This animation illustrates the human respiratory system in an unprecedented way. Let's do this fantastic journey together. Not only oxygen, which is important for us, is part of the air we breathe. Water also enters our respiratory system, as well as other gases like krypton, or even radioactive radon. In addition, small and large particles are part of the air, which shouldn't enter our lower respiratory tract.
For this reason, the upper airways provide certain protective mechanisms. Large dirt particles or insects are stopped in the nasal cavity by our nasal hair. Small particles are trapped by the nasal mucosa.
Ciliated cells are located on the nasal mucosa. These cilia move in a wave-like manner. This allows the cilia to push the nasal mucus produced by the goblet cells towards the pharynx. Consequently, small particles that have been caught by the nasal mucus are swallowed. This process is called mucociliary clearance.
Furthermore, the upper airways such as the nasal and oral cavities warm and moisten inspired air. During the act of swallowing, the epiglottis, which is connected to the tongue, ensures that no food or liquid can enter the lower respiratory tract. To do this, the epiglottis closes the larynx during swallowing so that the bolus slides into the esophagus. The trachea, right below the larynx, is surrounded by incomplete rings of hyaline cartilage for reinforcement. Near the heart, the trachea branches into two main bronchi.
The main bronchi lead to the left and right lungs. The left lung has only two lobes, upper and lower, whereas the right lung has three lobes. The centrally located heart pumps deoxygenated blood to the lungs through the pulmonary arteries.
Oxygenated blood returns to the heart through the pulmonary veins and eventually to all organs. The main bronchi form the trunks for the bronchial tree. Like the branches of a tree, the tubular system of the lung starts here, into finer and finer branches. The right lung has three lobes with 10 lung segments. Each lung segment receive its own air and blood supply.
At the ends of the bronchial tree are tiny air sacs called alveoli. It is estimated that humans have 300 to 400 million alveoli. Large branches with cartilage are called bronchi. Thin branches at the end of a bronchial tree are called bronchioles. Instead of cartilage, bronchioles are surrounded by elastic fibers and smooth muscle.
The exchange of gases occurs with the help of the alveoli. Individual alveoli are found on the walls of the bronchioli respiratory. Several alveoli are grouped together at the end of a bronchioli respiratory to form an alveolar sac, which is supplied by one alveolar duct. Alveoli are approximately 50 micrometers in size.
They enlarge considerably during inhalation. Alveoli are largely composed of thin cells called type 1 pneumocytes. These cells are extremely thin, allowing oxygen and carbon dioxide to diffuse. Air, with the required oxygen, enters the alveoli via the alveolar duct. This is where gas exchange begins.
All alveoli are covered with a network of thin blood vessels. Deoxygenated blood can thus be enriched with oxygen and at the same time release unneeded carbon dioxide into the alveoli. This is done with the help of red blood cells that erythrocytes. Erythrocytes move through the blood vessels and take up the oxygen, shown here in blue.
Iron, Fe, in these blood cells is responsible for binding the oxygen. An iron ion can bind to one oxygen molecule so that the oxygen can be transported. At the same time, the carbon dioxide in the bloodstream and emitted by red blood cells diffuses into the alveoli.
This is made possible by diffusion. In the alveoli, we see a lot of oxygen, whereas in the blood vessels, there is a lot of carbon dioxide. This difference in concentration is eventually balanced by diffusion. This is how the differences in concentration are equalized. Let's now look at how air and therefore oxygen is transported into our lungs.
Our body has various muscles that inflate and deflate the lungs. The muscles of the neck are responsible for fixing and raising the sternum and upper ribs, and certain muscles between the ribs raise and lower all the other ribs. However, the most important muscle of respiration is not found in the neck or chest area, but near the abdomen.
The thoracic diaphragm, or simply diaphragm, is responsible for most of the work of breathing. First, let's take a closer look at chest breathing through the neck and rib muscles. Due to their arrangement and the contraction of the rib muscles, the ribs rotate outward. This causes an increase in volume, particularly in the lower regions, that is the caudal ribs.
The rib movement can be imagined similar to the handle of a bucket. The handle is shown here in red. Therefore it is called bucket handle motion. The increase in chest volume occurs not only laterally, but also sagittally. The sternum rotates as well, as seen here.
This is called pump-handle motion, because the movement of the sternum can be thought of as the motion of a pump handle. Thus, one can easily visualize the increase and decrease in volume of the lungs. When the lungs inflate, a negative pressure is created in the lungs and we breathe in. When the lungs deflate, positive pressure is created and air is forced out of our lungs.
We breathe out. Inhalation. Exhalation. Inhalation, exhalation. Here we can see the inhalation and exhalation process from below.
As noted earlier, in addition to chest breathing, we can use diaphragmatic breathing. It can be performed separately or in cooperation with chest breathing. Diaphragmatic breathing is the natural way of breathing at rest.
During diaphragmatic breathing, the diaphragm rises and lowers. When it rises, we exhale. When it lowers, we breathe in. In order for the lungs to inflate and deflate, the body has a pleura. The pleura serves as a lube outside of the lungs, to allow for up and down motions against the chest wall.
For this reason, the inner pleura covers the lungs. The outer pleura lines the ribcage and diaphragm. This allows the inner pleura to shift against the outer pleura. Between these two layers is the pleural cavity, shown here in yellow.