Respiratory System Physiology. Dr. Vedat Evren

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1 Respiratory System Physiology Dr. Vedat Evren

2 Respiration Processes involved in oxygen transport from the atmosphere to the body tissues and the release and transportation of carbon dioxide produced in the tissues to the atmosphere 3 systems must work in coordination Respiratory system Erythrocytes Circulatory system

3 Respiratory System Airways Lungs Thorax and the muscles of respiration Pulmonary circulation

4 Pulmonary Ventilation Boyle s Law: Gas pressure in closed container is inversely proportional to volume of container Air flow is a result of pressure differences

5 Ventilation Movement of air in and out of lungs Inspiration (inhalation): Breathing in Expiration (exhalation): Breathing out

6 Main Structure

7 Pleura

8 Pleura

9 Pleura

10 Importance of Pleura

11 Airway Structure

12 Alveoli

13 Alveoli

14 Respiratory Epithelium Epithelial and Goblet cells Lines entire airway passage Moisten and protect Mucociliary clearance (1-2 cm/hour upwards) Mucus: 100 ml/day

15 Respiratory Epithelium

16 Pressures Atmospheric pressure: 760 mmhg Intrapleural pressure: 756 mmhg Intrapulmonary pressure: Varies!!! Transpulmonary pressure: Pressure difference between intrapleural and intrapulmonary pressure!!!

17 Inspiration Intrapulmonary pressure must decrease in order to inhale! Thoracic cavity volume increases Lung volume increases IP pressure decreases... (~758 mmhg)

18 Expiration Intrapulmonary pressure must increase in order to exhale Thoracic cavity volume decreases Lung volume decreases (elastic recoiling mostly) IP pressure increases... (~763 mmhg)

19 Pulmonary Air Flow F = P / R Diameter of airways (especially bronchioles) Autonomic innervation Sympathetic Parasympathetic

20 Muscles

21 Intercostal Muscles

22 Respiratory Volumes and Capacities Tidal Volume (TV): 500 ml Inspiratory reserve volume (IRV): 3000 ml Expiratory reserve volume (ERV): 1100 ml Residual volume (RV): 1200 ml

23 Respiratory Volumes and Capacities Inspiratory Capacity: TV + IRV Functional Residual Capacity: ERV + RV Vital Capacity: IRV + TV + ERV Total Lung Capacity: IRV + TV + ERV + RV

24 Surface Tension Remember (!): Properties of water molecule... Surface tension tends to oppose alveoli expansion Pulmonary surfactant reduces surface tension

25 Surfactant Type II alveolar epithelial cells Detergent properties Reduces surface tension Prevents collapse

26 Surfactant

27 Matching Alveolar Air Flow with Blood Flow Pulmonary vessels Vessels can constrict in areas where oxygen flow is low Respiratory passageways Airways can dilate where carbon dioxide levels are high

28 Perfusion Lung blood circulation 5 25 L / minute 24 / 8 mmhg

29 Gas Exchange Partial Pressure Each gas in atmosphere contributes to the entire atmospheric pressure, denoted as P Gases in liquid Gas enters liquid and dissolves in proportion to its partial pressure O 2 and CO 2 Exchange by DIFFUSION PO 2 is 105 mmhg in alveoli and 40 in alveolar capillaries PCO 2 is 45 in alveolar capillaries and 40 in alveoli

30 Partial Pressures Oxygen is 21% of atmosphere 760 mmhg x.21 = 160 mmhg PO2 This mixes with old air already in alveolus to arrive at PO 2 of 105 mmhg

31 Partial Pressures Carbon dioxide is.04% of atmosphere 760 mmhg x.0004 =.3 mm Hg PCO 2 This mixes with high CO 2 levels from residual volume in the alveoli to arrive at PCO 2 of 40 mmhg

32 Partial Pressures

33 Partial Pressures

34 Gas Transport O 2 transport in blood Hemoglobin O 2 binds to the heme group on hemoglobin, with 4 oxygen / Hb PO 2 PO 2 is the most important factor determining whether O 2 and Hb combine or dissociate O 2 - Hb Dissociation curve

35 Oxygen Release

36 Influencing Factors ph CO 2 Temperature DPG

37 DPG 2,3-Bisphosphoglyceric acid Present in erythrocytes 5 mmol/l Binds and stabilizes deoxyhemoglobin (T state) Can t bind to oxyhemoglobin (R state) When there is need for oxygen for the tissues, 2,3DPG increases

38 Curve Shift

39 Curve Shift

40 Carbon Dioxide Transport 7% in plasma 23% in carbamino compounds (bound to globin part of Hb) 70% as Bicarbonate

41 Carbon Dioxide (CO 2 ) + (H 2 O) (H 2 CO 3 ) (H + ) + (HCO 3- ) Enzyme is Carbonic Anhydrase Chloride shift to compensate for bicarbonate moving in and out of RBC

43 Controls of Respiration Medullary Rhythmicity Area Medullary Inspiratory Neurons are main control of breathing Pons neurons influence inspiration, with Pneumotaxic area limiting inspiration and Apneustic area prolonging inspiration. Lung stretch receptors limit inspiration from being too deep

44 Controls Medullary Rhythmicity Area Medullary Expiratory Neurons Only active with exercise and forced expiration

46 Controls of rate and depth of respiration Arterial PO 2 When PO 2 is VERY low, ventilation increases Arterial PCO 2 The most important regulator of ventilation, small increases in PCO 2, greatly increases ventilation Arterial ph As hydrogen ions increase, alveolar ventilation increases, but hydrogen ions cannot diffuse into CSF as well as CO 2

47 EXERCISE Neural signals (rate & depth) PCO 2 (PO 2 and ph) Cardiac Output Maximal Hb saturation Dilate airways

Physiology Unit 4 RESPIRATORY PHYSIOLOGY

Physiology Unit 4 RESPIRATORY PHYSIOLOGY In Physiology Today Respiration External respiration ventilation gas exchange Internal respiration cellular respiration gas exchange Respiratory Cycle Inspiration