Respiration is an act of breathing:
- Exhalation (Expiring) – Giving off carbon dioxide
- Inhalation (Inspiration) – Taking in oxygen
Respiratory system comprises of the organs involved in breathing. These organs include:
- Trachea
- Larynx
- Pharynx
- Lungs
- Nose
- Bronchi
Organs in upper respiratory tract include:
- Trachea
- Frontal sinuses
- Nose
- Maxillary sinus
- Ethmoidal air cells
- Larynx
- Nasal cavity
Organs in lower respiratory tract include:
- Alveoli
- Lungs
- Bronchi
Upper Respiratory Tract:
Nose is made up of cartilage, muscle and bone. Air enters from the external nostrils that are lined with hairs for removing large debris from inhaled air. Air flows into nasal cavity, located behind the nose. Nasal cavity is made up of nasal passages, known as meatuses. Nasal conchae curl into cavity for creating meatuses.
Mucus membrane surrounds nasal cavity. This membrane contains cilia, hair-like structures. It also contains goblet cells for the secretion of mucus. Both cilia and mucus trap particles which enter nasal cavity through air. Cilia pushes foreign particles towards pharynx. In pharynx, these particles are swallowed and broken down in the stomach.
Mucus membrane contains network of blood vessels. Heat produced by the blood vessels is transferred to nasal cavity and air is warmed. Water gets evaporated from mucous and contributes for the air warmth.
Many sinus cavities are situated round the nasal cavity. These are filled with air and also lined with mucus membrane which continues from nasal cavity.
Pharynx serves as a way for air from nasal cavity and also for food from oral cavity. Food gets into esophagus while swallowing, that makes a cartilage flap, known as epiglottis. This covers the opening of larynx for preventing food from entering airways.
Lower Respiratory Tract:
Epiglottis remains open for air to enter into larynx. Larynx contains vocal cords. These vibrate when sir forces them and sound is produced.
Trachea is 12 cm long, that is lined with cilia and mucus membrane, similar to nasal cavity. Further mucous warms the incoming air and cilia moves trapped particle towards pharynx for swallowing.
Trachea gives rise to primary bronchi which supply left and right lungs. Left bronchus divides into inferior and superior bronchi. Right bronchus is further divided into 3 lobar bronchi which supply oxygen to various parts of lungs: inferior, middle and superior. These secondary bronchi are further divided into segmental or tertiary bronchi. These are nearly 8 – 10 in each lung.
Bronchi branches into bronchioles that further divide till they supply alveolar ducts. These terminate at alveolar sacs. These alveolar sacs consists of alveoli.
The microscopic blood vessels surround the alveoli. These blood vessels begin as arterioles and carry blood from heart to alveoli in lungs. Arterioles become capillaries. Exchange of gas takes place between blood and air in the capillaries. This is known as external respiration. Capillaries become venules. These venules carry oxygenated blood back to heart for circulating in the entire body.
Respiratory system organs work combinedly to clean and warm the air which bring oxygen to alveoli sac in the lungs. Removal of carbon dixoide from blood is done and exits the body through which it entered originally. This is called respiration.
