Breathing and Exchange of Gases

Breathing and Exchange of Gases

Introduction

• Organic compounds like carbohydrates, proteins, and fats are broken down to derive energy, requiring oxygen (O2) and releasing carbon dioxide (CO2).
• The process of exchanging O2 from the atmosphere with CO2 produced by cells is called breathing or respiration.

Respiratory Organs

• The mechanism of breathing varies among different animal groups, depending on their habitats and levels of organization.
• Lower invertebrates like sponges, coelenterates, and flatworms exchange O2 and CO2 through simple diffusion over their entire body surface.
• Earthworms use their moist cuticle, and insects have a network of tubes (tracheal tubes) to transport atmospheric air within the body.
• Aquatic arthropods and molluscs use gills (branchial respiration), while terrestrial forms use lungs (pulmonary respiration) for gas exchange.
• Vertebrates like fishes use gills, while amphibians, reptiles, birds, and mammals respire through lungs.

Human Respiratory System

• Nose:
• A pair of external nostrils leads to a nasal chamber, which opens into the pharynx, a common passage for food and air.
• Pharynx:
• The pharynx opens into the larynx region, which leads to the trachea.
• Larynx:
• The larynx is a cartilaginous box that helps in sound production and is called the sound box.
• During swallowing, the glottis can be covered by a thin elastic cartilaginous flap called the epiglottis to prevent food from entering the larynx.
• Trachea:
• The trachea is a straight tube that extends up to the mid-thoracic cavity, dividing into a right and left primary bronchi at the level of the 5th thoracic vertebra.
• Bronchi and Bronchioles:
• Each bronchi undergoes repeated divisions to form secondary and tertiary bronchi and bronchioles, ending in very thin terminal bronchioles.
• The tracheae, primary, secondary, and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings.
• Each terminal bronchiole gives rise to a number of very thin, irregular-walled, and vascularized bag-like structures called alveoli.

Learn about the role of oxygen and carbon dioxide in cellular respiration, and how they are exchanged during breathing. Understand the importance of oxygen for energy production and the removal of carbon dioxide.