Thorax

The lung

The lung


Shape and location Color and consistency Lobes and fissures Differences Surfaces Mediastinal surface of the right lung Mediastinal surface of the left lung

Borders Tracheo-bronchial tree Broncho-pulmonary segments Bronchography Postural drainage

Lung development

Shape

Each lung has the shape of a half cone

lung

lung

Location

The lungs occupy most of the space in the thoracic cavity and are separated from each other by the structures in the mediastinum

lung

Location


The lungs occupy most of the space in the thoracic cavity and are separated from each other by the structures in the mediastinum

Location

Each lung lies within its own pleural sac within which it is free to expand and contract

Location


Its most fixed part is the hilum, where the structures which enter and leave the lung form the root of the lung

Color & consistency

In the adult, the lung is gray and its surface is mottled especially in people living in industrial areas and in smokers

Color & consistency

On close examination, the mottling is seen to consist of lines marking small polyhedral areas, within which are finer lines subdividing these areas The lines are due to deposition of fine particles of carbon, which have been inhaled and deposited in the areolar tissue near the surface of the lung

Color & consistency

In the child, the lung is pink and the lines are very faint

Color & consistency

Due to its elasticity, the lung shrinks when the chest is opened but does not expel all the air contained in it. The result is that the lung post-mortem remains crepitant to the touch, produces frothy fluid if the cut surface is squeezed, and floats in water.

Color & consistency

In an infant who has never breathed (stillborn), the lung is firm to touch, does not produce frothy fluid from its cut surface and sinks in water. This is of some forensic (medico-legal) importance in determining whether a dead infant has breathed after birth

Color & consistency

In an embalmed cadaver, the lungs are hardened and have impressions formed by adjacent structures, whereas the fresh lungs usually do not

Lobes & fissures

The right lung usually has three lobes, the left only two Do not try to side a lung by counting its lobes, as there may be variations You can tell the side quite easily by looking at the general shape and mentally try to fit it into your own chest

Oblique fissure

In each lung an oblique fissure extends from the surface to the hilum (i.e. a deep fissure) and divides the organ into separate upper and lower lobes

Oblique fissure

In each lung an oblique fissure extends from the surface to the hilum (i.e. a deep fissure) and divides the organ into separate upper and lower lobes

Oblique fissure

On the surface of the body, the oblique fissure starts at the level of the second thoracic spine, follows the medial border of the scapula when the arm is abducted

Oblique fissure

On the surface of the body, the oblique fissure reaches the lower border of the lung, in front, at the sixth costochondral junction

Oblique fissure

Horizontal fissure


On the right lung a horizontal fissure passes from the anterior margin into the oblique fissure to separate a wedge-shaped middle lobe from the upper lobe.

Horizontal fissure

On the surface of the body, this passes forwards from the oblique fissure following the line of the fourth rib

Horizontal fissure

On the surface of the body, this passes forwards from the oblique fissure following the line of the fourth rib

Horizontal fissure

On the surface of the body, this passes forwards from the oblique fissure following the line of the fourth rib


There is no middle lobe in the left lung but there is a tongue-like projection of the upper lobe at the cardiac notch, which corresponds to the right middle lobe and is called the lingula



The cardiac notch is produced on the superior lobe of the left lung owing to the bulging of the heart

Fissures

The visceral pleura, clothing the surface of the lung, extend inwards to line the depths of the fissures

Fissures

Thus the oblique fissure of each lung makes a slippery surface between the two halves; this produces easy and more uniform expansion of the whole lung

Fissures

Owing to the obliquity of the oblique fissure, the lower lobe lies posterior and inferior to the upper lobe

Fissures

Movements of the chest wall and diaphragm are of greater range towards the base of the lung Although elasticity of the lung encourages equal expansion throughout

Fissures

The apex of the lung is greatly helped to expand by the lower part of the upper lobe being so near the diaphragm and lower chest wall

Fissures

Thus the obliquity of the fissure is functional, for if the lung were divided into two halves by a horizontal fissure; this would have less effect on apical expansion

Right lung

Left lung

Right/ left lung differences

The relation of the medial surfaces

Right/ left lung differences

The cardiac notch


2
3

Right/ left lung differences

The number of lobes

Right/ left lung differences

The right lung is larger than the left

Right/ left lung differences

The right lung is larger than the left The base of the lung (diaphragmatic surface) is more concave on the right than that on the left, this is produced by the underlying liver thus making the right lung shorter than the left

Surfaces and borders

Each lung has an apex, three surfaces, and three borders. The apex extends into the root of the neck

Surfaces

Costal surface

Surfaces

Medial surface

Surfaces


Diaphragmatic surface (or the base since it is opposite the apex; remember that the lung is a half cone).

