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33 Cards in this Set
- Front
- Back
what does the circulatory system do? |
transport nutrients, wastes, gases... *essential for the maintenance of cell function and homeostasis * associated with all tissues |
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capillary beds
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* ensure that no substance has very far to diffuse * are the sites of material exchanges between blood plasma and interstital fluid (the extracellular fluid, ECF, between the cells of other tissues) |
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in most tissues... |
• O2 and nutrients diffuse from blood into interstitial fluid and from interstitial fluid into tissue • CO2 and wastes diffuse from tissue into interstitial fluid and from interstitial fluid into blood |
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The indirect exchange of materials between blood plasma and tissue cells occurs through |
interstitial fluid |
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the circulatory system also functions in homeostasis by... |
• aiding in the exchange of molecules with interstitial fluid and |
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hemolymph
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the fluid that moves through an insect’s open circulatory system
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Open Circulatory System |
* hemolymph is pumped by 1 or more pumps / tubular hearts through open-ended vessels and is released into the spaces between cells |
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blood vessels in a closed circulatory system...
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* arteries * arterioles * capillaries * venules * veins |
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arteries |
carry blood away from the heart |
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arterioles |
carry blood from an artery to a capillary bed |
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capillaries |
sites of exchange with interstitial fluid |
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venules |
carry blood from a capillary bed to a vein |
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veins |
return blood to the heart |
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what advantages are there to a closed vs. an open circulatory system?
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• rapid delivery |
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2 chambered heart and a single circuit (single circulation) |
• blood must pass through 2 capillary beds during each circuit ex) fish |
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3 chambered heart and two circuits (double circulation) |
* 2 circuits improves the efficiency and capacity of the system
* both the lungs and the skin are sites of re-oxygenation and so use a pulmocutaneous circuit * some mixing occurs in the single ventricle, but channels in the ventricle wall help divert the blood to the correct circuit * Ex) amphibians |
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4 chambered heart and double circulation
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• 2 atria and 2 ventricles Ex) birds and mammals
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arteries Structure & Function
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* thick-walled... connective tissue & smooth muscle provide reinforcement * smooth muscle constricts to regulate flow |
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veins Structure & Function
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• similar in structure to arteries, but have
valves to prevent backflow away from the heart
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capillaries Structure & Function
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* thin walls (only 1 cell layer) facilitate diffusion of substances * ~80-100,000 kms of capillaries in your body! |
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Smooth Muscle
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Helps to Control the Distribution of Blood *blood supply varies in all tissues (except brain & heart) * arteriole constriction * thoroughfare channel * precapillary sphincters |
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arteriole constriction |
(under control of nerves & hormones) can reduce flow to capillaries |
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thoroughfare channel |
allows flow through centre of capillary bed |
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precapillary sphincters |
control passage of most blood into the bed |
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Capillaries Allow Transfer of Some Substances Through Their Walls |
* site where plasma & interstitial fluid exchange materials
* water & small water-sol molecules can “leak” between endothelial cells * lipid-souble molecules can pass through the endothelial cells * blood pressure actively forces fluid out of capillaries, & osmosis tends to cause fluids to move in * some proteins are exchangeable between the plasma and interstitial fluid via endocytosis and exocytosis * most plasma proteins are retained |
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Lungs |
* highly vascularized internal sacs of the body surface
* since lungs are localized in the body, the circulatory system must be employed to transport gases |
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why is respiratory medium is air rather than water? |
air is less dense easier to pump / move than water; less energy needed to ventilate lungs
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the respiratory surface is
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the moist epithelial lining of the alveoli
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lungs require less thorough ventilation than gills since
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* gases diffuse faster in air than in water * there is more dissolved O2 in air than in water |
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* water loss is an issue when compared to the use of water as a respiratory medium because |
* (exhaled air is moist)... breathing air could dry out the respiratory surface |
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oxygen- poor blood is arriving from the |
pulmonary artery |
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oxygen-rich blood is going to the |
pulmonary vein |
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Dalton’s Law |
every gas in a mixture contributes to the total pressure of the mixture, each gas has a partial pressure
• the direction of diffusion for any gas at any body site is determined by differences in the partial pressures of that gas at those sites o differences in partial pressures allow for gas exchange at various sites in the body |