Human Anatomy Vol 1

The nnterior sternal end is oval and concave for
articulation with its costal cartilage.
T};.e posterior or oertebral end is made up of the
following parts.
1 The head has two facets that are separated
by a crest. The lower larger facet articulates with the
body of the numerically corresponding vertebra
while the upper smaller facet articulates with the next
higher vertebra (Figs 13.2 and 13.20).
2 The neck lies in front of the transverse process of its
own vertebra, and has two surfaces; anterior and
posterior and two borders; superior and inferior. The
anterior surface of the neck is smooth. The posterior
surface is rough. The superior border or crest of the
neck is thin. The inferior border is rounded.
3 The tubercle is placed on the outer surface of the rib
at the junction of the neck and shaft. Its medial part
is articular and forms the costotransverse joint with
the transverse process of the corresponding vertebra.
The lateral part is non-articular (Fig. 13.1).
The shaft is flattened so it has two surfaces-outer
and inner; and twoborders, upper and lower. The shaft
is curved with its convexity outwards (Fig. 13.3). It is
bent at the angle which is situated about 5 cm lateral to
the tubercle. It is also twisted at the angle.
L The outer surface; The angle is marked by an oblique
line on the outer surface directed downwards and
laterally.
2 The inner surface is smooth and covered by the pleura.
This surface is markedby a ridge which is continuous
behind with the lower border of the neck. The costal
groove lies between this ridge and the inferior
border. The costal groove contains the posterior
intercostal vessels and intercostal nerve.
3 The upperborder is thick and has outer and inner lips.

Sacrospinalis

Crest of

the neck

Upper

smaller facel

Head

Lower

larger facet

Pit for costal

cartilage

Costal groove

Thoracolumbar fascia

Fig. 13.2: A typical rib viewed obliquely from behind

BONES AND JOINTS OF THORAX

Costal cartilage

Sternum

Fig. 13.3: A costal arch (side view)

L Anteriorly, the head provides attachment to the

radiate ligament (Fig. 13.a) and is related to the

sympathetic chain and to the costal pleura.

2 The crest of the head provides attachment to the

intra-articular ligament of the costovertebral joint.

3 Attachments to the neck:

a. The anterior surface is covered by costal pleura.

b. The inferior costotransverse ligament is attached

to the rough posterior surface (Fig. 13.5).

c. The two laminae of the superior costotransverse

ligament are attached to the crest of the neck

(Fig. 13.6).

4 The lateral non-articular part of the tubercle gives

attachment to the lateral costotransverse ligament

(Fig. 13.s).

5 Attachments on the shaft

a. The thoracolumbar fascia and the lateral fibres of

the sacrospinalis muscle are attached to the angle.

Medial to the angle, the leaator costae and the

sacrospinalis are attached (Fig. 13.2). About 5 cm

from the anterior end there is an indistinct oblique

line, known as the anterior angle,which separates

the origins of the external oblique from serratus

anterior in case of fifth to eighth ribs. The anterior

External intercostal

Posterior intercostal vessels

lntercostal nerve

lnternal intercostal

lnnermost intercostal

lnner border of first rib

Tubercle

Fig. 13.4: The afticulations at the two ends of a costal arch