CHAPTER 7 Skeletal System: Gross Anatomy

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Carpalbones (proximalrow)

ScaphoidLunateTriquetrumPisiform

Digits

boneboneTriquetrum bonebone

Carpalbones (proximalrow)

Metacarpalbones

(a) Posterior view

(b) Anterior view

FIGURE 7.27 Bones of the Right Wrist and Hand

thumb and the hook of the hamate at the base of the little finger.A ligament stretches across the wrist from the tubercle of the tra-pezium to the hook of the hamate to form a tunnel on the anteriorsurface of the wrist called the carpal tunnel. Tendons, nerves,and blood vessels pass through this tunnel to enter the hand (seeClinical Impact, “Carpal Tunnel Syndrome”).Treatments for carpal tunnel syndrome vary, depending on theseverity of the condition. Mild cases can be treated nonsurgicallywith either anti-inflammatory medications or stretching exercises.However, if symptoms have lasted for more than 6 months, surgeryis recommended. Surgical techniques involve cutting the carpal liga-ment to enlarge the carpal tunnel and ease pressure on the nerve.

The five digits of each hand include one thumb and four fingers.Each digit consists of small long bones called phalanges (f ă -lan′j ē z;sing. phalanx). The thumb has two phalanges, called proximal anddistal. Each finger has three phalanges, designated proximal, middle,and distal. One or two sesamoid (ses′ ă -moyd) bones (not shown infigure 7.27) often form near the junction between the proximalphalanx and the metacarpal bone of the thumb. Sesamoid bonesare small bones located within some tendons that increase themechanical advantage of tendons where they cross joints.

Predict 5

Explain why the “fingers” appear much longer in a dried, articulatedskeleton than in a hand with the soft tissue intact.

Hand

Five metacarpal bones are attached to the carpal bones andconstitute the bony framework of the hand (figure 7.27). Theyare numbered one to five, starting with the most lateral metacar-pal bone, at the base of the thumb. The metacarpal bones forma curve so that, in the resting position, the palm of the hand isconcave. The distal ends of the metacarpal bones help form theknuckles of the hand (see figure 7.26). The spaces between themetacarpal bones are occupied by soft tissue.

ASSESS YOUR PROGRESS

27. Describe how the upper and lower limbs are attached tothe axial skeleton.

28. Name the bones that make up the pectoral girdle.Describe their functions.

29. What are the functions of the acromion process and thecoracoid process of the scapula?