Lungs, Pleura and Airways

Question 1

[6-minute video]: the Hilum of the Lung

Answer 1

🙂

Question 2

The thoracic cavity is divided into three compartments: right and left lateral compartments and middle compartment.
(a) Each lateral compartment is occupied by a lung enclosed in the serous sac called ____________________.
(b) The mass of tissues and organs occupying the middle compartment form a mobile septum known as the ____________________ that completely separates the two pleural cavities.

Answer 2

(a) pleural cavity
(b) mediastinum
[Diagram]

Question 3

Briefly discuss the pleura of the lungs and the pleural cavity.

Answer 3

✓ The visceral pleura invests all the surfaces of the lung forming its shiny outer surface.
✓ The parietal pleura lines the pulmonary cavity i.e. the thoracic wall and mediastinum.
✓ The space between the visceral and parietal pleura is called pleural cavity.
✓ The pleural cavity is normally filled with a thin film of tissue fluid, which lubricates the adjoining surfaces of the pleura and allows them to move on each other without friction.
✓ The two layers meet at the root of the lung and form the pulmonary ligament.
[Diagram]

Question 4

Name the four subdivisions of the parietal pleura.

Answer 4

1. Costal pleura: It lines the inner surface of the thoracic wall (consisting of ribs, costal cartilages, and intercostal spaces) to which it is loosely attached by a thin layer of loose areolar tissue called endothoracic fascia. In living beings, endothoracic fascia is easily separable from the thoracic wall.
2. Diaphragmatic pleura: It covers the superior surface of the diaphragm. In quiet respiration, the costal and diaphragmatic pleura are in opposition to each other below the inferior border of the lung.
3. Mediastinal pleura: It lines the corresponding surface of the mediastinum and forms its lateral boundary. It is reflected as a cuff over the root of the lung and becomes continuous with the visceral pleura.
4. Cervical pleura: called cupola and covers the apex of the lung (check out its relations)
5. [Diagram]

Question 5

What are pleural recesses?

Answer 5

These are reserve spaces of pleural cavity for the lungs to expand during deep inspiration.

Question 6

Name the two pleural recesses and state their locations.

Answer 6

1. Costodiaphragmatic recess: along the inferior border of the pleura
2. Costomediastinal recess: along the anterior border of the lung. The left costomediastinal recess is large due to the presence of cardiac notch in the left lung.
3. [Diagram]

Question 7

State the clinical significance of the pleural recesses.

Answer 7

Pleural effusion
This refers to collection of fluid in the pleural cavity mostly in the costodiaphragmatic recess.
[Chest X-ray showing pleural effusion]

Question 8

State the sites of extension of pleura beyond the thoracic cage.

Answer 8

(1) on either side in the root of the neck (as domes of pleura)
(2) in the right infrasternal angle
(3) on either side in the costovertebral angle
(4) [Diagram]

Note that the pleura can be punctured inadvertently at these sites during surgical procedures.

Further notes:
The costovertebral angle is the acute angle formed on either side of the human back between the twelfth rib and the vertebral column. It’s the 90-degree angle formed between the curve of that rib and the spine.

Question 9

Outline the blood supply of the parietal pleura.

Answer 9

The blood supply to the parietal pleura is similar to that of the chest wall.
1. Intercostal arteries
2. Internal thoracic artery
3. Musculophrenic artery
4. Superior phrenic artery

Further notes:
The veins accompany the arteries.

Question 10

Outline the blood supply of the visceral pleura.

Answer 10

Bronchial arteries
The blood supply to the visceral pleura is similar to that of the lung.

Further notes:
Venous drainage is by bronchial veins.

Question 11

Outline the nerve supply of the pleura.

Answer 11

The nerve supply to the parietal pleura is similiar to that of the chest wall. The parietal pleura develops from somatopleuric layer of the lateral plate of mesoderm, hence it is supplied by the somatic nerves and is sensitive to pain.
✓ The costal pleura and peripheral part of the diaphragmatic pleura is supplied by the intercostal nerves.
✓ The mediastinal pleura and central part of the diaphragmatic pleura is supplied by the phrenic nerve.

