Pleura & Lung Anatomy

PLEURAE

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Q.1 What is pleura?

It is a serous membrane, lined by mesothelium. There are two pleural sacs, one on either side of the mediastinum.

Q.2 What are the parts of the pleura?

Outer layer: Parietal pleura.

Inner layer: Visceral pleura.

The two layers are continuous with each other at the hilum of the lung.
The two layers enclose between them a potential space known as the pleural cavity

Q.3 What are the parts of the parietal pleura?

Costal: Lines the thoracic wall and is loosely attached to it by areolar tissue.

Diaphragmatic: Lines upper surface of diaphragm.

Mediastinal: Lines mediastinum.

Cervical: Extends into the neck and covers the apex of the lung. Covered by Sibson’s fascia.

Q.4 What is the extent of cervical pleura in the neck?

It extends two inches above the first costal cartilage and one inch above medial ½ of clavicle.

Q.5 What are the relations of cervical pleura?

Anteriorly: Subclavian artery and Scalenus anterior muscle.

Posteriorly: Neck of first rib with its relations.

Medially: Large vessels of neck.

Laterally: Scalenus medius 

Q.6 What is ‘Pulmonary ligament’? What are its functions?

It is parietal pleura surrounding the root of the lung which hangs down as a fold called pulmonary ligament.

Functions:

• It provides dead space into which veins of lung can expand when venous return increases.
• Because of it, lung root can descend with the descent of diaphragm.
  
  

Q.7 What are the ‘recesses of pleura’?

These are folds of parietal pleura, which act as reserve spaces, into which lungs can expand during deep inspiration.

 Three in number:

• Costomediastinal recess:
  Present in cardiac notch of left lung anteriorly, between costal and mediastinal pleurae.
  
  
• Costodiaphragmatic recess:
  On both sides inferiorly, between costal and diaphragmatic pleurae.
  
  

Q.8 What are the parts of the lung not covered with visceral pleura?

At hilum and along the attachment of pulmonary ligament where it is continuous with parietal pleura.

Q.9.1 What is the nerve supply of pleura?

• Parietal pleura: Pain sensitive.

Intercostal nerves: Costal and diaphragmatic pleurae at periphery

Phrenic nerves: Mediastinal and central part of diaphragmatic pleurae.

• Visceral pleura: Pain insensitive. 

Sympathetic nerves (T2-T5).

Q.9 What is the arterial supply of pleura?

Parietal pleura:
Intercostal arteries, Internal thoracic arteries, and Musculophrenic arteries.

Visceral pleura: Bronchial arteries

Q.10 What is the lymphatic drainage of pleura?

Parietal pleura:
Lymphatics drain into intercostal, internal mammary, mediastinal and diaphragmatic lymph nodes.

Visceral pleura:
Drained by bronchopulmonary lymph nodes.

Q.11 What is the developmental origin of pleura?

Parietal pleura:
Somatopleural layer of lateral plate mesoderm.

Visceral pleura:
Splanchnopleural layer of lateral plate mesoderm.

Q.12 What is the surface marking of the pleura?

Cervical pleura:
Curved line forming a dome over the medial 1/3 of the clavicle. The apex of the curve lies 2.5 cm. above the clavicle.

Anterior margin:

• On the right side:
  From sternoclavicular joint downwards and medially to midpoint of sternal angle, where it continues vertically downwards to the midpoint of the xiphisternal joint.
  
  
• On the left side:
  Same course up to fourth costal cartilage, where it arches and descends along the sternal margin of 6th costal cartilage, about 3 cm from the midline.
  
  
• Inferior margin:
  Laterally from the lower limit of anterior margin, so that it crosses the 8th rib in the midclavicular line, 10th rib in mid axillary line, and 12th rib at lateral border of sacrospinalis. Then horizontally to lower border of T12 vertebra, about 2 cm from the midline.
  
  
• Posterior margin:
  From a point 2 cm lateral to 12th thoracic spine to a point 2 cm lateral to 7th cervical spine.
  
  

 Q.13 What are the places at which pleura descends below the costal margin?

• Right costoxiphoid angle.
• Right costovertebral angle below 12th rib.
• Left costovertebral angle below 12th rib.
  
  

 Q.14 What is Pneumothorax?

 A pneumothorax is produced by the presence of air in the pleural cavity.

 Q.15 What is hemothorax?

It is the blood in the pleural cavity.

Q.16 What is pleural effusion?

It is the accumulation of free fluid in the pleural cavity.

Q.17 What is empyema?

It is the accumulation of pus in the pleural cavity.

Q.18 What is ‘Paracentesis thoracis’ and from which site it is done?

It is the process of aspiration of any fluid from the pleural cavity.

Done in 6th intercostal space in mid axillary line.

Q.19 What are the structures pierced during paracentesis?

The structures pierced from outward to inwards in the midaxillary line are:

Skin, fascia, serratus anterior muscle, intercostal muscles, and parietal pleura to reach the pleural cavity.

Q.20 What precaution should be taken during aspiration from the pleural cavity?

Needle should be pricked in the lower part of intercostal space to avoid injury to intercostal nerves and vessels in costal groove

Lungs

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Q.1 What is a bronchopulmonary segment?

The main bronchus on each side gives off branches to each lobe of the lung, lobar bronchus.

Each lobar bronchus then divides into segmental bronchi, each of which supplies a segment of the lung called a bronchopulmonary segment. Each segmental bronchus is accompanied by a branch of the pulmonary artery and a tributary of the pulmonary vein. The arteries lie posterolateral to the corresponding bronchi. Pulmonary veins tend to run between adjacent bronchopulmonary segments, therefore each vein may drain more than one segment.

