The circulatory system relies on a network of vessels to deliver oxygenated blood throughout the body. The wrist is an accessible location where these vessels run close to the surface, making it a crucial site for assessing circulatory health. Two major arteries pass through the wrist from the forearm into the hand, supplying blood to the fingers and the complex structures of the palm.
The Primary Arteries of the Wrist
The two main arteries supplying the wrist and hand are the Radial Artery and the Ulnar Artery. These vessels are the terminal branches of the larger Brachial Artery, which splits at the elbow in the area known as the cubital fossa. This division creates a dual blood supply system for the forearm and hand.
The Radial Artery descends along the lateral, or thumb, side of the forearm, following the radius bone. In the distal forearm, it is relatively superficial, passing between the tendons of the brachioradialis and the flexor carpi radialis muscles. This superficial course at the wrist makes it the most commonly used site for pulse checks.
The Ulnar Artery is generally the larger vessel and runs along the medial, or pinky, side of the forearm, following the ulna bone. It courses deeper through the forearm’s muscle tissue than the Radial Artery. At the wrist, the Ulnar Artery passes superficially, adjacent to the flexor carpi ulnaris tendon and the pisiform bone. Both arteries terminate in the hand by forming the superficial and deep palmar arches, which connect the blood supply.
Locating the Pulse Points
The superficial nature of these arteries allows for the palpation of a pulse, which is a detectable pressure wave caused by the heart’s contraction. To locate the Radial pulse, gently place the pads of two or three fingers on the inner wrist, just below the base of the thumb. The artery is felt by lightly pressing the fingertips against the radius bone, which acts as a firm surface.
The Ulnar pulse is less commonly checked but can be found on the opposite side of the wrist. It is located on the inner wrist near the pinky finger, positioned just lateral to the flexor carpi ulnaris tendon and often close to the pisiform bone. Finding the Ulnar pulse requires a slightly deeper and more deliberate touch because the artery is partially obscured by surrounding tissues.
When attempting to feel the pulse, use the pads of the index and middle fingers, not the thumb, as the thumb has its own strong pulse that could be mistaken for the patient’s. Applying moderate pressure is important; pressing too firmly can compress the artery and stop the flow, making the pulse undetectable. Once a regular pulse is felt, the rate and rhythm can be assessed.
Why These Arteries Matter Medically
The accessibility and dual nature of the wrist arteries make them invaluable in a clinical setting for diagnosis and procedures. The Radial Artery is routinely utilized to obtain a peripheral pulse rate, offering a quick assessment of heart rhythm, rate, and blood flow force. A strong, regular pulse indicates adequate circulation and cardiac output.
Beyond routine checks, the Radial Artery is the most common site for Arterial Blood Gas (ABG) sampling, a procedure that measures the levels of oxygen and carbon dioxide in the blood. Before this sampling, a test known as the Allen’s test is often performed to confirm that the Ulnar Artery can maintain blood flow to the hand on its own. This test verifies the concept of collateral circulation, where the palmar arches provide a redundant blood supply to the hand.
This redundancy is a biological safeguard; if one artery is blocked or damaged, the other can continue to supply blood to the entire hand, preventing tissue death. Assessing the integrity of both the Radial and Ulnar arteries is crucial following trauma or injury to the forearm or wrist. Ensuring the hand has a sufficient blood supply is a primary concern when treating wounds or fractures in this area.