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Questions and Answers
What are the three main components of the cardiovascular system?
Heart, blood vessels, and blood.
Explain the primary function of the heart in the cardiovascular system.
The heart acts as a pump to generate pressure in the blood, facilitating its movement through the blood vessels.
What are the differences between the atria and ventricles in terms of wall thickness?
Atria have thinner walls, while ventricles have thicker walls.
What role do valves play in the heart?
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Describe the significance of the pericardium in protecting the heart.
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What is cardiac output and how is it calculated?
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What is the purpose of the trabeculae carneae found in the ventricles?
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How does the autonomic nervous system influence the cardiovascular system?
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What is the primary role of epinephrine in the cardiovascular system during stress?
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Describe the function of the sinoatrial node in the heart.
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How does blood composition differentiate between plasma and formed elements?
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What is the significance of a biconcave shape in erythrocytes?
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Explain the term 'auto-rhythmicity' in the context of cardiac muscle.
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What are the primary components of the blood's plasma?
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Describe the difference in blood volume between an average male and female.
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What role do leukocytes play in the body's defense mechanisms?
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How do action potentials affect cardiac muscle contraction?
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What is the pH range of healthy human blood?
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What is the role of osmolarity in fluid movement outside the capillary?
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Explain why a pulse can only be felt in certain areas of the body.
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Describe the change in heart rate observed during the experiment after 5 minutes of recovery.
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What factors contribute to an increase in stroke volume as exercise intensity increases?
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What anatomical structures are involved in controlling blood flow from the left ventricle?
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What are the primary functions of neutrophils in the immune system?
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Why are platelets not considered true cells?
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Describe the structural differences between arteries and veins.
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What are precapillary sphincters and their function?
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What is the significance of the tunica media in blood vessels?
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How do capillaries facilitate the exchange of substances?
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Contrast the types of blood carried by arteries and veins.
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Explain the role of valves in veins.
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What happens to blood flow when smooth muscles in the tunica media contract?
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What are the main layers of a blood vessel from innermost to outermost?
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What are fenestrated capillaries and where are they commonly found?
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Explain the concept of capillary exchange and its importance.
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Describe how oxygen and carbon dioxide exchange occurs at the cellular level.
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What role does interstitial fluid play in nutrient delivery?
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How do lipid-soluble substances diffuse across capillary membranes?
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What consequences arise if the lymphatic system fails to function properly?
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What is the difference between fenestrated and sinusoidal capillaries?
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How does osmotic pressure affect fluid movement in capillaries?
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Identify factors that can lead to edema in tissues.
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What is the significance of the blood-brain barrier in relation to capillary structure?
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What effect does exercise have on blood pressure?
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How does epinephrine affect heart rate and stroke volume?
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What is the role of the sinoatrial node in the cardiac conduction system?
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Why do erythrocytes (red blood cells) lack organelles?
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Describe the composition of blood plasma.
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What defines the term 'auto-rhythmicity' in cardiac muscles?
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How do leukocytes respond to an infection?
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What is the significance of the biconcave shape of erythrocytes?
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What is the function of fibrinogen in blood?
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What is the typical blood volume for an average adult male?
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What is the primary physiological phenomenon driving fluid exchange out of capillaries into interstitial fluid?
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Why is it possible to palpate a pulse in certain areas of the body?
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How does heart rate change during physical activity, according to the provided experiment data?
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What happens to the stroke volume during exercise, based on the experiment's findings?
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What is the function of the bicuspid and tricuspid valves in the heart?
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What structural characteristic of fenestrated capillaries facilitates their permeability?
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Explain the importance of interstitial fluid in capillary exchange.
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How do pressure gradients affect the diffusion of gases like oxygen and carbon dioxide in capillaries?
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Describe the role of the lymphatic system in maintaining fluid balance within the body.
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What consequences arise from failure in the lymphatic system?
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Why is the structure of sinusoidal capillaries important for their function?
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Identify how capillary exchange impacts the delivery of nutrients and removal of waste.
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How do water-soluble molecules traverse the capillary wall?
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What is the significance of maintaining a pressure gradient in capillary function?
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In what way does the metabolic activity of cells impact the concentration gradient in tissue fluid?
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What anatomical feature prevents backflow of blood from the ventricles into the atria?
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What is the role of the pericardial fluid, and where is it located?
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How do trabeculae carneae contribute to heart function?
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What separates oxygenated and deoxygenated blood in the heart's anatomy?
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In which part of the heart does the majority of oxygenated blood enter?
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What is the significance of the fossa ovalis in heart anatomy?
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Describe the primary function of pulmonary circulation.
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What are the two types of valves in the heart and their respective functions?
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What is the primary function of platelets in the circulatory system?
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How do arterioles regulate blood flow to capillaries?
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What distinguishes elastic arteries from muscular arteries?
