The Lungs

Question 1

Answer 1

Question 2

• The lungs are the major organs of respiration. They are located in the chest, either side of the mediastinum.
• The function of the lungs is to oxygenate blood. They achieve this by bringing inspired air into close contact with oxygen-poor blood in the pulmonary capillaries.

Answer 2

Question 3

Anatomical Position and Relations

• The lungs lie either side of the mediastinum, within the thoracic cavity.
• Each lung is surrounded by a pleural cavity, which is formed by the visceral and parietal pleura.
• They are suspended from the mediastinum by the lung root – a collection of structures entering and leaving the lungs.
• The medial surfaces of both lungs lie in close proximity to several mediastinal structures:

Answer 3

Anatomical relations of the medial lung surface.

Question 4

Lung Structure?

Answer 4

The lungs are roughly cone shaped, with an apex, base, three surfaces and three borders.

• The left lung is slightly smaller than the right – this is due to the presence of the heart.

Each lung consists of:

• Apex – The blunt superior end of the lung. It projects upwards, above the level of the 1st rib and into the floor of the neck.
• Base – The inferior surface of the lung, which sits on the diaphragm.
• Lobes (two or three) – These are separated by fissures within the lung.
• Surfaces (three) – These correspond to the area of the thorax that they face. They are named costal, mediastinal and diaphragmatic.
• Borders (three) – The edges of the lungs, named the anterior, inferior and posterior borders.

Question 5

Lung StructAttach Imagesure - Lobes?

Answer 5

The right and left lungs do not have an identical lobular structure.

• The right lung has three lobes; superior, middle and inferior. The lobes are divided from each other by two fissures:
• Oblique fissure – Runs from the inferior border of the lung in a superoposterior direction, until it meets the posterior lung border.
• Horizontal fissure– Runs horizontally from the sternum, at the level of the 4th rib, to meet the oblique fissure.
• The left lung contains superior and inferior lobes, which are separated by a similar oblique fissure.

Question 6

Lung Structure - Surfaces?

Answer 6

Surfaces

• There are three lung surfaces, each corresponding to an area of the thorax.
• The mediastinal surface of the lung faces the lateral aspect of the middle mediastinum.
• The lung hilum (where structures enter and leave the lung) is located on this surface.
• The base of the lung is formed by the diaphragmatic surface. It rests on the dome of the diaphragm, and has a concave shape.
• This concavity is deeper in the right lung, due to the higher position of the right dome overlying the liver.
• The costal surface is smooth and convex. It faces the internal surface of the chest wall. It is related to the costal pleura, which separates it from the ribs and innermost intercostal muscles.

Question 7

Position of the Lungs?

Answer 7

Question 8

Lung Structure - Root and Hilum

Answer 8

• The lung root is a collection of structures that suspends the lung from the mediastinum.
• Each root contains a bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonary plexus of nerves and lymphatic vessels.
• All these structures enter or leave the lung via the hilum – a wedge shaped area on its mediastinal surface.

Question 9

Answer 9

Question 10

Lung Structure - Bronchial Tree?

Answer 10

The bronchial tree is a series of passages that supplies air to the alveoli of the lungs. It begins with the trachea, which divides into a left and right bronchus.

• Note: The right bronchus has a higher incidence of foreign body inhalation due to its wider shape and more vertical course.
• Each bronchus enters the root of the lung, passing through the hilum. Inside the lung, they divide to form lobar bronchi – one supplying each lobe.
• Each lobar bronchus then further divides into several tertiary segmental bronchi. Each segmental bronchi provides air to a bronchopulmonary segment – these are the functional units of the lungs.
• The segmental bronchi give rise to many conducting bronchioles, which eventually lead into terminal bronchioles.
• Each terminal bronchiole gives off respiratory bronchioles, which feature thin walled outpocketings that extend from their lumens.
• These are the alveoli – the site of gaseous exchange.

Question 11

Vasculature of the lung

Answer 11

Question 12

Structure of the Pleurae?

Answer 12

• The pleurae refer to the serous membranes that line the lungs and thoracic cavity.
• They permit efficient and effortless respiration.

Question 13

Structure of the Pleurae?

Answer 13

• There are two pleurae in the body – one covering each lung. They consist of a serous membrane – this is a layer of mesothelial cells, supported by connective tissue.

Each pleura can be divided into two parts:

• Visceral pleura – covers the lungs.
• Parietal pleura – covers the internal surface of the thoracic cavity.

These two parts are continuous with each other at the hilum of each lung. There is a potential space between the viscera and parietal pleura, known as the pleural cavity.

Question 14

Answer 14