BMSC2 week 3: myocardial infarction, valve disease, and heart failure
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- Where are discontinuous capillaries often found?
- sinusoids of liver, spleen, and bone marrow
- What characteristics of capillaries make them ideal for rapid diffusive exchange?
-
-extreme proximity to cells
-large surface/volume ratio
-low flow velocity
-thin walls - What metabolites can undergo transcellular transcapillary exchange?
-
small nonpolar molecules:
-O2
-CO2 - What metabolites can pass through intercellular clefts in transcapillary exchange?
-
-K+
-glucose
-Na+
-Cl- - What are the 3 mechanisms that can increase transcapillary exchange?
-
-capillary recruitment
-increased tissue concentration gradients
-increased blood flow - For what types of solutes will increased blood flow cause increased transcapillary exchange?
- small nonpolar molecules which cross capillary walls easily (e.g. O2)
- What is Starling's principle of fluid exchange?
-
-fluid filtration = k[(Pc - Pi) - (Ϭc - Ϭi)]
-fluid filtration = hydraulic drive - osmotic suction - What 4 parameters influence Pc most strongly?
-
-distance along capillary
-arterial and venous pressures
-gravity
-sympathetic vasomotor tone - How does arteriolar dilation affect fluid filtration in the capillaries?
- filtration becomes more prominent than absorption because hydraulic pressure increases
- How does arteriolar constriction affect fluid filtration in the capillaries?
- absorption becomes more prominent than filtration because hydraulic pressure decreases
- What are the 4 types of edema?
-
-inflammatory edema (increased permeability of endothelium)
-venous edema (increased venous pressure)
-hypoproteinemic edema (decreased plasma proteins)
-lymphatic edema (lymphatic obstruction) - What type of heart failure causes systemic edema?
- right heart failure
- What type of heart failure causes pulmonary edema?
- left heart failure
- What are the functions of the lymphatic system?
-
-returns excess interstitial fluid to the blood
-returns interstitial protein to the blood
-transports cells (immune)
-transports large molecules and debris - What factors contribute to circulation of lymph fluid?
-
-pressure gradients
-one way valves
-smooth muscle cells encircling lymphatics - What is filariasis?
- The parasitic worm Wuchereria bancroft forms nests in the lymphatic system, causing blockages. This results in edema.
- What does a p-value in statistical analysis indicate?
- large p-values in a comparison of two groups indicate that there is no difference between the two groups
- What is the difference between intent-to-treat analysis and treatment-received analysis?
-
-intent-to-treat: analysis is done assuming that all subjects received their assigned treatment
-treatment-received: results are analyzed using the actual treatment received by the patient - What aspects of a treatment are best measured using treatment-received analysis?
-
-efficacy of treatment
-analyzes therapy under ideal conditions - What aspects of a treatment are best measured using intent-to-treat analysis?
-
-effectiveness of treatment
-analyzes therapy under real-life conditions - What is a double blind study?
-
the following parties do not know what treatment group a subject has been assigned:
-subject
-personnel administering the treatment
-personnel assessing the outcomes/endpoints - What is a triple blind study?
-
the following parties do not know what treatment group a subject has been assigned:
-subject
-personnel administering the treatment
-personnel assessing the outcomes/endpoints
-personnel analyzing the study (statistician) - What is a Type I/α-error in statistical analysis? How is it identified?
-
-the result being due to chance
-present when the p-values are > 0.001 - What is a Type II/β-error in statistical analysis?
- sample size is too small to detect true differences
- What are the types of pleurae that encase the lungs?
-
-visceral (inner) pleura
-parietal (outer) pleura:
cervical
costal
diaphragmatic
mediastinal - How does the innervation of visceral and parietal pleura differ?
-
-visceral: supplied by autonomic nervous system (no pain)
-parietal: supplied by somatic nervous system (pain) → intercostal and phrenic nerves - What part of the parietal pleura is supplied by the intercostal nerves?
- costal
- What parts of the parietal pleura are supplied by the phrenic nerves?
-
-diaphragmatic
-mediastinal - What is pneumothorax? What causes it?
-
-collapse of the lung and separation of the two pleurae
-caused by introduction of air into pleural cavity - What is tension pneumothorax?
- pressure increase in the pleural cavity with a punctured lung causes mediastinal contents to be shifted to the other side, applying pressure to it
- Where is the apex of the lung with respect to the ribs?
- above the level of the 1st rib
- Where do the oblique fissures begin and end with respect to the lungs and ribs?
