Upper Limb

The upper limb is divided into four regions containing a total of 30 bones per limb:

1. The brachium51 (BRAY-kee-um), or arm proper, extends from shoulder to elbow. It contains only one bone, the humerus.

2. The antebrachium,52 or forearm, extends from elbow to wrist and contains two bones—the radius and ulna. In anatomical position, these bones are parallel and the radius is lateral to the ulna.

3. The carpus,53 or wrist, contains eight small bones arranged in two rows.

4. The manus,54 or hand, contains 19 bones in two groups—5 metacarpals in the palm and 14 phalanges in the fingers.

50glen = pit, socket 51 brachi = arm 52ante = before 53carp = wrist 54man = hand

50glen = pit, socket 51 brachi = arm 52ante = before 53carp = wrist 54man = hand

Scapula Anterior Posterior
Figure 8.31 The Right Scapula. (a) Anterior view; (fa) posterior view.

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Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

274 Part Two Support and Movement

Humerus

The humerus has a hemispherical head that articulates with the glenoid cavity of the scapula (fig. 8.32). The smooth surface of the head (covered with articular cartilage in life) is bordered by a groove called the anatomical neck. Other prominent features of the proximal end are muscle attachments called the greater and lesser tubercles and an intertubercular sulcus between them that accommodates a tendon of the biceps muscle. The surgical neck, a common fracture site, is a narrowing of the bone just distal to the tubercles, at the transition from the head to the shaft.

The shaft has a rough area called the deltoid tuberosity on its lateral surface. This is an insertion for the deltoid muscle of the shoulder. The distal end of the humerus has two smooth condyles. The lateral one, called the capitulum55 (ca-PIT-you-lum), is shaped somewhat like a fat tire and articulates with the radius. The medial one, called the trochlea56 (TROCK-lee-uh), is pulleylike and articulates with the ulna. Immediately proximal to these condyles, the humerus flares out to form two bony processes, the lateral and medial epi-condyles. The medial epicondyle protects the ulnar nerve, which passes close to the surface across the back of the elbow. This epicondyle is popularly known as the "funny bone" because striking the elbow on the edge of a table stimulates the ulnar nerve and produces a sharp tingling sensation.

The distal end of the humerus also shows three deep pits—two anterior and one posterior. The posterior pit, called the olecranon (oh-LEC-ruh-non) fossa, accommodates the olecranon of the ulna when the arm is extended. On the anterior surface, a medial pit called the coronoid fossa accommodates the coronoid process of the ulna when the arm is flexed. The lateral pit is the radial fossa, named for the nearby head of the radius.

Radius

The proximal head of the radius (fig. 8.33) is a distinctive disc that rotates freely on the humerus when the palm is turned forward and back. It articulates with the capitulum of the humerus and radial notch of the ulna. On the shaft, immediately distal to the head, is a medial rough tuberosity, which is the insertion of the biceps muscle. The distal end of the radius has the following features, from lateral to medial:

1. a bony point, the styloid process, which can be palpated proximal to the thumb;

2. two shallow depressions (articular facets) that articulate with the scaphoid and lunate bones of the wrist; and

6troch = wheel, pulley

Posterior View Upper Limb Bones
Figure 8.32 The Right Humerus. (a) Anterior view; (b) posterior view.

3. the ulnar notch, which articulates with the end of the ulna.

Ulna

At the proximal end of the ulna (fig. 8.33) is a deep, C-shaped trochlear notch that wraps around the trochlea of the humerus. The posterior side of this notch is formed by a prominent olecranon—the bony point where you rest your elbow on a table. The anterior side is formed by a less prominent coronoid process. Medially, the head of the ulna has a less conspicuous radial notch, which accommodates the head of the radius.

At the distal end of the ulna is a medial styloid process. The bony lumps you can palpate on each side of your wrist are the styloid processes of the radius and ulna. The radius and ulna are attached along their shafts by a ligament called the interosseous (IN-tur-OSS-ee-us) membrane, which is attached to an angular ridge called the interosseous margin on the medial side of each bone.

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Chapter 8 The Skeletal System 275

Olecranon

Radial notch of ulna

Head of radius

Neck of radius

Tuberosity of radius

Styloid process

Anterior surface Posterior surface

-Trochlear notch

Coronoid process Tuberosity of ulna

Anterior Posterior Interosseous Membrane

Coronoid process Tuberosity of ulna

Ulna Radius

Interosseous margins

Interosseous -membrane

Ulna Radius

Head of radius

Neck of radius

Interosseous margins

Interosseous -membrane

Ulnar notch of radius Head of ulna Styloid process Articular facets s

Olecranon

Head of radius

Neck of radius

Styloid process

Figure 8.33 The Right Radius and Ulna. (a) Anterior view; (b) posterior view.

