Respiratory System in Humans

Respiration is very essential for living organisms. While breathing is the exchange of O2 from the atmosphere with CO2 produced by the cells, respiration is the oxidation of nutrients in living cells to release energy for biological activities. Lungs and air passages are part of the human respiratory system. The lungs enable the regulation of blood pressure and facilitate gas exchange between the lungs and blood. They also protect against infection (the mucosal membrane is present inside the lungs) and help with homeostasis. The airway passage transports atmospheric air from the nose into the alveoli, cleans it of foreign particles, humidifies it, and brings it to body temperature.

Parts Of Respiratory System

• Nose

The nose includes external nostrils, vestibule, nasal cavity, sinuses, and internal nostrils which open into the nasopharynx. Respiratory epithelium is made up of mucus membrane that prevents entry of microbes. Hair prevents dust and pollutants from entering the respiratory pathway.

• Pharynx

The nasopharynx is a part of the pharynx and is a common passage for food and water.

• Larynx

The larynx is made up of cartilage which aids in the generation of sound. The vocal cords are situated in the larynx, which is also known as the soundbox or voice box. The epiglottis (a thin elastic cartilaginous flap) shuts the glottis during swallowing to prevent food from entering the larynx.

• Trachea

The trachea, all bronchi, and initial bronchioles are supported by incomplete rings of cartilage. The respiratory pathway from the trachea to the respiratory bronchioles is called the tracheobronchial tree. The trachea divides into the right and left bronchi, which enter into the right and left lungs respectively.

• Bronchi and bronchioles

The notch at which the bronchus enters into the lung is called a hilum. The bronchi divide, and form bronchioles (diameter 1 mm). 

• Lungs

Lungs are situated in the thoracic chamber and rest on the diaphragm. The human body contains paired lungs – The right lung and left lung. The two lungs are separated by the heart. The right lung has 3 lobes and is larger and heavier than the left lung, which has 2 lobes. 

Anatomy Of lungs –

• Lungs get surrounded by double-layered pleura (outer parietal pleura and inner visceral pleura).
• The fluid present between the parietal and visceral pleura is known as the pleural fluid. The fluid provides lubrication to the surface of the lungs and prevents friction between two membranes.
• Lungs include Bronchi, bronchioles and alveoli.
• Alveoli and associated ducts are the respiratory part or exchange parts of the respiratory system.
• Alveoli are the structural and functional units of lungs and approx. 700 million alveoli are present in total, 350 million in each lung.

Process Of Gaseous Exchange 

The pharynx collects air from the mouth or nose and transports it to the larynx. After travelling through the larynx, or voice box, it enters the trachea. The trachea is a strong tube with cartilage rings to keep it from collapsing. Within the lungs, the trachea divides into left and right bronchus. Bronchioles, which are tiny branches, are further divided. The smallest bronchioles terminate in air sacs called alveoli.

During inhalation, the lungs expand whereas during exhalation, the lungs contract. During the gaseous exchange, oxygen is transported from the lungs to the bloodstream. At the same time, carbon dioxide is delivered from the bloodstream to the lungs. This happens in the lungs, between the alveoli and a network of small blood vessels called capillaries that run through the alveoli’s walls. Capillaries show red blood cells moving across them. A membrane connects the alveolar and capillary walls. This allows oxygen and carbon dioxide to move easily from the lungs to the bloodstream. As red blood cells return to the heart, oxygen molecules bond to them. Whenever a person exhales, the carbon dioxide molecules in the alveoli are expelled out of the body at the same time. Gas exchange is how the body replenishes oxygen and removes carbon dioxide.

Conclusion

Respiration is the process through which the body expels out carbon dioxide by inhaling oxygen from the air. The air that enters the body is impure and unfit, so, the airway passage filters, humidifies, and brings the air to body temperature. Lungs are the primary organ of respiration and facilitate gaseous exchange between blood and lungs. The oxygen is then transported to tissues through blood and carbon dioxide is removed through blood.