Respiratory System Chapter 23

Functions of Respiratory System supply oxygen (O 2 ) remove carbon dioxide (CO 2 ) regulation of blood pH receptors for smell filters incoming air produces sound rid body of water and heat

Respiration 1. Union of oxygen with food in the cells with the subsequent release of energy for work, for heat, and for the release of carbon dioxide and water. 2. Overall exchange of gases between the atmosphere, blood, and cells.

Anatomy of Respiratory System Upper Respiratory System Nose Pharynx Lower Respiratory System Larynx Trachea Bronchi Lungs

Anatomy of Respiratory System

Nose (External)

Nose (Internal)

Larynx

Larynx - Movement

Trachea

Bronchial Tree

Lungs

Pleural Cavity

Lymphatic vessel Arteriole Venule Branch from Terminal Bronchi All wrapped in elastic tissue Lobule of the Lung

Alveolus

Mechanics of Breathing Pulmonary Ventilation - atmosphere and alveoli External respiration - alveoli and blood Internal Respiration - blood and tissues

Volume/Pressure Relation Boyle’s Law

Muscles of Inhalation and Exhalation

Pressure in the Thoracic Cavity Atmospheric Pressure = 760 mm Hg at sea level Intrapulmonary (alveolar) Pressure - pressure in alveoli Intrapleural Pressure - pressure within pleural cavity

- occurs when the diaphragm and intercostal muscles contract, increasing the dimensions (and volume) of the thorax - as the intrapulmonary pressure drops, air rushes into the lungs until the intrapulmonary and atmospheric pressures are equalized Inspiration

Pressure Changes During Ventilation

Expiration - is largely passive, occurring as the inspiratory muscles relax and the lungs recoil. When intrapulmonary pressure exceeds atmospheric pressure, gases out of the lungs

Review

Physical factors Influencing Pulmonary Ventilation 1. Airway Resistance 2. Alveolar surface tension forces 3. Lung compliance

Other Respiratory Movements

Respiratory volumes Tidal volume (TV) - amount of air that moves in and out of the respiratory system during normal quiet breathing. Residual volume (RV) - amount of air remaining in the lungs after maximum forced expiration Inspiratory reserve volume (IRV) - maximum amount of air that can be drawn into the lungs over and above the normal tidal volume. Expiratory reserve volume (ERV) - amount of additional air that can be voluntarily moved out after a normal tidal expiration.

Respiratory capacities Vital capacity (VC) - the greatest volume of air that can be moved in and out of the respiratory system. VC = TV + IRV + ERV Functional residual capacity (FRC) – volume of air remaining in the lungs after a normal tidal volume expiration. FRC = ERV + RV Inspiratory capacity (IC) - maximum amount of air that can be inspired after a normal expiration. IC = TV + IRV Total lung capacity (TLC) - maximum amount of air contained in the lungs after a maximum inspiratory effort. TLC = TV + IRV + ERV + RV or TLC = VC + RV

Spirogram

Pulmonary Function Tests Alveolar ventilation rate - the volume of air that actually reaches the respiratory zone. Takes into account anatomic dead space. (About 30%) Minute Ventilation (MV) – total volume of air inhaled and exhaled each minute. MV = RR x TV FVC test - forced vital capacity - measures the amount of gas expelled when a subject takes a deep breath and then forcefully exhales maximally and as rapidly as possible. Those with restrictive disease have a low FVC FEV test - forced expiratory volume – determines amount of air expelled during specific time intervals of the FVC test. (e.g. the volume exhaled during the first second – FEV 1.0 ). Those with healthy lungs can exhale about 80% of the FVC within one second. Those with obstructive pulmonary disease have a low FEV.

Gas Laws Dalton’s Law of partial pressures - each gas in a mixture of gases exerts its own pressure as if all other gases were not present. Partial pressure = multiply the % of the mixture the particular gas constitutes by the total pressure of the mixture Henry’s Law - the amount of gas that will dissolve in a liquid is proportional to the partial pressure of the gas. Higher pressure - more molecules forced into solution.

Gas Exchange

Transport of Gases in the Blood

Oxygen-Hemoglobin Dissociation

Bohr Effect

Oxygen-Hemoglobin Dissociation

Carbon dioxide Transport 1. Dissolved in plasma (7%) 2. Bound to hemoglobin (23%) 3. As bicarbonate ion - HCO 3 1- (70%) CO 2 + H 2 O ↔ H 2 CO 3 ↔ H + + HCO 3 -

Haldane Effect the lower the pO 2 and hemoglobin saturation with oxygen, the more CO 2 that can be carried. Allows more CO 2 to combine with Hb and more bicarbonates to form. Carbon dioxide Transport

Summary

Control of Respiration Respiratory Center 1. Medullary Rhythmicity Area in medulla - establishes the basic pace and depth of respiration 2.Pneumotaxic Area in the pons - modifies that pace set by the medulla. 3.Apneustic Area in the pons - stimulatory signals to inspiratory area to prolong inspiration

Control of Respiration

Mechanoreceptor reflexes: stretch receptors in the walls of the lungs (prevents over expansion) Hering-Breuer reflex (inflation reflex) Chemoreceptor reflexes: sensitive to concentration of O 2 and CO 2 (mostly CO 2 )

Control of Respiration

Regulation of Ventilation Rate and Depth

Asthma Chronic Obstructive Pulmonary Disease (COPD) Emphysema Chronic Bronchitis Lung Cancer Pneumonia Tuberculosis Influenza and Coryza Pulmonary Edema Cystic Fibrosis Respiratory Disorders