At the anterior end of intercostal space, the
intercostal nerve passes in front of internal thoracic
vessels, pierces internal intercostal muscle and anterior
intercostal membrane to continue as anterior cutaneous
branch which ends by dividing into medial and lateral
cutaneous branches.
Bronches
1 Communicating branches to the sympathetic
ganglion close to the beginning of ventral ramus. The
anterior or ventral ramus containing sympathetic
fibres from lateral hom of spinal cord gives off a white
rafitus communicans to the sympathetic ganglion.
These fibres get relayed in the ganglion. Some of
these relayed fibres pass via grey ramus communicans
to ventral ramus. Few pass backwards in the dorsal
ramus and rest pass through the ventral ramus.
These sympathetic fibres are sudomotor, pilomotor
and vasomotor to the skin and vasodilator to the
skeletal vessels.
2 Before the angle, nerve gives a collateral branch that
runs along the upper border of lower rib. This branch
supplies intercostal muscles, costal pleura and
periosteum of the rib.
3 Lateral cutaneous branch arises along the midaxillary
line. It divides into anterior and posterior branches.
4 The nerve keeps giving muscular, periosteal, and
branches to the costal pleura during its course.
5 Anterior cutaneous branch is the terminal branch of
the nerve. It divides into anterior and posterior
branches.
The thoracic spinal nerves and their branches which
do not follow absolutely thoracic course are designated
as atypical intercostal nerves. Thus first and second
intercostal nerves are atypical as these two nerves partly
supply the upper limb.
The first thoracic nerve entirely joins the brachial
plexus as its last rami or root. It gives no contribution
to the first intercostal space. That is why the nerve
supply of skin of first intercostal space is from the
supraclavicular nerves (C3, C4).
The second thoracic or second intercostal nerve runs
in the second intercostal space. But its lateral cutaneous
branch as intercostobrachial neroe is rather big and it
supplies skin of the axilla as well. Third to sixth
intercostal nerves are typical.
Also seventh, eight, ninth, tenth, eleventh intercostal
nerves are atypical, as these course partly through
thoracic wall and partly through anterolateral
abdominal wall. Lastly the twelfth thoracic is knownas subcostal nerve. It also passes through the
anterolateral abdominal muscles. These nerves supply
parietal peritoneum, muscles of the anterolateral
abdominal wall and overlying skin.Site of pericardial tapping: Removal of pericardial
fluid is done in left 4th or Sth intercostal spaces just
to the left of the sternum as pleura deviates exposing
the pericardium against the medial part of left 4th
and 5th intercostal spaces. Care should be taken to
avoid rrrlr.y to internal thoracic artery lying at a
distance of one cm from the lateral border of stemum.
Needle can also be passed upwards and posteriorly
fiom the left xiphicostal angle to reach the pericardial
cavity (see Fig. 18.6).
Eoreignbodies in trachea:Foreign bodies like pins,
coins entering the trachea pass into right bronchus;
Right bronchus wider shorter, more vertical and is
in line with trachea, so the foreign bodies in the
trachea travel down into righJ bronchus and then
into posterior basal segments of the lower lobe of
the lung.
Site of bone marrow puncture: The manubdum
sterni is the favoured site for bone marroTJJ puncture
in adults. Manubrium is subcutaneous and easily
approachable (see Fig. 13.1a). Bone marow studies
are done for various haematological disorders.
Another site is the iliac crest; which is the preferred
site in children.
Postare of a patient with respiratory dfficulty:
Such a patient finds comfort while sitting. as
diaphragm is lowest in this position' In lying
position, the diaphragm is highest and patient is very
uncomfortable (see Fig. 13.31).
In standing position, the diaphragm level is
midway. but the patient is too sick to stand-
Patient also fixes the arms by holding the arms of
a chair, so that serratus anterior and pectoralis major
can move the ribs and help in respiration.
Paracentesis thoracis or pleural tapping: Aspira-Some clinical conditions associated with the pleura
are as follows:
Pleurisy:Th ItmaY
be dr7r, but of tion of
fluid in the p called
the pleural effusion.