VI edit Pag 451-499 Chapter 13 The Respiratory System V edit. Pag 459-509
Tissue cell Alveoli of lungs Atmosphere 1 External respiration Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs C C Pulmonary circulation 2 Exchange of and C between air in the alveoli and the blood 3 Transport of and C between the lungs and the tissues Systemic circulation C 4 Exchange of and C between the blood and the tissues Food + C + H 2 O+ ATP Internal respiration
The Respiratory System Non-respiratory functions of the respiratory system 1) Water and heat elimination 2) Maintenance of acid-base balance 3) Speech and vocal functions 4) Provide defense against foreign organisms 5) Regulate the activity of passing substances like prostaglandins and angiotensin II
Nasal passages Mouth Pharynx Larynx Trachea Cartilaginous ring Right bronchus Bronchiole Terminal bronchiole Respiratory bronchiole Alveolar sac Terminal bronchiole
Terminal bronchiole Branch of pulmonary artery Respiratory bronchiole Alveolus Pores of Kohn Smooth muscle Branch of pulmonary vein Pulmonary capillaries Alveolar sac Alveoli are covered with a thin layer of fluid that facilitate gas exchange Alveoli clusters increase the surface area necessary for gas exchange
Structure of the Alveolus Type II alveolar cell Type I alveolar cell Interstitial fluid Alveolar fluid lining with pulmonary surfactant Alveolar macrophage Pulmonary capillary Alveolus Erythrocyte
Forces that Prevent the Collapse of Alveoli Interconnected alveoli Alveolus starts to collapse H 2 O molecules An alveolus Alveoli are interconnected by pores of Kohn. Collapsing of one alveolus will stretch the neighboring alveoli. Thin layer of water inside alveolus generates an inward surface tension that is counteracted by surfactants
Thoracic Cavity and Pleural Sac The lungs are located in thoracic cavity Outer wall of the thoracic cavity is formed by the ribs, sternum and thoracic vertebrae Intrapleural fluid The floor of the thoracic cavity is formed by diaphragm Pleural sac is a doublewalled, closed sac that separate the lungs from the thoracic wall
Pressures Required for Ventilation Air moves from areas of high pressure to areas of low pressure (intrapulmonary pressure)
Pressure Gradients (Air will move from areas of high pressure to areas of low pressure)
Intrapleural Pressure and Pneumothorax Intrapleural pressure maintains the alveoli distended. Puncture of the chest wall abolishes intrapleural pressure and results in pneumothorax
Respiratory Cycle Consist of alternating cycles of inspiratory and expiratory movements Inspiration Expiration Intra-alveolar pressure Atmospheric pressure Transmural pressure gradient across the lung wall Intraplural pressure http://www.smm.org/heart/lungs/breathing.htm
Accessory inspiratory muscles (rise the sternum and first two ribs) Inspiratory Muscles Inspiratory muscles generate volume changes in the thoracic cavity that allow the flow of air into the lungs Inspiratory muscles: Diaphragm Innervated by phrenic nerve (phrenic motoneurons) External intercostal muscles innervated by interscostal nerves
Respiratory Muscles Expansion of thoracic cavity reduce intra-alveolar pressure that allow air flow into the lungs
Respiratory Muscles Brooks/Cole - Thomson Learning
Breathing Cycle & Boyle s Law (if volume increases, pressures decreases because P 1 V 1 =P 2 V 2 ) http://www.smm.org/heart/lungs/breathing-f.htm
Forces that Prevent Lung Collapse during Expiration Interconnected alveoli Alveolus starts to collapse 1) Elastic recoil and compliance Figure 13.18a Page 476 Slide 26 2) Alveolar interdependence Airways 3) Surfactants in alveoli Alveoli Figure 13.17a Page 475 Slide 24
