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The fore- and hind limbs were evolved basically for PARTS OF THE UPPER IIMBbearing the weight of the body and for locomotion as It has been seen that the upper limb is made up of
is seen in quadrupeds, e.g. cows or dogs. The two pairs four parts: (1) Shoulder region; (2) arm or brachium;
of limbs are, therefore, built on the same basic principle. (3) forearm or antebrachium; and (4) hand or manus.
Each limb is made up of a basal segment or girdle, Further subdivisions of these parts are given in Table
and a free part divided into proximal, middle and distal 1..2 and Fig. 1.1.
segments. The girdle attaches the limb to the axial
skeleton. The distal segment carries five digits. 1 The shoulder region includes:
Table 1.1 shows homologous parts of upper and lower a. Thepectoral or breast region onthe front of the chest;
limbs. b. The axilla or armpit; and
However, with the evolution of the erect posture in c. The scapular region on the back comprising parts
man, the function of weight-bearing was taken over by around the scapula.
the lower limbs. Thus the upper limbs, especially the The bones of the shoulder girdle are the clavicle and
hands, became free and gradually evolved into organs the scapula.
having great manipulative skills. Of these, only the clavicle articulates with the axial
This has become possible because of a wide range of skeleton at the sternoclavicular joint. The scapula is
mobility at the shoulder. The whole upper limb works mobile and is held in position by muscles. The
as a jointed lever. The human hand is a grasping tool. clavicle and scapula articulate with each other at the
It is exquisitely adaptable to perform various complex acromioclavicular joint.
functions under the control of a large area of the brain. 2 The arm (upper arm or brachium) extends from the
The unique position of man as a master mechanic of shoulder to the elbow (cubitus). The bone of the arm
the animal world is because of the skilled movements is the humerus. Its upper end meets the scapula and
of his hands. forms the shoulder joint. The shoulder joint permits
movements of the arm.
Table 1.1: Homologous parts of the limbs
3 The forearm (antebrachium) extends from the elbow
to the wrist. The bones of the forearm are the radius
Upper limb Lower limb and the ulna. At their upper ends, they meet the
1. Shoulder girdle Hip girdle lower end of the humerus to form the elbow joint.
2. Shoulder joint Hip joint Their lower ends meet the carpal bones to form the
3. Arm with humerus Thigh with femur wrist joint. The radius and ulna meet each other at
4. Elbow joint Knee joint the radioulnar joints.
The elbow joint permits movements of the forearm,
5. Forearm with radius and ulna Leg with tibia and fibula
namely flexion and extension. The radioul:rar joints
6. Wrist joint Ankle joint permit rotatory movements of the forearm called
7. Hand with Foot with pronation and supination. Lr a mid-flexed elbow, the
a. Carpus a. Tarsus palm faces upwards in supination and downwards
b. Metacarpus b. Metatarsus and in pronation. During the last movement, the radius
c. 5 digits c. 5 digits
rotates around the ul:ra (seeFrg.10.23).
, UPPEH LIMB
Table 1.2: Parts of the upper limb
Parts Bones Joints
1. Shoulder region a. Pectoral region on the Bones of the shoulder girdle . Sternoclavicular joint
front of the chest a. Clavicle . Acromioclavicular joint
b. Axilla or armpit b. Scapula
c. Scapular region on the
back
2. Upper arm (arm or brachium) Humerus Shoulder joint
from shoulder to the elbow (scapulohumeral joint)
3. Forearm (antebrachium) a. Radius . Elbow joint
from elbow to the wrist b. Ulna . Radioulnar joints
4. Hand a. Wrist . Carpus, made up of . Wrist joint
I carpal bones (radiocarpal joint)
. lntercarpal joints
b. Hand proper . Metacarpus, made up of . Carpometacarpal joints
5 metacarpal bones
c. Five digits, numbered . 14 phalanges-two for . lntermetacarpal joints
from lateral to medial side the thumb, and three for
First = Thumb or pollex each of the four fingers . Metacarpophalangeal
Second = lndex or forefinger joints
Third = Middle finger ' Proximal and distal
Fourth = Ring finger interphalangeal joints
Fifth = Little finger
4 The hand (rr.ants) includes: The phalanges form metacarpophalangeal joints with
a. The wrist or carpus, supported by eight carpal the metacarpals and interphalangeal joints with one
bones arranged in two rows. another.
b. The hand proper or metacarpus, supported by five Movements of the hand are permitted chiefly at the
metacarpal bones. wrist joint. The thumb moves at the first carpometa-
c. Fiae digits (thurl:.b and four fingers). Each finger is carpal joint; where an exclusive movement of
supported by three phalanges, but the thumb has opposition besides the other usual movements are
only two phalanges (there being 14 phalanges in all). permitted. Each of the second to fifth digits move at
The carpal bones form the wrist joint with the radius, metacarpophalangeal, proximal and distal inter-
intercarpal joints with one another, and carpometa- phalangeal joints. Figure L.2 and Flow chart 1.1 shows
carpal joints with the metacarpals. the lines of force transmission.
Flow chafi 1.1 : Lines of force transmission
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CL
CL
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r Elbow joint
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INTRODUCTION 6 There is no medullary cavity.