The nerve supply to the visceral pleura is similar to that of the lung. The visceral pleura develops from splanchnopleuric layer of the lateral plate of mesoderm, hence it is supplied by the autonomic (sympathetic) nerves (T2–T5) and is insensitive to pain.

Question 12

Outline the lymphatic drainage of the parietal pleura.

Answer 12

The cervical and costal divisions of the parietal pleura drain into the intercostal and internal thoracic lymph nodes.
The mediastinal division of the parietal pleura drains into the posterior mediastinal lymph nodes.
The diaphragmatic division of the parietal pleura drains into the phrenic lymph nodes.
[Diagram]

Question 13

Outline the lymphatic drainage of the visceral pleura.

Answer 13

Brochopulmonary/hilar lymph nodes ⇒ Tracheobronchial lymph nodes ⇒ Brochomediastinal lymph trunk ⇒ Thoracic duct [on the left] / Right lymphatic duct [on the right]
[Diagram]

Question 14

State two functions of the pulmonary ligament.

Answer 14

1. It provides a dead space into which the pulmonary veins can expand during increased venous return as during exercise.
2. It allows the descent of the root of the lung with the descent of the diaphragm during inspiration.

Question 15

Explain the referred pain of pleura.

Answer 15

The pain from central diaphragmatic pleura and mediastinal pleura is referred to the neck or shoulder through phrenic nerves (C3, C4, and C5) because skin at these sites has same segmental supply through the supraclavicular nerves (C3, C4, and C5).

Question 16

The right lung has _________ lobes while the left lung has _______ lobes.

Answer 16

The right lung has 3 lobes while the left lung has 2 lobes. (For the left lung has no horizontal fissure)

Further notes:
➣ Each lung is large conical/pyramidal shaped with its base resting on the diaphragm and its apex extending into the root of the neck. The right lung is larger and heavier than the left lung.
➣ The lungs are attached to the trachea and heart by principal bronchi and pulmonary vessels, respectively.
➣ In the adults, the lungs are spongy in texture and crepitate on touch due to the presence of air in their alveoli. They float in water. In fetus and stillborn children, the lungs are solid and do not crepitate on touch due to the absence of air in their alveoli. They sink in water.

Question 17

What external features does the lung present?

Answer 17

1. Apex. 2. Base. 3. Three borders (anterior, posterior, and inferior). 4. Two surfaces (costal and medial).
   [Diagram]

Question 18

How do we side the lung?

Answer 18

The side of lung can be determined by holding the lung in such a way that:
(a) its conical end (apex) is directed upwards and its broader end (base) is directed downwards,
(b) its convex surface (costal surface) is directed outwards and its flat medial surface presenting hilum is directed inwards,
(c) its thin margin (anterior margin) should face forwards and its rounded border (posterior border) should face backwards.

[Diagram]

Note: The side should not be determined by number of fissures and lobes as they are variable.

Question 19

State the relations of the apex of the lungs.

Answer 19

Anterior: (a) Subclavian artery, (b) internal thoracic artery, and (c) scalenus anterior.
Posterior: Neck of 1st rib and structures in front of it, e.g., (a) ventral ramus of first thoracic nerve, (b) first posterior intercostal artery, (c) first posterior intercostal vein, and (d) sympathetic chain.

[Diagram]

Further notes:
➣ All the structures related to the apex are separated from it by suprapleural membrane.
➣ Apex is grooved by subclavian artery on the medial side and on the front.

Question 20

Discuss clinical features of Pancoast syndrome.

Answer 20

Pancoast syndrome occurs due to involvement of structures related to the posterior aspect of the apex of lung by the cancer of the lung apex.

Clinical features:
➣ Pain along the medial side of forearm and hand, and wasting of small muscles of the hand due to involvement of ventral ramus of T1.
➣ Horner’s syndrome, due to involvement of sympathetic chain.
➣ Erosion of first rib.

Cancer of lung apex may spread to involve neighboring structures, such as subclavian or brachiocephalic vein, subclavian artery, phrenic nerve causing following signs and symptoms.
➣ Venous engorgement and edema in neck, face, and arm due involvement of subclavian and brachiocephalic veins.
➣ Diminished brachial and/or radial pulse due to compression on subclavian artery.
➣ Paralysis of hemidiaphragm due to infiltration of phrenic nerve.

