Human Anatomy Vol 1

b. The superior costotransoerse ligament along the
lower border.
c. The inferior costotransaerse ligamenf along the
anterior surface.
d. The intertransrserseligaments and muscles to upper
and lower borders.
e. The leoator costae on the posterior surface.
4 The spines give attachment to the supraspinous and
interspinous ligaments. They also give attachment to
several muscles including the trapezius, the rhom-
boids, the latissimus dorsi, the serratus posterior
superior and the serratus posterior inferior, and
many deep muscles of the back.

FirslThoracic bro'

1 The body of this vertebra resembles that of a cervical
vertebra. It is broad and not heart-shaped. Its upper
surface is lipped laterally and bevelled anteriorly.
The superior costal facet on the body is complete
(Fig. 13.21). It articulates with the head of the first
rib. The inferior costal facet is a 'demifacet' for the
second rib.
2 The spine is thick, long and nearly horizontal.

Body cervical in type

Superior costal facet complete

Spine long and horizontal

lnferior costal demifacet

Superior cosial demifacet

lnferior costal facet missing

A single complete costal

facet along the upper margin

ofthe body

Costal facet complete and

encroaching on the pedicle

Transverse process does not

have articular facet

Costal facet complete and

on the pedicle

Transverse process is small

with three tubercles

Spine horizontal

lnferior articular facets everted

BONES AND JOINTS OF THOBAX

3 The superior vertebral notches are well marked, as

in cervical vertebrae.

The ninth thoracic vertebra resembles a typical thoracic

vertebra except that the body has only the superior

costal demifacets. The inferior costal facets are absent

(Fig.13.21).

fenthThoracic rlebra

The tenth thoracic vertebra resembles a typical thoracic

vertebra except that the body has a single complete

superior costal facet on each side, extending onto the

root of the pedicle (Fig. 13.21).

I The body has a single large costal facet on each side,

extending onto the upper part of the pedicle

(Fig.13.21).

2 The transverse process is small, and has no articular

facet.

Sometimes it is difficult to differentiate between

tenth thoracic and eleventh thoracic vertebrae.

Twelllhfhorscic bra

The shape of the body, pedicles, transverse processes

and spine are similar to those of a lumbar vertebra.

However, the bodybears a single costal facet on each

side, which lies more on the lower part of the pedicle

than on the body.

The transverse process is small and has no facet, but

has superior, inferior and lateral tubercles (Fig. 13.21).

The inferior articular facets are lumbar in type. These

are everted. and are directed laterally, but the superior

articular facets are thoracic in type.

The ossification is similar to that of a typical vertebra.

It ossifies in cartilage from three primary and five

secondary centres.

The three primary centres-one for the centrum

and one for each half of the neural arch, appear

during eighth to ninth week of fetal life. At birth the

vertebra consists of three parts, the centrum and two

halves of the neural arch. The two halves of the neural

arch fuse posteriorly during the first year of life. The

neural arch is joined with the centrum by the

neurocentral synchondrosls. Bony fusion occurs here

during the third to sixth year of life.

Five secondary centres-one for the upper surface

and one for the lower surface of the body, one for

each transverse process, and one for the spine appear

at about the 15th year and fuse with the rest of the

vertebra at about the 25th year (Fig. 1,3.22).

Fig. 13.21 : Features of atypical thoracic vertebrae