Circulatory System

icer215's version from 2016-08-18 02:28


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Circulatory Systemdelivers nutrients and building materials, and removes waste from the cells.
FunctionsCirculation creates an area for diffusion to occur, like a swap-meet. The vendors are cells, the money is nutrients, the items for sale are waste, the buyers are circulation cells such as red blood cells. Nutrients are exchanged for waste in stationary cells that depend on the circulating cells to keep functioning
Oxygenis taken into the body from the environment, travels to the circulatory system via the lungs, into the capillaries, where the oxygen binds to hemoglobin on red blood cells. needed to make ATP though cellular respiration.
Red blood cells travel through the body and back to the heart exchanging oxygen for waste.
Nutrientsare absorbed mainly by the small intestines and then transported to the blood stream.
Hormonesneed to travel in the circulatory system to get to their target.


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Fluids and ionscirculate making them available to cells (regulation of water and salt occurs in the kidney).
Waste in the form of urea travels in the blood, to the kidney to become urine
Role in ThermoregulationVasoconstriction & vasodilation
Vasoconstrictionconserves heat by keeping heat near the core.Feeling cold
Vasodilationcools the body by letting blood (with heat) near the surface of the body.Feeling hot
Systolic pressure left ventricle contracts (highest system pressure).blood is being pumped


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Diastolic pressure left ventricle relaxes (lowest system pressure).blood is not being pumped
Korotkoff sound the first sound that is heard
Blood pressurepressure blood exert on the walls of the blood vessel.
Pulmonary (the lungs) circulationblood comes from the heart via right ventricle, into the lungs via pulmonary arteries, then back to the heart (left atrium) via pulmonary veins.
Systemic (the whole body) circulation blood comes form the heart via left ventricle, into the body via the aorta, back to the heart via the inferior and superior vena cava into the right atrium.
Elastic Arteries have elastic tissue, they are not active in vasoconstriction, their layers are endothelium, smooth muscle and connective tissue.


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Muscular Arteriesare somewhat active in vasoconstriction, have a lot of muscle and distribute blood to specific organs.
Arteriolecontrols blood flow to capillaries, most active in vasoconstriction.
Capillarysingle cell of endothelium, diffusion occurs between blood and tissue solutes.
Venuleconduct capillaries to veins.
Veinhave valves to prevent the back flow of blood, layers endothelium, smooth muscle and connective tissue, vasoconstriction may occur, muscle movement (muscle milking) helps blood flow back to the heart.
Arteriesalways go away from the heart


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Arterioles and venules are smaller versions of arteries and veins.
Arteries have high pressure. flow turbulently
Veinshave low pressure. flow evenly
Capillary BedsOxygen and carbon dioxide are exchanged. Nutrients and wastes are exchanged. Heat can be lost due to dilation of capillaries in the extremities.
Diffusion is the main mechanism of gas and solute exchange, which is why high surface area is important at a cellular level (facilitating diffusion)
Continuous CapillaryBlood-brain barrier (seals clefts by tight junctions) and skin and muscle, no pores on endothelial cells, may have clefts.


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Right atriumReceives oxygen-depleted blood from the body (via superior vena cava and inferior vena cava) and pumps the blood into the right ventricle (via tricuspid valve)
Left atriumReceives oxygen-rich blood from the lungs (via pulmonary veins) and pumps the blood into left ventricle (via mitral valve)
Right ventricleReceives oxygen-depleted from the right atrium and pumps it into the lungs (via pulmonary valve and artery)
Left ventricleReceives oxygen-rich blood from the left atrium and pumps it through the aortic valve to the entire body (via aorta)
Valvesregulates blood flow through human’s heart
Tricuspid valveRegulates blood flow between right atrium and right ventricle
Pulmonary valve :Regulates blood flow from the right ventricle into the pulmonary arteries
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Mitral valveAllow oxygen-rich blood from lungs to pass from the left atrium into the left ventricle
Aortic valveAllow oxygen-rich blood to pass from the left ventricle into the aorta (largest artery that delivers blood to the rest of the body)