Each bronchopulmonary segment is therefore a self-contained, functionally independent respiratory unit of lung tissue. These segments are wedge-shaped with their apices at the hilum and bases at the lung surface. Each is surrounded by connective tissue continuous with that of the visceral pleura. There are also veins which run between the segments and are called intersegmental veins.

Q.2 Name the bronchopulmonary segments of the two sides.

Each bronchopulmonary segment receives its name from that of its supplying segmental bronchus.

Right side	Left side
Upper lobe	Upper lobe
Apical segment	Apical
Posterior segment	Posterior
Anterior segment	Anterior
Middle lobe	Lingular
Lateral segment	Superior lingular
Medial segment	Inferior lingular
Lower lobe	Lower lobe
Apical (superior) segment	Apical (superior)
Medial basal segment	Medial basal
Anterior basal segment	Anterior basal segment
Lateral basal segment	Lateral basal segment
Posterior basal segment	Posterior basal segment

On the left side, the upper lobe bronchus gives off a combined apico-posterior segmental bronchus whereas on the right they arise separately as apical and posterior segmental bronchi.

The left upper lobe has a lingular segment which is equivalent to the right middle lobe.
On the right side there is a medial basal segmental bronchus which is absent on the left.

Q.3 Why the knowledge of the bronchial tree and bronchopulmonary segments is important?

 It is important:

• During bronchoscopy
• For correct interpretation of bronchograms
• To determine the appropriate posture for promoting drainage of infected areas of lung
• For surgical resection of a single or a number of diseased bronchopulmonary segments without affecting the function of the remaining segments.
  
  

Q.4 How do the bronchopulmonary segments drain?

Each segment is drained by a vein and an artery. The vein is located in the periphery, whereas the artery and its branches are located in the center of the segment.

Q.5 What are the differentiating features of the two lungs?

The right lung has three lobes while the left lung has two lobes.

The thin, sharp anterior border of the right lung is vertical while that of the left lung presents a cardiac notch.

On the medial surface (mediastinal surface) of the lung, the cardiac impression is much deeper on the left than on the right.

The right lung is wider than the left because of the smaller cardiac impression.

The right lung is shorter than the left because of the higher position of the right dome of the diaphragm.

Q.6 Name the structures in the root of the lungs.

• Principal bronchus on the left side and eparterial and hyparterial bronchi on the right side.
• One pulmonary artery.
• Superior and inferior pulmonary vein.
• Bronchial arteries: One on right and two on the left side.
• Bronchial veins.
• Anterior and posterior pulmonary plexuses of nerves.
• Lymphatics of lung.
• Bronchopulmonary lymph nodes.
• Areolar tissue.
  
  

Q.7 At what level the root of lungs lie?

Opposite body of T5-7 vertebra.

Q.8 What is the blood supply of the lungs?

The bronchial arteries and not the pulmonary arteries supply the lungs. This is so as the pulmonary arteries carry the deoxygenated blood.

Q.9 What are the relations of the structures at the root of the lung?

From above downwards (differs on two sides)

Right lung	Left lung
• Eparterial bronchus • Pulmonary artery • Hyparterial bronchus • Inferior pulmonary vein	• Pulmonary artery • Bronchus • Inferior pulmonary vein

From before backward (similar on two sides):

• Superior pulmonary vein, • Pulmonary artery and • Bronchus

 

Q.10 What is the surface marking of the oblique fissure of the lung?

It corresponds approximately with the medial border of the scapula when the arm is raised above the shoulder. The fissure may be represented by a line drawn obliquely from a point 2 cm, lateral to the 4th thoracic spine on the right side and at a slightly higher level on the left side to another point on the 5th rib in the midaxillary line and a third point on the 6th costal cartilage about 7.5 cm from the midline.

Q.11 Where can the breath sound of the apical segment of the lower lobe be heard on auscultation?

Posteriorly below the upper end of the oblique fissure.

Q.12 Give the surface marking of the horizontal fissure of the right lung.

 It corresponds approximately with a line drawn horizontally at the level of the 4th costal cartilage anteriorly. This line meets that of the oblique fissure in the midaxillary line.

Q.13 WHAT IS THE ‘LINGULA’ OF THE LEFT LUNG?

The upper lobe of the left lung corresponds with the upper and middle lobes of the right lung. The part of it which corresponds to the middle lobe is called the ‘lingula’ because it projects anteriorly to form the lingula (tongue-shaped structure) below the cardiac notch.

Q.14 What is the ‘azygos lobe'?

The azygos vein is occasionally deeply embedded in the apex of the right lung, partly isolating its medial portion. This isolated medial portion of the right lung is referred to as the ‘azygos lobe’.

Q.15 What is ‘sequestration of lung'?

An area of lung not having any communication with the bronchial passages. Most frequently seen in the lower lobe of the left lung.

Q.16 What is the lymphatic drainage of the lung?

The lymphatics of the lung drain centripetally from the pleura towards the hilum into the bronchopulmonary lymph nodes. Efferents of these nodes drain into the tracheobronchial nodes which drain into the paratracheal nodes and the mediastinal lymph trunks. These lymph trunks drain directly into the brachiocephalic vein, or occasionally, indirectly via the right lymphatic duct or the thoracic duct.

Q.17 What are the structures related to the medial side of the right lung?

The structures related to the medial side of the right lung include:

• Pulmonary veins
• Pulmonary artery
• Upper and main bronchus

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