Presentation on theme: "Cardiovascular System L-5 Special Circulations, hemorrhage and shock"— Presentation transcript:
1Cardiovascular System L-5 Special Circulations, hemorrhage and shock Dr Than KyawMarch 2012
2(Coronary, Pulmonary, and Cerebral circulations) Special circulation(Coronary, Pulmonary, and Cerebral circulations)IntroductionSpecial attention to circulation in coronary, pulmonary and brainDifferences in mechanisms to other systemsTheir importanceCoronary circulation is discussed in the previous lecture [(L-3 (b)]
3Pulmonary circulation Separate circulationLow pressure (right ventricle) than systemic (left ventricle)Deoxygenated venous blood from whole body pass through the lung to re-oxygenate
7Alveolar type I cells. Squamous cells, as thin as 0 Alveolar type I cells. Squamous cells, as thin as 0.05 m; 95% of the alveolar epithelial surface.Alveolar type II cells. Irregular, cuboidal shaped; cytoplasm contains a large number of granules (cytosomes) which secrete pulmonary surfactant (a mixture of proteins and phospholipids which reduce the surface tension of the alveoli, and prevent their collapse during exhalation, and act as a bactericide)
8Diffusion of respiratory gases Respiratory gases diffuse readily throughout the body tissuesCO2 - greater lipid solubility, diffuse about 20 times than O2 through the membranesDiffusion rate decreases in diseases like pulmonary edema
11Circulation to the Brain The inner surfaces of capillaries in the brain are lined by the single layer of endothelial cells.Unlike other organs, endothelial cells of the capillaries in the brain have tight junctions.So, most substances in the blood cannot readily enter the cells of CNS.This limitation is k/s Blood-brain-barrier.Lipid soluble substances like O2 and CO2 can readily diffuse.Some molecules, such as glucose, needs special methods (active transport)Transport for most substances is provided by astrocytes which are interposed between the CNS cells and capillaries.The BBB is not permeable to hydrogen ions
15Functions and properties of the BBB The BBB has several important functions:Protects the brain from "foreign substances" in the blood that may injure the brain.Protects the brain from hormones and neurotransmitters in the rest of the body.Maintains a constant environment for the brain.
16Functions and properties of the BBB General Properties of the BBBLarge molecules do not pass through the BBB easily.Low lipid (fat) soluble molecules do not penetrate into the brain. However, lipid soluble molecules rapidly cross the BBB into the brain.Molecules that have a high electrical charge to them are slowed.
17Blood requirement by the brain Need continuous supply of the blood for normal functioningOther tissues can deprived of a blood supply for extended periods and recover to normal function when blood supply resumes.5 to 10 min of little or no blood to the brain injure brain cells (cerebrum) no recoveryRespiratory and cardiovascular centers (medulla oblongata)more resistant to hypoxia revival after 10 minAdult brain less resistant to hypoxia than new born brain
19Hemorrhage and shock Hemorrhage (Bleed causing loss of blood) From injuries –ExternalInternalTraumaticNon-TraumaticAnatomical TypeArterialVenousCapillaryTiming – Acute/Chronic
20HemorrhageMay cause:Inadequate peripheral perfusion leading to failure of tissue oxygenationmay lead to anaerobic metabolismoxydative phosphorylation can’t occur without oxygenglycolysis can occur without oxygencellular death leads to tissue and organ deathcan occur even after return of perfusion organ or organism death
21Effect of anaerobic metabolism Inadequate cellular O2 deliveryInadequate energy productionanaerobic metabolismLactic acid productionMetabolic failureCellular deathMetabolic acidosis
22Maintaining perfusion requires Volume (normal cardiac out put, normal flow)Pump ( normal heart action, pressure)Vessels (normal transport and diffusion of substances)Failue of one or more of above causes shockexcessive hemorrhage affects these factors
23Shock Different types of shock Hypovolumic shock (low volume) Most common cause of shockTraumatic blood loss (intraperitoneal, intrathoracic)Non traumatic blood lossvomitingdiarrhoeaBurnsGI (melena)SweatingCardiogenic shock (Pump failure)when the heart is damaged or injured
24Shock- Inadequate delivery of oxygen and nutrients to maintain normal tissue and cellular function3 stages:(1) Compensatory: body try to maintain normal function(2) Progressive stage: body mechanism used up and blood started shuntting blood from extremities to vital organs(3) Irreversible stage- blood shunted from blood vessels and unable to sustain the pressure need to feed the heart and brain.
25Progressive Shock Low Cardiac Output Decreases arterial pressure and reduces transport of nutrients to tissuesBlood pH decreases because of lactic & carbonic acid buildup.Waste products lead to blood agglutination. Smaller vessels may become blocked, further decreasing nutrient transport
26Shock may be observed by Cool clammy extremitiestachycardia,weak or absent peripheral pulseshypotensionSuch apparent clinical shock results from at least 25 to 30% loss of the blood volume.However, substantial volumes of blood may be lost before the classic clinical signs of shock are evident.When a patient is significantly tachycardiac or hypotensive, this represents both significant blood loss and physiologic decompensation
27Immediate treatment necessary Fluid replacement (N/S; Ringer’s lactate solution)Coloids and Blood products (plasma, red cells)END OF LECTURE
28Assignment II Test I Title: Role of pancreas in digestion Submission date: 26 March 2012Test IDate and time: 12/3/ :00 AM to 11:00 AMTime allowed: 1 hourQuestion types: Multiple choice and short questionsReading: Both theory and practical