Human Anatomy Vol 1

a

I

-Sirlssoc Newton

INTRODUCTION

Joints are sites where two or more bones or cartilages
articulate. Free movements occur at the synovial joints.
Shoulder joint is the most freely mobile joint. Shoulder
joint gets excessive mobility at the cost of its own stability,
since both are not feasible to the same degree. The
carrying angle in relation to elbow joint is to facilitate
carrying objects like buckets without hitting the pelvis.
Supination and pronation are basic movements for
the survival of human being. During pronation the food
is picked and by supination it is put at the right place-
the mouth. While 'givtrtg' , one pronates, while 'getting'
one supinates.
The first carpometacarpal joint allows movements
of opposition of thumb with the fingers for picking up
or holding things. Thumb is the most important digit.
Remember Muni Dronacharya asked Eklavya to give
his right thumb as Guru-Dakshina, so that he is not able
to outsmart Arjuna in archery.

SHOULDER GIRDTE

The shoulder girdle connects the upper limb to the axial
skeleton. It consists of the clavicle and the scapula.
Anteriorly, the clavicle reaches the sternum and
articulates with it at the sternoclavicular joint. The
clavicle and the scapula are united to each other at the
acromioclavicular joint. The scapula is not connected
to the axial skeleton directly, but is attached to it
through muscles. The clavicle and the scapula have
been studied in Chapter 2. The joints of the shoulder
girdle are described below.

D!SSECIION

Remove the subclavius muscle from first rib at its

attachment with its costal cartilage. ldentify the costo-

clavicular ligament.

Define the sternoclavicular joint and clean the anterior

and superior surfaces of the capsule of this joint. Cut

carefully through the joint to expose the intra-articular

disc positioned between the clavicle and the sternum.

The fibrocartilaginous disc divides the joint cavity into a

superomedial and an inferolateral compartments.

Feotures

The sternoclavicular joint is a synovial joint. It is a

compound joint as there are three elements taking part

in it; namely the medial end of the clavicle, the

clavicular notch of the manubrium sterni, and the upper

surface of the first costal cartilage. It is a complex joint

as its cavity is subdivided into two compartments,

superomedial and inferolateral by an intra-articular disc

(Fig. 10.1).

The articular surface of the clavicle is covered with

fibrocartilage (as the clavicle is a membrane bone). The

surface is convex from above downwards and slightly

concave from front to back. The sternal surface is

smaller than the clavicular surface. It has a reciprocal

convexity and concavity. Because of the concavoconvex

shape of the articular surfaces, the joint can be classified

as a saddle joint.

The capsular ligament is attached laterally to the

margins of the clavicular articular surface; and medially

to the margins of the articular areas on the sternum

and on the first costal cartilage. It is strong anteriorly

and posteriorly where it constitutes the anterior and

posterior sternoclavicular ligaments.

However, the main bond of union at this joint is the

articular disc. The disc is attached laterally to the clavicle

on a rough area above and posterior to the articular

area for the sternum. Inferiorly, the disc is attached to

the sternum and to the first costal cartilage at their

junction. Anteriorly and posteriorly the disc fuses with

the capsule.

140