RADIOGRAPHY GROUP TWO PRESENTATION_014907.pptx

Pulmonary circulation and carbon dioxide transport physiology

1. PULMONARY CIRCULATION AND CO2 TRANPORT Radiography group two presentation

2. Pulmonary blood vessels Pulmonary artery carries deoxygenated blood to alveoli of lungs. Bronchial artery supply oxygenated blood to other structures of lungs. Pulmonary artery Deoxygenated blood from right ventricle to alveoli of lungs. After leaving right ventricle artery divides into right and left branches. Pulmonary artery divides in to small vessels forming capillary plexus intimate relationship to alveoli. Oxygenated blood is carried to left atrium by pulmonary vein.

3. Bronchial artery Arises from descending aorta Supplies arterial blood to bronchi ,connective tissue and other structures of lung Venous blood is drained by two bronchial veins. Bronchial veins from right drains to azygous vein and from left into hemi azygous vein or left superior intercostal veins. Blood from distal portion of bronchial veins drains in to pulmonary veins.( physiological shunt).

4. Physiological shunt Defined as diversion where venous blood mixed with arterial blood. Components : flow of deoxygenated blood from bronchial circulation into pulmonary veins without being oxygenated . Flow of thebesian veins in to cardiac chambers . Venous admixture is mixing of deoxygenated blood with oxygenated blood. Venous blood is not fully oxygenated and the rest is as wasted blood.

5. Characteristics of pulmonary blood vessels Pulmonary artery has thin wall. One third of thickness of systemic aortic wall. Highly elastic. Smooth muscle coat is not well developed. True arterioles have less smooth muscle fibers. Pulmonary capillaries are larger and dense than systemic capillaries. Vascular resistance is less. Only one tenth of systemic circulation. Low pressure vascular system Pulmonary artery carries deoxygenated blood from heart to lungs Pulmonary veins carries oxygenated blood from lungs to heart.

6. Pulmonary blood flow and blood pressure Accommodate amount of blood in lungs same as amount of blood in other parts of body. Blood pressure is less is pulmonary blood vessels . entire pulmonary vascular system is low vascular bed. Arterial pressure Systolic pressure :25mmhg Diastolic pressure :10mmhg Mean arterial pressure :15mmhg Capillary pressure : 7mmhg

7. Regulation of pulmonary blood flow Factors Cardiac output Vascular resistance Nervous factors Chemical factors Gravity and hydrostatic pressure Cardiac output : pulmonary blood flow is directly proportional to cardiac output. Regulated by four factors Venous return force of contraction Rate of contraction peripheral resistance

8. Vascular resistance Pulmonary blood flow is inversely proportional to pulmonary vascular resistance . It is low compared to systemic vascular resistance . During inspiration pulmonary blood vessels are distended because of decrease intrathoracic pressure .causes decrease in vascular resistance ,results in increses pulmonary blood flow. During expiration , increases pulmonary resistance increases results In decreased blood flow. Nervous factors stimulation of sympathetic nerves increases vascular resistance by vasocontriction Stimulation of parasympathetic such as vagus nerve decreases vascular resistance by vasodilation.

9. Chemical factors Excess of co2 or lack of oxygen causes vasoconstriction .cause for pulmonary constriction by hypoxia is not known. Gravity and hydrostatic pressure : blood pressure in lower extremity is high In standing position and upper parts above heart level is low.( effect of gravitational force). Apical portion zone 1 pulmonary capillary pressure is same as alveolar pressure So pulmonary arterial pressure flow of blood is just sufficient to alveolar capillaries If arterial pressure get decreases or alveolar pressure increases capillaries gets collapsed. prevents flow of blood to alveoli ( area of zero blood flow) No gaseous exchange in this zone .part of physiological dead space ventilated but not perfused Ventilation perfusion ratio increases . Growth of bacteria mainly tubercle bacillus lead to tubefrculosis .

10. portions Midportion zone 2 pressure in alveoli is less than pulmonary systolic pressure and more than pulmonary diastolic pressure . Blood flow increases during systole and decreases during diastole. (Area of intermittent blood flow) ventilation perfusion ratio is normal . Lower portion zone 3 pulmonary arterial pressure is high and more than alveolar pressure during both systole and diastole .(area of continuous blood flow ) ventilation prefusion ratio decreases .

11. Transport of Carbon Dioxide The partial pressures of carbon dioxide are Intracellular is 46 mmHg Extracellular is 45 mmHg Arterial blood entering tissues 40 mmHg Venous blood leaving tissues 45mmHg Blood entering pulmonary capillaries 45 mmHg Alveolar air 40 mmHg

12. Carbon dioxide is transported in the blood in three ways Physically dissolved Bound to hemoglobin As bicarbonate ion

13. Physically Dissolved Part of the carbon dioxide released from the tissues is dissolved in plasma. But only a small amount, typically just 7 – 10%, is transported this way 2.7ml per dL is dissolved at 45mmHg and 2.4 ml per dL at 40 mmHg.

14. Bound to Hemoglobin 30% of the CO 2 combines with Hb to form carbamino hemoglobin (HbCO 2 ) The unloading of O2 from Hb in the tissue capillaries therefore facilitates the picking up of CO2 by Hb 20-30% is transported by this route

15. As Bicarbonate ( HCO 3 ) Ion The most important means of CO 2 transport is as bicarbonate (HCO 3 ), with 60-70% of the CO 2 being converted into HCO 3 by the following chemical reaction in Erythrocytes by the help of enzyme Carbonic Anhydrase

16. Chloride Shift or hamburger shift The red blood cell membrane has a HCO 3 – Cl carrier that passively facilitates the diffusion of these ions in opposite directions across the membrane. Consequently, HCO 3 efflux and Cl influx occur, which is known as chloride shift The reverse takes place in the alveoli known as the reverse chloride shift

17. CO2 Dissociation curve

18. Factors affecting CO2-DC:Haldane Effect binding of O2 with hemoglobin tends to displace CO2 from the blood is known as the Haldane effect The Haldane effect results from the fact that combination of O2 with hemoglobin in the lungs causes the hemoglobin to become a stronger acid. This displaces CO2 from the blood and into the alveoli in two ways.

19. First, highly acidic hemoglobin has less tendency to combine with CO2 Second, the increased acidity of the hemoglobin also causes it to release an excess of hydrogen ions. These bind with bicarbonate ions to form carbonic acid, which then dissociates to CO2, and the CO2 is released from the blood into the alveoli Other factors include ; blood pH, temperature, presence of 2,3 bisphosphoglycerate (2,3 BGP), hemoglobin concentration

20. Applied physiology Hypoventilation Hyperventilation Apnea; it can be voluntary, sleep, drug induced, deglution , or adrenalin