joints between bones in the appendicular skeleton are synovial joints.


STRUCTURE OF SYNOVIAL JOINTS


The following seven structures characterize synovial, or freely movable, joints (Figure 10-3):



1. Joint capsule. Sleevelike extension of the periosteum of each of the articulating bones. The capsule forms a complete casing around the ends of the bones, thereby binding them to each other.


2. Synovial membrane. Moist, slippery membrane that lines the inner surface of the joint capsule. It attaches to the margins of the articular cartilage. It also secretes synovial fluid, which lubricates and nourishes the inner joint surfaces.


3. Articular cartilage. Thin layer of hyaline cartilage covering and cushioning the articular surfaces of bones.


4. Joint cavity. Small space between the articulating surfaces of the two bones of the joint. Absence of tissue between articulating bone surfaces permits extensive movement. Synovial joints are therefore diarthroses, or freely movable joints.


5. Menisci (articular disks). Pads of fibrocartilage located between the articulating ends of bones in some diarthroses. Usually these pads divide the joint cavity into two separate cavities. The knee joint contains two menisci (see Figure 10-10).


6. Ligaments. Strong cords of dense, white fibrous tissue at most synovial joints. They grow between the bones, and lash them even more firmly together than is possible with the joint capsule alone.


7. Bursae. Some synovial joints contain a closed pillowlike structure called a bursa, which consists of a synovial membrane filled with synovial fluid. Bursae tend to be associated with bony prominences (such as in the knee or the elbow), where they function to cushion the joint and facilitate movement of tendons.



TYPES OF SYNOVIAL JOINTS


Synovial joints are divided into three main groups: uniaxial, biaxial, and multiaxial. Each is subdivided further into two subtypes as follows:



1. Uniaxial joints. Synovial joints that permit movement around only one axis and in only one plane. Hinge and pivot joints are types of uniaxial joints (Figure 10-4, A and B).


a. Hinge joints. Those in which the articulating ends of the bones form a hinge-shaped unit. Like a common door hinge, hinge joints permit only back-and-forth movements, namely, flexion and extension. If you have access to an articulated skeleton, examine the articulating end of the humerus (the trochlea) and the ulna (the semilunar notch). Observe their interaction as you flex and extend the forearm. Do you see why you can flex and extend your forearm but cannot move it in any other way at this joint? The shapes of the trochlea and the semilunar notch (see Figure 9-18, p. 252, and Figure 9-19, p. 253) permit only the uniaxial, horizontal-plane movements of flexion and extension at the elbow. Other hinge joints include the knee and interphalangeal joints.


b. Pivot joints. Those in which a projection of one bone articulates with a ring or notch of another bone. Examples include a projection (dens) of the second cervical vertebra articulating with a ring-shaped portion of the first cervical vertebra and the head of the radius articulating with the radial notch of the ulna.


2. Biaxial joints. Diarthroses that permit movement around two perpendicular axes in two perpendicular planes. Saddle and condyloid joints are types of biaxial joints (Figure 10-4, C and D).


a. Saddle joints. Those in which the articulating ends of the bones resemble reciprocally shaped miniature saddles. Only two saddle joints—one in each thumb—are present in the body. The thumb’s metacarpal bone articulates in the wrist with a carpal bone (trapezium). The saddle-shaped articulating surfaces of these bones make it possible for the thumb to swing in an arc to touch the tips of the fingers—that is, to oppose the fingers. How important is this? To answer this for yourself, consider the following. Opposing the thumb to the fingers enables us to grip small objects. Were it not for this movement, we would have much less manual dexterity. A surgeon could not grasp a scalpel or suture needle effectively, and none of us could easily hold a pen or pencil for writing.


b. Condyloid (ellipsoidal) joints. Those in which a condyle fits into an elliptical socket. Examples include condyles of the occipital bone fitting into elliptical depressions of the atlas and the distal end of the radius fitting into depressions of the carpal bones (scaphoid, lunate, and triquetrum).


3. Multiaxial joints. Joints that permit movement around three or more axes and in three or more planes (Figure 10-4, E and F).


a. Ball-and-socket joints (spheroid joints). Our most movable joints. A ball-shaped head of one bone fits into a concave depression on another, thereby allowing the first bone to move in many directions. Examples include the shoulder and hip joints.


b. Gliding joints. Characterized by relatively flat articulating surfaces that allow limited gliding movements along various axes. Examples include the joints between the articular surfaces of successive vertebrae. (Articulations between the bodies of successive vertebrae are symphysis-type cartilaginous joints.) As a group, gliding joints are the least movable of the synovial joints.



Table 10-3 summarizes the classes of synovial joints.



TABLE 10-3


Classification of Synovial Joints
































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May 25, 2016 | Posted by in ANATOMY | Comments Off on Articulations
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    TYPES EXAMPLES STRUCTURE MOVEMENT
    Uniaxial     Around one axis; in one place
    image Elbow joint Spool-shaped process fits into a concave socket Flexion and extension only
    image Joint between the first and second cervical vertebrae Arch-shaped process fits around a peglike process Rotation
    Biaxial     Around two axes, perpendicular to each other; in two planes
    image