radiology anatomy of chest.ppt

1
RADIOLOGICAL ANATOMY
OF LUNGS

2
• The lungs
• The central airways
• The pleura
• The mediastinum
• The hila
• The diaphragm

3
LUNGS
• Pair of respiratory organs.
• Situated in thoracic cavity.
• Invaginates the pleural cavity.
• Right and left lungs separated by
mediastinum.

4
NORMAL LUNG ANATOMY
• Composed of anatomical units that
include
• Lung
• Lobes
• Segments
• Sub segments
• Secondary lobules and
• Acini.

5
LUNG
• Each lung is conical in shape.
• It has
-Apex
-Base
-Anterior border
-Posterior border
-Inferior border
-Costal surface
-Medial surface .

6
LOBES AND FISSURES
• Three lobes on the right .
-Upper
-Middle and
- Lower.
• Two On the left.
-Upper and
-Lower.

7
FISSURES
• Lobes are separated by fissures.
• Oblique and horizontal fissures.
• Fissures are frequently incomplete.
• Average thickness is about 0.2 mm.

8
OBLIQUE(MAJOR) FISSURE
• Oblique fissure-
separates the whole
thickness of lung ,
except at the hilum.
• Due to oblique plane
-Lower lobe more posterior
and
- Upper lobe more
anterior.

9
OBLIQUE FISSURE
• Major fissure can be seen in lateral view.
• They run forward and downwards, start
posteriorly from the 4th or 5th thoracic
vertebra.
• Passes through the hilum.
• Then it usually parallels the 6th rib and
reaches the diaphragm several centimeters
behind the anterior costophrenic angle.

11
OBLIQUE FISSURE
ON CT
• Occasionally visible as a line.
• Relatively avascular zone that forms the
outer cortex of the lobe.
• Running transversely across the lung.

12
•Major fissures-
above the hilum
• Major fissures –
below the hilum

13
HORIZONTAL(MINOR) FISSURE
• In frontal view , it running from the hilum
to the region of the 6th rib in the mid
axillary line.
• In lateral view, meets the oblique septum in
the midaxillary line at the level of the 5th
rib/ interspace.
• It is gently curved , with convexity upward.

15
MINOR FISSURE ON CT
• Represented by an area of paucity of blood
vessels at the level of the bronchus
intermedius.

16
AZYGOS FISSURE AND LOBE
-Due to failure of normal migration of the
azygos vein.
-The parietal and visceral pleura form a
mesentery like structure –the mesoazygos
contains the azygos vein at its lower end.
-Comma shaped with triangular base
peripherally.
-Commoner on right side.

17
Azygos lobe
-Enlargement occurs in supine position
-Postmortem incidence is 1% and radiologically
0.4%.
-There is no alteration in the segmental
architecture of the lung.
-When left sided , fissure contains the
accessory hemiazygos vein.
-Trigonum parietale

19
Left azygos lob Trigonum parietale.

20
SUPERIOR ACCESSORY FISSURE AND
LOBE
-Separates the apical from the basal
segments of the lower lobes.
-Commoner on right side.
-Incidence of 5% at postmortem.
-On PA film resembles the minor fissure.
-On lateral film it runs posteriorly from
the hilum.(differentiated from the HF)

22
Inferior accessory fissure and lobe
-Run obliquely upward and medially towards
the hilum from the diaphragm.
-Separates the medial basal from other
basal segments.
-More common on right side.
-Incidence of 5-8% on chest
film.

34
Left sided horizontal fissure.
•Separates the lingula from upper lobe segments.

39
PULMONARY SEGMENTS ,
SUBSEGMENTS AND BRONCHI

40
Segments and subsegments
• Pulmonary segments are surgical units and
consequently resectable.
• Boundaries are complex and no septation
between them.
• Localized on the basis of the division of
bronchi.
• At the subsegmental level lung is composed
of secondary pulmonary lobules and acini.

