RESPIRATORY SYSTEM

The epiglottis is a flap of cartilage located in the throat behind the tongue and in front of the larynx. The epiglottis is usually upright at rest allowing air to pass into the larynx and lungs. When a person swallows the epiglottis folds backward to cover the entrance of the larynx so food and liquid do not enter the windpipe and lungs. After swallowing the epiglottis returns to its original upright position.

Vital capacity is the amount of air that one can inhale with maximum effort and also exhale with maximum effort. Vital Capacity (VC) = Tidal Volume (volume of air normally expired or inspired in one breath without effort) + Inspiratory Reserve Volume (Extra air inhaled forcibly after normal inspiration) + Expiratory Reserve Volume (Extra air exhaled forcibly after normal expiration). Total lung capacity (TLC) is the sum of VC and residual volume (RV) which is left in the lung after forced expiration. Thus, we can say that, VC = TLC-RV.

• Atmospheric oxygen is lower at higher altitudes. In higher altitudes, the air pressure is lower, meaning that there are fewer molecules of oxygen present in the air. The body acclimates to this in various ways, a major one of which is by increasing the number of red blood cells. This helps in distributing the available oxygen faster and more efficiently.

• Gills are feathery organs full of blood vessels. A fish breathes by taking water into its mouth and forcing it out through the gill passages. As water passes over the thin walls of the gills, dissolved oxygen moves into the blood and travels to the fish’s cells.

Each lung is enclosed by two membranes known as pleura or pleural membranes. The outer membrane is in contact with the thoracic cavity whereas inner membrane is in close contact with lung surface.

When CO₂ concentration in blood increases, breathing becomes faster and deeper. The effect of rising CO₂ concentration is due to decrease in affinity of Hb for O₂. Thus, the CO₂ released in the tissues accelerates the delivery of O₂ (called Bohr effect), due to which breathing becomes faster and deeper.

The Cartilaginous disc in the trachea prevents the trachea from collapsing during the absence of air and protects it. These cartilaginous rings are C-shaped.

A total of 38 molecules of ATP are produced during aerobic respiration of one molecule of glucose.
Summary of ATP synthesis:
8 ATP from glycolysis
6 ATP from acetyl Co-A (Coenzyme-A)
24 ATP from Krebs’ cycle.
Total – 38 ATP from aerobic oxidation of one molecule of glucose.

Glycolysis is a part of cellular respiration and is common to both aerobic and anaerobic respiration. It occurs in the cytosol of the cells. It is an enzyme-controlled ten steps reaction by which glucose, fructose or sucrose is reduced to form 3 carbon compound pyruvate with the production of ATP and NADH.

The air sacs (alveoli) located in the lungs extract carbon dioxide brought by the blood from different parts of the body.

In some low-grade organisms, parasitic organisms, bacteria, yeasts and animal tissues, glucose is partially broken down into lactic acid or ethyl alcohol for energy. It is called anaerobic respiration because oxygen is not used in it.