General structure of the hand
The hand is designated in Latin by the term manus. Anatomically, it is divided into three parts: the carpus (carpus), metacarpus (metacarpus), and phalanges of the fingers (phalanges digitorum). Each part has a characteristic bony structure and its own clinically significant landmarks.
The carpus is formed by eight short spongy bones arranged in two rows — proximal and distal. The metacarpus is represented by five tubular bones, and the skeleton of the fingers consists of phalanges: three for digits II–V and two for the thumb.
Proximal row of carpal bones
There are four bones in the proximal row. To memorize them, the mnemonic word "LaPoT" is used, where each letter corresponds to the first letter of the bone's name (taking into account that the soft sign "ь" resembles "г" when flipped):
- La — scaphoid bone, os scaphoideum;
- Po — lunate bone, os lunatum;
- T — triquetral bone, os triquetrum;
- ь → г — pisiform bone, os pisiforme.
The pisiform bone belongs to the sesamoid bones — that is, bones located within the thickness of a tendon (in this case, the tendon of the flexor carpi ulnaris). This fact is frequently tested during oral questioning.
Distal row of carpal bones
The distal row also consists of four bones. For memorization, it is convenient to use an associative image: two "little eyes" (rounded bones) and a hook at the end. The listing goes from the radial side to the ulnar side:
- Trapezium bone (multangular), os trapezium; it has a characteristic tubercle and a groove through which the tendon of the flexor carpi radialis runs;
- Trapezoid bone, os trapezoideum;
- Capitate bone, os capitatum — the largest carpal bone, it has a rounded "head";
- Hamate bone, os hamatum; on its palmar surface is located the hook — hamulus ossis hamati.
Carpal arch and sulcus
Together, the carpal bones form the bony carpal arch, concave facing the palmar side. Along its floor runs the carpal sulcus, sulcus carpi. The transverse carpal ligament is stretched across this sulcus, resulting in the formation of the carpal canal (canalis carpi) — a clinically important structure through which the finger flexor tendons and the median nerve pass.
Metacarpal bones
The metacarpus is represented by five metacarpal bones (ossa metacarpi), numbered from I to V starting from the thumb. Each metacarpal bone has three parts:
- base — basis;
- body — corpus;
- head — caput.
The first metacarpal bone (os metacarpi I) differs from the others: its base has a saddle-shaped articular surface that articulates with the trapezium bone, forming the carpometacarpal saddle joint of the thumb — thanks to this, opposition of digit I is possible.
Finger phalanges
The fingers of the hand are designated in Latin as digiti manus and have both ordinal and individual names:
- digitus primus / pollex — thumb;
- digitus secundus / index — index finger;
- digitus tertius / digitus medius — middle finger;
- digitus quartus / digitus anularis — ring finger;
- digitus quintus / digitus minimus — little finger.
Each finger, except the thumb, consists of three phalanges: proximal (phalanx proximalis), middle (phalanx media), and distal (phalanx distalis). The thumb has only proximal and distal phalanges. Like the metacarpal bones, each phalanx consists of a base, body, and head.
On the palmar surface of the distal phalanx is located the tuberosity of the distal phalanx — tuberositas phalangis distalis, to which the tendons of the deep flexors and extensors of the fingers attach.
Key points
- The hand (manus) is divided into the carpus, metacarpus, and phalanges of the fingers.
- The proximal row of carpal bones is memorized using the mnemonic "LaPoT": scaphoid, lunate, triquetral, pisiform.
- The pisiform bone is sesamoid — lying within the thickness of a tendon.
- Distal row: trapezium, trapezoid, capitate, and hamate (with a hook — hamulus).
- The carpal bones form the bony arch and the sulcus carpi, which participate in the formation of the carpal canal.
- The first metacarpal bone has a saddle-shaped articular surface for articulation with the trapezium bone.
- Metacarpal bones and phalanges share a single structural plan: base, body, head.
- On the distal phalanx, there is a tuberosity for tendon attachment.