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What are the structural characteristics of capillaries that facilitate their function?
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How do veins prevent the backflow of blood?
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What is the significance of blood vessel lumen shape in arteries and veins?
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What role do the tunica media and tunica externa play in blood vessels?
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What prevents bleeding from minor cuts in the circulatory system?
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How do precapillary sphincters impact blood distribution in the body?
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Describe the function of neutrophils in the blood.
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Study Notes
Cardiovascular System Components
- Heart: A muscular pump responsible for generating pressure to move blood throughout the body.
- Blood Vessels: Conduits for blood transportation. Include arteries, veins, and capillaries.
- Blood: A connective tissue consisting of plasma, formed elements (red and white blood cells), and platelets. Responsible for transporting substances throughout the body.
Cardiovascular System Functions
- Transport: Carries gases (oxygen, carbon dioxide, nitrogen), nutrients (glucose, amino acids), metabolic waste (urea, uric acid), regulatory molecules (hormones, enzymes), and processed molecules (proteins, enzymes, carbohydrates, lipids).
- Protection: Involves inflammation, phagocytosis, antibodies, and platelets for clotting.
- Regulation: Maintains fluid balance, pH, body temperature, blood pressure, and exchange between blood, extracellular fluid, and cells.
Heart Anatomy and Function
- Location: Situated in the thoracic cavity, obliquely in the mediastinum, medial to the lungs, and superior to the diaphragm.
- Size: The size of a closed fist weighing approximately 300g (250-350g), slightly smaller in women.
- Shape: Blunt cone-shaped, with 2/3 towards the left side of the midline.
- Function: Pumps blood through the circulatory system.
- Routs blood: Separate pulmonary and systemic circulation. This is achieved through its design, separating deoxygenated blood from oxygenated blood.
- One-way flow: Achieved through pressure gradients.
- Regulates blood supply: Influenced by cardiac output and the heart adjusts to the body's needs (homeostasis).
Pericardium
- Fibrous Pericardium: Tough outer layer that prevents overdistension and anchors the heart.
-
Serous Pericardium: Thin inner layer with two continuous parts:
- Parietal Pericardium: Lines the fibrous outer layer.
- Visceral Pericardium: Covers the surface of the heart (epicardium).
- Pericardial Cavity: Space between the two layers containing pericardial fluid, which reduces friction and distributes pressure.
- Pericarditis: Infection of the pericardium.
Heart Morphology
-
Sulci (Grooves):
- Coronary Sulcus: Separates the atria and ventricles.
- Anterior Interventricular Sulcus: Separates the right and left ventricles on the anterior side.
- Posterior Interventricular Sulcus: Separates the right and left ventricles on the posterior side.
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Pericardial and Epicardial Fat:
- Pericardial Fat: Located between the visceral and parietal pericardium.
- Epicardial Fat: Located between the outer layer of the myocardium and visceral pericardium (epicardium).
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Chambers:
- Atria (Superior Chambers): Thin-walled collecting chambers.
- Ventricles (Inferior Chambers): Thick-walled discharging chambers.
Heart Wall Layers
- Epicardium: Outer layer composed of serous membrane, simple squamous epithelium over areolar tissue.
- Myocardium: Middle layer, thickest layer, composed of cardiac muscle cells responsible for contractility.
- Endocardium: Inner layer, smooth inner surface of heart chambers, simple squamous epithelium over areolar tissue, covers valve surface and continuous with endothelium.
Heart Anatomy
- Interventricular Septum: The separation between the two ventricles.
- Interatrial Septum: The wall between the atria, containing the fossa ovalis, a remnant of the fetal opening (foramen ovale) between the atria.
- Left Ventricle Wall: Significantly thicker than the right ventricle wall.
- Pectinate Muscles: Muscular ridges in the auricle and atrial walls, aiding in contraction.
- Trabeculae Carnae: Muscular ridges and columns on the inside of the ventricle wall, creating turbulence in the blood.
Heart Chambers
- Right Atrium: Thin-walled receiving chamber, mostly on the posterior side.
- Right Ventricle: Pumping chamber, mostly on the anterior side.
- Left Atrium: Thin-walled receiving chamber, mostly on the posterior side.
- Left Ventricle: Pumping chamber, forms the apex and posteroinferior aspect.
Great Blood Vessels of the Heart
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Blood into the Heart:
- Right Atrium: Receives deoxygenated blood through the superior and inferior vena cava from systemic circulation and the coronary sinus from the coronary circulation.
- Left Atrium: Receives oxygenated blood through four pulmonary veins from the pulmonary circulation.
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Blood Out of the Heart:
- Right Ventricle: Sends deoxygenated blood through the pulmonary trunk (which splits into two pulmonary arteries) to the pulmonary circulation.
