Do you really know where the lungs are?

The lung is a very important organ in the human body and an important part of the respiratory system. However, most people do not know much about the lungs. Many people do not know where the lungs are. In fact, the lungs are located in the chest, connected to the throat, one on each side. Let's take a closer look at them!

The lungs are located in the chest and connected to the throat. There is one lung on each side. They are the highest organs in the human body, so they are called the canopy of the five internal organs. Because the lung lobes are delicate, cannot tolerate cold or heat, and are easily invaded by pathogens, they are also called the "delicate organ." It is the place of the soul and the master of qi, and belongs to metal in the five elements. The hand Taiyin lung meridian and the hand Yangming large intestine meridian are interconnected and belong to the lung and large intestine, so the lung and large intestine are the exterior and interior of each other. The blunt and rounded end of the lung is called the apex, which protrudes upward through the upper opening of the thorax into the base of the neck. The bottom is located above the diaphragm. The surface facing the ribs and intercostal spaces is called the costal surface, and the surface facing the mediastinum is called the medial surface. The entrance and exit of the bronchi, blood vessels, lymphatic vessels and nerves in the center of this surface is called the hilum. These structures entering and exiting the hilum are wrapped together by connective tissue and are called the lung root. The left lung is divided into two lobes, the upper and lower lobes, by the oblique fissure. In addition to the oblique fissure, the right lung is also divided into three lobes, the upper, middle, and lower lobes, by a horizontal fissure. It is one of the important organs of the human body.

Before the fetus is born, the lungs have no respiratory function, are densely structured, have a specific gravity greater than 1 (1.045-1.056), and will sink when put into water. After birth, the baby begins to breathe. The alveoli are filled with air, becoming spongy and with a specific gravity of less than 1 (0.345-0.746), so it can float in water. Forensic scientists often use this to determine the time of fetal death.

Alveoli: Hemispherical sacs composed of a single layer of epithelial cells. The bronchi in the lungs branch repeatedly into countless bronchioles, whose ends swell into sacs, surrounded by many protruding small vesicles, which are alveoli. The alveoli vary in size and shape, with an average diameter of 0.2 mm. An adult has about 300 to 400 million alveoli, with a total area of ​​nearly 100 square meters, which is several times larger than the surface area of ​​human skin. Alveoli are the main site of gas exchange in the lungs and are also the functional units of the lungs. Oxygen diffuses from the alveoli to the blood through four membranes: the liquid membrane on the inner surface of the alveoli, the alveolar epithelial cell membrane, the interstitium between the alveolar epithelium and the endothelium of the pulmonary capillaries, and the endothelial cell membrane of the capillaries.

Composition of alveoli: Small alveolar cells, also known as type I alveolar cells, are about 0.1 microns thick, have a basement membrane at the base, and have no ability to proliferate.

Large alveolar cells, also known as type II alveolar cells, secrete surfactant (dipalmitoylphosphatidylcholine) to reduce alveolar surface tension.

Lung macrophages are derived from blood monocytes. Those that engulf more dust particles are called dust cells, while heart failure cells are macrophages that appear in the lungs of heart failure patients and engulf the iron-containing hemoglobin that is broken down by hemoglobin.

The alveoli are closely connected to the pulmonary capillaries. The membranes of the two are mostly fused, which facilitates the rapid diffusion of gases. The alveolar surface liquid layer, type I alveolar cells and basement membrane, thin layer of connective tissue, capillary basement membrane and endothelium constitute the so-called air-blood barrier.