Lungs

The left and right lungs sit on either side of the heart and great vessels which occupy the mediastinum. The bronchi, bronchioles, alveoli, blood vessels, together with a small amount of connective tissue and nerves and lymphatic vessels, form the substance of the left and right lungs.

Each lung has an oval area on its posterior aspect which is the communication between each lung and the rest of the body, this is called the hilus where the main bronchi and pulmonary blood vessels enter and leave.

The main bronchus enters each lung root with the corresponding pulmonary artery carrying deoxygenated blood from the heart. Two pulmonary veins leave the root, carrying oxygenated blood back to the heart. A small bronchial artery accompanies or is embedded in the wall of each bronchus.

Right Lung

The right lung has three lobes separated by the following fissures:

  1. Horizontal fissue

  2. Oblique fissure

The superior and middle lobes are separated by the oblique fissure and the middle and interior lobes by the oblique fissure.


The posterior surface of the right lung lies adjacent to the following structures:

  1. The heart

  2. Superior and inferior vena cava

  3. Azygos vein

  4. Esophagus

Left Lung

left lung.jpg

The left lung is slightly smaller than the right because the heart decreases the size of the left pleural cavity. The left left has two lobes separated by the following fissure:

  1. Oblique fissure

The posterior surface of the left lung lies adjacent to the following structures:

  1. The heart

  2. The aortic arch

  3. Thoracic aorta

  4. Esophagus

Pulmonary Vessels and Nerves:

  1. Pulmonary blood vessels - these vessels are part of pulmonary circulation and include the right and left pulmonary arteries that first branch off to lobar arteries and later tertiary segmental arteries. The pulmonary arteries are responsible for carrying deoxygenated blood.

  2. Bronchial blood vessels - these vessels are part of systemic circulation and small bronchial arteries are responsible fore conveying oxygenated blood to the lungs, while bronchial veins drain the lungs of deoxygenated blood, directly into the left atrium of the heart.

  3. Pulmonary nerves - the parietal pleura is innervated by nerves that also innervate the cutaneous layer and therefore pain associated with parietal pleura may be local or referred to the region of the same spinal dermatomes. The visceral pleura is innervated by nerves that innervate the viscera and therefore pain associated with viscera pleura may be referred to the region of C3 - C5 spinal nerves which is the region of the shoulder and root of the neck.