- Left Ventricle: Sends oxygenated blood through the aorta to the systemic circulation.
Heart Valves
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Atrioventricular Valves:
- Located between atria and ventricles.
- Have leaf-like cusps.
- Attached to papillary muscles by chordae tendineae.
- Right side: Three cusps (tricuspid, right AV valve).
- Left side: Two cusps (bicuspid, left AV valve).
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Semilunar Valves:
- Located at the base of large blood vessels (exit of ventricles).
- Cup-shaped valves.
- Pulmonary SL valve: At the base of the pulmonary trunk.
- Aortic pulmonary valve: At the base of the aorta.
Blood Flow through the Heart
- Superior and inferior vena cava and coronary sinus -> right atrium -> tricuspid valve -> right ventricle -> pulmonary semilunar valve -> pulmonary trunk -> pulmonary arteries -> lung tissue -> pulmonary veins -> left atrium -> bicuspid valve -> left ventricle -> aortic semilunar valve -> aorta -> coronary arteries or body tissues
Heart as a Pump
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Pulmonary Circulation:
- Deoxygenated blood is transported to the lungs for oxygenation and then returned to the heart.
- Deoxygenated blood enters the right atrium, flows into the right ventricle, exits through the pulmonary trunk, and travels through the pulmonary arteries to the lungs for gas exchange.
- Oxygenated blood returns to the heart through the pulmonary veins into the left atrium.
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Systemic Circulation:
- Oxygenated blood is transported to the body tissues and then returned to the heart.
- Oxygenated blood enters the left atrium, flows into the left ventricle, exits through the aorta, and is delivered to body cells for exchange.
- Deoxygenated blood returns to the heart through the vena cava into the right atrium.
- Coronary Circulation: A part of systemic circulation that supplies blood to the heart.
Cardiac Cycle
- Contraction and Relaxation: Repetitive contraction (systole) and relaxation (diastole) of the heart chambers, moving blood through the heart and body.
- Blood flow: Proportional to the metabolic needs of tissues.
- Cardiac Output: The amount of blood ejected from the heart per minute (heart rate x stroke volume).
- Nervous System Control: The autonomic nervous system maintains blood pressure and blood flow, rerouting blood flow as needed.
- Hormonal Control: Epinephrine (adrenaline) increases heart rate and stroke volume by inducing vasoconstriction, a stress response.
Conducting System
- Cardiac Conducting System: Internal pacemaker and nerve-like pathways through the myocardium that trigger heart contractions.
- Action Potential: A rapid change in membrane potential that acts as an electrical signal.
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Auto-rhythmicity: Repetitive contractions caused by autorhythmic contractile cells:
- Sinoatrial Node (SA Node): Located in the atrial wall, acts as the pacemaker, generating action potentials at regular intervals.
- Atrioventricular Node (AV Node): Located at the junction of the atrium and ventricles.
- Atrioventricular Bundle (Bundle of His): Nerve tissue that continues from the AV node.
- Right and Left Bundle Branches: Branches of the AV bundle that extend to the apex of the heart and through the myocardium.
- Purkinje Fibers: Branches given off by the right and left bundle branches, extending throughout the ventricular walls.
Blood Composition
- Plasma: Extracellular matrix of blood, composed of water, proteins, and other solutes.
- Buffy Coat: Contains white blood cells and platelets.
- Formed Elements: Composed of erythrocytes (red blood cells).
- Erythrocytes (Red Blood Cells): Biconcave disc-shaped cells that lack a nucleus and organelles. They transport oxygen and carbon dioxide.
- Leukocytes (White Blood Cells): Complete cells with a nucleus and organelles. They are involved in protection and immune responses.
- Platelets: Cytoplasmic fragments of large cells that are essential for blood clotting.
Blood Vessels
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Arteries: Carry blood away from the heart, containing blood under pressure.
- Elastic Arteries: Large arteries like the aorta and pulmonary trunk, able to withstand high pressure.
- Muscular Arteries: Facilitate vasoconstriction and vasodilation.
- Arterioles: Smaller arteries that feed into capillaries.
- Precapillary Sphincters: Regulate blood flow to specific areas.
- Capillaries: The site of exchange with tissues.
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Veins: Carry blood towards the heart, containing blood under low pressure.
- Venules: Smallest veins.
- Valves: Prevent backflow of blood.
Histology of Blood Vessels
- Tunica Intima: Innermost layer composed of simple squamous endothelium, a basement membrane, lamina propria, and elastic tissue.
- Tunica Media: Middle layer with smooth muscle cells and elastin arranged circularly. Responsible for vasoconstriction and vasodilation.
- Tunica Externa: Outer layer of connective tissue that merges with surrounding tissue.
