Chapter 13 The Respiratory System by Dr. Jay M. Templin Brooks/Cole - Thomson Learning
Atmosphere Tissue cell External respiration Alveoli of lungs 1 Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs O 2 CO 2 CO 2 O 2 2 Exchange of O 2 and CO 2 between air in the alveoli and the blood Pulmonary circulation 3 Transport of O 2 and CO 2 between the lungs and the tissues Systemic circulation CO 2 O 2 4 Exchange of O 2 and CO 2 between the blood and the tissues Food + O 2 CO 2 + HO 2 + HTP Internal respiration
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 Smooth muscle Branch of pulmonary vein Respiratory bronchiole Alveolus Pulmonary capillaries Pores of Kohn Alveolar sac
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
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 The floor of the thoracic cavity is formed by diaphragm
Pressures Required for Ventilation
Pressure Gradients
Intrapleural Pressure and Pneumothorax Intrapleural pressure maintains the alveoli distended. Puncture of the chest wall abolishes intrapleural pressure and results in pneumothorax
Respiration 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
Inspiratory Muscles Inspiratory muscles: Intercostal muscles (external and internal) innervated by interscostal nerves Diaphragm Innervated by phrenic nerve
Respiratory Muscles http://www.openteach.com/biology/applets/breath/breath.html
Respiratory Muscles Brooks/Cole - Thomson Learning
Breathing Cycle http://www.smm.org/heart/lungs/breathing-f.htm
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
Spirometer and Changes in Lung Volume
Measured Air Volumes
Total Lung Capacity Total volume of air that lungs can hold ~5700 ml
Tidal Volume Amount of air entering/leaving lungs during one breath ~ 500 ml
Vital Capacity Total volume of air that can be moved out during a single breath following an inspiration ~4500 ml
Residual Volume Volume of air remaining in lungs after a maximal expiration ~1200 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) Deep Breathing: 1200 ml TV, 5 breath/min = 6000 ml/min PV and 4200 ml/min AV 2) Shallow Breathing: 150 ml TV, 40 breath/min = 6000 ml/min PV but 0 ml/min AV Fresh air from inspiration 150 Airway dead - space volume (150 ml) Alveolar air Old alveolar air that has exchanged O 2 and CO 2 with the blood Fresh atmospheric air that has not exchanged O 2 and CO 2 with the blood After inspiration, before expiration
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 (0.79 x 760).
http://www.openteach.com/biology/applets/breath/breath.html Gasses Move Down Their Partial Pressures - Partial Pressure Gradient 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 Atmospheric air Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for O 2 and CO 2 between the lungs and tissues
In the Lungs: Alveolar P O2 is Lower Than Atmospheric P O2 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
In the Lungs: Alveolar P CO2 is Higher Than Atmospheric 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
In the Tissues: Systemic Blood P O2 is Higher Than Tissue P O2 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
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
Other Factors that Regulate Gas Exchange 1) Partial Pressures 2) Surface area - emphysema 3) Thickness of alveolar wall - pulmonary edema, pulmonary fibrosis 4) Diffusion coefficient - diffusion coefficient for CO 2 is 20> than for O 2 Notice however that equal volumes of CO 2 and O 2 are exchange in the alveoli and tissues, why?
Gas Transport Polypeptide chain Polypeptide chain Oxygen is transported to tissue: 1) Dissolved in blood ~1.5% 2) Bound to hemoglobin ~98.5% Hb + O 2 <> HbO 2 Polypeptide chain Heme groups Polypeptide chain Binding and dissociation of O 2 is described by the law of mass action
Only Dissolved O 2 Drives Gas Exchange Hb acts as a O 2 -sink in lungs 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 Atmospheric air Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for O 2 and CO 2 between the lungs and tissues
O 2 -Hb Dissociation Curve
Factors that Regulate O 2 Unloading 1) CO 2 concentration - CO 2 has higher affinity for reduced Hb 2) Acidosis - H + binding to reduced Hb causes conformational change in the molecule that reduce O 2 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 CO 2 H + O 2 CO
Transport of CO 2 Across pulmonary capillaries: O 2 partial pressure gradient from alveoli to Inspiration 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 Atmospheric air Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for 2 O and CO 2 between the lungs and tissues 1) Dissolved in plasma ~10 % 2) Bound to Hb - CO 2 has higher affinity for reduced Hb than O 2 (~30%) 3) As bicarbonate HCO 3 - (~60%)
Transport of CO 2 in Blood
Effect of Ventilation on Arterial PO 2 and PCO 2 Hypoxia: Insufficient PO 2 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 Hyperoxia: Abnormally high PO 2 at tissue level
Effect of Ventilation on Arterial PO 2 and PCO 2 Hypercapnia: high PCO 2 in arterial blood. May result in respiratory acidosis. Why? Hb + O 2 <> HbO 2 Hypocapnia: Below-normal PCO 2 in arterial blood. May result in respiratory alkalosis. Why? Hb + O 2 <> HbO 2
Generation of Respiratory Activity 1) Generation of alternating inspiratory/expiratory movements (rhythm) 2) Regulation of ventilation
Generation of Respiratory Rhythm 1) Involve pacemaker cells in Pre-Botzinger complex
Respiratory Rhythm Generator and Control Center in Brainstem
Respiratory Reflex- The Hering Breuer Reflex Input from other areas some excitatory, some inhibitory Inspiratory neurons in DRG (rhythmically firing) Medulla Spinal cord Phrenic nerve Diaphragm
Regulation of Ventilation Across pulmonary capillaries: O 2 partial pressure gradient from alveoli to Inspiration 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 Atmospheric air Pulmonary circulation Systemic circulation Expiration Alveoli Net diffusion gradients for 2 O and CO 2 between the lungs and tissues Ventilation depends on the concentration of CO 2, O 2 and H + in blood Blood content of CO 2, O 2 and H + can be regulated by alterations in breathing rate and depth of breathing. Changes in ventilation relay in peripheral ands central chemoreceptors
Peripheral Chemoreceptors: Sense Changes in PO 2
Peripheral Chemoreceptors Detect Changes in PO 2
PO 2 Regulation Does Not Play a Critical Role in Normal Breathing
Peripheral Chemoreceptors: Sense Changes in H + H + ions can not cross the blood-brain barrier H + concentration in blood may change independently of CO 2 levels. For example following production of ketonic acids Regulation of H + is used to control plasma ph
Effect of H + on Ventilation
Central Chemoreceptors: Sence Changes in PCO 2
Effect of CO 2 on ventilation
Effect of Exercise on Ventilation During exercise: O 2 consumption increases (decrease PO 2 in tissue) CO 2 production increases (increased PCO 2 ) Lactic acid production increase (increased H + concentration in blood) Compensatory mechanisms: 1) Increase heart rate-to bring more O 2 to tissues and remove more CO 2 2) Stimulation of sympathetic NSincreased blood flow to skin to cool off body
Effect of High Altitude and Deep- Sea Diving on Ventilation At high altitude (>18K ft): atmospheric PO 2 decrease to ~80 mm Hg (vs 160 at sea level) Consequence: hypoxic hypoxia, hypocapnia-induced alkalosis CO 2 + 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 Consequence: upon ascent, N 2 form bubbles that can disrupt blood flow (decompression sickness)