AssessmentsBlood vessels and nerves of the hand
Blood Vessels and Nerves of the Hand
A professional cyclist comes to you after getting in an accident where they landed on the medial aspect of their hand. They have full function of their hands, but numbness over the 5th digit and medial half of the 4th digit. What nerve is most likely damaged?
Content Reviewers:Scott Caterine, BSc (Hons.), MSc, MB, BCh, BAO (Hons.), Viviana Popa, MD
Contributors:Ursula Florjanczyk, MScBMC, Elizabeth Nixon-Shapiro, MSMI, CMI, Sam Gillespie, BSc, Evode Iradufasha, MD
All hands on deck everyone!
We’re taking a deep dive into the blood supply and nerves of the most mobile and dexterous parts of our musculoskeletal system, the hands.
Human hands are supplied by an intricate network of blood vessels and nerves, which all work hand-in-hand to deliver the necessary blood supply and coordination in order for the hand muscles to be able to type, draw, suture, climb and everything else hands do.
The hand’s blood supply comes entirely from two main sources: the ulnar and radial arteries, which both originate from the brachial artery.
Both the ulnar and the radial arteries enter the hand from the wrist.
Let’s look at the ulnar artery first.
When entering the wrist, the ulnar artery passes superficiall to the transverse carpal ligament, also known as the flexor retinaculum, and enters the hand through a small tunnel called the ulnar canal, or Guyon’s canal.
The ulnar canal has a roof, made up by the thickened superficial palmar fascia, a floor made up by the transverse carpal ligament, a medial wall, consisting of the pisiform and pisohamate ligament, and a lateral wall made up by the hook of the hamate.
The ulnar canal also allows the ulnar nerve to pass through, medial to the ulnar artery.
The superficial palmar arch is the main termination of the ulnar artery and starting in the medial part of the hand it courses towards the lateral part of the hand to anastomose with the superficial branch of the radial artery.
Along its course, the superficial palmar arch gives rise to three branches known as the common palmar digital arteries.
Each of these divides into a pair of proper palmar digital arteries, which run along the sides of the 2nd to 5th digits.
In the lateral part of the wrist, the radial artery gives off the superficial palmar branch that completes the superficial palmar arch and then it curves towards the back of the hand around the scaphoid and trapezium.
It then crosses the floor of the anatomical snuffbox which is a triangular space formed on the lateral aspect of the wrist, at the base of the thumb.
The radial artery then enters the palm where it forms the deep palmar arch which travels across the metacarpals just distal to their bases before anastomosing with the deep palmar branch of the ulnar artery.
Along this course, the deep palmar arch gives off the princeps pollicis artery which supplies the thumb, the radialis indicis artery, which supplies the second digit, or index finger - and may arise directly from the princeps pollicis artery and finally the three palmar metacarpal arteries.
Okay, now, for a quick break - can you try to remember the direct branches of the superficial palmar arch?
Alright, now let’s look at the veins of the hand.
The hand has the superficial veins, which run close to the skin; and the deep veins, which run deep in the tissues alongside arteries.
Some of the superficial veins drain the dorsum of the hand, so they’re called dorsal venous network.
The dorsal venous network starts as dorsal digital veins in the fingers, which drain into dorsal metacarpal veins in the hand.
In the palmar part of the hand, the veins of the hand converge to form superficial and deep venous palmar arches which run with the superficial and deep palmar arterial arches.
Both these arches drain into the deep veins of the forearm.
Alright, now let’s switch gears, and talk about the nerves of the hand.
At the wrist, the median nerve gives off the palmar cutaneous branch right before entering the hand.
This branch passes superficially to the flexor retinaculum and enters the hand to provide sensory innervation to the skin of the central palm.