The human hand, the most distal part of the upper limb, is a remarkable feat of engineering and evolution. It is strong enough to allow climbers to tackle any mountain, but also sufficiently precise for the manipulation of some of the world’s smallest objects and the performance of complex actions.
The hand itself consists of specific bones onto which various muscles are attached, and a collection of neurovascular structures responsible for drainage and innervation. However, the intrinsic muscles of the hand are only partially responsible for all its range of motion. The other major contributors are actually the forearm muscles, which project tendons towards the hand via an equally complex and flexible anatomical structure, called the wrist.
A solid understanding of the hand requires good grasp (pun intended) of its entire anatomy, so in this page we will look at all of the above structures.
Carpals: scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate
Metacarpals: base, shaft, head
Phalanges: proximal, middle, distal phalanges
Thenar group: abductor pollicis brevis, adductor pollicis, flexor pollicis brevis, opponens pollicis
Hypothenar group: abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, palmaris brevis
Metacarpal group: lumbircals, palmar interossei, dorsal interossei
Mnemonic: 'Rule of 3s'
Median nerve and its branches (common and proper palmar digital nerves) predominantly supply the thenar muscles.
Radial nerve provides cutaneous innervation along the outisde of the thumb.
Ulnar nerve and its branches (superficial, deep and dorsal) innervate the hypothenar and metacarpal groups
Mnemonic: Ulnar nerve supplies all intrinsic muscles of the hand except the LOAF muscles (Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis)
All the branches originate from the radial and ulnar arteries. They include: palmar arches (superficial, deep), palmar digital arteries (common, proper), dorsal carpal arch, dorsal metacarpal arteries, dorsal digital arteries, principal artery of the thumb.
Dorsal venous network of hand: predominant drainage route of the hand (also receiving palmar venous return via perforating veins). Gives rise to cephalic and basilic veins.
Palmar venous arches: Receives palmar metacarpal and digital veins. Drain into radial and ulnar veins.
|Wrist||It is capable of various movements like flexion, extension, abduction and adduction. It also facilitates the passage of tendons and various neurovascular structures from the forearm to the hand.|
The bones of the hand can be divided into three distinct groups:
Each group of hand bones is important in its own right, but the eight carpals are especially interesting because they are arranged in two distinct rows and are direct contributors to the formation of the wrist. We’ll come back to the wrist later on.
In the meantime, it would be beneficial for you to take a closer look at the carpal bones with the following learning materials, because they are the most difficult hand bones to get your head around.
The muscles of the hand consist of five groups:
- Thenar muscles
- Hypothenar muscles
- Palmar interossei
- Dorsal interossei
The thenar muscles are four in total; they are evident and easy to palpate on the radial side of the palmar surface of the hand, at the base of the thumb. They form the ‘ball’ or ‘fleshy’ part of the thumb known as the thenar eminence, and are named as follows: abductor pollicis brevis, adductor pollicis, flexor pollicis brevis, and opponens pollicis.
Use the following mnemonic to easily remember them
APB is A Friend Of Police
- Abductor pollicis brevis
- Adductor pollicis
- Flexor pollicis brevis
- Opponens Pollicis
|Abductor pollicis brevis||
Origin - tubercles of the scaphoid and trapezium; flexor retinaculum
Insertion - base of the proximal phalanx 1 (via radial sesamoid bone)
Innervation - Recurrent branch of median nerve (C8, T1)
Function - thumb abduction (moving away from the hand) at carpometacarpal joint 1
Origin - palmar base of third metacarpal (transverse head), capitate bone and palmar bases of second and third metacarpals (oblique head)
Insertion - base of proximal phalanx, ulnar sesamoid bone
Innervation - deep branch of ulnar nerve
Function - thumb adduction (moving towards the hand)
|Flexor pollicis brevis||
Origin - flexor retinaculum, tubercle of trapezium (superficial head), trapezoid and capitate bones (deep head)
Insertion - radial sesamoid bone and base of the proximal phalanx (superficial head), base of first phalanx, radial sesamoid bone (deep head)
Innervation - median and ulnar nerves
Function - thumb flexion (bending)
Origin - flexor retinaculum, tubercle of trapezium bone
Insertion - first metacarpal bone
Innervation - Recurrent branch of median nerve (C8, T1)
Function - thumb flexion, abduction, and medial rotation resulting in a combined movement called opposition
APB is A Friend Of Police
The thenar muscles are capable of various thumb movements; abduction, adduction, flexion, and opposition. Watch the following video to learn more about the thenar muscles.
Also on the palmar surface of the hand, the thenar eminence has a corresponding, ‘fleshy’ region on the ulnar side of the hand. It is easily palpated and visible at the base of the little finger. This region is called the hypothenar eminence and consists of the four hypothenar muscles: abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, and palmaris brevis. This group of muscles are expert movers of the little finger (fifth digit); they abduct, flex, and bring it towards the thumb to facilitate opposition.
The last three groups of hand muscles, that is the lumbricals, dorsal interossei, and palmar interossei, are situated in the deepest layer of the hand and are commonly taken together as one big group called the metacarpal muscles of the hand. They work in unison to help with the extension, flexion, abduction, and adduction of the phalanges.
Check out our study unit about the muscles of the hand.
