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Questions and Answers
What is the primary function of capillary exchange in the circulatory system?
What is the primary function of capillary exchange in the circulatory system?
Through which of the following routes do chemicals NOT typically pass through capillary walls?
Through which of the following routes do chemicals NOT typically pass through capillary walls?
Which mechanism of capillary exchange is responsible for moving fatty acids and albumin across the endothelium?
Which mechanism of capillary exchange is responsible for moving fatty acids and albumin across the endothelium?
What force primarily drives fluid out of the capillary at the arterial end?
What force primarily drives fluid out of the capillary at the arterial end?
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What is the net effect of colloid osmotic pressure (COP) in capillaries?
What is the net effect of colloid osmotic pressure (COP) in capillaries?
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If capillaries typically reabsorb about 85% of the fluid they filter, what happens to the remaining 15%?
If capillaries typically reabsorb about 85% of the fluid they filter, what happens to the remaining 15%?
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Which of the following is NOT a primary cause of edema?
Which of the following is NOT a primary cause of edema?
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Which of the following poses the most immediate threat to life in cases of pulmonary edema?
Which of the following poses the most immediate threat to life in cases of pulmonary edema?
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Which mechanism of venous return relies on the expansion of the thoracic cavity during inhalation?
Which mechanism of venous return relies on the expansion of the thoracic cavity during inhalation?
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How does the skeletal muscle pump contribute to venous return?
How does the skeletal muscle pump contribute to venous return?
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What effect does exercise have on venous return?
What effect does exercise have on venous return?
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What is the primary cause of venous pooling shock?
What is the primary cause of venous pooling shock?
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What is the underlying cause of hypovolemic shock?
What is the underlying cause of hypovolemic shock?
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Which type of shock is characterized by loss of vasomotor tone leading to vasodilation?
Which type of shock is characterized by loss of vasomotor tone leading to vasodilation?
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What is the critical outcome in decompensated shock if the positive feedback loops are not broken?
What is the critical outcome in decompensated shock if the positive feedback loops are not broken?
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What is the primary chemical stimulus that regulates cerebral blood flow?
What is the primary chemical stimulus that regulates cerebral blood flow?
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Which condition results from decreased carbon dioxide levels leading to vasoconstriction and potentially dizziness?
Which condition results from decreased carbon dioxide levels leading to vasoconstriction and potentially dizziness?
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Brief episodes of cerebral ischemia causing temporary neurological deficits are characteristic of what condition?
Brief episodes of cerebral ischemia causing temporary neurological deficits are characteristic of what condition?
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What is the most likely underlying cause of a cerebral vascular accident (CVA)?
What is the most likely underlying cause of a cerebral vascular accident (CVA)?
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What physiological response occurs in skeletal muscles during exercise to increase blood flow?
What physiological response occurs in skeletal muscles during exercise to increase blood flow?
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In the pulmonary circuit, what unique response occurs when an area of the lung experiences hypoxia?
In the pulmonary circuit, what unique response occurs when an area of the lung experiences hypoxia?
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Which arteries supply blood to right shoulder and upper limb?
Which arteries supply blood to right shoulder and upper limb?
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What significant role does the Circle of Willis play in the cerebral blood supply?
What significant role does the Circle of Willis play in the cerebral blood supply?
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The vertebral arteries combine to form which artery?
The vertebral arteries combine to form which artery?
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What volume of air entering a coronary artery is potentially fatal?
What volume of air entering a coronary artery is potentially fatal?
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The internal thoracic, anterior intercostal and pericardiophrenic arteries arise from which artery?
The internal thoracic, anterior intercostal and pericardiophrenic arteries arise from which artery?
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Obstruction of hepatic circulation can lead to portal hypertension. What is the primary symptom related to this condition?
Obstruction of hepatic circulation can lead to portal hypertension. What is the primary symptom related to this condition?
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As the subclavian artery passes between the clavicle and first rib, what does it become?
As the subclavian artery passes between the clavicle and first rib, what does it become?
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Hypertension is defined as a common cardiovascular disease, what percentage of Americans over 50 does it affect?
Hypertension is defined as a common cardiovascular disease, what percentage of Americans over 50 does it affect?
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Which of the following is considered a potential cause of secondary hypertension?
Which of the following is considered a potential cause of secondary hypertension?
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Flashcards
Total blood flow to brain
Total blood flow to brain
Constant flow of 700 mL/min necessary for brain function.
