1. Respiratory Physiology Ventilation Gas exchange Oxygen uptake & utilization & removal of carbondioxide

2. From this study you should be able to: Describe the need to breath as a part of a metabolic process Describe the function of the respiratory conducting zone Describe pulmonary ventilation Briefly explain how surface tension arises & is stabilized Define lung volumes & lung capacities Explain gas movement during external & internal respiration Briefly describe neurological control of breathing with description of the stimulation of central chemoreceptor State the role of Haemoglobin in gas movement Explain how O 2 & CO 2 are carried in the blood

3. The Need to Breath  The Primary function of the respiratory system is to supply oxygen to the tissues of the body and to remove carbondioxide and to regulate acid base balance Oxygen helps us to release energy from food we eat Every cell in the body needs energy Glucose + Oxygen = Energy + Carbondioxide + water + Heat (ATP) From the atmosphere Waste products of energy production

4. Dealing with waste products Carbondioxide + water CO 2 plus H 2 O= COO + HHO H 2 CO 3 A weak acid substance CARBONIC ACID

5. Respiration Ventilation: Breathing. Gas exchange: Occurs between air and blood in the lungs. Occurs between blood and tissues. Oxygen (0 2 ) utilization: Cellular respiration and removal of carbondioxide

7. Respiratory System

9. Mucocilliary escalator

10. Covers most of the trachea, bronchi, bronchioles and nose- consists of goblet cells and ciliated columnar epithelium There is synchronous regular beating of cilia of the mucous membrane Wafts mucous and adhered particles (dust, bacteria etc) up towards the larynx Mucous is then expectorated or swallowed. Involved in non-specific immunity What happens in people who smoke?

13. The Pleura 2 layers- Visceral & Parietal. Intrapleural space -a film of fluid-secreted by the pleura & NO AIR The lungs remain in contact with the chest wall –allowing them to move with the thoracic cavity

14. Pleura

15. Pulmonary Ventilation: Inspiration and expiration

16. Quiet Inspiration - Process Contract your diaphragm, to achieve vertical expansion of your lungs. Contract your Intercostal Muscles, to increase thoracic volume laterally.

17. Muscles of respiration

18. % of gases in inspired air Oxygen-- 20-21 Carbondioxide – 0.04 Nitrogen - 78 Inert gases – 1% Water vapour - variable

19. % of expired air Oxygen – 16 Carbondioxide- 4 Nitrogen = 78 Inert gases – 1 Water vapour – more on expiration

20. Pressure changes on Quiet Inspiration Atmospheric pressure (at sea level) = 760 mmHg The chest expands (actively) Intrapulmonary press 757 mmHg so air moves into the lungs Pulmonary pressure rises by + 3 mm Hg.

21. Expiration Hold your breath- After stretching the lungs ( by contracting both diaphragm and thoracic muscles), the diaphragm and thoracic muscles relax & the thorax and lungs recoil The decrease in lung volume raises the pressure inside to above 763mmHg This is greater than atmospheric pressure- so air moves out of the lungs. Are your respiratory muscles getting tired?

24. Recap

25. Inspiration Figure 22.13.1

26. Expiration Inspiratory muscles relax and the rib cage descends due to gravity Thoracic cavity volume decreases Elastic lungs recoil passively and intrapulmonary volume decreases Intrapulmonary pressure rises above atmospheric pressure (+1 mm Hg) Gases flow out of the lungs down the pressure gradient until intrapulmonary pressure is 0

27. Lung expansion

28. BOYLE’S LAW. THE RELATIONSHIP BETWEEN THE PRESSURE AND VOLUME OF GASES IS GIVEN BY BOYLE’S LAW. IT STATES THAT WHEN THE TEMPERATURE IS CONSTANT, THE PRESSURE OF A GAS VARIES INVERSELY WITH ITS VOLUME

29. PRINCIPLE 1 Boyle’s Law Changes in intrapulmonary pressure occur as a result of changes in lung volume. (Pressure of gas is inversely proportional to its volume). Increase in lung volume decreases intrapulmonary (alveolar) pressure. Air goes in. Decrease in lung volume, raises intrapulmonary pressure above atmosphere. Air goes out. animation

30. Dead Space Air passes thro’ 150 ml of space before reaching the respiratory zone. Air is Warmed and humidified, Filters and cleaned: (Mucous traps particles ) Mucous moved by cilia to be expectorated.