Blood Vessels Comparison
Characteristic | Arteries | Veins |
---|---|---|
Direction | Carries blood away from the heart to the tissues | Carries blood to the heart from the tissues |
Location | Located deep in the muscle | Located closer to the surface of your body |
Wall Thickness | Have very thick walls | Have thinner walls than arteries |
Blood Type | Carry mainly oxygenated and some deoxygenated blood | Carry mainly deoxygenated and some oxygenated blood |
Valves | Have no valves due to high pressure | Have valves to prevent backflow of blood as there is low pressure |
Pressure | Carry blood under very high pressure | Carry blood under very low pressure |
Lumen | Round lumen (holds its shape) | Flat lumen (looks collapsed) |
Capillaries
- Structure: Composed of endothelial cells, a basement membrane, and a delicate layer of loose connective tissue.
-
Types:
- Continuous Capillaries: No gaps between endothelial cells, less permeable to large molecules.
- Fenestrated Capillaries: Windows in endothelial cells allow for greater permeability.
- Sinusoidal Capillaries: Large gaps and irregular lumen allow free exchange of large protein molecules.
Capillary Types
- Fenestrated Capillaries: Have pores in the endothelial cells (fenestrae) and highly permeable. Found in intestinal villi and the glomeruli of the kidney.
- Sinusoidal Capillaries: Have a large diameter and irregular, incomplete walls of endothelial cells with less basement membrane. Found in endocrine glands and the liver as large molecules cross their walls.
Capillary Structure
- Capillaries only have tunica intima, no media or externa.
- Capillaries have a diameter of 7-9 microns, smaller than red blood cells (7.5 microns).
Capillary Exchange
- Substances must pass through the interstitial fluid to reach their destinations.
- Diffusion is driven by pressure gradients.
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Source and Sink Principle:
- Cells use oxygen, lowering its concentration. Freshly oxygenated blood flowing through capillaries maintains a concentration gradient, driving oxygen movement out of blood and into cells.
- Cells produce carbon dioxide, increasing its concentration. Freshly oxygenated blood with low CO2 levels maintains a concentration gradient, driving carbon dioxide movement out of cells and into blood.
Transport Across Capillaries
- Lipid-soluble substances like oxygen, carbon dioxide, steroid hormones, and fatty acids diffuse through the plasma membrane of endothelial cells.
- Water-soluble molecules like glucose and amino acids diffuse through intercellular spaces or fenestrations.
- The small spaces between cells restricts movement of large molecules in most capillaries.
- The blood-brain barrier is a specialized capillary system with tight junctions that restrict the passage of most substances into the brain.
- Larger spaces between endothelial cells in the liver or spleen allow proteins and even whole cells to pass.
Lymphatic System
- Lymphoid Organs: Spleen, thymus, tonsils.
- Lymphoid Tissues & Cells: MALT, Peyer's patches, lymphocytes (B and T cells).
- Lymph: Fluid that circulates through lymphatic vessels.
- Lymph Nodes: Filter and trap foreign substances from the lymph.
Connection between Cardiovascular and Lymphatic Systems
- Capillary permeability, blood pressure, and osmotic pressure influence fluid movement from capillaries.
- Fluid leaks out of capillaries into the interstitial space, and most returns to the capillaries due to osmotic pressures.
- The lymphatic system collects the remaining fluid in tissues and carries it back to venous circulation.
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Importance of the Lymphatic System:
- Prevents fluid accumulation (edema) and swelling.
- Maintains blood volume and pressure.
- Regulates fluid balance.
Edema
- Swelling caused by excess fluid in tissues (interstitial space).
- Causes: Capillary leakiness, heart failure, kidney disease, liver problems, pregnancy, lymphatic system problems, standing/walking in hot weather, high salt intake.
- Leaky capillaries can allow proteins into the interstitial fluid, increasing its osmotic pressure and drawing more fluid out of capillaries.
Cardiovascular System Components
- Heart: A muscular pump that generates pressure within blood to circulate it throughout the body.
- Blood Vessels: Conduits for blood transport, including arteries, veins, and capillaries.
- Blood: Carries dissolved and suspended substances, delivering them to various locations throughout the body.
Cardiovascular System Functions
-
Transport:
- Gases: Oxygen, carbon dioxide, and nitrogen.
- Nutrients: Glucose, amino acids, vitamins, proteins, and lipids.
- Metabolic Waste: Urea, uric acid, creatine, and ammonium ions.
- Regulatory Molecules: Hormones and enzymes.
- Processed Molecules: Proteins, enzymes, carbohydrates, and lipids.
-
Protection:
- Inflammation: Triggered by infections or injuries.
- Phagocytosis: The process where cells engulf and destroy foreign particles.
- Antibodies: Proteins that identify and neutralize pathogens.
- Platelets: Small cell fragments that help with blood clotting.
-
Regulation:
- Fluid Balance: Regulates water content in the body.
