The respiratory system - The lungs Flashcards
What does each lung consist 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.
Describe the lobes of the lungs
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.
Describe the surfaces of the lungs?
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
Describe the anterior, posterior, and inferior borders of the lungs
The anterior border of the lung is formed by the convergence of the mediastinal and costal surfaces. On the left lung, the anterior border is marked by a deep notch, created by the apex of the heart. It is known as the cardiac notch.
The inferior border separates the base of the lung from the costal and mediastinal surfaces.
The posterior border is smooth and rounded (in contrast to the anterior and inferior borders, which are sharp). It is formed by the costal and mediastinal surfaces meeting posteriorly.
What is the lung root and what does it contain?
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.
Where do the structures of the lung leave?
All these structures enter or leave the lung via the hilum – a wedge shaped area on its mediastinal surface.
Describe the vasculature of the lungs
The lungs are supplied with deoxygenated blood by the paired pulmonary arteries. Once the blood has received oxygenation, it leaves the lungs via four pulmonary veins (two for each lung).
The bronchi, lung roots, visceral pleura and supporting lung tissues require an extra nutritive blood supply. This is delivered by the bronchial arteries, which arise from the descending aorta.
The bronchial veins provide venous drainage. The right bronchial vein drains into the azygos vein, whilst the left drains into the accessory hemiazygos vein.
