Upper Limbs - Position, Hands, Forearm, Joint Disorders
Know your Body

A Peek Into Your Hands (Upper Limbs)

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 11 Feb 2014 - 14:16.
Upper Limbs
"One hand I extend into myself, the other toward others", said Dejan Stojanovic, The Shape. That's what a noble hand can do. Let's find out all about the anatomy of our upper limbs (hands), the organs which we can't live without.
The two upper limbs (hands) like the lower limbs (legs) are identical in shape, size and functions except that one is on the right side and the other is on the left side of the body. Since both the upper limbs are identical, the same description holds good for both the upper limbs.
The common perception is that each upper limb is called as hand, which is not appropriate. Each upper limb consists of three parts, the arm, the forearm and the hand. The arm joins the trunk at the shoulder joint. The forearm joins the arm at the elbow joint. The hand joins the forearm at the wrist. It now becomes clear that by hand, we actually mean the extreme part of the upper limb, which joins the forearm at the wrist joint.
Hand position: The anatomical position of the whole limb is determined when the palm of the hand faces frontwards with the limb hanging at the side of the trunk. With the palm facing the front we designate various positions of the limb as anterior (the portion facing frontwards), posterior (the portion which is behind) medial (the portion which is towards the midline) lateral (the portion which is away from the midline) superior or proximal (the part which is upwards) and inferior or distal (the portion which is downwards). Having said this, we proceed from below upward i.e. from distal to proximal ends of the extremity starting from the hand.
Hand: The side facing the front side in the anatomical position is called the palm, which is covered by a very thick skin and has several creases, which are attachments to the structure beneath. Astrologers call these creases as lines in palmistry denoting the readings of life of the owner. A thin skin covers the back of the hand and veins and tendons of muscles for the fingers are visible in thin persons.
The hand comprises of eight carpal bones, which form the wrist joint where the hand joins the forearm. The bones from the wrist joint to the fingers are called metacarpals, one for each finger. The hand has five fingers. The one, which is away from the midline in anatomical position, is big and short and is called thumb. The fingers in that order are called the index finger, middle finger, ring finger and the little finger. Each finger has three small bones called phalanxes except the thumb, which has only two phalanxes.
The joints between each phalanx are called inter-phalangeal joints. And those between metacarpal and phalanx are called metacarpo-phallangeal joints. All the joints, tendons, muscles and tissues inside the hand have their own individual blood supply, venous drainage and nerve supply for proper functioning of each joint and muscle.
Next in order, is the wrist joint formed with the eight carpal bones and the lower ends of the two bones in the forearm called radius and ulna. With the limb in anatomical position the bone towards the thumb is known as the radius and the one towards the little finger is the ulna. Though not a ball and socket joint, the wrist joint can move the hand forwards, backwards and to some extent sideways and circular movements.
The Forearm: is the portion of the limb, which joins the arm at the elbow joint and the hand at the wrist joint. It has two bones named radius, which is fairly thick and strong, and the ulna, which is very thin. Between themselves these bones form radio-ulnar joints at the top which enables the forearm to indicate yes/no signs by means of rotating through a circular ligament encircling the upper radial end.
At their lower or distal end they form the wrist joint with the help of the carpal bones. The forearm joins the arm at the elbow joint formed with the help of the lower end of the arm bone called humerus and the upper ends of the bones in the fore arm the radius and the ulna. The elbow joint is a hinge joint which allows only forward and backward movements of the forearm like a door and cannot go beyond 90 degrees range over the elbow joint.
The Arm: has one large, strong and thick bone called the humerus. At its lower end it forms the elbow joint. The upper end of the humerus has a neck and a head. The head rotates over a cavity called the glenoid cavity forming the shoulder joint where the arm joins the trunk. The shoulder joint is formed with a combination of three bones namely the scapula behind, the clavicle in front and the humerus in the arm. The shoulder joint is a ball and socket type of joint enabling wide range of movements over the shoulder namely front, back, sideways (both towards trunk and away from the trunk) and full range of circular movement upto 360 degrees range.
All the joints big or small in the entire upper limb have ligaments and muscles to perform wide range of movements with rich blood supply venous drainage and nerve supply.
Conditions of upper limbs: There are so many conditions that affect the upper limbs and all its joints, that it is beyond the scope of this article to describe all of them. It suffices to mention that the upper limbs are prone to injuries with or without fractures and dislocations depending upon the nature and extent of the injury. Carpal Tunnel Syndrome is a common wrist joint disorder. Though not uncommon some congenital deformities do affect the limbs.
It is important to regularly exercise all parts of the upper limbs to prevent stiffness, unless it is due to some disease affecting any part of the limb. Exercising is all the more important with advancing age to keep the tone and shape of the muscles. A free moving, flexible hand is a blessing you can have, and its yours, if you take care of it.
*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.