Upper Limb

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43 Topographic Anatomy

STUDYAIMS

At the end of your study, you should be able to:

Identifythe bonylandmarks: acromion, coracoid process of scapula, olecranon and head of ulna, medial, and lateral epicondyles, radial styloid process

Identifythe muscle masses of the deltoid, biceps, triceps, brachioradialis, and thenar and hypothenar eminences Identifythe deltopectoral triangle and cubital fossa

Identifythe course of the cephalic, basilic, and median cubital veins

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GUIDE

Upper Limb: Topographic Anatomy

[Plate 400, Upper Limb]

Bones

Clavicle: Subcutaneous; palpable throughout its length

Acromion: Easilypalpable, traced mediallyto acromioclavicular joint (see Section 6-2: Upper Limb: Shoulder and Axilla) Coracoid process of scapula: Palpable deep and lateral to the deltopectoral triangle

Head of humerus: Palpable deep to deltoid inferior to lateral edge of acromion when arm is rotated

Elbow: Palpable medial and lateral epicondyles of humerus and visible olecranon process of ulna (see Section 6-4: Upper Limb: Elbow and Forearm)

Head of radius: Palpable as it rotates during pronation and supination on posterolateral aspect of extended elbow, just distal to lateral epicondyle

Ulnar head: Visible on the medial side of the dorsal aspect of the wrist (see Section 6-5: Upper Limb: Wrist and Hand) Radial styloid: Palpable in the anatomical snuff boxon the lateral side of the wrist

Ulnar styloid: just distal to ulnar head with hand supinated Pisiform: hard, round structure on anteromedial aspect of wrist

Tubercles of scaphoid and trapezium: Palpable at proximal end of thenar eminence

Muscles and Tendons

Deltoid muscle: Overlies the shoulder giving it a rounded appearance

Biceps: Bulge on anterior aspect of arm

Biceps brachii tendon: Palpable in cubital fossa, lateral to midline with arm flexed

Flexor tendons: Wrist and finger flexors visible distallyon ventral aspect of forearm

Extensor tendons: Wrist and finger flexors visible on the dorsum of the hand

Thenar eminence: Muscles at the base of the thumb (see Section 6-5: Upper Limb: Wrist and Hand)

Hypothenar eminence: Muscles at the base of the little finger (see Section 6-5: Upper Limb: Wrist and Hand)

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Arteries and Veins

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Brachial artery

Pulsations can be palpated deep to medial border of biceps muscle

Used to determine heart rate in children

Radial artery: Pulse can be felt bycompressing arteryagainst distal end of radius

Median cubital vein (see Section 6-4: Upper Limb: Elbowand Forearm)

Traverses the cubital fossa connecting cephalic to basilic veins

Often used for venipuncture

Cephalic vein ascends along lateral forearm and arm (see Section 6-6: Upper Limb: Neurovasculature)

Basilic vein ascends along medial forearm and distal arm (see Section 6-6: Upper Limb: Neurovasculature)

Dorsal venous network seen on the dorsum of the hand

Nerves

Ulnar nerve can be felt under the medial epicondyle

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FACTS & HINTS

HIGH-YIELD FACTS

Anatomic Points

Functional Overview

The upper limb is highlymobile and characterized byits abilityto perform a wide range of controlled movements to manipulate the surrounding environment. It is suspended from the trunk at the shoulder, and its stabilityhas been sacrificed to gain mobility. Clinicallythe limb is divided into four regions: pectoral girdle, arm, forearm and hand.

Upper Limb Development

The upper limb buds from the embryonic trunk and rotates 90 degrees laterally, such that in the anatomic position, the ventral structures face anteriorlyand the dorsal structures posteriorly. This contrasts with the medial rotation of the lower limb. Thus, the upper and lower limbs are 180 degrees out of phase. Flexors of all joints in the upper limb are anterior, and extensors are posterior.

Clinical Points

Winged Scapula

Normallythe scapula is held closelyagainst the posterior thoracic wall. Damage to the long thoracic nerve to serratus anterior (which courses superficiallyover the muscle) causes "winging" of the scapula as its medial border lifts awayfrom the thoraxwhen the arm is raised. This is accentuated when the individual leans on the hand or pushes the upper limb against a wall. Most importantly, the arm cannot be abducted above the horizontal plane because glenoid cavitycannot be rotated upward without the action of the serratus anterior.

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44 Shoulder and Axilla

STUDYAIMS

At the end of your study, you should be able to:

Identifythe different parts and surface markings of the clavicle and scapula

Describe the sternoclavicular, acromioclavicular, and glenohumeral joints, their movements, and supporting ligaments Understand the organization of the scapular muscles

Know the origins, insertions, and actions of the intrinsic scapular muscles Identifythe boundaries of the axilla and describe its contents

Describe the organization of the deep fascia

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