Radiological anatomy of chest including lungs,mediastinum and thoracic cage

Dr. Pankaj Kaira
JR – I Radiodiagnosis
SRMSIMS Bareilly,India

Chest
 The chest consists of bony skeleton of the spine and
ribs, chest wall and diaphragm, the mediastinum and
great vessels, the airways, lung parenchyma and
pulmonary vessels.

COMPONENTS OF THORACIC CAGE:
 Sternum
 Manubrium, Body (Gladiolus), Xiphoid process
 Ribs
 7 True Ribs
 5 False Ribs (including 2 floating ribs)
 Clavicle Pectoral
 Scapula girdle
 12 Thoracic Vertebrae (T1 - T12)

Thoracic Cage
 It forms a conical enclosure for the lungs and heart and
provides attachment for the pectoral girdle and upper limb.
 It has a broad base and a narrower superior apex; it is
rhythmically expanded by the respiratory muscles to create
a vacuum that draws air into the lungs.
 The inferior border of the thoracic cage is formed by a
downward arc of the ribs called the costal margin.
 The ribs protect the thoracic organs and spleen, most of
the liver, and to some extent the kidneys.

Sternum/Breast bone
 Flat bone, with 3 parts:
1. Manubrium sterni
2. Body/Gladiolus
3. Xiphoid process

PARTS OF STERNUM:
1. Manubrium sterni
 Jugular/suprasternal notch
 Articulates with Clavicles
and Ribs 1 and 2
 Lies opposite to T3 and T4
vertebrae
 Manubriosternal joint
inferiorly – called Sternal
Angle/Angle of Louis –
opposite articulation with
2nd rib – at the level of
intervertbral disc between
T4 and T5 vertebrae
(imp. for counting the ribs)

PARTS OF STERNUM:
2. Body/Gladiolus
 Articulates with Ribs 2-7
 Xiphisternal joint inferiorly-
opposite to T9 vertebra
3. Xiphoid process
 Cartilaginous - calcifies
through time
 Allows attachment of
muscles
 Tip of xiphoid – at level of
T10

Ribs
 Typical Ribs 2-7
 Head
 Neck
 Tubercle
 Angle
 Shaft
 Subcostal groove
 Atypical Ribs 1, 8 -10
•Rib 1 - short, flat and
supports Subclavian
vessels
• Ribs 1, 10-12 - articulate
with only 1 vertebra
• Ribs 11 and 12 –
“floating ribs” – do not
articulate with Transverse
processes of Vertebrae or
Sternum

 Typical ribs: 1 – 7 pairs of
ribs are attached anteriorly to
the sternum by their costal
cartilages.
 Atypical ribs: 8th, 9th and
10th pairs of ribs are attached
anteriorly to each other and to
the 7th rib by means of their
costal cartilages and small
synovial joints.
 Floating ribs :The 11th and
12th pairs have no anterior
attachment. They are
embedded in the abdominal
muscles.

Typical Ribs (2 -7)
• Long, twisted, flat bone
• The anterior end of each rib is attached to the corresponding costal
cartilage
• A rib has a head, neck, tubercle, shaft, and angle
• Head – located posteriorly - has 2 facets for articulation – one for the
numerically corresponding vertebral body and the other for the vertebral
body immediately above it.
• Neck is a constricted portion - between the head and the tubercle.
• The Tubercle is a prominence on outer surface of the rib - at the
junction of the neck with the shaft. It has a facet for articulation with the
transverse process of the numerically corresponding vertebra.
• The Shaft is thin, flat and twisted on its long axis.
• It has a rounded, smooth superior border and a sharp, thin inferior
border which has costal groove (it accommodates the intercostal
vessels and nerve (VAN ) The angle is where the shaft of the rib bends
sharply forward.

Atypical Rib (1st Rib)
• The first rib has a close relationship to the lower nerves of the
Brachial plexus, Subclavian artery and vein.
• This rib is shortest with a prominent tubercle for the attachment
of Scalenus anterior muscle.
• Anterior to the attachment of Scalenus anterior, the Subclavian
vein crosses the rib.
• Posterior to the attachment of Scalenus anterior, the Subclavian
artery and the lower trunk of the Brachial plexus cross the rib
and lie in contact with the bone.