Stroke (CVA)
Stroke (CVA)
Sudden brain tissue death due to ischemia, leading to possible paralysis or loss of speech.
Transient Ischemic Attack (TIA)
Transient Ischemic Attack (TIA)
Brief cerebral ischemia that may warn of an impending stroke.
Hypercapnia
Hypercapnia
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Hypocapnia
Hypocapnia
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Cerebral blood regulation
Cerebral blood regulation
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Skeletal muscle blood flow
Skeletal muscle blood flow
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Pulmonary blood flow
Pulmonary blood flow
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Circle of Willis
Circle of Willis
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Air embolism
Air embolism
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Portal hypertension
Portal hypertension
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Primary hypertension
Primary hypertension
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Secondary hypertension
Secondary hypertension
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Atherosclerosis
Atherosclerosis
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Aortic arch arteries
Aortic arch arteries
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Capillary Exchange
Capillary Exchange
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Routes of Chemical Transport
Routes of Chemical Transport
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Diffusion
Diffusion
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Transcytosis
Transcytosis
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Filtration and Reabsorption
Filtration and Reabsorption
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Edema
Edema
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Hydrostatic Pressure
Hydrostatic Pressure
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Colloid Osmotic Pressure (COP)
Colloid Osmotic Pressure (COP)
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Mechanisms of Venous Return
Mechanisms of Venous Return
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Thoracic Pump
Thoracic Pump
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Cardiac Suction
Cardiac Suction
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Circulatory Shock
Circulatory Shock
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Hypovolemic Shock
Hypovolemic Shock
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Compensated Shock
Compensated Shock
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Decompensated Shock
Decompensated Shock
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Study Notes
Circulatory System II
- 100,000 miles of blood vessels exist in an adult human body.
- Capillary exchange is the most important blood exchange in the body, occurring only through capillary walls.
- Fluid moves across capillary walls in two directions.
- Key substances transported are: water, oxygen, glucose, amino acids, lipids, minerals, antibodies, hormones, wastes, carbon dioxide, and ammonia.
- Chemicals pass through capillary walls via three routes: endothelial cell cytoplasm, intercellular clefts, and filtration pores (fenestrations).
- Mechanisms involved in capillary exchange include diffusion, transcytosis, filtration, and reabsorption.
Diffusion
- Diffusion is the most crucial form of capillary exchange.
- Glucose and oxygen diffuse out of the blood.
- Carbon dioxide and other waste diffuse into the blood.
- Capillary diffusion occurs when the endothelial cell membrane is permeable to the solute, and the solute can pass through filtration pores or intracellular clefts.
- Lipid-soluble substances (e.g., steroid hormones, O2, CO2) diffuse easily through plasma membranes.
- Water-soluble substances (e.g., glucose, electrolytes) must pass through filtration pores and intercellular clefts.
- Large particles, like proteins, cannot pass through and are retained.
Transcytosis
- Transcytosis is vesicle-mediated transport across endothelium.
- It involves pinocytosis or receptor-mediated endocytosis to pick up materials and exocytosis on the other side.
- Transcytosis accounts for a small portion of solute exchange.
- It's crucial for fatty acids, albumin, and some hormones (like insulin).
Filtration and Reabsorption
- Fluid filters out of the arterial end of capillaries and reenters via the venous end due to osmotic forces.
- This process delivers materials to cells and removes metabolic wastes.
- Forces (e.g., hydrostatic and osmotic pressures) determine the net filtration or reabsorption pressure.
- At the arterial end, filtration pressure (13 mm Hg) is greater, and at the venous end, reabsorption pressure (7 mm Hg) dominates.
- 85% of the filtered fluid is reabsorbed; the remaining 15% is collected by the lymphatic system.
Variations in Capillary Filtration and Reabsorption
- Filtration typically occurs at the arterial end, and reabsorption happens at the venous end.
- Some locations, such as glomeruli in kidneys, are specialized for filtration, while alveolar capillaries in lungs prioritize reabsorption.
- Activity or trauma can increase filtration.
Edema
- Edema is the accumulation of excess fluid in tissues.
- Fluid filters into tissues faster than absorption occurs, leading to swelling.
- Three primary causes include increased capillary filtration, reduced capillary reabsorption, and obstructed lymphatic drainage.
- Conditions like kidney failure, histamine, old age, and poor venous return can result in excess filtration. Also, hypoproteinemia (low protein in blood), liver disease, and dietary protein deficiency can lead to reduced absorption.
