Human Anatomy Vol 1

(^5) The ligamenta flaza (singular = ligamentum flavum)
connect the laminae of adjacent vertebrae. They are
made up mainly of elastic tissue.
Movemenls of lh6 Veileblol Column
Movements between adjacent vertebrae occur
simultaneously at all the joints connecting them.
Movement between any two vertebrae is slight.
However, when the movements between several
vertebrae are added together the total range of
movement becomes considerable. The movements are
those of flexion, extension, lateral flexion and a certain
amount of rotation. The range of movement differs in
different parts of the vertebral column. This is
influenced by the thickness and flexibility of the
intervertebral discs and by the orientation of the
articular facets. Flexion and extension occur freely in
the cervical and lumbar region, but not in the thoracic
region. Rotation is free in the thoracic region, and
restricted in the lumbar and cervical regions.
lnlroduclion
The lungs expand during inspiration and retract during
expiration. These movements are governed by the
following two factors.
1 Alterations in the capacity of the thorax are brought
about by movements of the thoracic wall. Increase
in volume of the thoracic cavity creates a negative
intrathoracic pressure which sucks air into the lungs.
Movements of the thoracic wall occur chiefly at the
costovertebral and manubriosternal joints.
2 Elastic recoil of the pulmonary alveoli and of the
thoracic wall expels air from the lungs during expira-
tion.
erpfes of fufavernemfs
1 Each rib may be regarded as a lever, the fulcrum of
which lies just lateral to the tubercle. Because of the
disproportion in the length of the two arms of the
lever, the slight movements at the vertebral end of
the rib are greatly magnified at the anterior end
(Fig. 13.28).
2 The anterior end of the rib is lower than the posterior
end. Therefore, during elevation of the rib, the
anterior end also moves forwards. This occurs mostly
in the vertebrosternal ribs. In this way, the
anteroposterior diameter of the thorax is increased.
Along with the up and down movements of the
second to sixth ribs, the body of the sternum also
moves up and down called pump-handle moaements
(Fig. 13.29). This results in formation of sternal angle.
BONES AND JOINTS OF THORAX
Fig. 13.29: Diagram showing how 'pump-handle' movements
of the sternum bring about an increase in the anteroposterior
diameter of the thorax
The middle of the shaft of the rib lies at a lower level
than the plane passing through the two ends.
Therefore, during elevation of the rib, the shaft also
moves outwards. This causes increase in the
transverse diameter of the thorax.
Such movements occur in the vertebro-chondral ribs,
and are called bucket-handle moaements.
The thorax resembles a cone, tapering upwards. As
a result each rib is longer than the next higher rib.
On elevation the larger lower rib comes to occupy
the position of the smaller upper rib. This also
increases the transverse diameter of the thorax
(Fig. 13.30).
Lateral wall of
thorax before
and after
expansron
Rib before
and after
being raised
Fig. 13.30: Scheme showing how 'bucket-handle' movements
of the vertebrochondral ribs bring about an increase in the
transverse diameter of the thorax