41
Right lung
• Upper lobe
apical
anterior
posterior
• Middle lobe
Lateral
Medial
• Lower lobe
Superior
Medial basal
Anterior basal
Lateral basal
Posterior basal
Left lung
• Upper lobe
Apico posterior
Anterior
Lingular
Superior
Inferior
• Lower lobe
Superior
Anteromedial
Lateral basal
Posterior basal

43
Normal segmental bronchi of right lung
AP and RPO

44
Normal segmental bronchi of left lung
AP and LPO

45
Normal right pulmonary segments,frontal view
6

46
Right pulmonary segment lateral view
6

47
Left pulmonary segments,
frontal view
6

48
Left pulmonary segments,lateral vie

49
CT identification of bronchial and segmental
anatomy.
-Using spiral CT technique and collimation of 3-
5mm all segmental bronchi should be visible.
-Bronchi less than 2mm diameter and
closer than 2cm to the pleural surface
are not visible on HRCT.
-It is equivalent to between 7th and 9th
generation of airways.

53
• At the level of origin of the segmental
airways thin septum or a triangular wedge
of tissue along the edge of a bronchus can
be seen .
• These spur serves as precise anatomic
landmarks.And frequent sites of bronchial
disease.

54
Lobar and segmental bronchi
-Bronchi are composed of cartilagenous and
fibromuscular elements.
-Airways are divided into approximately 23
generations of branches from the trachea to
alveoli.
- Bronchi taper and become thinner
walled as they branch.

56
Right and left main bronchi
The right main bronchus
is shorter,steeper and
wider than the left.
• Dividing into right
upper lobe bronchus
and bronchus
intermedius.
• Left main bronchus is
longer than right.
• It devides into upper
and lower lobe
bronchus.

57
Right and left main bronchi

58
RIGHT AND LEFT UPPER LOBE
• The upper lobe bronchus
arises from 2.5cm below
the carina.
• 1-2cm long.
• Divides into apical
,anterior and posterior
segmental bronchus.
• The upper lobe bronchus
arises from 5cm below
the carina.
• 2-3 cm long.
• superior and lingular
divisions.
• superior > apicoposterior
and anterior segmental
bronchi.
• Lingular bronchus >
superior and inferior
segmental bronchus.

60
RIGHT AND LEFT UPPER LOBE
• 15% of individuals
present four
segments.
• Resulting from a
double origin of the
posterior bronchus
• Supplies the axillary
region.
• In 25%cases –Upper
lobe bronchus
trifurcates into
–apicoposterior
-anterior and
-lingular.

61
Level of right upper lobe bronchus

62
Apical segment
bronchus
First branch of
right
upper lobe
• Appears as circular
lucency.
Apico posterior segment
bronchus
Sequential section
through the lower
trachea and carina
represents section
through the apical
posterior
segmental bronchus
of the left upper
lobe.

65
Anterior segmental bronchus

67
BRONCHUS INTERMEDIUS
• 3-4cm long
• Begins at the level of the right upper lobe
bronchus.
• Gives rise to middle lobe and lower lobe
bronchi.
• Lies posterior to the right main pulmonary
artery.

71
Middle lobe bronchus and Lateral and medial
segments.
• From anterolateral wall of the bronchus
intermedius.
• Dividing into its lateral and medial segmental
branches.
• The lateral and medial segmental bronchi are equal
in size.(50%)
• Common variant- small lateral segment and large
medial one.
• Less commonly it trifurcates into the medial
segment and two lateral sub segments.

74
Right and left lower lobe bronchi
• It is short
• Divides into four
basal segmental
branches of the right
lower lobe.
• Has same branching
pattern as the RLLB.
• But only 3 basal
segments-
anteromedial ,lateral
and posterior.

75
Right and left lower lobe bronchi

76
Right and left superior basal segmental
bronchus
• Arises from the
posterior aspect of
the LLBbronchus.
• In some case it arise
at a level higher to the
origin of the middle
lobe.
• In some patients two
superior segmental
bronchi may be
present.
Superior segment
rests obliquely on
the basal segments.

79
Trunchus basalis and basal segmental bronchi
• Trunchus basalis 5-
10mm
• Visualized as circular
lucency.
• The lower lobe bronchi
always lie medial and
anterior to the
corresponding lower
lobe pulmonary
arteries.
• Arises within 1cm of
the origin of the
superior segment
• Longer than the right
TB.

80
• The basal segment
bronchi-
medial,anterior,lateral,post
erior.
• The medial basilar
segmental bronchus arises
first .
• Segment parallels the
posterior portion of the
right heart border.
• After giving the two
branches the stem
bronchus continues for a
variable distance before
its final bifurcation.
• Medial and anterior basilar
bronchi originate as a
common trunk.
• Identification of the
BSB—their relative
position as they course to
the corresponding basilar
lung segments.