- pH: Maintains the body's pH level.
- Body Temperature: Regulates body temperature through blood flow.
- Blood Pressure: Maintains blood pressure for efficient blood circulation.
- Exchange: Facilitates exchange between blood, interstitial fluid, and cells.
Heart
-
Function:
- Pump: Creates pressure for blood movement through blood vessels.
- Routing: Separates pulmonary and systemic circulatory pathways.
- One-way flow: Achieved through pressure gradients.
- Regulation: Blood supply adjusted to meet body demands (homeostasis).
-
Protection:
- Rib cage, protective membranes, and fluid (pericardium): Provide a physical barrier for the heart.
-
Location:
- Thoracic cavity, within the mediastinum, medial to the lungs, and superior to the diaphragm.
- Size: Approximately the size of a closed fist, weighing around 300g (250-350g), with females having slightly smaller hearts.
- Shape: Blunt-cone shaped, with 2/3rd towards the left side of the midline.
- Apex: Rounded end, pointing anteriorly and inferiorly, above the diaphragm.
- Base: Broader end, directed posteriorly and slightly superiorly.
- Position: Sits between the second rib and the 5th intercostal space.
Pericardium
-
Fibrous Pericardium: Tough outer layer that prevents over-distension and anchors the heart to surrounding tissues.
-
Serous Pericardium: Thin inner layer, composed of simple squamous epithelium.
- Parietal: Lines the fibrous outer layer.
- Visceral: Covers the heart's surface, resembling cling film.
- Pericardial Cavity: Space between parietal and visceral layers, filled with pericardial fluid which reduces friction and distributes pressure.
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Protection: The pericardium provides protection for the heart.
-
Attachments: Attached to the large blood vessels (aorta and pulmonary trunk).
-
Pericarditis: Infection of the pericardium.
Heart Morphology
-
Anterior & Posterior Sides: Contain major blood vessels.
-
Sulci (Grooves):
- Coronary Sulcus: Separates the atria and ventricles.
- Anterior Interventricular Sulcus: Separates the right and left ventricles (anterior side).
- Posterior Interventricular Sulcus: Separates the right and left ventricles (posterior side).
-
Pericardial & Epicardial Fat:
- Pericardial Fat: Between visceral and parietal pericardium.
- Epicardial Fat: Between outer layer of myocardium and visceral pericardium (epicardium).
-
Superior Chambers (Collecting): Atria with thinner walls.
-
Inferior Chambers (Discharging): Ventricles with thicker walls.
Heart Wall
- Epicardium: (Visceral Pericardium) Outer layer, serous membrane, simple squamous epithelium over areolar tissue, providing a smooth surface.
- Myocardium: Middle layer, thickest layer, composed of cardiac muscle cells, responsible for contractility, branched cells, and uninucleate.
- Endocardium: Inner layer, smooth, simple squamous epithelium over areolar tissue, covers the valve surface, continuous with endothelium, and very smooth.
Heart Anatomy
- Interventricular Septum: Wall separating the two ventricles.
- Interatrial Septum: Wall separating the atria, containing the fossa ovalis, a remnant of the fetal opening (foramen ovale) between the atria.
- Left Ventricle Wall: Significantly thicker than the right ventricle wall.
- Pectinate Muscles: Muscular ridges in the auricle and atrial walls, allowing for muscle stretching during blood inflow and aiding in contraction.
- Trabeculae Carnae: Muscular ridges and columns on the ventricle wall's inner surface, creating turbulence within blood.
Chambers
-
Right Atrium: Thin-walled receiving chamber, primarily on the posterior side.
- Auricles: Extensions increasing volume.
- Pectinate Muscles: Allow for large force of contraction.
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Blood Inflow: Receives deoxygenated blood through three openings:
- Superior and inferior vena cava
- Coronary Sinus
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Right Ventricle: Pumping chamber, mainly on the anterior side.
- Wall Thickness: Thicker than the atria.
- Blood Flow: Receives deoxygenated blood from the right atrium, and pumps blood to the pulmonary trunk.
- Trabeculae Carnae: Present within this chamber.
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Left Atrium: Thin-walled receiving chamber, predominantly on the posterior side, forming the heart's base.
- Auricles: Extensions increasing volume.
- Pectinate Muscles: Allow for Large force of contraction.
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Blood Inflow: Receives oxygenated blood through four openings:
- Four Pulmonary Veins
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Left Ventricle: Pumping chamber, forms the apex and posteroinferior aspect.
- Wall Thickness: Thickest chamber of the heart.
- Blood Flow: Receives oxygenated blood from the left atrium and pumps blood to the aorta.
- Trabeculae Carnae: Present within this chamber.
Great Blood Vessels of the Heart
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Blood into the Heart:
-
Right Atrium: Receives blood from:
- Superior and Inferior Vena Cava (Systemic Circulation): Deoxygenated blood.
