Human Anatomy Vol 1

Radial nerve and

profunda brachii

vessles in radial

groove

Long head of triceps

Lateral head of triceps

Tendon of trlceps

Fig. 8.20: The triceps brachii muscle

The lateral head arises from an oblique ridge on the

upper part of the posterior surface of the humerus,

corresponding to the lateral lip of the radial (spiral)

groove.

Themedialhead arises from a large triangular area on

the posterior surface of the humerus below the

radial groove, as well as from the medial and lateral

intermuscular septa. At the level of the radial

groove/ the medial head is medial to the lateral head

(Fig. 8.21).

ARM

Insertion

The long and lateral heads converge and fuse to form

a superficial flattened tendon which covers the

medial head and are inserted into the posterior part

of the superior surface of the olecranon process. The

medial head is inserted partly into the superficial

tendon, and partly into the olecranon. Although the

medial head is separated from the capsule of the

elbow joint by a small bursa, a few of its fibres are

inserted into this part of the capsule: This prevents

nipping of the capsule during extension of the arm.

These fibres are referred to as the articularis cubiti, or

as the subanconeus.

Nerve Supply

Each head receives a separate branch from the radial

nerve (C7, C8). The branches arise in the axilla and in

the radial groove.

. In radial nerve injuries in the arm, the triceps
brachii usually escapes complete paralysis because
the two nerves supplying it arise in the axilla.
. Physician holds the flexed forearm firmly. Patient
is requested to extend his elbow against the
resistance of the physicians hand. The contracting
triceps brachii is felt (Fig. 8.22).

Aclions

The triceps is a powerful active extensor of the elbow.

The long head supports the head of the humerus in the

Musculocutaneous nerve

Biceps brachii

Brachial artery and vena comitantes

Median nerve

Basilic vein

Medial cutaneous nerve offorearm

Superior ulnar collateral vessels

Ulnar nerve

Medial head

Long head of triceps brachii

Cephalic vein

Brachialis

Humerus

Radial nerve

Radial collateral vessels

Middle collateral vessels

Lateral head of triceps brachii

Fig. 8.21 : Transverse section through the arm a little below the insertion of the coracobrachialis and deltoid showing arrangement
of three heads of the triceps, and the radial nerve in the radial groove

Il

E

=

o

CL

CL

f

C

.9

oo

a