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(a) Hand (palm anterior)

(a) Frontal view of the left upper limb with the hand, palm anterior and (b) with the hand, palm posterior. (c) Posterior view of the right elbow. (d) Radiograph of the left elbow and forearm, viewed (b) Hand (palm posterior) anteriorly.

Radius

The radius, located on the thumb side of the forearm, is somewhat shorter than its companion, the ulna (fig. 7.46). The radius extends from the elbow to the wrist and crosses over the ulna when the hand is turned so that the palm faces backward.

A thick, disklike head at the upper end of the radius articulates with the capitulum of the humerus and a notch of the ulna (radial notch). This arrangement allows the radius to rotate freely.

On the radial shaft just below the head is a process called the radial tuberosity. It is an attachment for a muscle (biceps brachii) that bends the upper limb at the elbow. At the distal end of the radius, a lateral styloid (sti'loid) process provides attachments for ligaments of the wrist.

Ulna

The ulna is longer than the radius and overlaps the end of the humerus posteriorly. At its proximal end, the ulna has a wrenchlike opening, the trochlear notch (semilunar

Greater tubercle

Greater tubercle

Capitulum Humerus

Head

Anatomical neck

Surgical neck

Medial epicondyle

Lateral epicondyle

Capitulum

Trochlea

Figure 7.45

(a) Posterior surface and (b) anterior surface of the left humerus.

Lateral epicondyle

Capitulum

Head

Anatomical neck

Surgical neck

Greater tubercle

Intertubercular groove

Lesser tubercle

Coronoid fossa

Medial epicondyle

Trochlea

Figure 7.45

(a) Posterior surface and (b) anterior surface of the left humerus.

Greater tubercle

Intertubercular groove

Lesser tubercle

- Deltoid tuberosity

Coronoid fossa

Capitulum

Trochlea

Capitulum

Trochlea

notch), that articulates with the trochlea of the humerus. A process lies on either side of this notch. The olecranon process, located above the trochlear notch, provides an attachment for the muscle (triceps brachii) that straightens the upper limb at the elbow. During this movement, the olecranon process of the ulna fits into the olecranon fossa of the humerus. Similarly, the coronoid process, just below the trochlear notch, fits into the coronoid fossa of the humerus when the elbow bends.

At the distal end of the ulna, its knoblike head articulates laterally with a notch of the radius (ulnar notch)

and with a disk of fibrocartilage inferiorly (fig. 7.46). This disk, in turn, joins a wrist bone (triquetrum). A medial styloid process at the distal end of the ulna provides attachments for ligaments of the wrist.

Wrist and Hand

The wrist joint is at the junction of the forearm and the hand. The skeleton of the wrist consists of eight small carpal bones that are firmly bound in two rows of four bones each. The resulting compact mass is called a carpus (kar'pus).

Trochlear notch Coronoid process Head of radius

Radial tuberosity

Olecranon process

Radius

Styloid process

Olecranon process

Trochlear notch Coronoid process Head of radius

Radial tuberosity

Radius

Styloid process

Olecranon process

Trochlear notch

Coronoid process Radial notch

Head of ulna

Styloid process Ulnar notch of radius

Figure

{a) The head of the right radius articulates with the radial notch of the ulna, and the head of the ulna articulates with the ulnar notch of the radius. {b) Lateral view of the proximal end of the ulna.

Olecranon process

Trochlear notch

Coronoid process Radial notch

Head of ulna

Styloid process Ulnar notch of radius ure 7.46

Figure

{a) The head of the right radius articulates with the radial notch of the ulna, and the head of the ulna articulates with the ulnar notch of the radius. {b) Lateral view of the proximal end of the ulna.

The carpus is rounded on its proximal surface, where it articulates with the radius and with the fibrocar-tilaginous disk on the ulnar side. The carpus is concave anteriorly, forming a canal through which tendons and nerves extend to the palm. Its distal surface articulates with the metacarpal bones. Figure 7.47 names the individual bones of the carpus.

The hand is composed of a palm and five fingers. Five metacarpal bones, one in line with each finger, form the framework of the palm. These bones are cylindrical, with rounded distal ends that form the knuckles of a clenched fist. The metacarpals articulate proximally with the carpals and distally with the phalanges. The metacarpal on the lateral side is the most freely movable; it permits the thumb to oppose the fingers when grasping something. These bones are numbered 1 to 5, beginning with the metacarpal of the thumb (see fig. 7.47).

The phalanges are the finger bones. There are three in each finger—a proximal, a middle, and a distal phalanx— and two in the thumb. (The thumb lacks a middle phalanx.) Thus, each hand has fourteen finger bones. Table 7.10 summarizes the bones of the pectoral girdle and upper limbs.

Lunate Hamate Triquetrum Pisiform

Carpals

Metacarpals

Lunate Hamate Triquetrum Pisiform

Metacarpals

Distal : phalanx

Radius Ulna

Scaphoid Capitate Trapezoid Trapezium

Proximal phalanx

Middle phalanx

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