JOINTS OF STERNUM
1. MANUBRIOSTERNAL JOINT:
 cartilaginous joint, symphysis
 between Manubrium and body of Sternum
2. XIPHISTERNAL JOINT
 cartilaginous joint
 between Xiphoid process and body of Sternum
 The Xiphoid process usually fuses with the body of the
Sternum during middle age

JOINTS OF RIBS
1. COSTOVERTEBRAL JOINTS:
 2 joints between heads of the Ribs and bodies of
Vertebrae (corresponding and upper)- Synovial joints
 1st, 10th, 11th and 12th rib has 1 synovial joint with the
corresponding vertebra, the rest have 2 each; one for the
corresponding vertebra and the other for the vertebra
above it
 1 joint between tubercle of Ribs and transverse
process of Vertebra (corresponding) - Synovial joint (1st-
10th Rib)
 Intra articular ligament connects head of Rib to the
intervertebral disc

Cervical Rib (Accessory Rib)
 Occurs in 0.5% population
 There is an extra pair of ribs just above the 1st rib
 They arise from the transverse process of C7 vertebrae
 Anteriorly, they may be attached to 1st Rib or may be
free
 Clinical Anatomy: Cervical Rib may compress Brachial
plexus/Subclavian artery; causing Klumpke’s
paralysis/Ischemia

Intercostal Muscles
 External intercostals
 Internal intercostals
 Innermost intercostal muscles which is separated from
the internal intercostal muscles by neurovascular
bundle with the vein lying in a groove on the under
surface of the corresponding rib and the artery and
nurve lying more inferiorly (VAN).

Blood Supply
 Anterior intercostal arteries arise from internal thoracic
artery.
 The posterior intercostal arteries of first two space arise
from the costo-cervical trunk (branch of subclavian artery)
and posterior intercostal arteries of lower nine spaces arise
from the descending thoracic artery.
 Intercostal veins drain into azygous and hemiaygous veins,
except 1st on right drains into vertebral or brachiocephalic
vein and 2nd and 3rd on left form the superior intercostal
vein to drain into left brachiocephalic vein.

DIAPHRAGM
 Seperates the thorax from the abdomen.It consists of
 1)A peripeheral muscular part arising from margins of
thoracic outlet.
 2)Right crus arises from the front of vertebral bodies of L1-
3.
 3)Left crus from the lateral aspect of vertebral bodies of L1-
2.
 4)Arcuate ligament from the fascia of the psoas and
guadratus lumborum.
 5)Central tendon which is partly fused with the fibrous
layer of pericardium.

Main openings in Diaphragm
 Aortic opening (T12) – transmitting the aorta, thoracic
duct and the azygous vein.
 Oesophageal opening (T10) –
Oesophagus,oesophageal branches of left gastric
artery, vein and B/L Vagus nerve.
 Vena caval opening (T8) – Inferior vena cava and right
phrenic nerve.

TRACHEA
 The trachea connects the upper
respiratory tract to the lungs via
the bronchial tree, enabling gas
exchange.
 The trachea extends from the
larynx at the level of the cricoid
cartilage (C6) and branches into
the right and left main bronchus at
the carina (T4/5)
 There are 12-16 incomplete
cartilaginous rings.The posterior
wall is fibrous tissue.Rings may
calcify in older people.

 Usually situated in a
midline position and is
slightly deviated to the
right .
 length : 9 – 12 cms .
intrathoracic portion about
6-9 cm.
 Trachea bifurcates into
right & left main bronchus .
 Normal Carina Angle : 60 to
70 Degrees.

BRONCHOPULMONARY SEGMENTS
 Bronchopulmonary segments are anatomic, functional and surgical
units of lung.
 Well defined areas of lungs, each of which is aerated by a segmental/
tertiary bronchus
 These segments are pyramidal in shape with apex towards the root of
lung
 Each segment is an independent respiratory unit.
 In each bronchopulmonary segment the segmental bronchus is
accompanied by a branch of pulmonary artey, lymphatics and
autonomic nerve supply.
 Pulmonary veins run in intersegmental planes between adjoining
segments

Broncho-Pulmonary Segments of the Right Lung
 Superior Lobe –
Apical (1)
 Anterior (2)
 Posterior (3)
 Middle Lobe –
 Lateral (4)
 Medial (5)
 Inferior Lobe –
 Superior (6)
 Medial basal (7)
 Anterior basal (8)
 Lateral basal (9)
 Posterior basal (10)

Broncho-Pulmonary Segments Of The Left Lung
 Upper Lobe :
 Apico -posterior (1-3)
 Anterior (2)
 Superior lingular (4)
 Inferior lingular (5)
 Lower Lobe :
 Superior (6)
 Anterior basal (8)
 Lateral basal (9)
 Posterior basal (10)

Right Main Bronchus (Eparterial)
 Wider, Shorter, and more Vertical
 25 degrees to the median plane
 2.5 cms long
 Enters the right lung nearly opposite the T5 vertebra
 It lies inferolateral and posterior to pulmonary artery.

