1. Gas Exchange Chapter 11

2. What is gas exchange? Gas Exchange: The physical methods of obtaining oxygen from the surroundings and removing excess carbon dioxide. Gas Exchange is not Cellular Respiration. Oxygen is needed for cellular respiration. CO 2 is produced during cellular respiration.

3. Respiratory Surfaces The respiratory system must contain a respiratory surface. O 2 or CO 2 must diffuse through a membrane or boundary surface. This surface must be: thin-walled to allow for rapid diffusion moist – the gases must be dissolved first. in contact with a source of O 2 in surroundings in contact with transport system (if multi- cellular) so blood can obtain O 2 to carry it around.

4. Diffusion of gases: Gases move from high to low concentration. As O 2 is used up inside organism, more diffuses in. When excess CO 2 is formed inside, it diffuses out. More gases can diffuse if the respiratory surface is greater (meaning: a greater surface area) Small organisms (protists, hydra) can exchange gases directly from the environment. Large organisms need a system since: not all their cells are in contact with the environment they have protective coverings (feathers, skin, fur) that block air flow.

5. Paramecium CO 2 O 2 Protists and Hydras 1.Cells are in contact with source of oxygen dissolved in water. 2.Oxygen enters the organism through the body surface (cell membrane). 3.Carbon dioxide diffuses out. 4.The cell membrane is the respiratory surface. 5.No special structures are needed.

6. Problems with Larger Organisms Larger organisms can NOT use just diffusion: They need larger amounts of oxygen. They need a respiratory system to reach all cells. Respiratory surfaces must be kept moist. Having the system inside the body prevents evaporation. Animals living in water have more problems: The percentage of oxygen in water is much lower (1%) than the percent of oxygen in the air (21%). Oxygen diffuses more slowly in water than in air.

7. Respiratory Pigments: Chemicals that have a color that carry oxygen and carbon dioxide between the respiratory surface and the body cells. These pigments allow blood to carry much more gas than would normally dissolve. Compare: 100mL of water carries 0.2mL O 2 and 0.3 mL CO 2 100mL of blood carries 20mL O 2 and 30-60mL CO 2

9. Gas Exchange in the Earthworm Respiratory Surface is the skin. They have many capillaries just below the skin. Oxygen diffuses from the air through the skin into the capillaries. Blood, which contains hemoglobin, picks up the oxygen. Transport system takes oxygen to body cells where cellular respiration occurs and carbon dioxide is produced and carried to the capillaries in the skin. Carbon dioxide diffuses from the capillaries through the skin, into the air.

10. Gas Exchange in the Earthworm

12. Earthworm Issues Earthworms must be kept moist, but not soaked! When it rains, the worms must leave the soil because they get their oxygen from air in the soil, not water. (Remember: water does not contain enough oxygen.) If they stay in the soaked ground, they will drown. When exposed to air for too long, the skin dries out and they suffocate.

13. Gas Exchange in the Grasshopper Gas exchange in the grasshopper is separate from the transport system. This is because the blood does not have hemoglobin, so it doesn’t carry O 2 or CO 2.)

14. Parts of the system Tracheal tubes: - branching air tubes. They branch smaller and smaller and end in a fluid-filled area where gas exchange occurs with body cells. Spiracles: Openings to let air in and out. There are 10 pairs of spiracles; the front 4 let in air, the back 6 let out air. Air sacs: Balloon-like chambers help pump air in and out.

15. How it works Contractions of muscles expand the area around the tracheal tubes and air enters through the front 4 pairs of spiracles into the tracheal tubes. Air enters air sacs which help pump air in and out of tubes. When the area around the tracheal tubes contracts, four pairs of spiracles close, and the rear six pairs are used to release air from the grasshopper..

17. Gas Exchange Through Gills Gills: respiratory structures specialized for gas exchange in water. Fish gills can extract more than 80% of the oxygen dissolved in water. Fish gills contain many thin layers of tissue, called filaments, that increase their respiratory surface area. Gills contain many small water-bearing channels surrounded by capillaries. Because the water channels and capillaries are so close to one another, O 2 and CO 2 readily diffuse between the blood and water.

18. Gills

19. Human Respiratory System System consists of: Lungs and system of tubes to carry O 2 and CO 2 to and from the lungs.

20. The Nose Air enters through nostrils into nasal passages. The nose has hair, mucous membranes and capillaries near the surface so that the it can filter, moisten and warm the air. Hairs and cilia - prevent foreign matter from entering lungs (filter). Mucous membranes – trap bacteria and dust. Moisten the air. Capillaries - warm the air. Breathing through your mouth does not accomplish these things

21. Then the air goes to the…. Pharynx: - back of throat Larynx: voice box, made of cartilage. Contains two pairs of membranes stretched across – called the vocal cords. When air passes by, they vibrate. Epiglottis prevents choking during eating.