82
Cross sectional anatomy of lung segments
• Aortic arch level
Po
AP
AN
AN
Ap P

83
Left pulmonary artery level
A
N
P
s
AN
Ap P
s
A
p

84
Right pulmonary artery level
s
s
an
m
IL SL

85
Cardiac ventricular level.
M
I
L
mb
pb
lb
ab
am
b
lb
pb

86
Lung interstitium
• Supported by a network of connective
tissue fibers-lung interstitium.
• Strong enough to maintain the potency of
the alveoli, airways and vessels.

87
• Lung interstitium is made up of 3 fiber
system.
- Peribronchovascular interstitium.
- Sub pleural interstitium
-Intra lobular interstitium.
-These 3 form a continuous fibrous
skeleton that support lung parenchyma.

89
Peribroncho vascular interstitium
• System of fibers that invest bronchi and
pulmonary arteries and support the
medullary structures of lung.
• In the perihilar region- it forms a strong
connective tissue sheath- surrounds the
large bronchi and arteries.
• Described as axial fiber system.

91
Sub pleural interstitium
-Located beneath the visceral pleura.
-Covers the lung in a fibrous sac from which
connective tissue septa –the inter lobular
septa, penetrate the lung parenchyma.
- The sub pleural interstitium and
interlobular septae are part of the
peripheral fiber system
-support the cortical lung parenchyma.

93
Intra lobular interstitium
• Network of thin fibers that form a fine
connective tissue mesh in the walls of the
alveoli.
• Bridges the gap between the
peribronchovascular interstitium and sub
pleural interstitium.
• Corresponds to the septal fibers.

95
SECONDARY PULMONARY LOBULES
AND ACINI
• Smallest unit of the lung structure
marginated by connective tissue septa.
• Irregularly polyhedral in shape and variable
in size- approximately 1-2.5 cm in diameter
• Supplied by small bronchiole and and
pulmonary artery.

97
Pulmonary Acinus
• Portion of the lung parenchyma .
• Distal to the terminal bronchiole.
• Supplied by a first order respiratory
bronchiole.

99
Pulmonary Acinus
• Comprised of
respiratory bronchioles
, alveolar ducts,
alveolar sacs, and
alveoli.
• Secondary pulmonary
lobules are made up of
a limited number of
pulmonary acini – vary
from 3-24.

101
• Respiratory bronchioles are the largest
airway that have alveoli in their walls.
• Acinus is the largest lung unit in which all
airways participate in gas exchange.
• 6-10mm in diameter.

102
Interlobular septa
• Secondary lobules are marginated by inter
lobular septa .
• It extends inward from the pleural
surface.
• These septa are part of the sub pleural
interstitium.

103
• A rich lymphatic system drains the visceral pleura
and courses within the interlobular septa.
• It is in parallel with septal veins .
• Ultimately leads to lymphatics and nodes within
the hila.

105
Regions where interlobular septa are thickest and most
numerous.
• Apical, anterior and lateral aspect of the upper
lobe.
• Anterior and lateral aspect of the middle lobe and
lingula,
• Anterior and diaphragmatic surface of the lower
lobe, and and along the mediastinal pleural
surface.
• Secondary lobules are best defined in these areas.

106
• Within the central lung,interlobular
septa are thinner and less well
defined than peripherally.

107
Dimensions of secondary lobular structure and
visibility on high resolution.

109
THE CENTRILOBULAR REGION OR
LOBULAR CORE
• It is the central portion of the lobule.
• Contains the pulmonary artery and
bronchiolar branches and some supporting
connective tissue.

110
• The branching of the lobular bronchiole
and artery are irregularly dichotomous-
when they divide, divide into two branches
which are usually of different sizes.
• One branch is nearly the same size as the
one it arose from and the other is smaller.

111
Peripheral or cortical lung
• Consists of 2-3 rows of well organized
secondary pulmonary lobules form 3-4 cm
thickness at the lung periphery and lung
surfaces adjacent to fissures.
• Lobules are larger than those in the
medullary lung.
• Uniform in appearance.
• Cortical arteries and veins visible on HRCT

112
Central or medullary lung
• Pulmonary lobules are smaller and irregular
in shape.
• Peripheral vessels and bronchi are seen

114
TRACHEA
• It is a cartilaginous and
fibro muscular tube.
• Extend from the inferior
aspect of the cricoid
cartilage to the carina.(C6-
T5).
• Length 10-12cm.

