Everything about Carpal totally explained
In
tetrapods, the
carpus is the cluster of
bones in the
wrist between the
radius and
ulna and the
metacarpus. The bones of the carpus don't 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 and horizontally.
Variations
In some
macropods, the scaphoid and lunar bones are fused into the scapholunar bone.
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 |
Mnemonics
There exist several
mnemonics to remember these bones:
- Sally left the party / to take Cathy home.
- Some lovers try positions / that they Can't handle.
Common characteristics of the carpal bones
Each bone (excepting the pisiform) presents six (6) 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're in contact with contiguous bones, otherwise they're rough and tuberculated.
The structure in all is similar:
cancellous tissue enclosed in a layer of
compact bone.
Further Information
Get more info on 'Carpal'.
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