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Dissection of arm and forearm
This specimen shows the muscles, arteries and the nerves of the front of the upper limb
The front of the upper limb is made up of the flexor muscles. The deltoid (1) muscle is situated in the shoulder. The biceps brachii, the brachialis, the median nerve, the ulnar nerve and the brachial artery is seen in the arm. The radial artery, the median nerve, the ulnar nerve and the ulnar artery can be seen in the forearm. The superficial palmar arch is seen in the palm.
Deltoid:
The deltoid is a muscle of the shoulder. It takes origin from the clavicle, the spine of the scapula and the acromion process. It insertion lies at the deltoid tuberosity of the humerus. It is supplied by the axillary nerve. It mainly brings about flexion, extension and abduction of the shoulder joint. It is mainly used to give intramuscular injections.
Biceps brachii:
The biceps brachii muscle, is the muscle of the front of the arm. It has two heads of origin: short head and long head. These heads arise from the scapula. Its rounded tendon inserts into the radial tuberosity and its aponeurosis (bicipital aponeurosis) inserts into the skin along the medial aspect of the forearm. It is supplied by the musculocutaneous nerve. Its main action is supination of forearm when the elbow is flexed.
Brachialis:
The brachialis forms the floor of the cubital fossa. It takes origin from the front of the humerus and inserts into the ulnar tuberosity. It is supplied by the musculocutaneous nerve and the radial nerve. It is a weak flexor of the forearm.
Median nerve:
The Median nerve is a branch of the brachial plexus. It has two roots coming from the medial cord and the lateral cord of brachial plexus. It traverses through the front of the arm and passes through the cubital fossa to enter the front of the forearm. It supplies most of the muscles of the forearm and the hand that are involved in coarse movements. Hence this nerve is also known as labourer’s nerve. Before passing into the hand, the nerve could be trapped in the wrist, causing a clinical condition called, the carpal tunnel syndrome. This syndrome is manifested by numbness, tingling sensation or weakness in the hand.
Brachial artery:
The Brachial artery is a continuation of the axillary artery at the lower border of teres major muscle. It passes through the front of the arm and the cubital fossa and bifurcates into two terminal branches at the level of the neck of the radius into the radial artery and the ulnar artery. It is usually used to check blood pressure around the lower part of the arm.
Ulnar nerve:
The ulnar nerve is a branch of the medial cord of the brachial plexus. It traverses through the arm, passes posterior to the medial epicondyle of the humerus and enters the forearm. Here it supplies flexor carpi ulnaris and medial part of the flexor digitorum profundus. It then enters the hand and supplies the intrinsic muscles of the hand, that are concerned with fine movements. Therefore, this nerve is also known as the musician’s nerve.
Ulnar artery:
The ulnar artery is the terminal branch of the brachial artery. It passes along the medial aspect of the forearm and enters the palm to for the superficial palmar arch.
Radial artery:
The radial artery is the terminal branch of the brachial artery. It passes along the lateral aspect of the forearm. At the lower part of the forearm, the artery is usually palpated to check the pulsations. It then passes into the palm to complete the superficial palmar arch.
Superficial palmar arch:
The superficial palmar arch is an arterial arch in the palm. It is mainly formed by the ulnar artery and completed by the branches of the radial artery. It supplies the structures in the palm.
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