A “fingertip” knowledge of lobar and segmental anatomy is indispensable for understanding patterns of lung collapse and patterns of lung disease. Some diseases have lobar or segmental distributions; others do not. Understanding the lobar anatomy also is important for planning bronchoscopy, surgery, radiation therapy, and postural drainage.
1
The inner thoracic wall is lined by the _______________ pleura, whereas each lobe is surrounded by the _______________ pleura.
A.
thoracic
B.
pulmonary
C.
visceral
D.
parietal
1
D. parietal
C.
visceral
The space between the visceral pleura and parietal pleura is cleverly named the pleural space.
2
The space between the lobes of the lung, where the _______________ pleural surfaces touch, is called the interlobar fissure or septum.
A.
thoracic
B.
pulmonary
C.
visceral
D.
parietal
2
C. visceral
Because the visceral pleura is less than 1 mm thick, the x-ray beam must strike it parallel to its surface if it is to be visible on the radiograph. If any plane is _______________ to the x-ray beam, it will not be visible. (Choose one or more.)
A.
parallel
B.
perpendicular
C.
oblique
B.
perpendicular or C. oblique
3
In Figure 5-1A , the x-ray beam is _______________ to the fissure or septum.
A.
perpendicular
B.
parallel
Figure 5-1
3
B. parallel
The fissure _______________ be visible on the radiograph.
A.
will
B.
will not
A.
will
In Figure 5-1B , the x-ray beam is _______________ to the visceral pleural surfaces and not visible.
A.
perpendicular
B.
parallel
C.
oblique
C.
oblique
The visceral pleura bordering the adjacent surfaces of two lobes form the septa, which separates the lobes. The space between two adjacent visceral pleural surfaces is a fissure. Get the distinction? A fissure is a narrow space; a septum is a divider. Examples are the nasal septum and an anal fissure. If in doubt, palpate. The two terms, fissure and septum, are often used interchangeably in the thorax, but most use the term interlobar fissure.
4
We challenge you to test your anatomic recall:
4
Which lung is smaller? _______________
A.
right
B.
left
B.
left, because heart is on left
Therefore the right lung has _______________ lobes and the left has two.
A.
one
B.
two
C.
three
D.
four
C.
three
Name the lobes of the right lung: _______________, _______________, and _______________.
A.
upper
B.
anterior
C.
posterior
D.
middle
E.
lower
A.
upper, D. middle, E. lower
Name the lobes of the left lung: _______________ and _______________.
A.
upper
B.
anterior
C.
posterior
D.
middle
E.
lower
A.
upper (lingula is part of left upper lobe), E. lower
TRIVIA: How many lobes does a dog’s lung have? ANSWER: SIX. The right has cranial, middle, caudal and accessory lobes. The left has a cranial (two sublobes) and caudal lobe.
5
Figure 5-2A shows that, in the left lung, the upper lobe ( U ) is separated from the lower lobe ( L ) by the _______________ fissure ( arrows ). (Choose one or more.)
A.
major
B.
minor
C.
oblique
D.
vertical
Figure 5-2A
5
A. major or C. oblique or D. vertical; most use major fissure
The major fissure (touched up for easy visibility) is _______________ to the x-ray beam only in the lateral projection.
A.
perpendicular
B.
parallel
C.
oblique
B.
parallel
The fissure _______________ visible on the frontal (posteroanterior [PA]) projection?
A.
is
B.
is not
B.
is not
Figure 5-2B is a parasagittal computed tomography (CT) reconstruction showing the left major fissure ( arrows ).
The major fissure runs obliquely downward from approximately the level of the fifth thoracic vertebra to the diaphragm, where it ends at a point just short of the anterior chest wall ( Figures 5-2A and 5-2B ).
6
The major (oblique, vertical) fissure is not visible on the normal frontal projection because _______________.
A.
it is often anatomically absent
B.
it is not parallel to the x-ray beam
C.
it has the same roentgen density as lung tissue
D.
it is radiolucent
6
B. it is not parallel to the x-ray beam
7
In the right lung, the major fissure separates the right upper and middle lobes from the _______________.
A.
right lower lobe
B.
lingula
C.
cranial lobe
7
A. right lower lobe
On the left, the major fissure separates the _______________ and _______________.
A.
left upper lobe
B.
lingula
C.
left lower lobe
D.
left middle lobe
A.
left upper lobe (lingula is part of left upper lobe); C. left lower lobe
The fissure normally appears as a thin white line (two layers of visceral pleura surrounded by air) as in Figure 5-3A ( arrowheads ). There are two exceptions:
1.
If a lobe is consolidated, the fissure appears as an edge, delineating that lobe. In Figure 5-3A , the lower fissure is a line ( arrowheads ), but the upper fissure is an edge ( arrows ) because the upper lobe is consolidated or airless, but the lower lobe is aerated.
2.
If pleural fluid enters a fissure, the fissure thickens. Note the thick major fissure ( arrowheads ) and normal minor fissure ( arrow ) in Figure 5-3B .
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