Human Anatomy Vol 1

The fore- and hind limbs were evolved basically for
bearing the weight of the body and for locomotion as
is seen in quadrupeds, e.g. cows or dogs. The two pairs
of limbs are, therefore, built on the same basic principle.
Each limb is made up of a basal segment or girdle,
and a free part divided into proximal, middle and distal
segments. The girdle attaches the limb to the axial
skeleton. The distal segment carries five digits.
Table 1.1 shows homologous parts of upper and lower
limbs.
However, with the evolution of the erect posture in
man, the function of weight-bearing was taken over by
the lower limbs. Thus the upper limbs, especially the
hands, became free and gradually evolved into organs
having great manipulative skills.
This has become possible because of a wide range of
mobility at the shoulder. The whole upper limb works
as a jointed lever. The human hand is a grasping tool.
It is exquisitely adaptable to perform various complex
functions under the control of a large area of the brain.
The unique position of man as a master mechanic of
the animal world is because of the skilled movements
of his hands.

Table 1.1: Homologous parts of the limbs

PARTS OF THE UPPER IIMB

It has been seen that the upper limb is made up of

four parts: (1) Shoulder region; (2) arm or brachium;

(3) forearm or antebrachium; and (4) hand or manus.

Further subdivisions of these parts are given in Table

1..2 and Fig. 1.1.

1 The shoulder region includes:

a. Thepectoral or breast region onthe front of the chest;

b. The axilla or armpit; and

c. The scapular region on the back comprising parts

around the scapula.

The bones of the shoulder girdle are the clavicle and

the scapula.

Of these, only the clavicle articulates with the axial

skeleton at the sternoclavicular joint. The scapula is

mobile and is held in position by muscles. The

clavicle and scapula articulate with each other at the

acromioclavicular joint.

2 The arm (upper arm or brachium) extends from the

shoulder to the elbow (cubitus). The bone of the arm

is the humerus. Its upper end meets the scapula and

forms the shoulder joint. The shoulder joint permits

movements of the arm.

3 The forearm (antebrachium) extends from the elbow

to the wrist. The bones of the forearm are the radius

and the ulna. At their upper ends, they meet the

lower end of the humerus to form the elbow joint.

Their lower ends meet the carpal bones to form the

wrist joint. The radius and ulna meet each other at

the radioulnar joints.

The elbow joint permits movements of the forearm,

namely flexion and extension. The radioul:rar joints

permit rotatory movements of the forearm called

pronation and supination. Lr a mid-flexed elbow, the

palm faces upwards in supination and downwards

in pronation. During the last movement, the radius

rotates around the ul:ra (seeFrg.10.23).

Upper limb

1. Shoulder girdle


2. Shoulder joint

Lower limb

Hip girdle

Hip joint

3. Arm with humerus Thigh with femur


4. Elbow joint Knee joint


5. Forearm with radius and ulna Leg with tibia and fibula


6. Wrist joint Ankle joint


7. Hand with Foot with
   a. Carpus a. Tarsus
   b. Metacarpus b. Metatarsus and
   c. 5 digits c. 5 digits