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The thumb contrasts with each of the other four fingers by being the only one that: Is opposable to the other four fingers; Has two phalanges rather than three. However, recently there have been reports that the thumb, like other fingers, has three phalanges, but lacks a metacarpal bone. [3]
Three phalanges are present on each finger and toe, with the exception of the thumb and big toe, which possess only two. The middle and far phalanges of the fourth and [citation needed] fifth toes are often fused together (symphalangism). [1] [2] The phalanges of the hand are commonly known as the finger bones. The phalanges of the foot differ ...
The palm has five bones known as metacarpal bones, one to each of the five digits. Human hands contain fourteen digital bones, also called phalanges, or phalanx bones: two in the thumb (the thumb has no middle phalanx) and three in each of the four fingers. These are the distal phalanx, carrying the nail, the middle phalanx, and the proximal ...
At the palmar aspect of the first metacarpophalangeal joints are small, almost spherical bones called the sesamoid bones. The fourteen phalanges make up the fingers and thumb, and are numbered I-V (thumb to little finger) when the hand is viewed from an anatomical position (palm up). The four fingers each consist of three phalanx bones ...
Left hand shown with thumb on left. The metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed. The peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity.
A long bone is one that is cylindrical in shape, being longer than it is wide. However, the term describes the shape of a bone, not its size, which is relative. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges).
The carpometacarpal joint connects the carpal bones to the metacarpus or metacarpal bones which are joined at the intermetacarpal articulations. In the fingers, finally, are the metacarpophalangeal joints (including the knuckles ) between the metacarpal bones and the phalanges or finger bones which are interconnected by the interphalangeal joints .
The first metacarpal bone is short and thick with a shaft thicker and broader than those of the other metacarpal bones. Its narrow shaft connects its widened base and rounded head; the former consisting of a thick cortical bone surrounding the open medullary canal; the latter two consisting of cancellous bone surrounded by a thin cortical shell.