the lungs and breathing 2.2.2

• diffusion is the net movement of particles from an area of high concentration to an area of low concentration, down a concentration gradient
• an exchange surface is a specialised structure in the body that allows the exchange of materials to the body and environment
• alveoli are small gas exchange structures in the lungs
• through the alveoli, oxygen moves into blood through diffusion and carbon dioxide moves out of the blood by diffusion
• ventilation moves in and out of the alveoli and helps maintain a steep diffusion gradient
• the alveoli has very thin alveolus walls that give a short diffusion distance to make diffusion easy
• the spherical shape of the alveolus gives a relatively large surface area for diffusion
• the alveoli has a good blood supply that maintains the concentration gradient for diffusion by removing oxygen and bringing lots of carbon dioxide
• the process of gas exchange happens continually in the lungs and the alveoli
• the diaphragm separated the lungs from the abdomen
• the ribcage protects the lungs
• the lungs are located in the upper part of the body (thorax)
• the trachea carries air from the nose
• as the ribs move up and out, and the diaphragm flattens, the volume of the chest increases, the increased volume means there’s a lower pressure in the chest, contrasting to the higher pressure outside the lungs, causing air to be drawn in
• as the ribs fall and the diaphragm moves up, the volume of the chest gets smaller and the decreased volume means an increased pressure in the chest which is higher than the outside pressure so air is forced out of the lungs
• Deoxygenated blood arrives at the lungs from the heart via the pulmonary artery. The lungs oxygenate (supply oxygen to) the blood before it returns to the heart through the pulmonary vein
• The trachea divides into two tubes called the bronchi.
• The bronchi divide to form bronchioles
• The bronchioles divide until they end up in tiny air sacs called alveoli.
• there are millions of alveoli that are surrounded by a network of capillaries, allowing for oxygen and carbon dioxide to be exchanged between the blood in the capillaries and the air in the lungs.