Question 21

On the right side, the lung is separated from the ____(a)____ by the right dome of the diaphragm, and on the left side, the left lung is separated from the ____(b)____ and ____(c)____ by the left dome of the diaphragm.

Answer 21

(a) liver
(b) spleen and (c) fundus of stomach

Note
The base of the right lung is deeper (i.e., more concave) because right dome of diaphragm rises to the more superior level due to the presence of liver underneath it.

Question 22

Describe the morphology of the borders of the lungs.

Answer 22

1. Anterior border: It is thin and shorter than the posterior border. The anterior border of right lung is vertical. The anterior border of left lung presents a wide cardiac notch, which is occupied by the heart and pericardium. In this region, the heart and pericardium is uncovered by the lung. Hence this region is responsible for an area of superficial cardiac dullness. Below the cardiac notch, it presents a tongue-shaped projection called lingula.
2. Posterior border: It is thick and rounded. It extends from spine of C7 vertebra to the spine of T10 vertebra.
3. Inferior border: It is semilunar in shape and separates the costal and medial surfaces.
4. [Diagram: Borders of lungs]

Question 23

The costal surface of the lung is large, smooth and convex, and covered by the costal pleura and endothoracic fascia. State its relations.

Answer 23

It is related to the lateral thoracic wall. (In embalmed and hardened lung, the costal surface presents impressions of the ribs.)
The number of ribs related to this surface is as follows:
➣ Upper 6 ribs in midclavicular line.
➣ Upper 8 ribs in midaxillary line.
➣ Upper 10 ribs in scapular line.

Question 24

The medial surface of the lung is divided into a small posterior vertebral part, and large anterior mediastinal part. State the relations of the vertebral part.

Answer 24

Vertebral column, posterior intercostal vessels, and greater and lesser splanchnic nerves.

Question 25

State the structures related to the mediastinal surface of the right lung.

Answer 25

1. Right atrium
2. Superior and inferior vena cavae
3. Azygos vein
4. Right brachiocephalic vein
5. Esophagus and trachea
6. Right phrenic nerve
7. Right vagus nerve
8. Right sympathetic chain
9. [Diagram 1] [Diagram 2]

Question 26

State the structures related to the mediastinal surface of the left lung.

Answer 26

1. Left ventricle
2. Ascending aorta
3. Arch of aorta and descending thoracic aorta
4. Left subclavian and left common carotid arteries
5. Esophagus and thoracic duct
6. Left phrenic nerve
7. Left vagus nerve
8. Left sympathetic chain
9. Left recurrent laryngeal nerve
10. [Diagram 1] [Diagram 2]

Question 27

The right lung is divided into superior, middle and inferior lobes by two fissures: ______(a)_____ and _____(b)_____. The left lung is divided into superior and inferior lobes by _____(a)_____.

Answer 27

(a) oblique fissure
(b) horizontal fissure

Question 28

The _______________________________ is a short broad pedicle connecting the medial surface of the lung with the mediastinum. It consists of structures entering and leaving the lung at hilum.

Answer 28

root of lung

Note:
The root of lung is surrounded by a tubular sheath derived from the mediastinal pleura.

Question 29

The __________ is the area on the mediastinal surface of the lung through which structures enter or leave the lung.

Answer 29

hilum

Question 30

The root of lung consists of the following structures:

Answer 30

1. Principal bronchus in the left lung, and eparterial and hyparterial bronchi in the right lung.
2. Pulmonary artery.
3. Pulmonary veins (two in number).
4. Bronchial arteries (one on the right side and two on the left side).
5. Bronchial veins.
6. Lymphatics of the lung.
7. Anterior and posterior pulmonary plexuses of the nerves.

Question 31

Arrangement of structures in the roots of the lungs from before backwards (it is more or less similar on two sides):

Answer 31

(a) Pulmonary vein (superior)
(b) Pulmonary artery
(c) Bronchus (left principal bronchus on the left side, and eparterial, and hyparterial bronchus on the right side).
Mnemonic: VAB (Vein, Artery, and Bronchus).

