% Bronchopulmonary segments are of consider-able clinical significance as disease in the lung may be limited to one or more bronchopulmonary ments. The arrangement of lung tissue into seg-ments also permits the surgeon to remove diseased parts of the lung, with minimal disturbance to the surrounding healthy lung tissue.
The general arrangement of the segments can best be understood by reference to Fig. 4.16 and
mebooksfree.com
41
The lungs
of the right upper lobe. The lower branch of the left superior lobar bronchus supplies the superior lingular and inferior lingular segments. The lingular segments make up a sec-tion which corresponds to, but is smaller than, the middle lobe of the right. The arrangement of the tertiary bronchi to the inferior lobe is similar in both lungs. The inferior lobar bronchus sup-plies five bronchopulmonary segments—apical, medial basal, anterior basal, lateral basal, and posterior basal. (A separate medial basal bronchus is not normally recognized in the left lung because it is usually a small branch of the anterior basal bronchus.)
Smaller units of lung tissue are bound by connec-tive tissue and are known as pulmonary lobules.
They are not discernable in gross specimens.
Dissection 4.2 instructs how the structures in the root of the lung should be identified.
by dissecting out the main branches of the bron-chi and vessels close to the hilus of the lung. The pattern in the superior lobes of the two lungs dif-fers because of the presence of a middle lobe in the right lung and the resulting earlier division of the right principal bronchus. The right supe-rior lobar bronchus (also known as the eparterial bronchus as it lies superior to the pulmonary ar-tery) divides into three to supply the apical, pos-terior, and anterior bronchopulmonary seg-ments. The right middle lobar bronchus divides to supply the lateral and medial segments of the middle lobe. The left superior lobar bronchus is larger than the right one because the superior lobe of the left lung corresponds to the superior and middle lobes of the right. The upper branch of the left superior lobar bronchus supplies three segments—apical, posterior, and anteri-or. These correspond to the same three segments
Scalenus anterior Brachial plexus
First rib
Right vagus N.
Right superior lobe bronchus
Right middle lobe bronchus
Phrenic N.
Parietal pleura, cut edge
Rami communicantes
Pulmonary plexus
Oesophageal plexus
Greater splanchnic N.
Lesser splanchnic N.
Right inferior lobe bronchus
Sympathetic trunk (B)
Fig. 4.13 (Continued)
mebooksfree.com
42
The cavity of the thorax
First left aortic intercostal A.
Left subclavian A.
Left common carotid A.
Left superior intercostal V.
Cut edge of pleura Ascending aorta Pulmonary trunk
Infundibulum of right ventricle Anterior interventricular branch of left coronary A.
Thoracic duct Arch of aorta
Left pulmonary A.
Upper left pulmonary V.
Lower left pulmonary V.
Circumflex branch, left coronary A.
Descending aorta
Oesophagus
Diaphragm Left ventricle
(A)
Brachial plexus
First rib Recurrent laryngeal N.
Oesophagus Vagus N.
Phrenic N.
Costal pleura, cut edge
Mediastinal pleura, cut edge
Pericardium, cut edge
Greater splanchnic N.
Sympathetic trunk Left auricle Left bronchus (B)
Fig. 4.14 (A, B) The left side of the mediastinum and thoracic vertebral column. The pleura has been removed, together with part of the pericardium.
mebooksfree.com
43
The lungs
DISSECTION 4.2 Root of the lungs Objective
I. To study the structures in the roots of the lungs.
Instructions
1. With the help of Figs. 4.11, 4.12, 4.13, and 4.14, check the positions of the structures in the sec-tioned roots of the lungs. These are the bronchi, pulmonary artery, and pulmonary veins. Note the
difference in the arrangement of the bronchi in the two lung roots due to the earlier division of the right principal bronchus. In addition to these structures, there are a number of lymph nodes which are easily distinguished by the black carbon deposits in them.
It may be possible to see the branches of the bron-chial arteries on the posterior surfaces of the main bronchi.
Upper lobe
Lower lobe (A)
Upper lobe
Middle lobe
Lower lobe (B)
Fig. 4.15 Computer-aided automatic lung segmentation. (A) Upper and lower lobes of the left lung. (B) Upper, middle, and lower lobes of the right lung.
1
1
3 6
2
9 10 5
1 2
4 5 7
8 10
9
6 6
10 8 97
11 12 3 1, 2
2 1
2 6 3
10 9
11 12 3
6
7 8 13 12 3
2 3 6
8 7
4 5
14 13
15
Fig. 4.16 The bronchi and bronchopulmonary segments. Each segmental bronchus has the same name as the subdivision of the lung supplied by it. The anterior and medial basal bronchi arise from a common stem in the left lung. This is often called the anteromedial basal bronchus. 1 = apical; 2 = posterior; 3 = anterior; 4 = lateral—middle lobe; 5 = medial—middle lobe; 6 = apical (inferior lobe);
7 = anterior basal; 8 = lateral basal; 9 = medial basal; 10 = posterior basal; 11 = inferior lingular; 12 = superior lingular; 13 = left principal bronchus; 14 = right principal bronchus; 15 = trachea.
mebooksfree.com
44
The cavity of the thorax
Trachea Tracheal bifurcation
Fig. 4.17 Volume-rendered image of the central tracheobronchial tree.
Fig. 4.18 Volume-rendered image of the intraparenchymal tracheobronchial tree.
Internal thoracic vessels
Right auricle
Anterior papillary M.
A
P
R L
Infundibulum
Left semilunar valvule Left coronary A.
Left phrenic N.
Left auricle
Left principal bronchus
Left vagus N.
Descending aorta
Accessory hemiazygos V.
Orifice of right coronary A.
Ascending aorta Superior vena cava Right phrenic N.
Right pulmonary A.
Right principal bronchus
Right ventricle
Right vagus N.
Tracheobronchial lymph nodes
Oesophagus Vena azygos Thoracic duct
Sixth rib
Fig. 4.19 A horizontal section through the thorax at the level of the intervertebral disc between the fifth and sixth thoracic vertebrae.
mebooksfree.com
45
The lungs
There are usually two bronchial arteries to the left lung and one to the right. The left bron-chial arteries arise from the descending aorta. The right arises either from the first right posterior in-tercostal artery or from the superior left bronchial artery. The bronchial arteries are the nutrient arter-ies of the lung. The blood they carry is returned either through the pulmonary veins or through the bronchial veins. The bronchial veins drain into the azygos vein on the right and into the accessory hemiazygos vein on the left. % In some congenital abnormalities of the heart or of the great vessels, the blood going to the lungs through the pulmo-nary arteries is inadequate. In these cases, the bron-chial arteries may enlarge to take over this function.
Dissection 4.3 describes the dissection of the intra-pulmonary structures.