Human Anatomy Vol 1

INTRODUCTION

The arm extends from the shoulder joint till the elbow
joint. The skeleton of the arm is a 'solo' bone, the
humerus. Medial and lateral intermuscular septa divide
the arm into an anterior or flexor compartment and a
posterior or extensor compartment, to give each
compartment its individuality and freedom of action.
Since the structures in the front of arm continue across
the elbow joint into the cubital fossa, the cubital fossa
is also included in this chapter. The arm is called
brachium, so most of the structures in this chapter are
named accordingly, like brachialis, coracobrachialis and
brachial artery.

The following landmarks canbe felt inthe living subject.
1 The greater tubercle of the humeras is the most lateral
bony point in the shoulder region. It can be felt just
below the acromion, deep to the deltoid when the
arm is by the side of the trunk (Fig. 8.1).
2 The shaft of the humerus is felt only indistinctly
because it is surrounded by muscles in its upper
half. In the lower half, the humerus is covered
anteriorly by the biceps brachii and brachialis, and
posteriorly by the triceps brachii.
3 The medial epicondyle of the humerus is a prominent
bony projection on the medial side of the elbow. It
is best seen and felt in a mid-flexed elbow.
4 The lateral epicondyle of the humeras is less prominent
than the medial. It can be felt in the upper part of
the depression on the posterolateral aspect of the
elbow in the extended position of the forearm.
5 The medial and lateral supracondylar ridges are better
defined in the lower portions of the medial and
lateral borders of the humerus. They can be felt in

-Aristotle

Greater

tubercle

Lesser

tubercle

Sternal angle

Coracoid process

Nipple

Anterior axillary

fold

Tendon of biceps

brachii

Medial epicondyle

Fig.8.1: Surface landmarks-front of upper arm

the lower one-fourth of the arm as upward

continuations of the epicondyles.

The deltoid forms the rounded contour of the

shoulder. The apex of the muscle is attached to the

deltoid tuberosity located at the middle of the

anterolateral surface of the humerus.

The coracobrachinlis forms an inconspicuous rounded

ridge in the upper part of the medial side of the arm.

Pulsations of the brachial artery can be felt in the

depression behind it.

Thebicepsbrachii muscle is overlapped above by the

pectoralis major and by the deltoid. Below these

muscles the biceps forms a conspicuous elevation

on the front of the arm. Upon flexing the elbow, the

contracting muscle become still more prominent.

The tendon of the biceps can be felt in front of the