115
TRACHEA
• Divided into extra thoracic (2-4cm) and intra
thoracic (6-9 cm).
• It is considered intrathoracic at which it
passes posterior to the manubrium.
• Contains 16-22 cartilaginous rings-which are
incomplete posteriorly.
• Between the open ends there is a thin fibro
muscular membrane –posterior tracheal
membrane.

116
• In man, tracheal diameter averages 19.5mm
(ranges from 13-25mm) in coronal plane.
13-27mm in sagital plane.
• In women, average 17.5mm
(ranges from 10-21mm in coronal plane .
10-23 in sagital plane.

117
• In adult tracheal
narrowing is often seen at
the level of the aortic
arch.
• The tracheal wall appears
as a thin (12mm soft
tissue stripe) ,well defined
internally by air in the
tracheal lumen and
externally by mediastinal
fat.
• Tracheal wall normally
appears thinner
posteriorly where tracheal
cartilage is lacking.

118
• The position of the trachea within the
mediastinum varies ,depending on the level of
section.
• At thoracic inlet it angles posteriorly and
appears more posteriorly at more caudal
levels.

120
• The normal tracheal
dimensions vary
considerably with
respiration.
• On expiration the carina
moves upward about 1cm.
• The carinal angle normally
averages about 60 degrees.
• On inspiration it increases
10-15 degrees.

127
HILA
Composed of
-Pulmonary arteries and their branches,
-Upper lobe pulmonary veins,
-Major bronchi and
-Lymph glands.
Normal hilar shadows consists mostly of
Large pulmonary arteries and Upper lobe
veins.

128
• Left hilum is higher than the right(97%).
• At the same level(3%).
• Equal density and similar size with clearly
defined lateral borders.
Descending branch of right pulmonary
artery-10-16mm in man and 9-15 mm in
women.

129
HILUM
• Central portion of the right hilum –
right pulmonary artery and superior
pulmonary vein.
• Rounded shadow of more than 1 cm
(shortest diameter) in the angle
between MLB and LLB on right and ULL
and LLB on left is unlikely a normal
vessel.

130
THE PULNMONARY BLOOD VESSELS
• Responsible for the linear markings within
the lung on X-ray and CT.
• Well seen in the medial portion of the base
of right lung.
• IN the upper lobes , vessels show gently
curving vertical orientation.
• Lower lobe veins run more horizontally and
arteries more vertically.

131
• Bronchi and pulmonary vessels are closely
associated and branch in parallel.
• Each pulmonary artery is positioned adjacent
to the bronchus (posterosuperior) of similar
diameter(4-5mm).
• This relationship maintained from the hila to
the level of respiratory bronchioles.
• Vessel in the first anterior interspace should
not exceed 3mm in diameter.

136
• Central heart shadow on PA chest
film—mediastinum,heart,spine and
sternum
• 2/3s of the heart shadow is to the
left and 1/3 to the right.
• Normal transverse cardiac diameter
• F-14.5cm and M-15.5cm.
• Cardio thoracic ratio<50%

MEDIASTINUM.
• This is the space btw the rt. and lt. pleurae in and near
the median sagittal plane of the chest.
• It is bounded by posterior surface of the sternum and the
anterior surface of the thoracic vertebrae.
• It contains all the thoracic viscera except for the lungs.
• It is divided into superior and inferior parts by an
imaginary horizontal line passing through the sternal
angle of Louis backwards to the lower border of T4
vertebrae.
• The inferior is further divided into the ant, middle and
post by the fibrous pericardium.

139
• Mediastinum-
superior,anteri
or,middle and
posterior
compartments.

ANTERIOR MEDIASTINUM
• This is bounded above by thoracic inlet,
laterally by the pleural , anteriorly by the
sternum and posteriorly by the pericardium
and the great vessels.
• It contains loose areolar tissue , lymph nodes,
lymphatic vessels , thyroid, thymus,
parathyroid and internal mammary vessels.
• It is seen as a triangular area of radiolucency
btw the sternum and heart on lat view
radiograph .