- Coronary Sinus (Coronary Circulation): Deoxygenated blood.
-
Left Atrium: Receives blood from:
- Four Pulmonary Veins (Pulmonary Circulation): Oxygenated blood.
-
Right Atrium: Receives blood from:
-
Blood out of the Heart:
- Right Ventricle: Blood exits through the pulmonary trunk (dividing into two pulmonary arteries for each lung) to the pulmonary circulation (deoxygenated).
- Left Ventricle: Blood exits through the aorta to the systemic circulation (oxygenated).
Valves of the Heart
-
Atrioventricular (AV) Valves: Between atria and ventricles.
- Leaf-like Cusps: Structure of the valves.
- Chordae Tendineae: Tendons attaching cusps to papillary muscles.
- Atrioventricular Canal: Canal formed by open valves.
-
Right Side (Tricuspid Valve): Three cusps.
- Left Side (Bicuspid or Mitral Valve): Two cusps.
- Function: Allow blood flow from atrium to ventricle when open, and close to prevent blood flow back into the atrium when the ventricle contracts.
-
Semilunar (SL) Valves: At the base of large blood vessels (exit of ventricles).
- Cup-shaped Structure: Their shape.
- Pulmonary SL Valve: Located at pulmonary trunk base.
- Aortic SL Valve: Located at aorta base.
-
Function:
- Close when cups are filled, preventing blood backflow into the heart.
- Open when cups are empty allowing blood flow freely out of the heart.
-
Specific Valve Functions:
- Chordae Tendineae: Prevent atrioventricular valves from bulging into the aorta.
- Papillary Muscles: Pillar-like muscles in ventricles, preventing atrioventricular valve prolapse.
Blood Flow through the Heart
- Path: Superior and inferior vena cava & coronary sinus - > right atrium -> tricuspid valve -> right ventricle -> pulmonary semilunar valve -> pulmonary trunk -> pulmonary arteries -> lung tissue -> pulmonary veins -> left atrium -> bicuspid valve -> left ventricle -> aortic semilunar valve -> aorta -> coronary arteries or body tissues.
Heart as Pump
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Pulmonary Circulation: Deoxygenated blood travels to the lungs for oxygenation and returns to the heart, completing a double cycle.
- Flow: Deoxygenated blood enters the right atrium, moves into the right ventricle, exits through the pulmonary trunk, branches into left and right pulmonary arteries, reaches the lungs for gas exchange, oxygenated blood travels through pulmonary veins back to the left atrium.
-
Systemic Circulation: Oxygenated blood circulates to body tissues and returns to the heart.
- Flow: Oxygenated blood enters the left atrium, flows into the left ventricle, is pumped out of the heart through the aorta, branches into ascending aorta, aortic arch, and descending aorta, delivers blood to all body cells for gas/nutrient/fluid exchange, deoxygenated blood returns to the heart through the vena cava, entering the right atrium.
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Coronary Circulation: A part of systemic circulation, supplying blood specifically to the heart.
Cardiac Cycle
-
Contraction: The heart's contraction creates the pressure for blood movement, causing the flow from regions of higher to lower pressure within the circulatory system.
-
Cycle: Repetitive contraction (systole) and relaxation (diastole) of the heart chambers, moving blood through the heart and body.
-
Blood Flow Adjustment: Blood flow is adjusted according to the metabolic needs of different tissues.
- High Need Tissues: The brain, kidneys, liver, and exercising skeletal muscles require increased blood flow.
-
Cardiac Output (CO):
- Formula: CO = Heart Rate x Stroke Volume.
- Stroke Volume: Amount of blood ejected with each heartbeat.
- Heart Rate: Number of heartbeats per minute.
- CO Measurement: Usually measured in milliliters per minute (ml/min), ranging from 5-6 L/min at rest in a normal adult.
Cardiac Control
-
Nervous System Control: The autonomic nervous system regulates blood pressure and blood flow:
- Blood Pressure Maintenance: The autonomic system manages blood pressure.
- Blood Flow Rerouting: The nervous system redistributes blood flow depending on need, for example, increasing blood flow to the muscles during exercise. Additionally, it reroutes blood away from vital organs and the skin towards the brain and cardiac muscles in emergency situations like blood loss or injury.
-
Hormonal Control: Hormones like epinephrine (adrenaline) released by the adrenal glands increase heart rate and stroke volume, causing vasoconstriction as a response to stress.
Conducting System
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Cardiac Conducting System: Internal pacemaker and nerve-like pathways within the myocardium.
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Action Potential: A rapid change in membrane potential that functions as an electrical impulse.
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Signal Transmission: Action potentials spread through the conducting system, initiating contraction of cardiac muscle cells, ultimately pumping blood.