-
-begin at the posterior medial edge of the lung at the level of the base of the scapular spine
-end at the inferior border of the lung at costochondral junction of the 6th rib - The horizontal fissure meets the anterior border of the right lung at the level of which rib?
- rib 4
- The midclavicular line intersects the bottom of the lung at the level of which rib?
- rib 6
- The midaxillary line intersects the bottom of the lung at the level of which rib?
- rib 8
- The scapular line intersects the bottom of the lung at the level of which rib?
- rib 10
- The midclavicular line intersects the bottom of the parietal pleura at the level of which rib?
- rib 8
- The midaxillary line intersects the bottom of the parietal pleura at the level of which rib?
- rib 10
- The scapular line intersects the bottom of the parietal pleura at the level of which rib?
- rib 12
- How would injury to the phrenic nerve affect breathing?
- The affected side of the diaphragm would be paralyzed.
- How does the shape of the thoracic cage change with deep breathing?
-
-upper ribs: increase the anteroposterior dimension
-lower ribs: increase the transverse dimension - What grooves/impressions are present in the left lung and not in the right?
-
-brachiocephalic vein groove
-aortic impression
-cardiac notch - Where is the trachea with respect to the esophagus? Where does it bifurcate with respect to the spinal cord?
-
-the trachea is anterior to the esophagus
-it bifurcates at the level of T4-T5 - From what structure do the pulmonary arteries arise? What is their purpose?
-
-pulmonary tract
-convey poorly oxygenated blood to the lungs - What is the mean pulmonary arterial pressure?
- 15 mmHg
- Into what structure do pulmonary veins drain? What is their function?
-
-left atrium
-convey well oxygenated blood from the lungs - From what structures do bronchial arteries arise? What is their function?
-
-thoracic aorta
-posterior intercostal arteries (right)
-right bronchial artery may arise from the left
-carry well oxygenated blood to supply walls of bronchi and pleura - Into what structure do bronchial veins drain? What is their function?
-
-azygos vein (right)
-accessory hemiazygos vein (left)
-carry poorly oxygenated blood from the lungs - What is the superficial (subpleural) lymphatic plexus? To where does it drain?
-
-drains the surface of visceral pleura
-drains to bronchopulmonary (hilar) nodes - What is the deep lymphatic plexus? To where does it drain?
-
-follows the bronchi and pulmonary vessels
-drains to bronchopulmonary (hilar) nodes - What are the tracheobronchial lymph nodes? To where do they drain?
-
-drain the bronchopulmonary (hilar) lymph nodes
-drain into paratracheal nodes - To where do paratracheal lymph nodes drain?
-
-bronchomediastinal trunk → subclavian veins
-thoracic duct (left side) - Which pulmonary lobes are drained by the left paratracheal lymph nodes? Which are drained by the right?
-
-left: drain left superior lobe
-right: drain right lung, left inferior lobe - What is the effect of efferent vagal stimulation on the lungs?
- bronchoconstriction
- What is the effect of afferent vagal stimulation on the lungs?
-
-cough reflex
-stretch reception
-vasodilation - What is the effect of efferent sympathetic stimulation on the lungs?
-
-bronchodilation
-vasoconstriction - What is the effect of afferent sympathetic stimulation on the lungs?
- none
- Which ganglia supply the lungs with sympathetic stimulation?
- upper four thoracic ganglia
- What is the pulmonary edema safety factor?
- pressure difference between the capillaries and alveoli assures that absorption > filtration along the length of the pulmonary capillaries → water is always absorbed from the lung
- What effect do inotropic drugs have on left ventricle performance?
- increase stroke volume and cardiac output
- What effect do vasodilators have on left ventricle performance?
-
-decrease left ventricle end-diastolic pressure
-increase stroke volume and cardiac output - What effect do diuretics have on left ventricle performance?
- decrease left ventricle end-diastolic pressure
- What is the difference between vascular response to hypoxia in the systemic tissues vs. the lungs?
-
-systemic tissues: hypoxia/ischemia → vasodilation
-lungs: hypoxia → vasoconstriction - What is the sequence of events that occur with High Altitude Pulmonary Edema?
-
-pulmonary hypoxic vasoconstriction
-pulmonary hypertension
-pulmonary edema
-impaired gas exchange
-positive feedback loop - What is the foramen ovale? What happens to it following birth?
-
-shunt which allows highly oxygenated blood to enter the left atrium from the right atrium
-often sealed in the first year following birth as a result of left atrium pressure rising above right atrium pressure - What is the ductus arteriosus? What happens to it following birth?
