the respiritory system

• Bronchioles are smaller tubes branching off from bronchi, which lead to alveoli.
• Alveoli are tiny air sacs where gas exchange occurs between blood vessels and capilliaries.

  
• Each bronchus divides into many smaller branches called bronchioles.
• Bronchi are smaller tubes branching off from the trachea, with one going to each lung.
• Bronchioles are smaller tubes branching off from bronchi, which lead to alveoli.
• Lungs are protected by ribcage and diaphragm.
• Diaphragm is a muscle separating thoracic cavity from abdominal cavity, it contracts downward when we breathe in.
• Intercostal muscles are located between ribs, they contract upward during breathing out.
• Alveoli are tiny air sacs where gas exchange occurs.
• Capillaries surround alveoli, allowing oxygen to diffuse across them and enter bloodstream.
• Capillaries surround alveoli, allowing gases to diffuse across them.
• Oxygenated blood enters lungs through pulmonary veins, while deoxygenated blood leaves through pulmonary arteries.
• Carbon dioxide diffuses into alveoli through capillary walls.
• Oxygenated blood flows back to heart via pulmonary vein.
• The process of breathing involves inspiration (inhaling) and expiration (exhaling).
• Deoxygenated blood flows to lungs via pulmonary artery.
• Oxygenated blood enters left atrium through pulmonary vein.
• Deoxygenated blood leaves right ventricle through pulmonary artery.
• Pulmonary circulation carries deoxygenated blood from heart to lungs and back again.
• During inspiration, the diaphragm contracts downward, increasing volume of thorax and decreasing pressure inside it.
• Inspiration causes air to rush into lungs due to lower pressure inside compared to outside.
• Intercostal muscles are located between ribs and aid in breathing by expanding chest wall during inspiration.
• Expiration occurs when these muscles relax, causing the thorax to return to its original position and increasing pressure inside the chest cavity relative to atmospheric pressure.
• Inspiration is an active process that requires contraction of diaphragm and external intercostal muscles.
• Inspiration is caused by contraction of diaphragm muscle and external intercostal muscles, which increases thoracic cavity volume and decreases pressure inside it compared to atmospheric pressure outside.
• During inspiration, volume of thoracic cavity increases, causing pressure inside it to decrease relative to atmospheric pressure.
• The alveoli have thin walls with a single layer of epithelial cells called pneumocytes.
• Pulmonary capillaries surround the alveoli and exchange gases through diffusion.
• Breathing rate, also known as frequency, f, is the number of breaths taken in one minute.
• The average resting breathing rate is approximately 12-15 breaths in a minute.
• Tidal volume, TV, is the amount of air inspired or expired in a normal breath.
• The average resting tidal volume is approximately 500 ml.
• Minute ventilation, VE, is the amount or volume of air inspired or expired in one minute and can be calculated by multiplying tidal volume, TV, by breathing rate, f.
• The average resting TV is 500 ml and the average resting f is 15, so the average resting VE is 7500 ml/min or approximately 7.5 litres per minute.
• During sport and physical activity, tidal volume, f and therefore minute ventilation, VE, all increase to make more oxygen available for the working muscles.