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Auto-rhythmicity: The heart's ability to generate its own action potentials, resulting in repetitive contractions.
- Sinoatrial (SA) Node: This is the pacemaker, located in the right atrial wall. Its role is to generate action potentials at regular intervals.
- Atrioventricular (AV) Node: Found at the junction of the atrium and ventricle.
- Atrioventricular Bundle (Bundle of His): Nerve tissue extending from the AV node.
- Right and Left Bundle Branches: The bundle branches split from the AV bundle as it passes through the atrioventricular septum, extending to the apex of the heart, through the myocardium, and up to the atrioventricular wall.
- Purkinje Fibers: Branches given off by the right and left bundle branches, known as Purkinje branches. They are responsible for conveying the electrical signals within the ventricles.
Blood Composition
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Life-sustaining Fluid: Essential for various bodily functions.
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Diagnostic Tool: Blood analysis is commonly employed for disease diagnosis.
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Components (Centrifuged Blood):
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Plasma (55%): The extracellular matrix of blood.
- Water (91%): The primary component.
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Proteins (7%):
- Albumins (58%): Large proteins influencing osmotic balance.
- Globulins (38%): Transport proteins carrying lipid-soluble molecules and antibodies.
- Fibrinogen (4%): Fibrous proteins aiding in blood clotting.
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Other Solutes (2%):
- Ions: Sodium (Na), Potassium (K), Calcium (Ca), Magnesium (Mg).
- Nutrients: Glucose, amino acids, lipids, cholesterol.
- Waste Products: Urea, uric acid, creatine, ammonium ions.
- Gases: Oxygen, carbon dioxide, nitrogen.
- Regulatory Substances: Hormones, enzymes.
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Buffy Coat (Less than 1%): This thin layer contains white blood cells and platelets.
- White Blood Cells (5-10 thousand/cubic mm): Important for immune responses.
- Platelets (250-400 thousand/cubic mm): Essential for blood clotting.
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Formed Elements (45% - Haematocrit): Primarily composed of red blood cells.
- Red Blood Cells (4.2-6.2 million/cubic mm): Responsible for oxygen transport.
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Plasma (55%): The extracellular matrix of blood.
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Connective Tissue: Blood is classified as a connective tissue due to its few cells with an abundance of extracellular matrix.
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Blood Volume: Typically 5-6 liters in males, 4-5 liters in females.
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Blood pH: 7.35-7.45.
Blood Cells
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Erythrocytes (Red Blood Cells):
- Shape: Biconcave discs.
- Size: 7.5 micrometers.
- Nucleus: Non-nucleate and lack organelles, making them unable to reproduce, with a lifespan of 120 days.
- Hemoglobin: Contains the protein hemoglobin, which contains iron and carries oxygen.
- Oxygen Transport: 1.5% oxygen is dissolved in plasma, while 98.5% is bound to hemoglobin.
- Carbon Dioxide Transport: 7% in plasma, 23% attached to hemoglobin, and 70% exists as bicarbonate ions (HCO3).
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Leukocytes (White Blood Cells):
- High Count: Indicates potential infection.
- Complete Cells: Possess a nucleus and organelles.
- Types: Neutrophils, lymphocytes, monocytes, eosinophils, basophils.
- Protection: Responsible for phagocytosis, immune responses (cell-mediated and antibody-mediated), differentiate into macrophages, and release histamine.
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Platelets:
- Not True Cells: Cytoplasmic fragments of large cells.
- Blood Clotting: Essential for stopping bleeding.
- Blood Clot Formation: Adhere to fibrin, forming a plug/clot to stop bleeding.
Blood Vessels
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Arteries: Carry blood away from the heart.
- Pressure: Blood flows under pressure.
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Types:
- Elastic Arteries: Large arteries (aorta and pulmonary trunk), capable of withstanding high pressure due to their proximity to the heart.
- Muscular Arteries: Facilitate vasoconstriction and vasodilation.
- Arterioles: Smaller arteries leading to capillaries.
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Precapillary Sphincters: Control blood flow to certain areas.
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Capillaries: Sites of exchange between blood and tissue interstitial fluid.
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Veins: Carry blood towards the heart.
- Pressure: Low blood pressure.
- Wall Thickness: Thinner walls compared to arteries, with less elastic tissue and smooth muscle.
- Valves: Present to prevent backflow of blood due to low pressure, helping to counteract gravity's influence.
- Types: Venules, small, medium, and large veins, with venules being the smallest.
Blood Vessel Histology
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Tunica Intima (Interna): Innermost layer, composed of simple squamous endothelium, basement membrane, lamina propria, and elastic tissue.
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Tunica Media: Middle layer, containing smooth muscle cells and elastin arranged circularly.
- Smooth Muscle Function: Controls the diameter of the lumen.