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Fenestrated Capillary Small intestines, endocrine organs, kidneys (allow blood filtration), pores allow fluid out, but not blood cells.
Sinusoidal CapillaryLyphoid tissue, liver, spleen and bone marrow, large pores allow blood cells to leak out, facilitation their travel.
Composition of Blood55% plasma (top layer), 44 % red blood cells (no nucleus, bottom layer), 1% white blood cells (middle layer with platelets). White blood cells: 60% neutrophils, 40% T and B lymphocytes.
Blood plasmaThere are water molecules, ions, gases, hormones, wastes, nutrients and clotting factors
Chemicals in blood include clotting factors or hormones.
Blood cellscan be red blood cells (erythrocyte), that carry oxygen and carbon dioxide or white blood cells (leukocyte), that fight pathogens.


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Plateletsare not cells, but are fragments of huge cells used for clotting.
Bone marrow makes RBCs from stem cells.
Spleendestroys aged and damaged RBCs.
Ironis recycled, heme turns into bilirubin, then bile and is excreted in the feces, globin is broken down into amino acids to be reused.
Higher blood osmolaritywater goes into blood → higher blood volume
Lower blood osmolaritywater goes into tissues → lower blood volume


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ADH (vasopressin)water reabsorption in kidney
Aldosteronesalt reabsorption, leads to ↑ water reabsorption in kidney
Plateletscontain enzymes and chemicals needed involved in the clotting process.
Liver produces clotting factors (eg. fibrinogen), which circulates in blood plasma.
Coagulation liquid blood → gel
Platelet plug formationwound + platelets → platelets clump at wound, release chemicals, activates clotting factors.


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Coagulation series of clotting factor/enzyme activation that ends in fibrinogen → fibrin. Fibrin being the fiber mesh that seals the clot.
Retraction and repairclot contracts, gets compact, but after the wounded blood vessel repairs itself, the clot dissolves.
Transport of oxygen and carbon dioxidein the blood is carried out by red blood cells, which contain hemoglobin to bind the gases to the protein.
Hemoglobin is the molecule in red blood cells that carries oxygen. Each red blood cell has millions of hemoglobin molecules.
Hematocrit is the percentage of blood that is made red blood cells (by volume).
Oxygen ContentEach hemoglobin can have up to four oxygen molecules (one for every iron atom).


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Oxygen AffinityThe more oxygen binds onto hemoglobin, the easier it is for more oxygen to bind due to a relaxed conformation of the other subunits. Carbon monoxide binds to hemoglobin better then oxygen, ruining red blood cells in cases of carbon monoxide poisoning (the blood still looks bright red).
Hemoglobin contains 4 heme groups (which contain iron), allowing up to 4 molecules of oxygen to bind to hemoglobin (allowing transport to cells for cellular respiration).
Carbon dioxideis also transported by hemoglobin as well as nitric oxide.
Hemoglobin is famous for having a quaternary structure composed of 4 protein subunits in a tetrahedral arrangement.
Modification of Oxygen AffinityConditions of stress (high temperature, low pH, and high carbon dioxide) cause lowering of oxygen affinity to hemoglobin, thereby allowing it to be delivered to cells that need it.


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Endothelial CellsAlso can be called as endothelium. Thin layer of simple squamous cells.Line the interior surface of blood vessels à direct contact with blood .Found in all circulatory system including arteries, veins, and capillaries
Simplesingle layer of cells
Squamousflat shaped
Provide barrierSemi-permeable barrier between the vessel lumen and tissues near by. Fluid filtration.Form new blood vessels.Control blood pressure by vasoconstriction and vasodilation
Pulmonary circulationHeart ➙ lungs ➙ back to heart (oxygenated blood into heart). Shorter than systemic circulations ➙ less resistance ➙ less blood pressure. Vasoconstriction (remember from feeling cold?): when oxygen levels are low ➙ less blood flow to low oxygen/blocked alveoli ➙ more blood flow to good alveoli where gas exchange occurs
Systemic circulationHeart ➙ body ➙ back to heart (oxygenated blood to body). Vasodilation (remember from feeling hot?): when oxygen levels are low ➙ more blood flow to oxygen-depleted tissues