Left Main Bronchus (Hyparterial)
 40 degrees to the median plane
 5 cms long
 1.2 cms wide
 Courses below the arch of aorta entering the hilum at T6
then courses inferolaterally to the pulmonary artery.
 Nearly 5 cm long
 Enters root of left lung at level of T6 vertebrae

HILUM
 It is a large depressed area that lies near the centre of the medial surface of lung.
 Various structures enter and leave the lung via its root.
 Each hilum contains major bronchi, pulmonary vessels and lymph nodes.
 The left hilum is higher than the right in 97% of people and equal in 3%.
 Both have clearly defined concave lateral borders
 Lymph nodes are also present on each side but are not visible unless abnormal

LUNGS
 Lungs are a pair of respiratory organs situated in thoracic
cavity
 Right lung is larger than the left
 Right lung has 3 lobes
 Left lung has 2 lobes

FISSURES
ACCESSORY FISSURES :
• Azygous fissure
• Superior Accessory fissure
• Inferior Accessory fissure
• Left transverse Fissure
MAIN FISSURES :
 RIGHT LUNG :-
i. Horizontal fissure
ii. Oblique fissure
 LEFT LUNG :-
i. Oblique fissure

 Oblique ( Major ) Fissure :
 Right oblique fissure separates the lower lobe from the middle and upper
lobes where as left oblique fissure separates lower lobe from upper lobe.
 Extends from T4/T5 posteriorly to the diaphragm anteroinferiorly.
 The left oblique fissure is more vertically oriented than the right.
 ends just behind the anterior costophrenic angle, passing through the
hilum.
 is usually visible on a lateral radiograph and on a high resolution CT scan as
a curvilinear band from the lateral aspect to the hilum.

Horizontal ( Minor ) Fissure :
 Separates upper lobe from the middle lobe of the right
lung.
 Is short as compared to oblique fissure
 Runs horizontally from the hilum to the anterior and
lateral surface of the right lung at the level of the 4th costal
cartilage.
 The posterior limit is the right oblique fissure which it
meets at the level of 6th rib in midaxillary line.
 Anatomically complete on in 1/3rd of the subjects.

FISSURES AND LOBES OF THE RIGHT LUNG

Accessory fissures of the lung
 Accessory fissures of the lung usually occur at the
borders of bronchopulmonary segments.
 Azygous fissure
 Inferior accessory fissure
 Superior accessory fissure
 Left minor fissure

Azygous fissure
 On the right side.
 Occurs due to anomalous
development of azygous vein
and terminates in tear drop
opacity.
 Consists of 4 layers of pleura
and supplied by right apical
bronchus or its branches.
 Seen in 0.5% of CXR with
male:female ratio of 2:1.

SUPERIOR ACCESORY FISSURE
 Separates the apical from the basal segments of the lower
lobe.
 It is commoner on right side.
 It is seen in 5% of the PA chest radiograph.

INFERIOR ACCESSORY FISSURE
 It seperates the medial basal broncho pulmonary segment from the
rest of the lower lobe.
 Common on the right than left
 This fissure may also be referred to as Twining's lines .
 It is seen in 8% of PA chest radiographs.

LUNG ZONES
 Lungs are assessed by dividing
them into 3 zones:
 Upper zone : upto 2nd rib
 Middle zone: 2nd to 4th rib
 Lower zone: 4th and below

LOBES OF THE LUNGS
 Right lung
has three lobes :
a) upper lobe
b) middle lobe
c) lower lobe

ARTERIAL SUPPLY :
 Dual supply i.e Bronchial artery and Pulmonary artery.
 Systemic circulation :
- Bronchial arteries (oxygenated blood from left ventricle)
and originates directly from descending thoracic aorta
between T5 and T6 vertebrae.
- Supply blood to the bronchi, the visceral pleura and
connective tissue of the bronchial tree
- The most common pattern is two on the left and one on the
right that arises as an intercostobronchial trunk (ICBT)
(41%).

