Carpal bones

Carpals
Carpals
	BONES OF HAND; Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform; Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate
Details
Identifiers
Latin	ossa carpi
MeSH	D002348
TA98	A02.4.08.001
TA2	1249
FMA	23889
	Anatomical terms of bone [edit on Wikidata]

In tetrapods, the carpals is the sole cluster of the bones in the wrist between the radius and ulna and the metacarpus. The bones of the carpus do not belong to individual fingers (or toes in quadrupeds), whereas those of the metacarpus do. The corresponding part of the foot is the tarsus. Carpal bones are not considered part of the hand but are part of the wrist. The carpal bones allow the wrist to move and rotate vertically, horizontally and laterally.

In crustaceans, "carpus" is the scientific term for the claws or "pincers" present on some legs.

Variations

In some macropods, the scaphoid and lunar bones are fused into the scaphollunar bone.^[1]

The carpus

Row	Name	Proximal/radial articulations	Distal articulations	Metacarpal articulations
Proximal	Scaphoid	radius, lunate	trapezium, trapezoid, capitate	-
Proximal	Lunate	radius, scaphoid, triquetral	capitate, hamate	-
Proximal	Triquetral	lunate, pisiform (but NOT ulna)	hamate	-
Proximal	Pisiform (sesamoid bone)	triquetral	-	-
Distal	Trapezium	scaphoid	trapezoid	#1 and #2
Distal	Trapezoid	scaphoid	trapezium, capitate	#2
Distal	Capitate	scaphoid, lunate	trapezoid, hamate	#2, #3 and #4
Distal	Hamate	triquetral, lunate	capitate	#4 and #5

The mnemonic "She Looks Too Pretty. Try To Catch Her" can be used to remember the carpal bones.^[2]

Characteristics

Almost all carpals (except the pisiform) have six surfaces. Of these the palmar or anterior and the dorsal or posterior surfaces are rough, for ligamentous attachment; the dorsal surfaces being the broader, except in the lunate.

The superior or proximal, and inferior or distal surfaces are articular, the superior generally convex, the inferior concave; the medial and lateral surfaces are also articular where they are in contact with contiguous bones, otherwise they are rough and tuberculated.

The structure in all is similar: cancellous tissue enclosed in a layer of compact bone.

Additional images

Human hand bones
Bones of the left hand. Palmar surface.
Bones of the left hand. Dorsal surface.
Vertical section through the articulations at the wrist, showing the synovial cavities.