Respiratory System at Rest

Structure of the Respiratory System

The respiratory system is composed of a group of organs and tissues that help you breathe.
This includes the nasal cavity, pharynx, larynx, trachea, bronchi, and lungs. Together they filter, warm, and humidify air on its way to the lungs.
The pleura is a membrane that covers the lungs and lines the inside of the chest cavity to reduce friction as you breathe.
The lungs are a pair of organs located within the chest; they are made of spongy, elastic tissue that stretches and constricts as we breathe.
Inside the lungs are branching passages called bronchi and bronchioles, which end in tiny air sacs called alveoli.

The process of breathing, or respiration, is controlled by the respiratory centre in the brainstem, which sends signals to the respiratory muscles.
Diaphragm and intercostal muscles play a vital role in the mechanism of respiration.
As the diaphragm contracts and the intercostal muscles lift the ribs, the chest cavity expands, causing air to flow into the lungs.
As the diaphragm and intercostal muscles relax, the chest cavity contracts, pushing air out of the lungs.
Inhalation is the process of taking air into lungs and exhalation is the process of breathing out.
At rest, an adult breathes in and out gently about 12-20 times per minute.

The primary function of the respiratory system is to supply the body with oxygen and remove carbon dioxide.
This occurs in the alveoli, which are surrounded by a network of tiny blood vessels called capillaries.
Oxygen is transported from the alveoli into the blood stream, then circulated to cells throughout the body.
At the same time, waste carbon dioxide moves in the opposite direction – from the capillaries to the alveoli – and is then exhaled.
This process of gas exchange is done via diffusion - moving from an area of high concentration to an area of lower concentration.

The protein molecule in red blood cells called haemoglobin binds with oxygen molecules in the lungs.
Each molecule of haemoglobin can bind with up to four molecules of oxygen.
The oxygenated blood then travels back to the heart to be pumped around the rest of the body.
As cells use the oxygen in cellular respiration, haemoglobin releases oxygen and picks up the produced carbon dioxide.

Lung capacity, the total amount of air that can be held in the lungs, can be increased with regular aerobic exercise and training.
Optimal lung function is key to physical performance and overall health as it ensures that every cell in the body receives sufficient oxygen for metabolism.
The health of the respiratory system can be negatively impacted by factors like smoking, air pollution, and exposure to allergens and irritants.