Pathological Consequences of Edema
- Edema can lead to tissue necrosis (tissue death) due to impaired oxygen delivery and waste removal, particularly in the lungs (pulmonary edema) and brain (cerebral edema).
- This can cause symptoms ranging from headaches and nausea to seizures and coma, as well as circulatory shock, causing low blood volume and pressure.
Lymphedema
- This is a specific type of edema due to impaired lymphatic drainage.
Mechanisms of Venous Return
- Venous return involves pressure gradient, gravity, skeletal muscle pump, thoracic pump, and cardiac suction to move blood back to the heart.
- Blood pressure, particularly venous pressure (7-13 mm Hg), is a significant driver.
- Gravity assists in draining blood from the head and neck.
- Contracting muscles compress veins, aiding blood movement.
- Valves prevent backflow.
- The thoracic pressure changes during breathing (inhalation & exhalation) push blood upward and further facilitate venous return.
Venous Return and Physical Activity
- Exercise increases venous return, including faster and stronger heartbeats and dilated blood vessels, increasing blood flow.
- These factors also enhance respiratory and skeletal muscle pump actions.
Circulatory Shock
- Circulatory shock occurs when cardiac output is insufficient to meet the body's metabolic needs.
- Three main forms of low venous return (LVR) shock include hypovolemic shock (loss of blood volume), obstructed venous return shock (a blocked vein), and venous pooling shock (blood pooling).
- Neurogenic shock, septic shock (bacterial toxins), and anaphylactic shock (immune reaction) are other types.
Responses to Circulatory Shock
- Compensated shock involves successful homeostatic mechanisms restoring normal bodily functions.
- Decompensated shock occurs when these compensatory mechanisms fail, leading to worsening conditions and potentially fatal consequences.
Brain
- Brain blood flow is relatively constant (700 mL/min), but active areas temporarily get more blood than others.
- Brain regulates blood flow based on the chemical stimulus of pH, mainly affected by CO2 concentration.
- Hypercapnia (high CO2) leads to vasodilation.
- Hypocapnia (low CO2) leads to vasoconstriction.
- Transient ischemic attacks (TIAs) are brief ischemic episodes (caused by blood vessel spasm) with symptoms like dizziness, vision loss, weakness, paralysis, or headache. This can be an early warning sign of stroke.
- Stroke (cerebral vascular accident) is the rapid death of brain tissue due to either ischemia (inadequate blood supply) or a ruptured blood vessel.
Skeletal Muscles
- Blood flow to muscles varies considerably based on activity levels.
- At rest, blood vessels constrict, reducing flow.
- During exercise, blood flow increases dramatically up to 20-fold in response to specific metabolic products.
Lungs
- Low pulmonary blood pressure (25/10 mm Hg) allows for efficient gas exchange.
- Oncotic pressure is more effective in shifting fluids compared to blood pressure.
- Pulmonary capillaries absorb fluid (no significant filtration).
- Blood flow through diseased areas in the lungs is redirected to better-ventilated regions in response to hypoxia.
Blood Vessels of the Thorax
- The thoracic aorta supplies blood to the visceral structures (organs) and the body wall.
- The bronchial, esophageal, and mediastinal branches are key to proper blood supply throughout the region.
- Posterior intercostal and phrenic arteries branch off the thoracic aorta to deliver blood to the posterior intercostal muscles and diaphragm.
- Internal thoracic, anterior intercostal, and pericardiophrenic arteries also provide significant blood supply originating from the subclavian artery.
Major Systemic Arteries, Veins, and Their Branches
- Diagrams and descriptions exist for arteries and veins in specific regions, including the head, neck, upper limb, lower limb, and abdomen.
Air Embolism
- Air entering the circulatory system from injured vessels can be severely harmful.
- Small volumes of air in crucial areas (e.g., coronary arteries) can cause cardiac arrest and death.
Hypertension (High Blood Pressure)
- Hypertension is a common and dangerous cardiovascular disease, affecting a significant proportion of the population.
- Hypertension is associated with heart failure, stroke, and kidney failure.
- Hypertension damages the heart by consistently increasing pressure.
- High blood pressure can be classified as primary (mostly lifestyle related) and secondary (due to other health conditions).
Other Important Highlights:
- Specific pressure point locations in the body for medical purposes.
- Various anatomical structures and their functions relating to the circulatory system.
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