Spirometer and Changes in Lung Volume
Measured Air Volumes
Total Lung Capacity Total volume of air that lungs can hold ~5700 ml
Residual Volume Volume of air remaining in lungs after a maximal expiration ~1200 ml
Tidal Volume Amount of air entering/leaving lungs during one single breath ~ 500 ml
Vital Capacity Maximal volume of air that can be moved out during a single forceful breath following a maximal inspiration ~4500 ml
Pulmonary Ventilation PV = Tidal Volume x Respiratory Rate Alveolar Ventilation AV = (Tidal Volume - Dead Space) x Respiratory Rate
Effect of Breathing Patterns on Gas Exchange 1) Normal Breathing: 500 ml TV, 12 breath/min = 6000 ml/min PV and 4200 ml/min AV 2) Deep Breathing: 1200 ml TV, 5 breath/min = 6000 ml/min PV and 4200 ml/min AV 3) Shallow Breathing: 150 ml TV, 40 breath/min = 6000 ml/min PV but 0 ml/min AV
Gas Exchange-Partial Pressures Each gas in a mixture of gases exerts a pressure that is proportional to its concentration in the mixture. Each gas exerts its part, its partial pressure. For example, 79 percent of the atmosphere is nitrogen. The partial pressure of this gas is 600 mm Hg (0.79 x 760 mm Hg). The partial pressure for oxygen is 160 mm Hg (0.21 x 760 mm Hg)
http://www.wisc-online.com/objects/framz.asp?objid=ap2404 Gases Move Down Their Partial Pressures - Partial Pressure Gradient Atmospheric air Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39
In the Lungs: Alveolar P O2 is lower than atmospheric P O2 and higher than capillary P O2 Atmospheric air Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39
In the Lungs: Alveolar P CO2 is lower than capillary P CO2 and higher than atmospheric P CO2 Atmospheric air Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39
In the Tissues: Systemic Blood P O2 is Higher Than Tissue P O2 Atmospheric air Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39
In the Tissues: Systemic Blood P CO2 is Lower Than Tissue P CO2 Atmospheric air Across pulmonary capillaries: O 2 partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) O 2 partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: O 2 partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) O 2 partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for O 2 and CO 2 between the lungs and tissues
Factors that Regulate Gas Exchange 1) Partial Pressures 2) Surface area - emphysema 3) Thickness of alveolar wall - pulmonary edema, pulmonary fibrosis, pneumonia 4) Diffusion coefficient - diffusion coefficient for C is 20> than for Notice however that equal volumes of C and are exchange in the alveoli and tissues, why?
Gas Transport Oxygen is transported to tissue: Polypeptide chain Polypeptide chain 1) Dissolved in blood ~1.5% 2) Bound to hemoglobin ~98.5% (does not contribute to P O2 ) reduced Hb + Hb Polypeptide chain Heme groups Polypeptide chain Binding and dissociation of is described by the law of mass action: if the concentration of one substance involved in a reversible reaction is increased, the reaction is driven to the opposite side
Only Dissolved Drives Gas Exchange Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Atmospheric air What factors determine - Expiration binding to Hb in lungs and tissue? Pulmonary circulation Systemic circulation Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39 1) P O2 (according to the law of mass action) 2) In lungs, Hb acts as a sink: reduced Hb + Hb 3) In tissue, Hb gives up WHY?
