Question

Gien below is a list of different steps (i-vi) involved in lofiction, 1 Utistion of \(\mathrm{O}_{2}\) by the cells for catabolic reactions. 12 Irensport of gases by the blood. (1) Plmonary ventilation by which atmospheric air is dam in and \(\mathrm{CO}_{2}\) is released out. \(x\) (iv) Release of resultant \(\mathrm{CO}_{2}\). (v) Diffusion of \(\mathrm{O}_{2}\) and \(\mathrm{CO}_{2}\) between blood and tissues. (vi) Diffusion of gases \(\left(\mathrm{O}_{2}\right.\) and \(\left.\mathrm{CO}_{2}\right)\) across alveolar tissues. Select an option which has correct sequence of all the steps. (a) (iii), (vi), (ii), (v), (i), (iv) (b) (iii), (vi), (i), (v), (ii), (iv) (c) (iv), (ii), (v), (iii), (i), (vi) (d) (iv), (vi), (ii), (v), (i), (iii)

Short answer

The correct sequence is (a) (iii), (vi), (ii), (v), (i), (iv).

Step-by-step solution

- Understanding the process of respiration

Recognize that the process of respiration involves several steps, beginning with the inhalation of oxygen (O2) from the atmosphere and ending with the release of carbon dioxide (CO2) as a waste product from the cells.

- Determining the Correct Order of Steps

The correct sequence of events in the respiration process should start with pulmonary ventilation (iii), then the diffusion of gases across the alveolar tissues (vi), followed by the transport of gases by the blood (ii), then diffusion between blood and tissues (v), utilization of O2 in the cells (i), and finally, release of CO2 (iv).

- Matching the Sequence to the Options

Compare the correct sequence of steps derived in the previous step to the options given. The option that correctly represents the sequence from pulmonary ventilation to the release of CO2 is the right answer.

Key concepts

Pulmonary Ventilation

Pulmonary ventilation, commonly referred to as 'breathing', is the process that initiates respiration by moving air into and out of the lungs. This mechanism involves two main phases: inhalation and exhalation.

Inhalation occurs when the diaphragm and intercostal muscles contract, enlarging the thoracic cavity and reducing the air pressure inside the lungs below that of the atmosphere, causing air to rush in. During exhalation, these muscles relax, the thoracic cavity decreases in size, and the air pressure within the lungs rises, pushing the air out.

Effective pulmonary ventilation maintains the concentration gradients necessary for the diffusion of gases, without which the respiratory system could not properly function.

Diffusion of Gases

The diffusion of gases is a critical process within the respiratory system, relying on simple passive diffusion principles. After pulmonary ventilation brings fresh air into the alveoli, diffusion moves oxygen from the alveoli into the blood and carbon dioxide in the opposite direction.

'Partial Pressure' - A Key Driver

Diffusion is driven by the partial pressure differences between the gases in the alveoli and the blood; oxygen diffuses into the blood where its partial pressure is lower, and carbon dioxide diffuses out into the alveoli where its partial pressure is lower compared to the blood.

Across Alveolar Membranes

The gases must pass through the alveolar and capillary walls, which are thin enough to allow efficient exchange and sustain life.

Transport of Gases by Blood

Once diffusion has occurred at the alveoli, the blood takes over the responsibility of transporting gases to and from the tissues. Oxygen is chiefly bound to hemoglobin in red blood cells, forming oxyhemoglobin, while a small fraction is dissolved in the plasma.

Carbon dioxide, being more soluble in plasma, is transported mainly in three forms:

• Bicarbonate ions, which form as a result of a reaction with water,
• Bound to proteins, particularly hemoglobin, as carbaminohemoglobin,
• Dissolved directly in the plasma.

These transport mechanisms work efficiently to provide oxygen to every cell and remove the metabolic waste product, carbon dioxide, maintaining the body's acid-base balance.

Respiratory System

The respiratory system is a complex network responsible for the exchange of gases vital to living organisms. This system includes both upper respiratory tract components, such as the nose and pharynx, and lower respiratory tract components, like the larynx, trachea, bronchi, and lungs.

The prime function of this system is to facilitate the process of gas exchange, providing oxygen to the bloodstream and expelling carbon dioxide from the body. Each component plays a role; the nose filters and humidifies air, the bronchi distribute air to the lungs, and the alveoli are the sites of gas exchange.

Moreover, the respiratory system contributes to vocalization, smell, and—with the help of the muscular and nervous systems—regulation of blood pH levels. It's integral to sustaining life, orchestrating with other systems to maintain homeostasis.