Respiratory system, Ventilation, Gas exchange. pg 33 & 35

• The lungs are in the thorax.
• The thorax is the top part of the body.
• The thorax is separated from the lower part of the body by a muscle called the diaphragm.
• The lungs are surrounded by the pleural membranes.
• The lungs are protected by the ribcage.
• The intercostal muscles run between the ribs.
• The air that you breathe in goes through the trachea. This splits into two tubes called bronchi, one going to each lung.
• The bronchi split into progessively smaller tubes called bronchioles.
• The bronchioles end as small bags called alveoli where the gas exchange takes place.
• Breathing in...

  1. Intercostal muscles and diaphragm contract (flattens out).
  2. Muscles between ribs pull ribcage and sternum up and out.
  3. Thorax volume increases.
  4. This decreases the pressure, drawing the air in.
• Breathing out...

  1. Intercostal muscles and diaphragm relax (moves up).
  2. Ribcage and sternum drop in and down.
  3. Thorax volume decreases.
  4. Air is forced out.
• Alveoli are little air sacs in the lungs which carry out gas exchange in the body.
• The blood passing next to the alveoli has just returned to the lungs from the rest of the body, so it contains lots of carbon dioxide and very little oxygen.
• Oxygen diffuses out of the alveolus (high concentration) into the blood (low concentration).
• Carbon dioxide diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out.
• When the blood reaches body cells, oxygen is released from the red blood cells (high concentration) and diffuses into the body cells (low concentration).
• Carbon dioxide diffuses out of the body cells (high concentration) into the blood (low concentration). It's then carried back to the lungs.
• The large number of microscopic alveoli give the lungs an enormous surface area.
• Alveoli have a moist lining for gases to dissolve in.
• The alveoli have very thin walls - only one cell thick, so the gases don't have far to diffuse.
• Alveoli have a great blood supply to maintain a high concentration gradient.
• Alveoli walls are permeable so gases can diffuse across easily.
• Smoking damages the walls inside the alveoli, reducing the surface area for gas exchange and leading to diseases like emphysema.
• The tar in cigarettes damages the cilia in your lungs and trachea.
• Cilia, along with mucus, catch a lot of dust and bacteria before they reach the lungs.
• The cilia help to keep the trachea clear by sweeping mucus back towards the mouth.
• When cilia are damaged, chest infections are more likely.
• Tar irritates the bronchi and bronchioles, and mucus is produced which can't be cleared very well by damaged cilia - this causes smoker's cough and chronic bronchitis.
• The carbon monoxide in cigarette smoke reduces the amount of oxygen the blood can carry. Consequently, heart rate increases, and so does blood pressure.
• High blood pressure damages the artery walls, making the formation of blood clots more likely. This increases the risk of coronary heart disease.
• Tobacco smoke contains carcinogens.
• Carcinogens: chemicals that can lead to cancer.