Pulmonary circulation :
- Pulmonary arteries (deoxygenated blood from right ventricle)
- They supply only the alveoli.
- These gives of a branch to each bronchopulmonary segment of lung
- The main pulmonary trunk arises from right ventricle and divides into a short left
pulmonary artery and longer right pulmonary artery.
- The right pulmonary artery runs between the superior vena cava and right main
bronchus and divides into :
- (a) upper truncus arteriosus which supplies the RUL and lies medial to the bronchus.
- (b) descending interlobar artey supplying the RML and RLL and lies lateral to the
bronchus.
- The left pulmonary artery arches over the left main bronchus and divides into :
- (a) an ascending branch which supplies the LUL and lies medial to the bronchus.
- (b) descending interlobar artey supplying the lingula and LLL and lies lateral to the
bronchus.

VENOUS DRAINAGE :
 Pulmonary veins : (oxygenated blood to left atrium)
 Two superior and two inferior
 Rt and lt superior veins drain superior , middle lobes Rt lung , superior
lobe Lt lung respectively
 Rt and Lt inferior pulmonary veins drain inferior lobe of their
respective lungs
 Bronchial veins :
- Only drain the part of blood delivered by bronchial arteries to the
bronchial tree
- Two bronchial veins : right and left bronchial vein

Lymphatic drainage of lungs :
 superficial, or subpleural and deep lymphatics of the lung
drain into lymph nodes called the tracheo-bronchial nodes
around the roots of the lobar and main bronchi and along
the sides of the trachea
Nerve supply of lungs :
 parasympathetic nerves are derived from the vagus and
sympathetic from 2nd to 5th spinal segments.

PLEURA
 Delicate serous membrane
 Which forms a closed invaginated sac enclosing the lungs and lines the
thoracic cavity.
 The pleura divides into:
 visceral pleura which covers the surface of the lung and dips into
the fissures between its lobes
 parietal pleura which lines the non pulmonary surface and named
according to the site it lines:
 costal pleura
 diaphragmatic pleura
 mediastinal pleura
 Apical pleura

 The Intrapleural Space is a true space between the visceral pleura and the
parietal pleura.
 The periphery of the base of each pleural cavity forms a deep gutter
around the dome of the corresponding diaphragm called as costophrenic
sulcus or angle
 The posterior costophrenic angle being the deepest and is visualized on a
lateral chest radiograph.
 Blood supply :
 Parietal by systemic circulation
 Visceral by both bronchial and pulmonary circulation.

MEDIASTINUM
 The mediastinum contains a group of non-deliniated organs and their
surroundingconnective tissue. It lies in the midline of
the chest between the pleural surfaces of each lung and extends from
the sternum to the vertebral column.
Anatomic Relations :
 Superiorly – Thoracic outlet and the root of the neck.
 Inferiorly – Diaphragm
 Anteriorly - chest wall
 Laterally - lungs and pleura
 posteriorly - Thoracic spine

The mediastinum is divided into superior and inferior medistina by an
imaginary plane passing from the sternal angle anteriorly to the lower
border of the body of the 4th thoracic vertebra posteriorly.
Inferior mediastinum is further subdivided into Anterior, middle and
posterior medistinum.

 Radiologically the mediastinum can be divided into :
 Anterior - Lying anterior to pericardium ,ascending aorta and
superior vena cava.
 Middle mediastinum - Contains heart , great vessels, hilum
and carina.
 Posterior mediastinum – retrocardiac and paravertebral
spaces.

The superior mediastinum contains the:
• Aortic arch and branches;
• B rachiocephalic veins and superior vena cava
• Trachea;
• Oesophagus;
• Thoracic duct;
• Lymph nodes; and
• Nerves.
The anterior mediastinum contains the:
• Thymus;
• Mammary vessels; and
• Lymph nodes.

The posterior mediastinum contains the:
• Descending aorta;
• Oesophagus;
• Azygos venous system;
• Thoracic duct; and
• Para-aortic, oesophageal and paraspinal nodes.
The middle mediastinum contains the:
• Heart and pericardium:
• Nerves;
• Lymph nodes; and
• Great vessels.

Mediastinal Lines
Anterior Junction line
 Contact of anterior lungs
 Lies posterior to the sternum
 Consists of 4 layers of pleura.
 Runs obliquely from the lower mediastinum inferiorly to
the left.
Posterior Junction line
 Contact of posterior lungs behind the oesophagus and
anterior to the spine
 Consists of 4 layers of pleura

Thymus
 It is the site for the development of T (thymic)
lymphocytes.
 It is related to the great vessels and pericardium and is
present between sternum and pericardium in the anterior
mediastinum.
 In newborn it shows maximum size,then shows regression
after puberty and fatty replacement in adults.
 CXR – it may be seen as a “sail sign” in children.In adults it
is not visualized.

Radiological anatomy of chest including lungs,mediastinum and thoracic cage

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