-Hb Dissociation Curve Unloading The relationship between P O2 and Hb saturation is not linear, it is S-shaped Plateau portion of curve represents level of saturation of Hb in lungs Steep portion of curve represents unloading of in the tissues
Factors that Regulate Unloading 1) C concentration - C has higher affinity for reduced Hb Unloading 2) Acidosis - H + binding to reduced Hb causes conformational change in the molecule that reduce affinity. Bohr Effect 3) Temperature 4) 2,3- Biphosphoglycerate (BPG) http://harveyproject.science.wayne.edu/development/respiration/gas_transport/applet1/graph.html
Binding Sites in Hb molecule C H + CO
Transport of C Atmospheric air Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39 1) Dissolved in plasma ~10 % 2) Bound to Hb - C has higher affinity for reduced Hb than (~30%) 3) As bicarbonate HCO 3 - (~60%)
Transport of C in Blood
Hyperoxia: Abnormally high P at tissue level Effect of Ventilation on Arterial P and PC Hypoxia: Insufficient PO2 in tissues 1) Hypoxic hypoxia abnormal gas exchange or high altitude 2) Anemic hypoxia low number of red blood cells 3) Circulatory hypoxia vascular spasm or blockage 4) Histotoxic hypoxia cyanide poisoning
Effect of Ventilation on Arterial P and PC Hypercapnia: high PC in arterial blood caused by hypoventilation. May result in respiratory acidosis. Why? C + H 2 O HCO 3- + H + Hypocapnia: Below-normal PC in arterial blood caused by hyperventilation. May result in respiratory alkalosis. Why? C + H 2 O HCO 3- + H +
Generation of Respiratory Activity 1) Generation of alternating inspiratory/expiratory movements (rhythm) 2) Regulation of ventilation (depth/rate of breathing) 3) Regulation of complementary respiratory activity
Pons Pons respiratory centers Pneumotaxic center Apneustic center Respiratory control centers in brain stem Medullary respiratory center Pre-Bötzinger complex Dorsal respiratory Group (Insp. Neurons) Ventral respiratory Group (Insp/Exp. Neurons) Medulla
Modulation of Respiration by the Pons Neurons in Pneumotaxic center switch off inspiratory neurons in DRG. Results in sighs Neurons in Apneustic center prevent inspiratory neurons in DRG from being turned off- Results in apnea or long gasps Pons respiratory centers Pneumotaxic center Apneustic center Respiratory control centers in brain stem Medullary respiratory center Pre-Bötzinger complex Dorsal respiratory Group (Insp. Neurons) Ventral respiratory Group (Insp/Exp. Neurons) Medulla
Regulation of Ventilation Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Atmospheric air Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39 Ventilation depends on the concentration of C, and H + in blood Blood content of C, and H + can be regulated by alterations in breathing rate and depth of breathing. Regulation of ventilation depends on peripheral ands central chemoreceptors
Peripheral Chemoreceptors: Sense Changes in P. Activated by P <60 mm Hg
Peripheral Chemoreceptors Detect Changes in P
P Regulation Does Not Play a Critical Role in Normal Breathing Across pulmonary capillaries: partial pressure gradient from alveoli to blood = 60 mm Hg (100 > 40) partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) Across pulmonary capillaries: partial pressure gradient from blood to alveoli = 6 mm Hg (46 > 40) partial pressure gradient from tissue cell to blood = 6 mm Hg (46 > 40) Tissue cell Inspiration Atmospheric air Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for and C between the lungs and tissues Figure 13.26 Page 485 Slide 39
Peripheral Chemoreceptors: Sense Changes in H + H + ions can not cross the blood-brain barrier H + concentration in blood may change independently of C levels. For example following increased production of ketonic acids Regulation of H + is used to control plasma ph
Effect of H + on Ventilation (exercise, fat metabolism)
Central Chemoreceptors: Detect Changes in H + generated by changes in PC
Effect of C on ventilation
Effect of Exercise on Ventilation During exercise: consumption increases (decrease P in tissue) C production increases (increased PC in tissue) Lactic acid production increase (increased H + concentration in blood) Compensatory mechanisms: 1) Increase heart rate-to bring more to tissues and remove more C 2) Stimulation of sympathetic NSincreased blood flow to skin to cool off body and muscle (for more supply)
Effect of High Altitude and Deep-Sea Diving on Ventilation At high altitude (>18K ft): atmospheric P decrease to ~80 mm Hg (vs 160 at sea level) Consequence: acute mountain sickness=hypoxic hypoxia= hypocapnia-induced alkalosis C + H 2 O > H 2 CO 3 <> HCO 3- + H + Compensatory mechanism: increase heart rate and red blood cell production Deep sea diving: concentration of N 2 in the blood increases Consequence: upon ascent, N 2 form bubbles that can disrupt blood flow (decompression sickness)