Respiratory Organs
The process of respiration involves the continuous exchange of oxygen (O2) and carbon dioxide (CO2) between cells and the environment. Different organisms have evolved unique adaptations for gas exchange:
- Lower invertebrates such as sponges and flatworms exchange gases through diffusion across their body surfaces.
- Earthworms utilize their moist skin, while insects employ a tracheal system for internal gas transport.
- Aquatic organisms like fish possess gills for branchial respiration, whereas terrestrial animals including mammals, amphibians, and reptiles breathe through lungs.
In particular, the human respiratory system features a complex structure:
1. Nasal Passage: Air enters through external nostrils leading to the nasal chamber, which warms and humidifies the incoming air.
2. Pharynx and Larynx: The pharynx serves as a common passage for air and food, leading to the larynx, also known as the sound box.
3. Trachea: The trachea divides into primary bronchi, which branch into secondary and tertiary bronchi, connecting to thousands of tiny alveoli where gas exchange occurs.
4. Lungs: The lungs, located in a thoracic cavity, are responsible for gas exchange via the alveoli, where oxygen diffuses into the blood, and carbon dioxide is expelled.
Breathing involves two primary processes: Inspiration (drawing air in) and Expiration (expelling air out), facilitated by muscular contractions that alter thoracic cavity volume. Key volumes associated with breathing, such as tidal volume, inspiratory reserve volume, and vital capacity, are clinical indicators of respiratory health. Overall, the human respiratory system is efficient in facilitating the essential exchange of gases necessary for cellular metabolism.