[Biology Class Notes] on Human Lung Pdf for EXAM

Respiration is carried out by different muscular systems in different species. Mammals, reptiles, and birds use their muscles to support breathing. In humans, the main muscle of respiration that supports breathing is the diaphragm. The lungs provide airflow that makes the vocal sounds including human speech possible.

In the respiratory system of humans, the lungs are considered the primary organs. In mammals and most other vertebrates, the lungs are located near the backbone on either side of the heart. The function of the lungs in the respiratory system is to carry oxygen from the atmosphere to the blood vessels and to release the carbon dioxide from the blood vessels into the atmosphere, in a process of gas exchange. 

Let us learn more about lungs, their features, anatomy, functions, and location. We will also discuss the disorders that can be caused.

Information about Lungs – Anatomy

• The lungs meaning is as follows are located on either side of the heart in the rib cage. The lungs are conical in shape, where the top of the lungs consists of a narrow round apex, and the base is broad concave-shaped. This base is situated on the surface of the diaphragm which is found to be convex-shaped. 

• The lungs can stretch from the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm.

• Some of the space that is dedicated to the left lung is shared with the heart and has an indentation in its border that is called the cardiac notch of the left lung. 

• The lungs are surrounded by the pulmonary pleura. The pleurae are two serous membranes; the inner wall of the rib cage is lined by outer parietal pleura lines and the surface of the lungs is lined by inner visceral pleura. The pleural cavity is present in between the potential space that is found in the structure called pleurae. This pleural cavity contains a thin layer of lubricating fluid called pleural fluid.

Right Lung

The right lung has different lobes and segments. The lobes are divided into three parts, an upper, middle, and lower lobe by two fissures that are oblique and horizontal. The upper horizontal fissure separates the upper lobe from the middle lobe. The lower oblique fissure separates the lower lobe from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.

The cardiac impression is the impression where the heart sits. The weight of the right lung varies between individuals in men and women, in men it varies from 155–720 g, and in the case of women, the weight of the right lung is about 100–590 g.

Left Lung

The left lung is divided into two lobes by an oblique fissure; they are an upper and a lower lobe. The left lung does not contain a middle lobe. There is a projection of the upper lobe that is termed as lingula means the “little tongue”, this projection is a homologous structure. The lingula on the left lung acts as the middle lobe, with both areas being predisposed to similar infections and anatomic complications. The lingula has two bronchopulmonary segments: superior and inferior.

The weight of the left lung in men is 110–675 g in women 105–515 g.

Features of Lungs

Lungs definition provides the major features of it, and the remaining ones are as follows:

• Humans have two lungs; they are right lung, and left lung, which is situated within the thoracic cavity of the chest. As the left lung shares some space with the heart, the right lung is said to be bigger than the left lung.

• The lungs together weigh approximately 1.3 kilograms. The lungs receive air breathed in via the conducting zone and are considered as the part of the lower respiratory tract that starts at the trachea and branches into the bronchi and bronchioles. 

• The conducting zone ends at the terminal bronchioles. These bronchioles divide into the respiratory bronchioles of the respiratory zone which divide into alveolar ducts that give rise to the alveolar sacs that include the alveoli that help in the exchange of gases.

• Alveoli are present on the walls of the respiratory bronchioles and alveolar ducts. The lungs contain 300 to 500 million alveoli and approximately 2,400 kilometers of airways. 

• Lung lobes definition is as follows, lungs are enclosed within a pleural sac that contains pleural fluid, which allows the inner and outer walls to slide over each other while the process of breathing, without much friction. This pleural sac helps to divide each lung into several sections called lobes. 

• The lobes are further divided into pulmonary lobules and bronchopulmonary segments. The lungs have a unique blood supply; they receive deoxygenated blood from the heart and release the carbon dioxide in the pulmonary circulation, and supply of oxygenated blood to the tissues of the lungs, in the bronchial circulation.

Conclusion

According to lungs meaning, it is understood that lungs are the most important organs that are required to survive. As every cell that is present in the body requires oxygen, and to gather oxygen that is present in the atmosphere is done by a process called breathing. This process of breathing is possible only in the presence of lungs in the body.