22. Larynx and vocal cords vocal cords pharynx

23. Trachea The windpipe - 12cm long and 2.5cm wide. Kept open by cartilage in the walls. Lined with ciliated mucous membranes. Cilia moves mucus with trapped particles to pharynx to be coughed out or swallowed.

24. Bronchus (bronchi (pl.): First two branches of trachea leading to lungs Contain cilia and branch into smaller bronchial tubes. Bronchial tubes

25. Lungs Coated with a 2-layered membrane – called the pleura. One covers lungs, other connect to diaphragm. The diaphragm is a muscle that moves to help you breathe. The lungs contains bronchial tubes, bronchioles, and alveoli (air sacs).

26. Bronchioles Smallest branches of bronchial tubes that end in alveoli

27. Alveoli Tiny air chamber with walls one cell thick Surrounded by capillaries Respiratory surface Lungs contain approx. 300 million alveoli Increases the surface area Oxygen and carbon dioxide move between the alveoli and the blood in capillaries.

28. Overall Diagram

29. Lungs

30. Four Stages of Gas Exchange Stage 1: Breathing: Movement of Gases into and out of lungs. Stage 2: External Respiration: Exchange of gases between blood and lungs (alveoli) Stage 3: Internal Respiration: Exchange of gases between blood and body cells Stage 4: Oxygen & Carbon Dioxide Transport Movement of gases between lungs and other body parts.

31. Stage 1: Breathing: Movement of Gases into and out of lungs. Involves two processese Inhalation: Moving air into lungs This is the Active Phase Exhalation: Moving air out of lungs This is the Passive Phase

32. Inhalation As the ribs expand and are pulled up and out. The diaphragm is pulled downward. This increases chest cavity area. Pressure in the chest cavity decreases so air is forced into the lungs.

33. Exhalation The diaphragm relaxes and moves up. Rib muscles relax, causing ribs to drop. This decreases chest cavity area. Pressure in the chest cavity increases so air is forced out of the lungs.

34. Animation of Breathing

35. Stage 2: External Respiration: Exchange of gases between blood and lungs After inhalation, oxygen in alveoli is greater than in blood. Oxygen dissolves into the moist lining of the alveoli and diffuses into the blood. Blood coming from body cells contains high concentrations of carbon dioxide, which diffuses from the blood into the alveoli. It is then exhaled.

36. Stage 3: Internal Respiration: Exchange of gases between blood and body cells In the capillaries, oxygen diffuses from the blood to the intercellular fluid to the body cells. Carbon dioxide produced in the cells diffuses from the cells to the intercellular fluid to the capillaries.

37. Oxygen and Carbon Dioxide Transport Movement of gases between lungs and organs This is the actual method that gases are carried by the blood. Two Types: Oxygen Transport Carbon Dioxide Transport

38. Oxygen Transport Most oxygen is carried by hemoglobin. Very little is dissolved in plasma. Oxygen bonds loosely with hemoglobin making oxyhemoglobin, which is bright red.

39. Carbon Dioxide Transport 70% is carried by combining with water to form carbonic acid which quickly turns into bicarbonate ions. 20% is carried by combining with hemoglobin to make carboxyhemoglobin. 10% is dissolved in the plasma.

40. Diseases of the Respiratory System Asthma – severe allergic reaction- causes wheezing, coughing, breathing difficulties. Bronchioles spasm and squeeze air passages. Bronchitis – bronchial tubes get irritated and swollen. Alveoli may swell and clog with mucus. Causes difficulties with breathing. Emphysema – lungs lose elasticity. Alveoli are damaged. Causes shortness of breath. Damage can not be reversed or cured. Pneumonia – alveoli fill with fluid preventing gas exchange. Lung Cancer – tumors grow in the lungs.

41. Asthma

42. Bronchitis

43. Emphysema

44. Pneumonia

45. Lung Cancer

46. Effects of smoking: Stops cilia movement – one cigarette stops cilia from moving for 20 minutes Increases amount of mucus in trachea Causes particles to get stuck in alveoli – resulting in inelastic scars to form. Extra tissue forms. Result: less functioning respiratory surface – emphysema Smoke containing carbon monoxide binds to hemoglobin instead of oxygen. Result: Less oxygen is carried by the blood - shortness of breath. Greater risk of bronchitis and lung cancer.