Respiratory System at Rest | Physical Education for A Level - Year 13 PDF Download

Structure of the Respiratory System

• The respiratory system comprises various organs and tissues that facilitate breathing. 
• These include the nasal cavity, pharynx, larynx, trachea, bronchi, and lungs, which collectively filter, warm, and moisten air as it travels to the lungs. 
• The pleura, a protective membrane, envelops the lungs and lines the chest cavity's interior, minimizing friction during breathing. 
• The lungs, located in the chest, are composed of spongy, elastic tissue that expands and contracts with each breath. 
• Within the lungs, air passes through branching airways known as bronchi and bronchioles, terminating in tiny air sacs called alveoli.

The Process of Breathing

• Breathing, or respiration, is regulated by the respiratory center in the brainstem, which sends signals to the respiratory muscles. 
• The diaphragm and intercostal muscles are critical to this process. 
• When the diaphragm contracts and the intercostal muscles elevate the ribs, the chest cavity enlarges, allowing air to enter the lungs.
•  When these muscles relax, the chest cavity shrinks, expelling air from the lungs. 
• Inhalation refers to drawing air into the lungs, while exhalation is the act of expelling it. 
• At rest, an adult typically breathes gently 12–20 times per minute.

Gas Exchange

• The respiratory system's main role is to deliver oxygen to the body and eliminate carbon dioxide. 
• This exchange occurs in the alveoli, which are surrounded by a network of small blood vessels called capillaries.
• Oxygen moves from the alveoli into the bloodstream and is distributed to cells throughout the body. Simultaneously, carbon dioxide, a waste product, travels from the capillaries to the alveoli and is exhaled. 
• This gas exchange happens through diffusion, where substances move from areas of higher concentration to areas of lower concentration.

Role of Haemoglobin

• Haemoglobin, a protein in red blood cells, binds with oxygen in the lungs. 
• Each haemoglobin molecule can carry up to four oxygen molecules. 
• The oxygen-rich blood is then transported back to the heart, which pumps it throughout the body. 
• As cells use oxygen for cellular respiration, haemoglobin releases the oxygen and collects carbon dioxide produced by the cells.

Respiratory Health and Efficiency

• Lung capacity, the maximum volume of air the lungs can hold, can be enhanced through regular aerobic exercise and training. 
• Efficient lung function is essential for physical performance and overall health, ensuring that all body cells receive adequate oxygen for metabolism. 
• The respiratory system's health can be compromised by factors such as smoking, air pollution, and exposure to allergens and irritants.