Out of 206 totalbones in man, the upper limbs contain 7 It is occasionally pierced by the middle supraclavicular
as many as 64 bones. Each side consists of 32 bones, nerve.
the distribution of which is shown in Table 7.2 and It receives weight of upper limb via lateral one-third
Fig. 1.1. The individual bones of the upper limb will be through coracoclavicular ligament and transmits
described one by one. Their features and attachments weight of upper limb to the axial skeletal via medial
should be read with the bones before undertaking the two-thirds part (see Flow chart 1.1).
dissection of the part concerned. The paragraphs on Feotules
attachments should be revised when the dissection of
Sf'rsff
a particular region has been completed.
The shaft (Figs 2.1a and b) is divisible into the lateral
one-third and the medial two-thirds.
Thelateral one-third of the shaft is flattened from above
downwards. It has two borders, anterior and posterior.
The clavicle (Latin a small key) is a long bone. It supports
The anterior border is concave forwards. The posterior
the shoulder so that the arm can swing clearly away border is convex backwards. This part of the bone has
from the trunk. The clavicle transmits the weight of the two surfaces, superior and inferior.The superior surface
limb to the sternum. The bone has a cylindrical part is subcutaneous and the inferior surface presents an
called the shaft, and two ends,lateral and medial. elevation called the conoid (Greek cone) tubercle and a
Side Delerminolion ridge called the trapezoid ridge.
The medial two-thirds of the shaft is rounded and
The side to which a clavicle belongs can be determined is said to have four surfaces. The anterior surface is
from the following characters. convex forwards. The posterior surface is smooth. The
1 The lateral end is flat, and the medial end is large superior surface is rough in its medial part. The inferior
and quadrilateral. surface has a rough oval impression at the medial end.
2 The shaft is slightly curved, so that it is convex The lateral half of this surface has a longitudinal
forwards in its medial two-thirds, and concave subclaaian groooe.Thenutrient foramen lies at the lateral
forwards in its lateral one-third. end of the groove.
3 The inferior surface is grooved longitudinally in its
middle one-third. A mfer*d ssr d &,tedjs{ Fr: ds
1 The lateral or acromial (Greek peak of shoulder) end
Peculiorilies of the Clovicle is flattened from above downwards. It bears a facet
that articulates with the acromion process of the
1 It is the only long bone that lies horizontally. scapula to form the acromioclavicular joint.
2 It is subcutaneous throughout. 2 The medial or sternal end is quadrangular and
3 It is the first bone to start ossifying. articulates with the clavicular notch of the
4 It is the only long bone which ossifies in membrane. manubrium sterni to form the sternoclavicular joint.
5 It is the only long bone which has two primary centres The articular surface extends to the inferior aspect,
of ossification. for articulation with the first costal cartilage.
, Shoulder
Clavicle (1)
Scapula (1)
Humerus (1)
Ulna (1)
Radius (1)
Carpal bones (8)
Metacarpal bones (5)
Phalanges (14)
Fig.1.2: Scheme of skeleton of upper limb showing lines of
Fig. 1,1: Parts and 32 bones of the upper limb force transmission
EVOTUTION OF UPPER TIMBS evolution and is seen in man. Ih some other species,
The forelimbs have evolved from the pectoral fins of however, the limbs are altogether lost, as in snakes;
fishes. In tetrapods (terrestrial vertebrates), all the four while in others the digits are reduced in number as in
limbs are used for supporting body weight, and for ungulates. The habit of brachiation, i.e. suspending the
locomotion. In arboreal (tree-dwelling) human ances- body by the arms, in anthropoid apes resulted in
tors, the forelimbs havebeen set free from their weight- disproportionate lengthening of the forearms, and also
bearing function. The forelimbs, thus 'emancipated', in elongation of the palm and fingers.
acquired a wide range of mobility and were used for Study of Anotomy
prehension or grasping, feeling, picking, holding,
sorting, breaking, fighting, etc. These functions became In studying the anatomy of any region by dissection, it
possible only after necessary structural modifications is usual to begin by studying features of the skin, the
such as the following, were done: superficial fascia and its contents, and the deep fascia.
This is followed by the study of the muscles of the
a. Appearance of joints permitting rotatory movements region, and finally, the blood vessels and nerves. These
of the forearrns (described as supination and descriptions should be read only after the part has been
pronation), as a result of which food could be picked dissected with the help of the steps of dissection
up and taken to the mouth. provided in the book.
b. Addition of the clavicle, which has evolved with the Before undertaking the study of any part of the body,
function of prehension. it is essential for the students to acquire some
c. Rotation of the thumb through 90 degrees, so that it knowledge of the bones of the region. It is for this reason
can be opposed to other digits for grasping. that a chapter on bones (osteology) is given at the lt
d. Appropriate changes for free mobility of the fingers E
beginning of each section. While reading the chapter,
and hand. the students should palpate the various parts of bones =o
The primitive pentadactyl limb of amphibians, on themselves. The next chapter must be studied with CL
CL
terminating in five digits, has persisted through the help of loose human bones. 3
c
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