Role of lungs

In humans and most animals, including a few fish and snails, the lungs are the major organs of the respiratory system. In mammals and many other creatures, two lungs are located near the backbone on either side of the heart. Gas exchange occurs in the respiratory system when oxygen is extracted from the atmosphere and transferred to the circulation, as well as when carbon dioxide is released from the lymph system. Various muscle mechanisms in different species promote respiration. The pharyngeal muscles drove air into the lungs in earlier tetrapods by buccal pumping, which is still found in amphibians. In humans, the diaphragm is the main respiratory muscle, and it is involved for breathing. The lungs also provide airflow, which allows for vocal sounds such as human speech.

STRUCTURE AND ANATOMY OF LUNGS

The lungs, also known as respiratory organs, are a duo of cone-shaped body parts that are divided from each other by the heart and other mediastinum frameworks in the thoracic cage.

It also features a medial surface, as well as anterior, posterior, and inferior borders. The rib cage is forced against the large coastal surface of the lungs, whereas the smaller mediastinal surface faces medially. 

The right lung is a little bit bigger and heavier than the left. Because the heart is on the left side, the left lung is smaller than the right and also has a myocardial appearance to support it. The lingual is a narrow tongue-like protrusion formed by indenting the inferior and anterior sections of the superior lobe.

Pleura

A serous pleural sac, made up of two continuous membranes, surrounds and invests each lung. The lungs are surrounded by the visceral or pulmonary pleura. The pulmonary cavities are lined by the parietal pleura, which is attached to the thoracic wall, mediastinum, and diaphragm.

The parietal pleura is divided into four sections: the costal pleura, which lines the internal surface of the thoracic wall, the mediastinal pleura, which lines the lateral aspect of the mediastinum, the diaphragmatic pleura, which lines the superior surface of the diaphragm on each side of the mediastinum, and the cervical pleura, which extends through the superior thoracic aperture into  root of the neck, forming a cup-shaped dome over the apex of  lung.

Pleural Cavity

The pleural cavity is the potential space between the visceral and parietal layers of the pleural membrane, and it includes a capillary layer of serous pleural fluid that lubricates the pleural surfaces and allows them to slide over each other smoothly during respiration. The cohesion that keeps the lung surface in touch with the thoracic wall is provided by the surface tension caused by the pleural cavity.

Lobes and Fissures of the Lungs: Fissures separate each lung into lobes.

An oblique fissure runs through both lungs, and a transverse fissure runs through the right. The superior and inferior lobes of the left lung are separated by an oblique fissure. The superior, middle, and inferior lobes of the lungs are separated by an oblique and horizontal fissure. As a result, the right lung has three lobes and the left has only two.

A lobar bronchus supplies each lobe. Bronchopulmonary segments, which are fed by segmental bronchi, separate the lobes.

Bronchopulmonary Segment

The lungs are functionally separated into bronchopulmonary segments. Bronchopulmonary segments are the lobe’s greatest subdivision. They are surgically respectable and are divided from adjacent segments by connective tissue septa. In the left lung, there are 10 bronchopulmonary segments and 8-10 in the right lung.

The bronchi divide further, eventually forming bronchioles with a diameter of less than 1mm. Each bronchiole is divided into 50 to 80 terminal bronchioles, which are the respiratory bronchioles’ ultimate branches. The respiratory bronchioles, alveolar ducts, and sacs, as well as the alveolar, make up the acinus, which is the functional unit of the lungs. From the trachea to the terminal bronchioles, there are approximately 16 generations of branching. The structure of the lungs’ walls changes as the air pathways become narrower.

ROLE OF LUNGS

Exchange of Gases: The following is how gas exchange happens:

Transport Of Oxygen

Oxyhemoglobin, a chemical composition of oxygen with hemoglobin, and oxygen solution in blood plasma are two types of oxygen in the blood that are delivered to the tissue.

When the concentration of oxygen in the blood is high, it mixes with hemoglobin to form hemoglobin. Oxyhemoglobin dissociates to release oxygen because it is unstable. Oxygen deprivation, moderate pH, and extreme heat speed up the dissociation process.

Internal Respiration

Internal respiration refers to the gaseous exchange that occurs within the tissues. The oxygen transported in the form of oxyhemoglobin is dissociated here, allowing oxygen to be released.

The glucose is broken down by the oxygen, releasing carbon dioxide, water, and energy. The body uses the energy as the carbon dioxide is released from the tissues.

Transport Of Carbon dioxide From Tissues to Lungs: There are three ways for transporting carbon dioxide:

• Carbonic acid is formed when carbon dioxide dissolves with plasma water.
• Bicarbonate ions are formed when carbonic acid are ionizes. Carbonic anhydrase is an enzyme that catalyzes the production of hydrogen ions. Sodium bicarbonate and potassium bicarbonate are formed when bicarbonate ions mix with sodium and potassium.
• Carbaminohemoglobin is formed when carbon dioxide interacts with hemoglobin.

Finally, it reaches the lungs and is expelled from the body during expiration.

Intrapleural Breathing

The pressure that exists in the space between the pleura and the lungs is referred to as intrapleural breathing. Pleural cavity is the name given to this area. Normally, the pressure in this area is lower than that of the surrounding atmosphere. Pleural pressure is also known as negative pressure because of this.

The pressure gradient that exists between the pleura and the lungs controls lung movement. Transpulmonary pressure is defined as the difference in pressure between the intrapulmonary and intrapleural pressures.

When you breathe, the pressure in your pleural cavity drops, while the transpulmonary pressure rises, causing your lungs to expand. As a consequence of an increase in thoracic pressure during expiration, the lungs rebound.

The production of negative intrapleural pressure is caused by conflicting forces inside the thorax, one of which is linked to the lungs’ flexibility. The lungs have elastic tissues that force them inwards away from the thoracic wall. The surface tension of the alveolar fluid also causes an inward pressure on the lung tissue. Forces from the thoracic wall and the pleural fluid oppose the inward tension caused by the lungs.

Respiratory Gas Transport

After the gases have dispersed in the lungs, causing the blood to become oxygenated and leaving carbon dioxide behind, the oxygen-rich blood is transported to the tissues in the next step. For the cycle to continue, the next round of deoxygenated blood must be delivered to the lungs.

The movement of gases happens throughout the body in the bloodstream, which is aided by the cardiovascular system, which includes the blood arteries and the heart. Blood containing oxygen exits the lungs and flows into the heart via the pulmonary veins, before being pumped to the rest of the body via the aorta and its branches from the left ventricle.

CONCLUSION

Gas exchange, endogenous and foreign agent metabolism, and disease and chemical harm defence are all roles performed by the respiratory system. Its physical features and large number of specialised cells make it ideal for such tasks.