Biology

Respiratory System
Respiratory System constitutes organs and other parts of body that help breathe. When the muscle located under lungs, the diaphragm contracts and moves downward, the chest cavity spaces increases allowing lungs to expand. This allows lungs to accommodate air. The air is inhaled through nose. It then passes to pharynx. The lower part of pharynx is where the pathways of air and food cross each other. The food from oral cavity passes to oesophagus and the air from pharynx passes to larynx. A flap called epiglottis controls the flow of air and food. The nose, nasal cavities, sinuses, pharynx and upper part of larynx form the upper respiratory tract. The air passes from larynx to trachea. At the lower end, the trachea divides as inverted Y into two main bronchi, one for the left lung and the other for the right lung. The bronchi is divided into bronchioles and it further branches out to alveoli which are small air sacs. The walls of alveoli are covered by blood capillaries which help in replacing carbon-dioxide with oxygen and removing carbon-dioxide. The lower part of larynx, trachea and lungs form the lower respiratory tract. When the diaphragm expands, the process reverses, and air is exhaled out.

Parts of the respiratory system
• Nose is from where humans breathe air
• Pharynx is the common pathway for air and food. Epiglottis controls the switch between these two pathways
• Larynx is the voice box and it aids in respiration
• Trachea is below larynx. Air enters trachea from larynx. The lower end of trachea splits into 2 bronchi, one each for left and right lungs
• Lungs located on either side of heart helps in exchange of gases between the blood and air

Functions of respiratory system
• Helps in breathing
• Provides oxygen to the cells
• Removes carbon-dioxide and other waste gases from the body
• Protects airways from harmful particles
• Helps to smell and create sound