34Cilia: Sticky. Beat create an upward current. Moves the mucus into the oesophagus to the stomach.Clearing our throats force mucus up and away from the vocal cords.
35All of these air pipes are lined with mucous secreting cells and tiny hairs called cilia.
36These trap particles such as dust, bacteria and viruses.
37Lungs: Large spongy structures. Where gaseous exchange takes place. Each lung is surrounded by the pleural membrane.The outer pleura lines the chest wall and diaphragm.The inner pleura lines the lungs.
38The gap between these 2 membranes is the pleural cavity and it is full of liquid. This liquid lubricates the membranes and reduces friction during breathing.
40Alveoli: Each bronchus divides into about a million bronchioles. These end in hollow, balloon-like air sacs called alveoli (or alveolus).700 million alveoli in the 2 lungs. Very large surface area for gas exchange = tennis court
41Each alveolus is 1 cell thick. Moist.Enclosed in a network of blood cappilaries (like the villi). When the gases are exchanged they only have to pass through the alveoli membrane and the capillary wall.
44Gas exchange: Respiration happens in cells to supply energy. Body cells use up oxygen and produce carbon dioxide and water.Eqn: C6H12O6 + 6O2 --- 6CO2 + 6H2O + energy.Enzymes
45Gaseous exchange = diffusion!!! CO2 and H2O diffuse out of cells and into the blood because the cytoplasm has a high conc of CO2 and H2O compared with the blood.In the lungs, CO2 and H2O diffuse out of the blood into the alveoli from ↑ conc to ↓ conc.
46Diffusion is: the movement from a high conc to a low conc. In the same way, O2 diffuses from the alveoli into the blood and then from the blood into body cells.Exhalation: body cells CO2 plasma (in blood) alveolus exhale.Inhalation: O2 from air alveolus blood body cells.
47Transport of gases:(1). O2 is mostly carried by haemoglobin (97%) + 3% carried in the plasma.(2). CO2 is dissolved in plasma and carried in blood. H2O is carried in plasma.
49Mechanism of breathing: Normally involuntary.At rest: 15 times per minute.In: inhalation/inspiration.Out: exhalation/expiration.
50The process:Medulla oblongata in the brain controls the rate of breathing.It sends a message to the diaphragm and intercostal muscles.Muscles contract = active process.
51(1) Ribs pull up and out/ Diaphragm moves down. Inhalation.(1) Ribs pull up and out/ Diaphragm moves down.Pressure in the chest cavity falls.Internal air pressure is now higher than the pressure of air in the chest.Air is forced into the lungs = inhalation.
52(2) Intercostal muscles and diaphragm relax. Exhalation.(2) Intercostal muscles and diaphragm relax.Ribs move down and in/ Diaphragm moves up.The volume of the chest cavity decreasesd.Thoracic pressure increases.Air is forced out = exhalation.
53Note:Exhalation is said to be passive because the muscles only have to relax. Nervous control is not needed.
55Effect of exercise on the rate of breathing: Respiration is using food to make energy.Therefore, exercise ↑ the rate of respiration, esp in muscle cells (↑ energy is needed so respiration ↑).During exercise:The medulla oblongata detects the ↑ level of exercise and therefore ↑ the rate of breathing.Exhalation is normally passive becomes active during exercise.Extra muscles are used to ↑ the depth of breathing.
56Asthma. Breathing disorder. Symptoms: -Narrowing of the bronchioles in the lungs.Appearance:-Noisy, wheezy breathing and a feeling of breathlessness.
57Cause: Not clear. May be triggered by inhaled allergens. -pollen. -animal dander.-dust and dust mites.-lung infections.-exercise.-stress.-anxiety.
58Incidence: 10% of children. Incidence is rising in developed countries.Around half of children affected grow out of it.
59Prevention: Identifying and avoiding those allergens. Tests can be taken to identify the allergens.
60Treatment:Inhalers: Drugs that widen the bronchioles to make it easier to breathe.Injection: In severe cases.
61Control of breathing: Respiratory centres in the medulla oblongata. Monitor levels of CO2 in the blood and tissue fluid.CO2 is slightly acidic it causes the pH to drop slightly.
62These respiratory centres detect this drop and react by sending out impulses to the diaphragm and intercostal muscles to help us breathe.Exercise increases CO2 in blood.