Lungs

The lungs are located in the thoracic cavity, above the diaphragm, and on either side of the mediastinum. The right lung is wide and short because the right side of the diaphragm is higher due to the influence of the liver, while the left lung is narrow and long due to the leftward position of the heart. The surface of the lungs is covered by the dirty pleura, which is smooth and moist. Many polygonal cells are visible through the dirty pleura, which is the outline of the lung lobules. Today we will give a comprehensive introduction to an important organ of the human body: the lung.

1. Location and shape of the lungs

The lungs are semi-circular vertebral in shape, with an apex, a base, two surfaces, and three margins. The apex of the lung is rounded and obtuse, and protrudes through the upper thoracic opening to the root of the neck, exceeding 2.5 cm above the medial 1/3 of the clavicle. the base of the lung, also known as the diaphragmatic surface, is adjacent to the diaphragm and slightly concave above. The ribbed surface is rounded and broad, adjacent to the ribs and intercostal muscles.

2. Lobulation of the lung

The left lung is divided into two lobes, the upper and lower, by an oblique fissure that slopes upward and downward from the posterior to the medial side. The right lung is divided into upper, middle, and lower lobes by the oblique and horizontal fissures. Three lobes are sometimes seen in the left lung, and the right lung may have five lobes.

The right pulmonary hilum has an esophageal indentation posteriorly and an odd vein groove above. Above and posterior to the left pulmonary hilar are indentations of the aortic arch and thoracic aorta. Cardiac indentation is present anteriorly and inferiorly in both pulmonary hilum, particularly in the left lung.

The anterior margin is the anterior displacement of the rib surface and the mediastinal surface, and the anterior margin is sharp. There is a left pulmonary cardiac notch on the lower part of the anterior margin of the left lung, and the tongue-like protrusion below the notch is called the left pulmonary uvula.

3. Pulmonary hilum and pulmonary root

The pulmonary hilum is a depression in the middle of the mediastinal surface of the lung and is the site of entry and exit of the main bronchus, pulmonary artery, pulmonary vein, bronchial artery, bronchial vein, lymphatic vessels, nerves, etc. It is clinically known as the first pulmonary hilum.

The structures entering and exiting the pulmonary hilum are wrapped in a bundle of connective tissue, called the pulmonary root. The important structures within the pulmonary root are arranged from anterior to posterior as the upper pulmonary veins, pulmonary arteries, main bronchi, and lower pulmonary veins. From top to bottom, the left pulmonary roots are, in order, the left pulmonary artery, left main bronchus, left upper pulmonary vein, and left lower pulmonary vein; the right pulmonary roots are the right upper lobe bronchus, right pulmonary artery, middle bronchus, right upper pulmonary vein, and right lower pulmonary vein.

4. Intrapulmonary bronchi and bronchopulmonary segments

The main bronchus divides into lobar bronchi near the pulmonary hilum, which then divides into segmental bronchi after entering the lung lobes. Later, they branch out at several levels to form a bronchial tree.

Each lung segment bronchus and the lung tissue to which it belongs are collectively called bronchopulmonary segments. Each lung segment is distributed by one segmental bronchus. The branches of the pulmonary arteries and the branches of the bronchi accompanying them enter the lung segments, while the branches of the pulmonary veins are located between the two segments. When the bronchus of an adjacent lung segment is obstructed, air entry and exit of this segment are blocked.

According to the distribution of bronchial branches in the lung segments, the right lung is divided into 10 lung segments, and the left lung is divided into 8-10 lung segments. The apical and posterior bronchial segments of the upper lobe of the left lung, the medial bottom segment of the lower lobe, and the anterior bottom segment of the bronchus often originate from a common stem, so the left lung can also be divided into 8 lung segments.

5. Blood vessels, lymph, and nerves of the lung

Vascular: The lung has two sets of vascular systems, one is the pulmonary artery and pulmonary vein, which are responsible for gas exchange and are the functional vessels of the lung; the other is the bronchial artery and vein, which are involved in the body circulation and supply oxygen and nutrients and are the nutritive vessels of the lung.

The pulmonary artery starts from the arterial trunk, which emanates from the right ventricle and travels upward to the left via the left main bronchus anteriorly and posteriorly to the aortic arch below the left and right pulmonary arteries. The right pulmonary artery is longer and enters the pulmonary hilum posterior to the ascending aorta and superior vena cava, below the arch of the odd vein.

Bronchial arteries: They originate from the thoracic aorta or the right posterior intercostal artery, often with two branches on each side, are small and travel with the bronchi, branching along the way to form a capillary network that nourishes the bronchial walls, pulmonary vascular walls, and pulmonary pleura in the lungs.

Lymph: The lymphatic vessels of the lung are very rich and are divided into two groups: superficial and deep. The superficial group of lymphatic vessels is on the deep surface of the pulmonary pleura, which receives lymph from the deep surface of the dirty pleura and converges into the bronchopulmonary lymph nodes.

Nerves: The nerves of the lungs come from the vagus nerve and branches of the thoracic sympathetic trunk. They form the pulmonary plexus anterior and posterior to the pulmonary roots, and branches of both plexuses enter the lung tissue with the bronchial branches.

The lungs are an important organ for gas exchange between our body and the outside world and are closely related to everyone’s health.  When the lungs are good, all diseases disappear. Improving the breathing ability of the lungs, lung health, and lung strength, can not be delayed.