Respiration

Introduction:

Last time we discussed about how blood gets to various parts of the body (i.e. blood circulation). Now we are going to discuss how oxygen from the atmosphere gets to the individual cells for metabolism (i.e. respiratory system).

The Lungs:

These paired organs are the most important organs of the respiratory system. They serve as the center where the exchange of gases majorly oxygen and carbon dioxide between the blood and air occurs. They are located at the left and right side of the thorax (chest). They are elastic and have the ability to recoil. They are covered by a fluid containing sac called pleura (the fluid help to resist friction).

Conducting tubes:

These are tubes that have air-conducting abilities generally called tracheobronchial tree. These tubes are lined by mucous which keeps them moist. These tubes are; the trachea, bronchus and bronchioles.

Note: for respiration to occur, 3 conditions are required; presence of blood vessels, presence of a thin membrane or surface (through which the air can pass through) and presence of a moist surface (to properly dissolve and conduct air)

Alveolar sacs:

These sacs are numerous in number and located at the end of the conducting tubes inside the lungs. They have two membranes; one containing air and the other containing blood vessels from the heart.

What is air?

Air with respect to respiration is a combination or mixture of gases mostly oxygen and carbon dioxide.

Why do we need air?

Oxygen present in the air is required by the cells for production of energy through metabolism. The equation below represents this reaction.

6O₂ (Oxygen) + C₆H₁₂O₆ (Glucose) => 6CO₂ (Carbon dioxide) + 6H₂O (Water vapor) + Energy (ATP)

In the above reaction (this occurs in the cell level), 6 molecules of oxygen (from the blood to the cells) combust one molecule of glucose (from digested food gotten from blood to the cells). 6 molecules of carbon dioxide, 6 molecules of water vapor and energy in form of ATP (adenosinetriphosphate) are produced. This energy is used by the cells while the carbon dioxide and the water vapor are carried via the blood to the lungs where they are exchanged, and further carried to the nose as air to be exhaled.

How oxygen gets to the cells:

Inspired (inhaled) air rich in oxygen are taken in through the nostrils. This air is conducted by the conducting tubes to the lungs. In the lungs, inside the numerous alveolar sacs, there are two membranes as stated above (one containing air and the other containing blood capillaries from the heart). There is exchange between the carbon dioxide-rich blood from the pulmonary artery of the heart and the oxygen-rich air in the alveolar sacs. After the exchange, the blood in these capillaries become rich in oxygen while the air in the lung’s alveolar sac become rich in carbon dioxide. The carbon dioxide- rich air flows out of the nostrils as it is exhaled while the oxygen-rich blood in the capillaries flows into the larger pulmonary vein and head straightway to the heart. Reaching the heart, the oxygen rich blood flows into the left atrium (a compartment in the heart) and the process continues as I explained in blood circulation.

How carbon dioxide gets to the lungs:

As I explained above, carbon dioxide is a by-product of metabolism (i.e. the breakdown of glucose by oxygen to produce energy). Carbon dioxide is not needed in the body and have to be taken out of the body. After the production of carbon dioxide as a result of metabolism, carbon dioxide is taken into the blood (into blood capillaries) from the cells. From these capillaries to the venules (smaller veins), from venules to veins, from veins to the heart. From the heart via the pulmonary artery to lungs where the blood is oxygenated (oxygen added and carbon dioxide removed).

Remember to visit your doctor whenever you observe any difficulty in breathing before it escalates to another serious issue. Stay healthy, live positive and breathe safely.