Respiratory System

Respiratory System Functions Gas exchange: Oxygen enters blood and carbon dioxide leaves Regulation of blood pH: Altered by changing blood carbon dioxide levels Voice production: Movement of air past vocal folds makes sound and speech Olfaction: Smell occurs when airborne molecules drawn into nasal cavity Protection: Against microorganisms by preventing entry and removing them

Respiratory System Divisions Upper tract Nose, pharynx and associated structures Lower tract Larynx, trachea, bronchi, lungs

Nose and Pharynx Common opening for digestive and respiratory systems Functions Passageway for air Cleans the air Humidifies, warms air Smell Along with paranasal sinuses are resonating chambers for speech Pharynx Common opening for digestive and respiratory systems Three regions Nasopharynx Oropharynx Laryngopharynx

Larynx Functions Maintain an open passageway for air movement Epiglottis and vestibular folds prevent swallowed material from moving into larynx Vocal folds are primary source of sound production

Vocal Folds

Trachea Windpipe Divides to form Primary bronchi Insert Fig 23.5 all but b

Tracheobronchial Tree

Bronchioles and Alveoli

Lungs Two lungs: Principal organs of respiration Right lung: Three lobes Left lung: Two lobes Divisions Lobes, bronchopulmonary segments, lobules

LUNG VOLUMES The total volume contained in the lung at the end of a maximal inspiration is subdivided into volumes and subdivided into capacities There are four volume subdivisions which: do not overlap can not be further divided when added together equal total lung capacity

Capacities Lung capacities are subdivisions of total volume that include two or more of the 4 basic lung volumes.

Basic lung volumes (memorize) Tidal Volume (TV). The amount of gas inspired or expired with each breath. Inspiratory Reserve Volume (IRV). Maximum amount of additional air that can be inspired from the end of a normal inspiration.

Basic lung volumes (memorize) Expiratory Reserve Volume (ERV). The maximum volume of additional air that can be expired from the end of a normal expiration. Residual Volume (RV). The volume of air remaining in the lung after a maximal expiration. This is the only lung volume which cannot be measured with a spirometer.

Basic lung capacities (memorize) Total Lung Capacity (TLC). The volume of air contained in the lungs at the end of a maximal inspiration. Called a capacity because it is the sum of the 4 basic lung volumes. TLC=RV+IRV+TV+ERV

Basic lung capacities (memorize) Vital Capacity (VC). The maximum volume of air that can be forcefully expelled from the lungs following a maximal inspiration. Called a capacity because it is the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume. VC=IRV+TV+ERV=TLC-RV

Basic lung capacities (memorize) Functional Residual Capacity (FRC). The volume of air remaining in the lung at the end of a normal expiration. Called a capacity because it equals residual volume plus expiratory reserve volume. FRC=RV+ERV

Basic lung capacities (memorize) Inspiratory Capacity (IC). Maximum volume of air that can be inspired from end expiratory position. Called a capacity because it is the sum of tidal volume and inspiratory reserve volume. This capacity is of less clinical significance than the other three. IC=TV+IRV

Now you are ready Look at the diaphram: for tenting free air abnormal elevation Margins should be sharp (the right hemidiaphram is usually slightly higher than the left)

Check the Heart Size Shape Silhouette-margins should be sharp Diameter (>1/2 thoracic diameter is enlarged heart) Remember: AP views make heart appear larger than it actually is.

R Atrium R Ventricle 3. Apex of L Ventricle Superior Vena Cava Cardiac Silhouette R Atrium R Ventricle 3. Apex of L Ventricle Superior Vena Cava Inferior Vena Cava 6. Tricuspid Valve Pulmonary Valve Pulmonary Trunk 9. R PA 10. L PA

Check the costophrenic angles Margins should be sharp

Loss of Sharp Costophrenic Angles

Check the hilar region The hilar – the large blood vessels going to and from the lung at the root of each lung where it meets the heart. Check for size and shape of aorta, nodes,enlarged vessels

Finally, Check the Lung Fields Infiltrates Increased interstitial markings Masses Absence of normal margins Air bronchograms Increased vascularity

Hemothorax

Changing Alveolar Volume Lung recoil Causes alveoli to collapse resulting from Elastic recoil and surface tension Surfactant: Reduces tendency of lungs to collapse Pleural pressure Negative pressure can cause alveoli to expand Pneumothorax is an opening between pleural cavity and air that causes a loss of pleural pressure

Pulmonary Volumes Tidal volume Inspiratory reserve volume Volume of air inspired or expired during a normal inspiration or expiration Inspiratory reserve volume Amount of air inspired forcefully after inspiration of normal tidal volume Expiratory reserve volume Amount of air forcefully expired after expiration of normal tidal volume Residual volume Volume of air remaining in respiratory passages and lungs after the most forceful expiration

Pulmonary Capacities Inspiratory capacity Functional residual capacity Tidal volume plus inspiratory reserve volume Functional residual capacity Expiratory reserve volume plus the residual volume Vital capacity Sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume Total lung capacity Sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume

Spirometer and Lung Volumes/Capacities

Minute and Alveolar Ventilation Minute ventilation: Total amount of air moved into and out of respiratory system per minute Respiratory rate or frequency: Number of breaths taken per minute Anatomic dead space: Part of respiratory system where gas exchange does not take place Alveolar ventilation: How much air per minute enters the parts of the respiratory system in which gas exchange takes place

Physical Principles of Gas Exchange Partial pressure The pressure exerted by each type of gas in a mixture Dalton’s law Water vapor pressure Diffusion of gases through liquids Concentration of a gas in a liquid is determined by its partial pressure and its solubility coefficient Henry’s law

Physical Principles of Gas Exchange Diffusion of gases through the respiratory membrane Depends on membrane’s thickness, the diffusion coefficient of gas, surface areas of membrane, partial pressure of gases in alveoli and blood Relationship between ventilation and pulmonary capillary flow Increased ventilation or increased pulmonary capillary blood flow increases gas exchange Physiologic shunt is deoxygenated blood returning from lungs

Oxygen and Carbon Dioxide Diffusion Gradients Moves from alveoli into blood. Blood is almost completely saturated with oxygen when it leaves the capillary P02 in blood decreases because of mixing with deoxygenated blood Oxygen moves from tissue capillaries into the tissues Carbon dioxide Moves from tissues into tissue capillaries Moves from pulmonary capillaries into the alveoli

Changes in Partial Pressures

Hemoglobin and Oxygen Transport Oxygen is transported by hemoglobin (98.5%) and is dissolved in plasma (1.5%) Oxygen-hemoglobin dissociation curve shows that hemoglobin is almost completely saturated when P02 is 80 mm Hg or above. At lower partial pressures, the hemoglobin releases oxygen. A shift of the curve to the left because of an increase in pH, a decrease in carbon dioxide, or a decrease in temperature results in an increase in the ability of hemoglobin to hold oxygen

Hemoglobin and Oxygen Transport A shift of the curve to the right because of a decrease in pH, an increase in carbon dioxide, or an increase in temperature results in a decrease in the ability of hemoglobin to hold oxygen The substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to release oxygen Fetal hemoglobin has a higher affinity for oxygen than does maternal

Oxygen-Hemoglobin Dissociation Curve at Rest

Oxygen-Hemoglobin Dissociation Curve during Exercise

Shifting the Curve

Transport of Carbon Dioxide Carbon dioxide is transported as bicarbonate ions (70%) in combination with blood proteins (23%) and in solution with plasma (7%) Hemoglobin that has released oxygen binds more readily to carbon dioxide than hemoglobin that has oxygen bound to it (Haldane effect) In tissue capillaries, carbon dioxide combines with water inside RBCs to form carbonic acid which dissociates to form bicarbonate ions and hydrogen ions

Transport of Carbon Dioxide In lung capillaries, bicarbonate ions and hydrogen ions move into RBCs and chloride ions move out. Bicarbonate ions combine with hydrogen ions to form carbonic acid. The carbonic acid is converted to carbon dioxide and water. The carbon dioxide diffuses out of the RBCs. Increased plasma carbon dioxide lowers blood pH. The respiratory system regulates blood pH by regulating plasma carbon dioxide levels

Carbon Dioxide Transport and Chloride Movement

Respiratory Areas in Brainstem Medullary respiratory center Dorsal groups stimulate the diaphragm Ventral groups stimulate the intercostal and abdominal muscles Pontine (pneumotaxic) respiratory group Involved with switching between inspiration and expiration

Respiratory Structures in Brainstem

Rhythmic Ventilation Starting inspiration Increasing inspiration Medullary respiratory center neurons are continuously active Center receives stimulation from receptors and simulation from parts of brain concerned with voluntary respiratory movements and emotion Combined input from all sources causes action potentials to stimulate respiratory muscles Increasing inspiration More and more neurons are activated Stopping inspiration Neurons stimulating also responsible for stopping inspiration and receive input from pontine group and stretch receptors in lungs. Inhibitory neurons activated and relaxation of respiratory muscles results in expiration.

Modification of Ventilation Chemical control Carbon dioxide is major regulator Increase or decrease in pH can stimulate chemo- sensitive area, causing a greater rate and depth of respiration Oxygen levels in blood affect respiration when a 50% or greater decrease from normal levels exists Cerebral and limbic system Respiration can be voluntarily controlled and modified by emotions

Modifying Respiration

Regulation of Blood pH and Gases

Herring-Breuer Reflex Limits the degree of inspiration and prevents overinflation of the lungs Infants Reflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungs Adults Reflex important only when tidal volume large as in exercise

Ventilation in Exercise Ventilation increases abruptly At onset of exercise Movement of limbs has strong influence Learned component Ventilation increases gradually After immediate increase, gradual increase occurs (4-6 minutes) Anaerobic threshold is highest level of exercise without causing significant change in blood pH If exceeded, lactic acid produced by skeletal muscles

Effects of Aging Vital capacity and maximum minute ventilation decrease Residual volume and dead space increase Ability to remove mucus from respiratory passageways decreases Gas exchange across respiratory membrane is reduced