Carpal Bones

The carpal bones, which form the wrist, are arranged in two rows of four bones each (fig. 8.34). These short bones allow movements of the wrist from side to side and up and down. The carpal bones of the proximal row, starting at the lateral (thumb) side, are the scaphoid (navicular), lunate, triquetrum (tri-QUEE-trum), and pisiform—Latin for boat-, moon-, triangle-, and pea-shaped, respectively. Unlike the other carpal bones, the pisiform is a sesamoid bone; it develops within the tendon of the flexor carpi ulnaris muscle.

The bones of the distal row, again starting on the lateral side, are the trapezium,57 trapezoid, capitate,58 and hamate.59 The hamate can be recognized by a prominent hook on the palmar side.

i7trapez = table, grinding surface 58capit = head + ate = possessing 59 ham = hook + ate = possessing

Metacarpal Bones

Bones of the palm are called metacarpals.60 Metacarpal I is located at the base of the thumb and metacarpal V at the base of the little finger. On a skeleton, the metacarpals look like extensions of the fingers, so that the fingers seem much longer than they really are. The proximal end of a metacarpal bone is called the base, the shaft is called the body, and the distal end is called the head. The heads of the metacarpals form knuckles when you clench your fist.

Phalanges

The bones of the fingers are called phalanges (fah-LAN-jeez); in the singular, phalanx (FAY-lanks). There are two phalanges in the pollex (thumb) and three in each of the other digits. Phalanges are identified by Roman numerals preceded by proximal, middle, and distal. For example, proximal phalanx I is in the basal segment of the thumb e0meta = beyond + carp = wrist

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Phalanges

Metacarpus

Carpus

Distal Middle

Head Body Base

Hamulus of hamate Hamate Pisiform Triquetrum-Lunate-

Hamulus of hamate Hamate Pisiform Triquetrum-Lunate-

Imagenes Phalanx Body

Head Body Base

Distal phalanx

Proximal phalanx

Head Body Base

Distal phalanx

Proximal phalanx

First metacarpal

Trapezoid Trapezium Capitate Scaphoid

Distal bones of carpus Proximal bones of carpus

Bones The Hand Mnemonic

Figure 8.34 The Right Wrist and Hand, Anterior (palmar) View. (a) Carpal bones are color-coded to distinguish the proximal and distal rows. Some people remember the names of the carpal bones with the mnemonic, "Sally left the party to take Charlie home." The first letters of these words correspond to the first letters of the carpal bones, from lateral to medial, proximal row first. (b) X ray of an adult hand. Identify the unlabeled bones in the X ray by comparing it to the drawing.

How does figure b differ from the X ray of a child's hand,figure 7.11?

Figure 8.34 The Right Wrist and Hand, Anterior (palmar) View. (a) Carpal bones are color-coded to distinguish the proximal and distal rows. Some people remember the names of the carpal bones with the mnemonic, "Sally left the party to take Charlie home." The first letters of these words correspond to the first letters of the carpal bones, from lateral to medial, proximal row first. (b) X ray of an adult hand. Identify the unlabeled bones in the X ray by comparing it to the drawing.

How does figure b differ from the X ray of a child's hand,figure 7.11?

Saladin: Anatomy & I 8. The Skeletal System I Text I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

(the first segment beyond the web between the thumb and palm); the left proximal phalanx IV is where people usually wear wedding rings; and distal phalanx V forms the tip of the little finger. The three parts of a phalanx are the same as in a metacarpal: base, body, and head. The ventral surface of a phalanx is slightly concave from end to end and flattened from side to side; the dorsal surface is rounder and slightly convex.

Table 8.7 summarizes the bones of the pectoral girdle and upper limb.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

14. Describe how to distinguish the medial and lateral ends of the clavicle from each other, and how to distinguish its superior and inferior surfaces.

15. Name the three fossae of the scapula and describe the location of each.

16. What three bones meet at the elbow? Identify the fossae, articular surfaces, and processes of this joint and state to which bone each of these features belongs.

17. Name the four bones of the proximal row of the carpus from lateral to medial, and then the four bones of the distal row in the same order.

18. Name the four bones from the tip of the little finger to the base of the hand on that side.

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Responses

  • Adiam
    Where is the interosseous in the radius?
    8 years ago
  • sirja laatikainen
    Is the humerus is a right bon in an anterior posterior view?
    7 years ago
  • Nikodem
    Which of the following is not a feature of the proximal end of the ulna?
    6 years ago
  • lobelia
    What theee bones meet at the elbow identify the fossae?
    4 years ago
  • Matthias
    Which bones of the upper limb have a styloid process?
    2 years ago

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