Human Anatomy Vol 1

THORAX

Manubrium

Clavicular notch

Notch for flrst

costal cartilage

Notch for second

costal cartilage

Body of sternu

Xiphoid process

Notch for fourth

costal cartilage

Notch for sixth

costal cartilage

Xiphisternal

junction

Fig. 13.11: The sternum: Lateral aspect

Monublium

The manubrium is quaddlateral in shape. It is the
thickest and strongest part of the sternum. It has two
surfaces, anterior and posterior; and four borders,
superior, inferior, and two lateral.

Tine anterior surface is convex from side to side and
concave from above downwards (Fig. 13.10).

Theposterior surface is concave and forms the anterior
boundary of the superior mediastinum.

T}ne superior border is thick, rounded and concave. It
is marked by the suprasternal notch or jugular notch
or interclavicular notch in the median part, and by the
clavicular notch on each side. The clavicular notch
articulates with the medial end of the clavicle to form
the sternoclavicular joint (Fig. 13.11).
The inferior border forms a secondary cartilaginous
joint with the body of the sternum. The manubrium
makes a slight angle with the body, convex forwards,
called t}ae sternal angle of Louis.
Thelateralborder forms a primary cartilaginous joint
with the first costal cartilage, and present a demifacet
for synovial articulation with the upper part of the
second costal cartilage.

A chmenls

1 The anterior surface gives origin on either side to:

a. The pectoralis major.

b. The sternal head of the sternocleidomastoid

(Fig. 13.e).

The posterior surface gives origin to:

a. The sternohyoid in upper part (Fig. 13.12).

b. The stemothyroid in lower part.

c. The lower half of this surface is related to the arch

of the aorta. The upper half is related to the left

brachiocephalic vein, the brachiocephalic aftety,

the left common carotid artery and the left sub-

clavian artery. The lateral portions of the surface

are related to the corresponding lung and pleura.

The suprasternal notch gives attachment to the lower

fibres of the interclavicular ligament, and to the two

subdivisions of the investing layer of cervical fascia.

The margins of each clavicular notch give attachment

to the capsule of the corresponding stemoclavicular

joint (see Chapter 10).

Left subclavian

Left common

carotid

Brachiocephalic

artery

Sternohyoid

Clavicular notch

Arch of aorta

Sternothyroid

Area related

to pleura

Area related to

pericardium

Sternocostalis

FIg. 13.12: Attachments on the posterior surface of the sternum

Body of the Slernum

The body is longer, narrower and thinner than the

manubrium. It is widest close to its lower end opposite

the articulation with the fifth costal cartilage' It has two

surfaces, anterior and posterior; two lateralborders; and

o ends, upper and lower.

The anterior surface is nearly flat and directed

forwards and slightly upwards. It is marked by three

ill-defined transverse ridges, indicating the lines of

fusion of the four small segments called sternebrae.

2 The posterior surface is slightly concave and is

marked by less distinct transverse lines.

3 The lateral borders form synovial joints with the

lower part of the second costal cartilage, the third to

sixth costal cartilages, and the uPPer half of the

seventh costal cartilage (Fig. 13.11).

4 The upper end forms a secondary cartilaginous joint

with the manubrium, at the sternal angle'

5 The lower end is narrow and forms a primary

cartilaginous joint with the xiphisternum'