Extensor carpi radialis brevis. This muscle is the shorter, wider counterpart to the extensor carpi radialis longus. Extensor digitorum. This muscle allows for the extension of the second, third, fourth, and fifth fingers. Extensor carpi ulnari. This muscle adducts the wrist.
Deep layer Supinator. This muscle allows the forearm to rotate outward so the palm faces up. Abductor pollicis longus. This muscle abducts the thumb, moving it away from the body. Extensor pollicis brevis. This muscle extends the thumb. Extensor pollicis longus. This is the longer counterpart to the extensor pollicis brevis. Extensor indices. This muscle extends the index finger. Explore the interactive 3-D diagram below to learn more about the arm.
Anatomy and function of arm nerves. Brachial plexus The brachial plexus refers to a group of nerves that serve the skin and muscles of the arm. The brachial plexus is divided into five different divisions: Roots.
This is the beginning of the brachial plexus. Three trunks form the brachial plexus roots. These include the superior, middle, and inferior trunks. The superior trunk is a combination of the C5 and C6 roots, the middle trunk is a continuation of the C7 root, and the inferior trunk is a combination of the C8 and T1 roots. Each of the three trunks contains an anterior and posterior division, meaning there are six divisions in total. The anterior and posterior divisions of the brachial plexus combine to form three cords, known as the lateral, posterior, and medial cords.
The branches of the brachial plexus go on to form the peripheral nerves that supply the arm. Peripheral nerves The peripheral nerves of the arm provide motor and sensory functions to the arm. The six peripheral nerves of the arm include the: Axillary nerve. The axillary nerve travels between the scapula and humerus. It stimulates the muscles in the shoulder area, including the deltoid, the teres minor, and part of the triceps.
Musculocutaneous nerve. This nerve travels in front of the humerus and stimulates the biceps, brachialis, and coracobrachialis muscles. The musculocutaneous nerve also provides sensation to the outside of the forearm. Ulnar nerve. The ulnar nerve is located on the outside of the forearm. It stimulates many muscles in the hand and provides sensation to the pinky finger and part of the ring finger. Radial nerve. The radial nerve travels behind the humerus and along the inside of the forearm.
It stimulates the triceps muscle of the upper arm as well as muscles in the wrist and hand. It provides sensation to part of the thumb.
Median nerve. The median nerve travels along the inside of the arm. It stimulates most of the muscles in the forearm, wrist, and hand. It also provides sensation for part of the thumb, the forefinger, middle finger, and part of the ring finger. Function and anatomy of arm blood vessels.
Below are some of the main veins and arteries of the arm. Upper arm blood vessels Subclavian artery. The subclavian artery supplies blood to the upper arm.
It begins close to the heart and travels under the clavicle and to the shoulder. Axillary artery. The axillary artery is a continuation of the subclavian artery. It can be found under the armpit and supplies blood to the shoulder area. Brachial artery. The brachial artery is a continuation of the axillary artery. It travels down the upper arm and splits into the radial and ulnar artery at the elbow joint.
Axillary vein. The axillary vein transports blood to the heart from the area of the shoulder and armpit. Cephalic and basilic veins. These veins travel upward through the upper arm. They eventually join the axillary vein. Brachial veins. The brachial veins are large and run parallel to the brachial artery. Radial artery.
This is one of two arteries that supply blood to the forearm and hand. It travels along the inner side of the forearm. Ulnar artery. The ulnar artery is the second of the two vessels supplying blood to the forearm and hand. It travels along the outside of the forearm.
Radial and ulnar veins. These veins are situated parallel with the radial and ulnar arteries. They join the brachial vein at the elbow joint. The humerus is the single bone of the upper arm, and the ulna medially and the radius laterally are the paired bones of the forearm.
The base of the hand contains eight bones, each called a carpal bone , and the palm of the hand is formed by five bones, each called a metacarpal bone. The fingers and thumb contain a total of 14 bones, each of which is a phalanx bone of the hand. The humerus is the single bone of the upper arm region Figure 6. At its proximal end is the head of the humerus. This is the large, round, smooth region that faces medially.
The head articulates with the glenoid cavity of the scapula to form the glenohumeral shoulder joint. The margin of the smooth area of the head is the anatomical neck of the humerus. Located on the lateral side of the proximal humerus is an expanded bony area called the greater tubercle. The smaller lesser tubercle of the humerus is found on the anterior aspect of the humerus.
Both the greater and lesser tubercles serve as attachment sites for muscles that act across the shoulder joint. The deltoid tuberosity is a roughened, V-shaped region located on the lateral side in the middle of the humerus shaft. As its name indicates, it is the site of attachment for the deltoid muscle. Distally, the humerus becomes flattened. The prominent bony projection on the medial side is the medial epicondyle of the humerus.
The much smaller lateral epicondyle of the humerus is found on the lateral side of the distal humerus. All of these areas are attachment points for muscles that act on the forearm, wrist, and hand. The powerful grasping muscles of the anterior forearm arise from the medial epicondyle, which is thus larger and more robust than the lateral epicondyle that gives rise to the weaker posterior forearm muscles.
The distal end of the humerus has two articulation areas, which join the ulna and radius bones of the forearm to form the elbow joint. The capitulum articulates with the radius bone of the forearm.
Just above these bony areas are two small depressions. These spaces accommodate the forearm bones when the elbow is fully bent flexed. Superior to the trochlea is the coronoid fossa , which receives the coronoid process of the ulna, and above the capitulum is the radial fossa , which receives the head of the radius when the elbow is flexed. Similarly, the posterior humerus has the olecranon fossa , a larger depression that receives the olecranon process of the ulna when the forearm is fully extended.
The ulna is the medial bone of the forearm. It runs parallel to the radius, which is the lateral bone of the forearm Figure 6. The proximal end of the ulna resembles a crescent wrench with its large, C-shaped trochlear notch.
This region articulates with the trochlea of the humerus as part of the elbow joint. The inferior margin of the trochlear notch is formed by a prominent lip of bone called the coronoid process of the ulna. Just below this on the anterior ulna is a roughened area called the ulnar tuberosity. To the lateral side and slightly inferior to the trochlear notch is a small, smooth area called the radial notch of the ulna.
This area is the site of articulation between the proximal radius and the ulna, forming the proximal radioulnar joint. The posterior and superior portions of the proximal ulna make up the olecranon process , which forms the bony tip of the elbow. More distal is the shaft of the ulna. The small, rounded area that forms the distal end is the head of the ulna. Wrist retinacula….
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