Human Anatomy Vol 1

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elbow. The tendon is a guide to the brachial artery
which lies on its medial side.
9 The brachial artery can be felt in front of the elbow
joint just medial to the tendon of the biceps brachii.
Brachial pulsations are used for recording the blood
pressure.
10 The ulnar nerae can be rolled by the palpating finger
behind the medial epicondyle of the humerus. During
leprosy this nerve becomes thick and enlarged.
11 The superficial cubital veins can be made more
prominentby applying tightpressure round the arm
and then contracting the forearm muscles by
clenching and releasing the fist a few times. The
cephalic vein runs upwards along the lateral border
of the biceps. The basilic vein can be seen along the
lower half of the medial border of the biceps. The
cephalic and basilic veins are connected together in
front of the elbow by the median cubital vein which
runs obliquely upwards and medially.

COMPARTMENTS OF THE ARM


The arm is divided into anterior and posterior
compartments by extension of deep fascia which are
called the medial and lateral intermuscular septa
(Fig. 8.2). These septa provide additional surface for the
attachment of muscles. They also form planes along
which nerves and blood vessels travel. The septa are
well defined only in the lower half of the arm and are
attached to the medial and lateral borders and
supracondylar ridges of the humerus. The medial
septum is pierced by the ul:rar nerve and the superior
ulnar collateral artery; the lateral septum is pierced by
the radial nerve and ihe anterior deicending branch of
the profunda brachii artery.
Two additional septa are present in the anterior
compartment of the arm. The transaerse septum


Transverse
intermuscular septum
Skin

Deep Muscles

Anteroposterior septum

Lateral intermuscular
septum

Extensor compartment

Fig. 8.2: Transverse section through the distal one-third of the
arm, showing the intermuscular septa and the compartments


ARM

separates the biceps from the brachialis and encloses
the musculocutaneous nerve. The anteroposterior septum
separates the brachialis from the muscles attached to
the lateral supracondylar ridge; it encloses the radial
nerve and the anterior descending branch of the
profunda brachii artery.

D]SSECTION
Make an incision in the middle of deep fascia of the
upper arm right down up to the elbow joint. Reflect the
flaps sideways.
The most prominent muscle seen is the biceps
brachii. Deep to this, another muscle called brachialis
is seen easily. ln the fascial septum between the two
muscles lies the musculocutaneous nerve (a branch of
the lateral cord of brachial plexus). Trace the tendinous
long head of biceps arising from the supraglenoid
tubercle and the short head arising from the tip of the
coracoid process of scapula. ldentify coracobrachialis
muscle on the medial side of biceps brachii. This muscle
is easily identified as it is pierced by musculocutaneous
nerve. Clean the branches of the nerve supplying all
the three muscles dissected.

Superficiol Muscles

Muscles of the anterior compartment of the arm are
the coracobrachialis, the biceps brachii and the
brachialis. They are described in Tables 8.1 and 8.2.

Chonges of lhe Level of Inseilion of Corocobrochiolis
I Bone: The circular shaft becomes triangular below
this level.
Fascial septa: The medial and lateral intermuscular
septa become better defined from this level dov,n.
Muscles
i. Deltoid and coracobrachialis are inserted at this
level.
ii. Upper end of origin of brachialis.
iii. Upper end of origin of the medial head of triceps
brachii.
Arteries
i. The brachial artery passes from the medial side
of the arm to its anterior aspect.
ii. The profunda brachii artery runs in the spiral
groove and divides into its anterior descending/
radial collateral artery and posterior descending/
middle collateral branches.
iii. The superior ulnar collateral artery originates
from the brachial artery, and pierces the medial
intermuscular septum alongwith the ulnar nerve.
iv. The nutrient artery of the humerus enters the
bone.


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Flexor compartment
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