Question 32

Arrangement of structures in the roots of the lungs from above downwards on the right side:

Answer 32

1. Eparterial bronchus
2. Pulmonary artery
3. Hyparterial bronchus
4. Inferior pulmonary vein

N.B. The difference in the arrangement of structures from above downwards on the two sides is because right principal bronchus before entering the lung at hilum divides into two lobar bronchi, the upper lobar bronchus passes above the pulmonary artery (eparterial bronchus) and lower lobar bronchus passes below the pulmonary artery (hyparterial bronchus).

Question 33

Arrangement of structures in the roots of the lungs from above downwards on the left side:

Answer 33

1. Pulmonary artery
2. Left principal bronchus
3. Inferior pulmonary vein

N.B. The difference in the arrangement of structures from above downwards on the two sides is because right principal bronchus before entering the lung at hilum divides into two lobar bronchi, the upper lobar bronchus passes above the pulmonary artery (eparterial bronchus) and lower lobar bronchus passes below the pulmonary artery (hyparterial bronchus).

Question 34

State the relations of the root of the lung.

Answer 34

Anterior:
➣ Phrenic nerve.
➣ Anterior pulmonary plexus.
➣ Superior vena cava (on right side only)
Posterior:
➣ Vagus nerve.
➣ Posterior pulmonary plexus.
➣ Descending thoracic aorta (on left side only).
Superior:
➣ Arch of azygos vein (on right side only).
➣ Arch of aorta (on left side only).
Inferior:
➣ Pulmonary ligament.

Question 35

Internal structure of lungs (airways). The lung is mainly made up of two things. State them.

Answer 35

1. Intrapulmonary bronchial tree; concerned with the conduction of air to-and-fro from the lung.
2. Pulmonary units; concerned with the gaseous exchange within the lung.

Question 36

The bronchial tree consists of? (4 things)

Answer 36

1. Principal bronchus (right and left)
   a. Right principal bronchus is shorter, wider, and more vertical. It is about 1 inch (2.5 cm) long and lies more or less in line with the trachea.
   b. Left principal bronchus is narrower, longer, and more horizontal than the right. It is about 2 inches (5 cm) long and does not lie in line with the trachea.
2. Lobar bronchi - On entering the lung, the right principal bronchus divides (gives off) three lobar bronchi, one for each lobe of the right lung. The left principal bronchus on entering the lung divides into two lobar bronchi, one for each lobe of the left lung.
3. Terminal bronchioles
4. Respiratory bronchioles

Important to note regarding number 3 and 4:
Each lobar bronchus divides into segmental (tertiary) bronchi, one for each bronchopulmonary segment.
The segmental bronchi divide repeatedly to form very small bronchi called terminal bronchioles. The terminal bronchioles give off respiratory bronchioles, which lack cartilage in their walls.
Each respiratory bronchiole aerates a small portion of lung called pulmonary units, which is concerned with gaseous exchange within the lung.

Question 37

What does each pulmonary unit contain?

Answer 37

(a) alveolar ducts, (b) atria,
(c) air saccules, and (d) alveoli

Note:
Emphysema: In this condition, alveoli of lungs are damaged by chemicals released by pollutants. Clinically it presents as shortness of breath and the chest appears barrel shaped in chest radiograph.

Question 38

The lungs are supplied by two sets of arteries, which are?

Answer 38

1. Bronchial arteries.
2. Pulmonary arteries.

Question 39

Describe the arterial supply of the lungs by bronchial arteries.

Answer 39

➣ The bronchial arteries supply nutrition to the bronchial tree and pulmonary tissue.
➣ The right lung is supplied by one bronchial artery, which arises from the right third posterior intercostal artery or from upper left bronchial artery.
➣ The left lung is supplied by two bronchial arteries, which arise from descending thoracic aorta.

Question 40

Describe the arterial supply of the lungs by pulmonary arteries.