-
-shunt which allows blood to enter the aorta from the right ventricle
-"functional closure" in 1-8 days following birth due to pulmonary artery pressure dropping below aortic pressure
-"anatomical closure" in 1-4 months following birth - What is Patent Ductus Arteriosus?
-
-failure of the ductus arteriosus to seal
-leads to pulmonary hypertension - How do systemic vascular resistance and arterial pressure change with birth? Why?
- 2-fold increase, due to increase in blood flow from the lungs to left ventricle
- How does pulmonary vascular resistance change with birth? Why?
- 10-fold decrease, caused by inflation of lungs and removal of fluid by coughing
- What is the ductus venosus?
-
-connects umbilical vein to the inferior vena cava
-carries highly oxygenated blood
-allows bypass of the fetal liver - How do the right and left ventricles change following birth? What is the electrical manifestation of this change?
-
-right ventricle atrophies
-left ventricle hypertrophies
-electrical axis of the heart swings to the left - Does gravity have a greater effect on venous or arterial pressure? Why?
-
-venous pressure
-because the veins are distensible - What is the effect of arising on mean arterial pressure and central venous pressure?
- small transient decrease (due to gravity)
- What is the effect of arising on heart rate?
- 30% increase (as compensation)
- What is the effect of arising on stroke volume?
- 40% decrease (Frank-Starling mechanism)
- What is the effect of arising on cardiac output?
- 25% decrease (combination of changes in heart rate and stroke volume)
- What is the effect of arising on systemic vascular resistance?
- increases (as compensation)
- What is the effect of arising on splanchnic, renal, and leg flow?
- 25% decrease (as compensation)
- What is the effect of arising on venous tone?
- increases (as compensation)
- What is the effect of arising on central blood volume?
- 400 mL decrease
- What is the effect of arising on blood volume in legs?
- 600 mL increase
- What is the cause of the increase in heart rate to 100 beats/min in response to exercise?
- withdrawal of vagal tone
- What is the cause of the increase in heart rate to 100-200 beats/min in response to exercise?
- sympathetic augmentation
- Why are athletes able to perform relatively more exercise at a given heart rate?
- larger stroke volume
- Why does arterial pressure remain relatively stable during exercise, in comparison with cardiac output increase?
- systemic vascular resistance decreases with exercise
- What is the sequence of events that leads to cardiogenic shock?
-
-myocardial failure
- ↓cardiac output
- ↓arterial pressure - What is the sequence of events that leads to hemorrhagic shock?
-
-blood loss
- ↓central venous pressure
- ↓cardiac output
- ↓arterial pressure - What is the sequence of events that leads to anaphylactic (septic) shock?
-
-vasodilator release
- ↓systemic vascular resistance
- ↓arterial pressure - What is the sequence of events that leads to neurogenic shock?
-
- ↓sympathetic drive
- ↓systemic vascular resistance
- ↓arterial pressure - How does the brain respond to shock (short-term)?
-
-cerebral ischemic response (below 60 mmHg)
- ↓parasympathetic activity
- ↑sympathetic activity - How does the heart respond to shock (short-term)?
-
- ↑heart rate
- ↑contractility
- ↑cardiac output - How does the vasculature respond to shock (short-term)?
-
- ↑vaso/venoconstriction
- ↑systemic vascular resistance
- ↓capillary pressure → transcapillary fluid absorption - How are the kidneys affected by shock?
-
-sympathetic augmentation (from brainstem)
- ↓renal perfusion (from ↓systemic vascular resistance) - How do the kidneys respond to shock (long-term)?
-
-RAA pathway
- ↓glomerular filtration
- ↓urine output
- ↑thirst
- ↑central venous pressure - How long can the brain and heart be deprived of blood flow before experiencing irreversible ischemic damage?
- 2-5 min
- How long can the kidney, lungs, and liver be deprived of blood flow before experiencing irreversible ischemic damage?
- 120-180 min
- How long can the skeletal muscle, gut, and skin be deprived of blood flow before experiencing irreversible ischemic damage?
- 360-600 min
- By what mechanisms is blood volume restored after hemorrhage?
-
-transcapillary refill
-renal fluid conservation
-thirst + sodium appetite - What are the decompensatory mechanisms in shock?
-
-intense sympathetic vasoconstriction
-ischemia of organs
-metabolic vasodilators override sympathetic input
- ↓mean arterial pressure
-positive feedback loop