31. Lung Volumes Tidal volume Volume of gas inspired/expired in an unforced breath Inspiratory reserve volume The maximum volume of air that can be inspired during forced breathing Expiratory reserve volume The maximum volume of gas that can be expired during forced breathing Residual volume The volume of gas remaining in the lungs after a maximum expiration

32. Lung Capacities Total lung capacity The total amount of gas in the lungs after a maximum inspiration Vital capacity The maximum amount of gas that can be expired after a maximum inspiration Inspiratory capacity The maximum amount of gas that can be inspired after a normal tidal expiration Functional residual capacity The amount of gas remaining in the lungs after a normal tidal expiration Peak Expiratory Flow Rate The maximum flow at the outset of forced expiration

33. Spirometry In obstructive lung disease, the FEV1 is reduced due to obstruction to air escape due to obstruction to air escape Thus, the FEV1/FVC ratio will be reduced.. A diagnosis of airflow obstruction can be made if the FEV1/FVC < 0.7 (i.e. 70%) and FEV1 < 80% predicted. (NICE 2004)

34. Respiratory Zone Where gas is exchanged between air and blood. Gas exchange occurs by diffusion.

35. Alveoli Clustered like a honeycomb. 300 million air sacs. Large surface area (60 – 80 m 2 ). Each alveolus is 1 cell thick. 2 types of cell: Alveolar type I: Structural cells. Alveolar type II: Secrete surfactant.

36. Lung alveoli and capillaries

37. Production of surfactant

38. Surface Tension a property of the surface of a liquid that allows it to resist an external force H 2 0 molecules at the surface are attracted to other H 2 0 molecules by attractive forces. What could happen to alveoli if this was not corrected? en.wikipedia.org/wiki/File:Amenbo_06f5520sx.jpg

39. Surfactant- reduces surface tension A phospholipid produced by alveolar type II cells. Function: Lowers surface tension. Think of a detergent Reduces attractive forces between H 2 0 molecules. As alveoli radius decreases, surfactant’s ability to lower surface tension increases- so the alveolus does not collapse

40. Principle 2 Gases move from an area of high concentration to an area of low concentration This movement is termed diffusion ( a passive process) Gas movement relies on concentration gradients

41. Diffusion of gases If I set off a stink bomb in the lecture theatre, those unfortunate to be near the front (an area of high concentration) would smell it. After a while the gases would attempt to fill the whole lecture theatre- the gases would diffuse from an area of high concentration to an area of low concentration (e.g. the back of the lecture theatre) when this occurs the molecules would be so far apart that no one would smell it.

42. Principle 3 Gas Exchange: Dalton’s Law Total pressure of a gas mixture is = to the sum of the pressures that each gas in the mixture would exert independently. Think of being in a crowded lift Now think of Partial Pressure

43. 43 Diffusion Gradients of Respiratory Gases at Sea Level Total100.00 760.0 760 760 H 2 O0.00 0.0 47 47 O 2 20.93 159.1 105 40 CO 2 0.03 0.2 40 46 N 2 79.04 600.7 569 573 Partial pressure (mmHg) % in Dry Alveolar Venous Gasdry air air air blood NB. CO 2 is ~20x more soluble than O 2 in blood => large amounts move into & out of the blood down a relatively small diffusion gradient.

44. 44 PO 2 and PCO 2 in Blood

46. External Respiration

47. Haemoglobin and 0 2 Transport Each haemoglobin has 4 protein chains and 4 hemes. Each heme has 1 atom iron that can combine with an 0 2 molecule.

48. C0 2 transported in the blood: HC0 3 - (70%). Dissolved C0 2 (10%). Carbaminohemoglobin (20%). CO 2 is ~20x more soluble than O 2 in blood. There for large amounts of CO 2 move into & out of the blood more easity C0 2 Transport

49. Internal Respiration

50. Recap-Blood P 02 & P C02 P 02 in systemic veins is about 40 mm Hg. P C02 in systemic veins is 46 mm Hg. After gas exchange, Arterial blood P0 2 is normally about 100 mm Hg & P C02 is 40mm Hg

51. Regulation of Breathing Neurons in the medulla oblongata forms the rhythmicity center: Controls automatic breathing. Brain stem respiratory centers: Medulla. Pons.

52. Chemoreceptor Control C 02 + H 2 O H + cannot cross the blood brain barrier. C0 2 can cross the blood brain barrier and will form Carbonic acid & then H+ H+H+ H 2 C0 3 HC0 3 What is this?Bicarbonate H+ is the trigger for the chemoreceptors This is Carbonic acid

53. Clinical relevance point 1 Haemoglobin production controlled by erythropoietin. (Produced re P 02 delivery to kidneys). Loading/unloading of gas on Hb depends on: Hb level & capacity in the blood Enzymes: ↑ 2,3 DPG - increases unloading of O2 Temp: ↑Heat increases unloading of O2 Acid/base: ↓pH increases unloading of O2 This enzyme is produced when Hb is low

55. Questions What are the three functions of the respiratory system? In order, list all of the components of the respiratory system What is the function of epiglottis? What is the function of the cilia in the trachea? What surrounds the trachea and helps to keep it open? What is the role of surfactant in the lungs? What is the composition of air in %. Which law governs movement of gases in out of the lungs? A) Boyles law or b) process of diffusion Where are the chemo-receptors situated? How does the respiratory system respond to increase in CO 2 in the blood? In what form, can carbondioxide be carried in the blood? – see slide no 49 for answer In what form can Oxygen be carried in the blood? – see slide no 49 for answer What is the name of chemical produced by the kidneys which stimulates production of Red Blood Cells from Red Marrow?