[Biology Class Notes] on Pleura Pdf for Exam

The human respiratory system is responsible for the process of respiration in human beings. The main organs of the respiratory system are the pair of lungs. The structures that are involved in the respiratory passage are the External nostril, nasal chambers, internal nares, nasopharynx, larynx, trachea, bronchi and bronchioles, and then alveoli at the last. The pleura is the name given to the covering that is present in the lungs. They have visceral and parietal pleura. This is the name given to the inner layer and external layer of the pleura. We will learn more about what is pleura, pleural membrane and pleura membrane. 

Lungs

There are a pair of lungs present in human beings. They are present in the thoracic cavity and it is an air-tight chamber. The thoracic cavity is also known as the chest cavity. This cavity is present on the dorsal side of the vertebral column, and on the ventral side, the sternum is present. Ribs are present on the lateral side of the lungs. Below the lungs, the diaphragm is present. This is a dome-shaped structure and it is made up of muscles. This is also responsible for separating the thoracic cavity and abdominal cavity. Pleura and pleural membrane are the two membranes that help in enclosing the lungs. With the thoracic cavity, the outer pleural membrane is in very close contact. And with the lung’s surface, the inner pleural membrane is in close contact. Pleural fluid is the fluid that is present in the fluid cavity. This fluid is secreted by the pleural membrane. The inner layer is called the visceral pleura and parietal pleura is the outermost layer. This helps us to understand what is pleura. 

[]

The Function of Pleural Fluid

As we read above about the pleura, pleural membrane and pleural fluid, now we will learn about the function of the pleural fluid. This fluid helps in lubricating the pleural membranes. This is because at the time of breathing these membranes may slide over each other and if friction is present then it will result in problems of the pleural membrane. So this fluid helps in reducing the friction. Any damage to the lungs or to the pleural membrane then it will affect the process of breathing. 

Structure of Lungs

After reading about what is pleura, now we will learn about the pleura anatomy and the structure of the lungs. At the time of birth, the lungs are pink in color. As we grow the lungs are covered with carbonaceous materials and due to this, they become dark grey and mottled. They become darker in color when they are exposed to smoking in adults and also when they are exposed to pollutants. Due to the raised position of the diaphragm, the right lung is smaller than the left lung and this is also due to the presence of the liver. Oblique fissure divides the left lung into two lobes and the right lung also has two fissures that are horizontal and oblique in nature. 

Steps Involved in Respiration

As we know, in human beings there are a lot of complex processes that take place in the process of respiration and breathing. 

There are Five Steps That are Involved in Respiration. 

• Breathing: Breathing is a simple process that involves taking in oxygen and then throwing out the carbon dioxide to the environment. Pulmonary ventilation is the other name for breathing. 

• Diffusion of Gases: After breathing, the gases are then diffused between the alveoli and the blood. Oxygen and carbon dioxide are exchanged across the alveolar membrane. This membrane is very thin and thus this helps in the exchange of gases.

• Transport of Gases: The gases are transported with the help of blood. 

• Diffusion of Gases Between Blood and Tissues: The oxygen is diffused into the blood and the carbon dioxide is diffused from the tissues to the blood. 

• Utilisation of Oxygen: The oxygen is then utilized by the cells and parts of the body.