Costal surface

Convex Shows impressions of the ribs in the embalmed cadavers



vertebral part: occupies the paravertebral gutter on each side of the thoracic part of the vertebral column
Vertebral part
Mediastinal part

Medial surface

mediastinal part: fits against the mediastinum and contains the root of the lungs

Cardiac impression

On each side, the mediastinal surface has a deep concavity, which accommodates the heart and thus is called the cardiac impression

Cardiac impression

This impression is larger and deeper on the left than on the right because the heart projects more to the left than to the right

Cardiac impression

The cardiac impression on the right is related mainly to the right atrium

Cardiac impression

The cardiac impression on the left is related to the left ventricle

cardiac impression

Hilum

Mediastinal surface

The hilum of each lung is located above and behind its cardiac impression. Other impressions are only evident in the lung of an embalmed cadaver

the cardiac impression is related mainly to the right atrium

The mediastinal surface of the right lung


Vertical grooves above and below the cardiac area indicate the position of the superior and inferior venae cavae respectively

The mediastinal surface of the right lung

The superior groove is in front of the hilum and a groove ending forward above the hilum marks the position of the azygos vein, which terminates into the superior vena cava

The mediastinal surface of the right lung

The superior groove also receives the right brachiocephalic vein, which makes a vertical impression that joins that of the superior vena cava

The mediastinal surface of the right lung

The esophagus grooves behind the hilum, its groove is interrupted by that of the arch of the azygos

The mediastinal surface of the right lung

The cardiac area of the left lung is related mainly to the left ventricle

The mediastinal surface of the left lung

There is a wide groove above and behind the hilum for the arch and the descending part of the thoracic aorta

The mediastinal surface of the left lung

Passing upward from the groove for the arch is a groove for the left common carotid artery

The mediastinal surface of the left lung

The esophagus makes an impression anterior to the descending aorta just above the inferior border

The mediastinal surface of the left lung

Borders of the lung

Anterior posterior inferior

Anterior border

Is thin and sharp

Anterior border

Is thin and sharp Apart from the cardiac notch of the left side, it corresponds more or less to the anterior border of the pleura

Anterior border

Is thin and sharp Apart from the cardiac notch of the left side, it corresponds more or less to the anterior border of the pleura

Posterior border

Thick and rounded

Inferior border

Surrounds the base of the lung Is thin and sharp when it extends into the costodiaphragmatic recess Is blunt where it divides the diaphragmatic from the mediastinal surfaces

Tracheo-broncheal tree

The trachea divides into right and left main (principal) bronchi at the level of the manubriosternal joint


70o

Tracheal bifurcation

The bifurcation of the trachea is found to have an angle of 70o


25o
2.5cm
T5

Tracheal bifurcation

the right main bronchus is 2.5cm long and lies at an angle of 25o to the vertical enters the lung at the level of the body of T5


45o
5cm
T6

Tracheal bifurcation

the left main bronchus is 5cm long and is at 45o to the vertical enters the lung at the level of T6

Tracheal bifurcation

The radiolucency of the trachea overlies the lower two cervical and upper five thoracic vertebra

Tomogram showing tracheal bifurcation

Tracheal bifurcation


The standard PA view shows the upper half clearly and special studies are needed to see the lower half and the bifurcation

Right bronchus

Since the trachea deviates slightly to the right in the lower part of its course, the right bronchus is shorter and more in line with the trachea than the left. It is also wider than the left

Right bronchus

Note that the right main bronchus is larger than the left due to the fact that the right lung is larger than the left (60%:40%)

Right bronchus

Since the right bronchus is more in line with the trachea than the left and since it is shorter and wider than the left, inhaled foreign bodies are more likely to be found in the right lung than the left

Lobar bronchi

Each main bronchus is divided symmetrically into lobar bronchi

Lobar bronchi

The right main bronchus as it approaches the hilum, gives off an upper lobe bronchus (outside the hilum) and then divides into a middle and lower lobe bronchus (within the hilum)



Lobar bronchi

On the left side, the middle lobe bronchus is replaced by the lingular bronchus

brochoscopy

Segmental bronchi

Each lobar bronchus divides into segmental bronchi Each segmental bronchus supplies one bronchopulmonary segment of the lung

Bronchioles

Within each segment there is further branching of the bronchi



Cast of the bronchial tree

Bronchioles

Within each segment there is further branching of the bronchi

Bronchopulmonary segment

The bronchopulmonary segments are roughly pyramidal in shape. Their apices towards the hilum, their bases on the surface of the lung

Bronchopulmonary segment

Bronchopulmonary segments have the same names and number as the segmental bronchi



Bronchopulmonary segment


Each segment has its own artery and vein The vessels accompany the bronchi and their subdivisions The artery is a branch of the pulmonary artery The vein is a tributary of the pulmonary vein.

Bronchopulmonary segment

The veins are intersegmental in position i.e. each vein drains more than one bronchopulmonary segment and each segment is drained by more than one vein

Cast of the bronchi and bronchial arteries

Bronchial arteries


The bronchial tree receives its blood supply by bronchial arteries which are direct branches of the aorta (usually one on the right and two on the left)



Bronchial arteries


They supply the bronchi from the carina to the respiratory bronchioles and also supply the connective tissue of the lung and the visceral pleura

Bronchial veins

The bronchial veins drain into the azygos vein on the right and the accessory hemiazgos on the left.