Answer 40

➣ The pulmonary arteries supply deoxygenated blood to the lungs. There is one pulmonary artery for each lung. They are the branches of the pulmonary trunk.
➣ The right and left pulmonary arteries lie anterior to the principal (primary) bronchi as they enter the hilum of their respective lungs. [Diagram: hila of the lungs]
➣ The right pulmonary artery is crossed superiorly by the arch of the azygos vein; whereas the left pulmonary artery lies inferior to the arch of aorta, at the level of T5 vertebra.
➣ The pulmonary arteries divide into lobar branches in the hilum and subsequently divide into terminal/segmental branches. The segmental branches branch successively corresponding with the segmental branches of the bronchial tree.

NB: All the arteries of the body supply oxygenated blood except pulmonary arteries, which supply deoxygenated blood to the lungs.

Question 41

State the venous drainage of the lungs.

Answer 41

Bronchial veins: The bronchial veins drain the deoxygenated blood from the bronchial tree and pulmonary tissue. There are two bronchial veins on each side:
➣ The right bronchial veins drain into azygos veins.
➣ The left bronchial veins drain into hemiazygos vein or left superior intercostal vein.

[5-minute video]: Azygos and Hemiazygos veins

Pulmonary veins: The pulmonary veins drain the oxygenated blood from the lungs. There are two pulmonary veins on each side.
➣ The pulmonary veins do not accompany the pulmonary arteries. The tributaries of pulmonary veins are intersegmental, while branches of pulmonary arteries are segmental in distribution.

Note: All the veins in the body drain deoxygenated blood except pulmonary veins, which drain the oxygenated blood from the lungs.

Question 42

Describe the nerve supply to the lungs.

Answer 42

➣ supplied by both parasympathetic and sympathetic nerve fibers, both providing motor supply to the bronchial muscles and secretomotor supply to the mucous glands of the bronchial tree.
➣ parasympathetic fibers cause bronchoconstriction/bronchospasm, vasodilatation, and increased mucous secretion.
➣ sympathetic fibres cause bronchodilatation, vasoconstriction, and decreased mucous secretion.
➣ the afferent impulse arising from the bronchial mucous membrane and stretch receptors in the alveolar walls pass to the central nervous system through both sympathetic and parasympathetic fibres.

Question 43

The bronchopulmonary segments are well-defined, wedge-shaped sectors of the lung, which are aerated by tertiary (segmental) bronchi. List the bronchopulmonary segments in the right lung.

Answer 43

Superior lobe:
➣ apical
➣ posterior
➣ anterior
Middle lobe:
➣ lateral
➣ medial
Inferior lobe:
➣ superior
➣ medial basal
➣ anterior basal
➣ lateral basal
➣ posterior basal

Question 44

List the bronchopulmonary segments in the left lung.

Answer 44

Superior lobe:
➣ apical
➣ posterior
➣ anterior
➣ superior lingular
➣ inferior lingular
Inferior lobe:
➣ superior
➣ medial basal
➣ anterior basal
➣ lateral basal
➣ posterior basal

Question 45

State the characteristic features of the bronchopulmonary segments.

Answer 45

1. It is a subdivision of the lobe of the lung.
2. It is pyramidal in shape with apex directed towards the hilum and base towards the surface of the lung.
3. It is surrounded by the connective tissue.
4. It is aerated by the segmental (tertiary) bronchus.
5. Each segment has its own artery, a segmental branch of the pulmonary artery.
6. Each segment has its own lymphatic drainage and autonomic supply.

Question 46

How has the knowledge of bronchopulmonary segments led to the advancement in conservation lung surgery?

Answer 46

Since each segment is an independent functional unit having its own bronchovascular supply and potential planes of separation exist between the segments. Localized chronic disease, such as tuberculosis, bronchiectasis or benign neoplasm is restricted to one segment; it is, therefore, possible to dissect out and remove the diseased segment leaving the surrounding tissue intact. This procedure is called segmental resection.

Further notes:
➣ During segmental dissection, it is important not to ligate intersegmental veins as they will interfere with the venous drainage of the surrounding healthy segments.
➣ Segmental resection is most often carried out in bronchiectasis. [Bronchiectasis is a long-term condition where the airways of the lungs become widened, leading to a build-up of excess mucus that can make the lungs more vulnerable to infection.]