We
pray with our hands and often communicate with them. We use them to eat,
work, and make love. We employ them as marvelous sophisticated instruments
of flexibility and strength, and when they are damaged, we anguish. (3)
The
hand is composed of many small bones
called carpals, metacarpals and phalanges. The two bones of the lower arm
-- the radius and the ulna -- meet at the hand to form the wrist.
The
carpal bones are a set
of eight short bones forming the wrist; they are disposed on two rows of
four bones each. These bones, the size of a marble, provide the wrist's
litheness and mobility.
The
palm of the hand is composed of five metacarpal
bones laid out from the wrist, as a fan. The articulation of the first
metacarpal bone with the carpal bones, permits the movement of touching,
with the thumb, the tips of all fingers.
It is from this movement that the human hand can
acquire the efficiency necessary to grab and manipulate objects.
Every
hand is composed of 14 long bones named the phalanges.
These bones compose the fingers and the thumb. Each finger has three phalanges
and the thumb only two.
(5)
(4)
The
bones
The
muscles
The
intrisic muscles of the hand are divided into three groups: (1) the thumb
or thenar muscles,
(2) the little finger or the hypothenar
muscles, and (3) the lumbrical muscles. With the lumbrical
muscles are the long flexor tendons, which are the extrinsic muscles
of the hand.
(5)
The
nerves and blood vessels
The
Median and Ulnar nerves
are the major nerves of the hand, running the length of the arm to transmit
electrical impulses to and from the brain to create movement and sensation.
Hand
facts
Each
hand contains (plus or minus... everyone is different, and everyone counts
these things differently...)
29 major and minor bones (many
people have a few more).
29 major joints.
At least 123 named ligaments.
34 muscles which move the fingers
and thumb:
17 in the palm of the hand,
and 18 in the forearm.
48 named nerves:3
major nerves.
24 named sensory branches. 21
named muscular branches.
30 named arteries and nearly
as many smaller named branches.(5)
The
muscles which power the fingers are strong - strong enough for some people
to climb vertical surfaces supporting their entire weight at times by a
few fingertips. The muscles which accomplish this feat are stronger than
you might imagine, for the biomechanics of the hand require that the force
generated by the muscles which bend the fingertips must be at least four
times the pressure which is produced at the fingertips.(5)
The
skin on the palm side of the hand and fingers is unique for these reasons
and more:
No hair (the medical term is glabrous).
Fingerprints.
Usually neither color nor the ability to tan.
Tough and durable, yet sensitive.
Anchored down to the bones beneath through an intermediate
layer of fascia. This arrangement keeps the skin of the palm from sliding
around like a rubber glove when we use our hands to grip and twist.
In some people, this layer of fascia shrinks and
thickens, leading to Dupuytren's disease.(5)
1-
2-
3-
