hand

The hand is a complex structure that represents the distal tetrapod limb segment.It is the modified end of the ancestral dish fin, a structure based on jointed bony rays. In the generalized reptilian hand, a set of small wrist bones (carpals) forms the foundation for five digits. Each digit is composed of one large proximal segment (a metacarpal) and a chain of additional bones (the phalanges). digital reduction and modification have occured in a great variety of mammals, from the wings of bats to the single tors of the modern horses. Humans have retained the generalized pattern of five digits. there are a total of 27 bones in each human hand, 8 carpal bones arranged in 2 rows, followed distaly by a single row of 5 proximal phalanges, a single row of 4 intermediate phalanges, and a dingle row of five distal/terminal phalanges.

In addition to the 27 major hand bones, there are small bones called SESAMOID bones(small ossified nodes) that lie with in tendors of the hand. In the hand, a pair of sesamoid is usally found in at the palmar surface of the first metacarpal head.

hand skeleton :

Carpals

Metacarpals

Hand phalanges

the term of RAY= often used to each finger/toe/ including the digit's phalanges and metacarpal

Thumb ray= Pollex= ray 1

Index finger= ray 2

Middle finser= ray 3

Ring finger= ray 4

Littel finger= ray 5