Pulmonary artery

Pulmonary vein
O2
CO2
Bronchial artery
General architecture of the lung bronchi (B), bronchioles (B1), alveoli (A), pleura (P)


The alveoli contain within their walls a rich capillary plexus which is fed with deoxygenated blood by the pulmonary artery

Pulmonary artery

Pulmonary vein
O2
CO2
Bronchial artery


The branches of the pulmonary artery although accompany the bronchial tree, supplies no bronchus but it does supply the alveoli giving them all they need except oxygen of which they have more than enough There is no anastomosis between bronchial and pulmonary arteries

Segmental bronchi

Each upper lobe bronchus gives rise to three segmental bronchi, the middle lobe bronchus gives off two segmental bronchi, and each lower lobe bronchus gives off five

Segmental bronchi

Upper lobe apical (1) posterior (2) anterior (3)

Segmental bronchi

Middle lobe lateral (4) medial (5)

Segmental bronchi

Lower lobe apical (6) medial basal (7) anterior basal (8) lateral basal (9) posterior basal (10)

Segmental bronchi

Note that the apical bronchus of the lower lobe originates at the same level as the middle lobe bronchus

Segmental bronchi

upper lobe apical (1) posterior (2) anterior (3) superior (lingular) (4) inferior lingular (5)

Segmental bronchi

Lower lobe apical (6) medial basal (7) anterior basal (8) lateral basal (9) posterior basal (10)

Bronchopulmonary segments

The segments differ on the two sides only in the different positions of the two segments of the middle lobe

Bronchopulmonary segments

The cardiac notch has not only obliterated the transverse fissure, but has rotated the lingula (middle lobe) so that the lateral and medial segments of the right lung have become superior and inferior on the left

Bronchopulmonary segments

The left upper lobe bronchus bifurcates into an upper lobe proper and a lingular segment in about 80% of cases In 20% there is a trifurcation with the anterior segmental bronchus coming between the upper lobe proper and the lingula below

Bronchopulmonary segments

The left upper lobe has four main bronchopulmonary segments: apicoposterior, anterior, superior lingular and inferior lingular. Notice that the apicoposterior bronchus quickly divides into the apical and posterior subsegments.

Clinical points

Bronchopulmonary segments

Pneumonia

Disease of the lung (tumor or abscess) may be limited to one segment before spreading to another.

Bronchopulmonary segments

Pulmonary angiogram demonstrating a large perfusion defect in the right lower lobe
Clinical points

Pulmonary embolism

A blood clot obstructs the flow of blood through a branch of the pulmonary artery resulting in destruction (infarction) of a lung segment or lobe

Bronchopulmonary segments

Bronchogram of the left lung PA projection
Clinical points

Bronchography

Allow the trachea and bronchi to be seen in outline performed after introducing a contrast medium is introduced into the respiratory tract

Bronchopulmonary segments

Bronchogram of the left lung oblique projection
1
2
3
5
4
Apicoposterior anterior superior lingular inferior lingular lower lobe bronchus
Clinical points

Bronchography

The contrast material is injected via a catheter after topical anasthesia of the nose, pharynx, larynx, and trachea

Clinical points

Bronchopulmonary segments
Bronchogram of the right lung oblique projection

Bronchography

the patient is postured in various positions to allow the contrast material to flow into all secondary and segmental (tertiary) branches

Clinical points

Bronchopulmonary segments
apical posterior anterior medial lateral apical basal medial basal anterior basal lateral basal posterior basal
1
5
2
3
4
6
7
9
10
8


Bronchography

Note that the apical bronchus of the lower lobe originates at the same level as the middle lobe bronchus ()

Bronchopulmonary segments

Lobectomy


The affected segment may be surgically removed (resected) without disrupting surrounding lung tissue

Bronchopulmonary segments

Clinical points

Atelectasis

Each segment is surrounded by connective tissue that prevents air from passing between segments. Air in a bronchopulmonary segment whose segmental bronchus is obstructed will be absorbed by the blood. This causes segmental atelectasis (collapse) of the tissue in the affected segment

Postural drainage of posterior basal segments of the lower lobes

Bronchopulmonary segments

Postural drainage

Physiotherapists who wish to drain one of the segments by different postures need to know about bronchopulmonary segments

Postural drainage of anterior basal segments of the lower lobes

Bronchopulmonary segments

Postural drainage

To drain sputum from the lung base, the patient need to be tilted head down

Postural drainage of the posterior segment of the left upper lobe

Bronchopulmonary segments

Postural drainage

The upper lobes are drained better with the sitting position.

Anterior projection

Bronchopulmonary segments
Surface projection of the lungs and pleura

Surface projection of lung segments

Posterior projection
Bronchopulmonary segments

Apical segment of the lower lobe

is located alongside the base of the scapular spine (where you can listen to this segment)

Bronchopulmonary segments

Clinical points

Apical segment of the lower lobe

Is the most dependant part of the lung when lying supine in bed and is the region where intrapulmonary fluid may collect in some conditions