Do you find it difficult to memorize the muscles of the hand? Take advantage of the following mnemonic to make your life a little easier!
'Rule of 3s'
- 3 thenar muscles: abductor pollicis brevis, flexor pollicis brevis, opponens pollicis (+adductor pollicis)
- 3 hypothenar muscles: abductor digiti minimi, flexor digiti minimi, opponens digiti minmi (+palmaris brevis)
- 3 metacarpal muscles: dorsal interossei, palmar interossei, lumbricals
- 3 abductors of digits: dorsal interossei, abductor pollicis brevis, abductor digiti minimi
Nerves, arteries & veins
The nerves of the hand and wrist originate from the structure called the brachial plexus which is located proximally in the root of the neck and axillary region. This plexus is formed from the combination of the anterior rami of the spinal nerves C5-T1 and is responsible for motor and sensory innervation of the upper limb.
The important nerves from the brachial plexus that innervate the hand and wrist are the median, ulnar, and radial nerves:
- The median nerve passes through the carpal tunnel under the flexor retinaculum of the hand and distally divides into recurrent and common palmar digital branches. The recurrent branch of median nerve provides motor supply for the three thenar muscles while the first and second lumbrical muscles are innervated by the palmar digital branches. In addition, proper palmar digital nerves provide palmar cutaneous innervation for the thumb, index, middle and lateral half of ring fingers as distal third of the dorsal aspect of the same digits.
- The ulnar nerve enters the hand under the superficial part of the flexor retinaculum (in Guyon’s canal) after which it divides into the deep and superficial branches. The deep branch is mainly motor and supplies the hypothenar, interossei and medial two lumbricals muscles. The superficial branch is mainly sensory but also innervates the palmaris brevis muscle; it provides palmar and dorsal cutaneous innervation to the little finger and medial half of the ring finger. Study tip: The ulnar nerve innervates all intrinsic muscles except the LOAF: Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis with supply by the medial nerve.
- The last nerve that has a role in the innervation of the wrist and hand is the radial nerve, namely its superficial branch. This nerve is completely sensory in the hand and gives off a number of dorsal digital branches over the anatomical snuffbox. These provide dorsal cutaneous innervation to the proximal two-thirds of the thumb, index, middle and lateral half of ring fingers, as well as the lateral aspect of the dorsum of the hand and thumb base.
Branches: Palmar branch, recurrent branch, common palmar digital branches, proper palmar digital branches
Muscle innervation: Thenar muscles and lumbrical muscles (1st & 2nd)
Cutaneous innervation: Lateral ⅔ of palm; palmar surface and dorsal distal ⅓ of lateral 3 ½ digits
Branches: Dorsal digital branches, palmar branch, superficial branch (common palmar digital nerves and proper palmar digital nerves), deep branch
Muscle innervation: Hypothenar, interossei muscles and lumbricals (3rd & 4th)
Cutaneous innervation: Medial ⅓ of palm; palmar/dorsal surfaces of medial 1 ½ digits
Branches: Superficial branch (dorsal digital branches)
Cutaneous innervation: Lateral ⅔ of dorsum of hand; dorsal proximal ⅔ of lateral 3 ½ digits
The following learning resources will explain everything you need to know about the innervation of the hand, as well as its origins.
Arteries & veins
Since the hand is the terminal region of the upper extremity numerous anastomoses take place here, resulting in quite a complex vascular network. All the hand arteries originate from two main, larger ones; the radial and ulnar arteries. These two blood vessels travel down the radial and ulnar sides of the forearm, respectively.
The radial and ulnar arteries give off the following specific branches in the hand:
- Superficial palmar arch
- Deep palmar arch
- Common palmar digital arteries
- Proper palmar digital arteries
- Dorsal carpal arch
- Dorsal metacarpal arteries
- Dorsal digital arteries
- Principal artery of the thumb
Understanding all the above arterial arches and anastomoses is easiest through a visual approach, therefore the video given below will clarify the entire neurovasculature of the hand.
The venous drainage does not follow directly follow the pathway of arterial supply. Watch the video mentioned above to learn all about the hand veins.
Venous drainage of the hand occurs mainly via the dorsal venous network, located across the dorsal metacarpal region, and drains into the cephalic (lateral aspect) and basilic veins (medial aspect). An accessory cephalic vein may drain the middle part of the dorsal network. The palmar venous arches receive palmar metacarpal and palmar digital tributaries, which is then returned to the deep veins of the forearm, namely the radial and ulnar veins. However, palmar venous return can also conducted to the dorsal venous network via perforating branches of the palmar metacarpal arteries to avoid restriction during gripping actions of the hand.
The main veins of the hand are:
- Superficial palmar venous arch
- Deep palmar venous arch
- Dorsal venous network of the hand
- Palmar metacarpal digital veins
- Palmar digital veins
The anatomy of the hand is incomplete without understanding the wrist. This complex structure connects the entire hand to the radius and ulna, facilitates the passage of tendons together with the above mentioned neurovascular structures from the forearm to the hand, and permits us to exploit all its movements. Those are flexion, extension, abduction, and adduction of the hand.
Take this specially designed quiz to test your knowledge about the hand and wrist. It specifically focuses on bones, muscles (including attachments, innervation, functions), arteries, veins, and nerves.