Respiratory SystemDr. Dini Sri Damayanti,MKes

RespirationExchange of gases (oxygen and carbon dioxide) between a living organism and its environment = respiration. In animals (people) this takes place in the lungs (alveoli) where the air and blood come in close contact.Pulmonary ventilation breathing, the process that moves air into and out of the lungs. Also called external respiration.

Internal respiration process by which an exchange of gases occurs between the blood and the cells of the body.Cellular respiration actual use of O2 by cells in the process of metabolism.

Mechanics of BreathingMuscles control the size of the chest cavity.External intercostals between the ribs move the chest up and out when they contract.Diaphragm dome shaped muscle between the thoracic and abdominal cavities, moves down when it contracts increasing the volume in the thorax. Hiccups (singultus) involuntary, spasmodic contraction of the diaphragm. Causes by irritation to the phrenic nerve or some types of brain injury.

Mechanics of BreathingPulmonary ventilation has 2 phases:Inspiration or inhalation moving air into lungs.Expiration or exhalation moving air out of the lungs.Inspiration occurs as the thorax enlarges (contraction of the external intercostals and diaphragm). Because of the positioning of the pleura, the lungs expand as the thorax expands and air rushes in and down to the alveoli.

Mechanics of BreathingExpirationPassive process that begins when the muscles relax decreasing the size of the thorax and lungs air moves out of the lungs.Forceful expiration internal intercostals and abdominal muscles contract and depress the rib cage decreasing the depth (front to back) of the thorax. Pressure increases and air flows out of the lungs.

Gas ExchangeCO2 moves into the lungs and leaves the body during expiration.At the tissues O2 is low and CO2 high whereas the blood reaching them is just the opposite. O2 moves out of and CO2 moves into the blood.Most of the CO2 is carried in the blood as a bicarbonate ion, some is dissolved in the plasma and some combines with hemoglobin to form carbaminohemoglobin.

Respiratory FunctionSpirometer - device used to measure the amount of air exchanged during breathing.Tidal volume amount of air taken into our lungs during normal inspiration; about 500 ml.Vital capacity largest amount of air that we can breathe in or out in one inspiration/expiration; about 4800 ml in normal young men.

Respiratory FunctionExpiratory reserve amount of air that can be forcibly exhaled after exhaling the tidal volume. Inspiratory reserve amount of air that can be forcibly inhaled over and above normal inhalation.Residual volume air that remains in the lungs after the most forceful expiration. Residual volume + Vital Capacity = Total Lung Capacity.

Physical Principles of Gas ExchangeDiffusion of gases through the respiratory membraneDepends on membranes thickness, surface areas of membrane, partial pressure of gases in alveoli and bloodRelationship between ventilation and pulmonary capillary flowIncreased ventilation or increased pulmonary capillary blood flow increases gas exchange

Oxygen and Carbon Dioxide Diffusion GradientsOxygenMoves from alveoli into blood. Blood is almost completely saturated with oxygen when it leaves the capillaryP02 in blood decreases because of mixing with deoxygenated bloodOxygen moves from tissue capillaries into the tissues Carbon dioxideMoves from tissues into tissue capillariesMoves from pulmonary capillaries into the alveoli

Changes in Partial Pressures

Hemoglobin and Oxygen TransportA 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 oxygenThe substance 2.3-bisphosphoglycerate increases the ability of hemoglobin to release oxygenFetal hemoglobin has a higher affinity for oxygen than does maternal

Oxygen-HemoglobinDissociation Curve at Rest

Bohr effect:

Temperature effects:

Shifting the Curve

Transport of Carbon DioxideCarbon 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 DioxideIn 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

CO2 Transport and Cl- Movement

Respiratory Areas in BrainstemMedullary respiratory centerDorsal groups stimulate the diaphragmVentral groups stimulate the intercostal and abdominal musclesPontine (pneumotaxic) respiratory groupInvolved with switching between inspiration and expiration

Respiratory Structures in Brainstem

Rhythmic VentilationStarting inspirationMedullary respiratory center neurons are continuously activeCenter receives stimulation from receptors and simulation from parts of brain concerned with voluntary respiratory movements and emotionCombined input from all sources causes action potentials to stimulate respiratory musclesIncreasing inspirationMore and more neurons are activatedStopping inspirationNeurons 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 VentilationCerebral and limbic systemRespiration can be voluntarily controlled and modified by emotionsChemical controlCarbon dioxide is major regulatorIncrease or decrease in pH can stimulate chemo- sensitive area, causing a greater rate and depth of respirationOxygen levels in blood affect respiration when a 50% or greater decrease from normal levels exists

Modifying Respiration

Regulation of Blood pH and Gases

Herring-Breuer ReflexLimits the degree of inspiration and prevents overinflation of the lungsInfantsReflex plays a role in regulating basic rhythm of breathing and preventing overinflation of lungsAdultsReflex important only when tidal volume large as in exercise

Ventilation in ExerciseVentilation increases abruptlyAt onset of exerciseMovement of limbs has strong influenceLearned componentVentilation increases graduallyAfter immediate increase, gradual increase occurs (4-6 minutes)Anaerobic threshold is highest level of exercise without causing significant change in blood pHIf exceeded, lactic acid produced by skeletal muscles

Effects of AgingVital capacity and maximum minute ventilation decreaseResidual volume and dead space increaseAbility to remove mucus from respiratory passageways decreasesGas exchange across respiratory membrane is reduced

pH DisturbancesRespiratory change in gas exchange; lungsAcidosis blood pH is acid due to increased levels of CO2 in the blood.Alkalosis blood pH is alkaline or basic due to decreased levels of CO2 in the blood.In any fluid that contains water:CO2 + H2O H2CO3 H+ + HCO3-The brain senses the H+ concentration that develops in the CSF because CO2 diffuses into the CSF from the blood.

Metabolic change in pH that is not due to changes in gas exchange in the lungs.Acidosis diabetes mellitus, kidney disease or severe diarrhea increase H+ in the blood. Respiratory compensation increased rate and depth.Alkalosis vomiting, medications decrease H+ in the blood. Respiratory compensation decreased rate and depth.