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Elastic Tissue Function: Allows for distension and recoil.
- Vasoconstriction: Smooth muscle contraction, reducing blood flow.
- Vasodilation: Smooth muscle relaxation, increasing blood flow.
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Tunica Externa (Adventitia): Outer layer, composed of connective tissue that transitions from dense to loose, merging with surrounding tissue.
- Blood Vessels & Nerves: Nerves and blood vessels pass through the tunica externa, supplying the smooth muscle with blood.
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Lumen: Blood vessel's inner space where blood flows.
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Variations: The structure of blood vessels can vary based on type and specific requirements.
Blood Vessel Comparison Table
Feature | Arteries | Veins |
---|---|---|
Function | Carries blood away from the heart to the tissues | Carries blood to the heart from the tissues |
Location | Deep within muscles | Closer to the surface of the body |
Wall Thickness | Thick walls | Thinner walls than arteries |
Blood Type | Mainly oxygenated, but some deoxygenated (pulmonary and umbilical artery) | Mainly deoxygenated, but some oxygenated (pulmonary and umbilical vein) |
Valves | No valves due to high pressure | Valves present to prevent backflow due to low pressure |
Blood Pressure | High pressure | Low pressure |
Lumen Appearance | Round lumen (holds its shape) | Flat lumen (collapsed appearance) |
Capillaries
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Size: Smallest blood vessel type.
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Structure: Walls composed of endothelial cells (simple squamous epithelium), basement membrane, and a delicate layer of loose connective tissue.
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Types:
- Continuous Capillaries: Lack gaps between endothelial cells, less permeable to large molecules.
- Fenestrated Capillaries: Have pores in the endothelial cells, more permeable to smaller molecules.
- Sinusoidal Capillaries: Have large gaps between endothelial cells, highly permeable to large molecules.
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Function: Exchange of substances between blood and tissues.
Capillary Types
- Fenestrated capillaries are highly permeable due to pores called fenestrae in the endothelial cells. These are found in places like intestinal villi and the glomeruli of the kidneys.
- Sinusoidal capillaries have a large diameter with an incomplete wall of endothelial cells and a reduced basement membrane. These are found in locations such as endocrine glands and the liver, allowing for the passage of large molecules.
- Capillaries only possess the tunica intima layer, lacking the media and externa layers.
- Capillaries have a diameter of 7-9 microns, which is comparable to the 7.5 micron diameter of a red blood cell.
Capillary Exchange
- Capillary exchange involves the movement of substances into and out of capillaries.
- Diffusion plays a crucial role in the movement of oxygen, hormones, and nutrients from the high concentration within the capillary to the lower concentration in the interstitial fluid.
- Lipid-soluble substances, such as O₂ , CO₂, steroid hormones, and fatty acids, diffuse directly through the plasma membrane of endothelial cells.
- Water-soluble molecules, such as glucose and amino acids, diffuse through intercellular spaces or through fenestrations in capillaries.
- The small spaces between cells restrict the passage of many molecules, as seen in the blood-brain barrier, where specialized capillaries control the substances entering the brain.
- Larger spaces between endothelial cells allow proteins and even whole cells to pass through, as observed in the liver and spleen.
Lymphatic System
- The lymphatic system features a network of vessels, tissues, and organs that help maintain fluid balance and immunity.
- Lymphoid organs include the spleen, thymus, and tonsils.
- Lymphoid tissues and cells consist of MALT (mucosa-associated lymphoid tissue), Peyer's patches, lymphocytes (B and T cells), and lymph, the fluid circulating through the lymphatic vessels.
- Lymphatic ducts, trunks, vessels, and capillaries form the network of fluid drainage.
- Lymph nodes act as filters for the lymph.
Connection Between Cardiovascular and Lymphatic Systems
- Capillary permeability, blood pressure, and osmotic pressure influence the movement of fluid between capillaries and interstitial space.
- While most fluid returns to capillaries due to osmotic pressures, some remains in the tissues.
- Lymphatic capillaries collect this residual fluid and ultimately return it to the venous circulation.
- The lymphatic system is essential for maintaining blood volume, pressure, and fluid balance.
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Edema – Swelling due to excess fluid in body tissues. Several factors can contribute to edema, including:
- Issues with capillaries
- Heart failure
- Kidney disease
- Liver problems
- Pregnancy
- Problems with the lymphatic system
- Standing or walking in hot weather
- Eating too much salt
Edema
- If capillaries become leaky to blood, proteins can leak into the interstitial fluid, increasing the osmotic pressure outside the capillary, drawing more fluid into the interstitial space.
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Test your knowledge on the key components and functions of the cardiovascular system. From the structure of the heart to the role of blood, this quiz covers essential topics including cardiac output, the sinoatrial node, and the significance of blood composition. Perfect for students studying human anatomy and physiology.