MIDDLE MEDIASTINUM
• It is also referred to as vascular space.
• It is bounded by anterior and posterior
mediastinum.
• It contains the heart ,pericardium ,ascending
and transverse arch of the aorta, SVC and
azygos veins that empties into it
brachiocephalic vs , the phrenic nv , the upper
vagus nerves, the trachea and it bifurcation, the
main bronchi, the pulmonary veins and
adjacent.

POSTERIOR MEDIASTINUM
• It is also known as post vascular space.
• It lies btw the heart anteriorly and the
thoracic vertebrae from the thoracic inlet to
the T12.
• It contains descending aorta ,oesophagus,
thoracic duct ,azygos and hemiazygos vein,
lymph nodes ,sympathetic chains and
inferior vagus nerves.

145
• Thymus-Anterior to
the aorta and
pulmonary artery.
• Before puberty-fill
most of the
mediastinum in front
of the great
.vessels.Homogenous=s
oft tissue in CT
• In adult bilobed or
triangular.Attenuation
value =fat.

MEDIASTINAL PLEURAL REFLECTION
• Anterior junction line: this a vertical line ant.
to the trachea,post.to the sternum and extends
downward to the left .(appositions of the pleura
of the upper lobes ant)
• Posterior junction line: This is a thin vertical
line posterior to the trachea and oesophagus,
extends from the T.inlet to the level of the
azygos and the aortic arches( represents the
approximation of parietal and viseral pleura of
the upper lobe posteriorly)

Cont’d
• Azygoesophageal recess:-this recess outlines the
medial aspect of the rt lower lobe & the lat. aspect
of the oesophagus.
• The rt paratracheal stripe:-This is a vertical stripe
consisting of the rt lat. tracheal wall and the
adj.parietal & viseral pleura of the rt upper
lobe.(significances-altered by mediastinum and
pleural dx)
• Para spinal interface(pleural reflection):- this is
the vertical line interface created on the rt side
posteriorly, due to closely applied pleura to lat.
aspect of the T.vertebra.while on the Lt a
paraspinal interspace is created btw the
descending aorta and lungs.

153
Lymph node.
• Widely distributed.
• Normally ,1cm in its short axis diameter.Parietal
node groups-Internal mammary,diaphragmatic,and
intercostal.
• Visceral node groups-Intra
pulmonary,Bronchopulmonary,Tracheobronchial,Par
atracheal,Paraesophageal,and anterior mediastinal.

161
The left cardiac border below the aortic arch
• Formed by main pulmonary artery and heart.
• Aortic pulmonary mediastinal stripe –lateral
extend of aorto pulmonary window.
• Left Para aortic line-Interface between the lung
and left wall of aorta.
• Aortic nipple- left superior intercostal vein.

162
Para spinal line
• Produced by normal soft tissue covering the bone.

163
Pleura
• Serous membrane.
• Has two layers.
• Visceral pleura- It covers the
surface and fissures of the lung
except at the hilum.
• Parietal pleura –Thicker than the
pulmonary pleura.
• Four parts-costal, diaphragmatic,
Mediastinal and cervical.

165
Recesses of pleura
• Costomediastinal recess
-Lies anteriorly between
costal and mediastinal
pleura.
• Costodiaphragmatic
recess
-Lies inferiorly between
costal and
diaphragmatic pleura.
• First part of the pleural
cavity to be filled up by
pleural effusion.

166
• Anterior junction line
-Two lungs separated
anteriorly by the four
layers of pleura
-Cannot be identified
above the level of the
clavicle.
-Inferiorly- deviating to
left
Junction lines

167
• Posterior junction line
-Behind the Oesophagus.
-Envelope the aortic arch.
-Superiorly extends to the
level of the lung apices.

168
Pulmonary ligament
• Two layers of the pleura
continuous at the hilum.
• A fold of parietal pleura
extends inferiorly to form
the inferior pulmonary
ligament.
• Contains loose areolar
tissue and lymphatics.
• Act as a dead space into
which the pulmonary vein
can expand during
increased venous return.

177
Diaphragm
• Normal right hemi diaphragm –anterior
portion of the 6th rib.
• 1.5-2.5 cm higher than the left.
• Same level (9%).
• In a few normal individuals – left is up to 1
cm higher than the right.
• Difference >3 cm considered significant.

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