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75 Cards in this Set
- Front
- Back
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Define circulatory system
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System responsible for moving oxygenated blood cells to body and then returning cells to lungs to be re-oxygenated
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Describe circulatory system
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A continuous, closed, system of endothelial lined tubes (simple squamous).
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Describe function of circulatory system.
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Perfusion of tissues with blood over a narrow range of hydrostatic pressure- exchange of fluid, gases, metabolites, hormones
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Describe flow variations.
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Capillaries- slower flow
Artery- faster (narrow deep river) |
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What is an artery?
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Conducting vessel.
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What is an arteriole?
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A resistance vessel.
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What are the 2 exhchange vessels?
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capillary and venule.
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What is a vein?
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Conduction vessel that also serves as reservoir.
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What is the basic plan of circulatory system (simple structural organization)?
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large vessels are organized into three layers. Tunica intima,Tunica media, Tunica adventitia. (may vary in name depending on organ system).
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What is tunica intima?
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Closest to blood lined in endothelium cells, may see nucleus. Has an elastic fiber sheet (basal lamina)
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What is subendothelial connective tissue.
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All endothelial linings have subendothelial connective tissue.
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Where is the internal elastic fiber.
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Under the subendothelial connective tissue. Ca
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What is tunica media.
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Middle layer with smooth muscle charateristic of cir system. With smooth muscle always have ECM. Bound by external elastic membrane between media and adventitia.
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What is tunica adventitia?
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Closest to surrounding tissue. If vessel is lying freely in body cavity, then lined with epithelial. May contain elastin fibers. Smaller blood vessels serve this blood vessel to provide enough materials. Has fibroblasts and ECM.
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What are vasa vasora?
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Small blood vessels that supply the tunica media.
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What is largest vessel (s)?
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Elastic arteries that have a predominance of elastic sheets as opposed to smooth muscle 40-70 layers (imagine layers of rubber sheets on a bed).
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What is role of elastic fibers in aorta and lg vessels?
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Responsible to maintaining resistance and tone to resist pressure esp in aorta. Ensures constant blood flow with intermittant heart pumping.
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Differentiate systole and diastole as relates to elastic fiber.
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Distention of elastic fiber in systole, recoil in diastole.
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Where are elastic fibers?
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They blend with internal and external elastic membranes (laminae).
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Describe muscular artery.
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Tunica media is comprised of smooth muscle 4-40 layers, with only scattered elastic fibers. Smaller muscular arteries lose the external elastic membrane.
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What vessel type is determinant of pressure?
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Arterioles which provide resistance 1-3 layers of SM. They are final segment of arterial system and they regulate flow to capp beds by sphincters.
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What is a metareriole?
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Muscle sphincter.
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What is vascular tone?
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state of smooth muscle contraction in Tunica media.
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What is role of sympathetic neural control?
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Norepinepherine causes vasocostriction.
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What is role of parasympathetic neural control?
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Vasodilation from actylcholine/nitric acid.
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How are smooth muscles arranged in arterioles?
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Smooth Muscles are arranged in spirals in arterioles for easy constriction.
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What type of junctions are found in arterioles.
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Tight junctions (zonula occludens)
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Describe visual appearance of contracted arteriole.
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Internal elastic membrane is squeezed in, epithelial cells are pushed inward.
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In dissection of arteriole, what else would you find?
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Neurovascular bundle.
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Describe structure of capillary.
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7-9 microns in diameter (RBC) must squeeze thru and this facilitates diffusion), single layer of enothelial cells and basal lamina. Endo cells joined together by zonula occludens in most cases.
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What is continuouis capillary?
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endothelial cell body formeds a continuous lining. Therefore transport of materials across endo is by diffusion and pinocytosis.
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What is pericyte?
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Pre-cursor (stem cells) to give rise to new capillaries.
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What are 4 types of capillary
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continuous (regular and of brain), fenestrated, discontinous (sinusoidal venules)
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Where is site of blood brain barrier?
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Zonula occludens (is this right?)
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Describe fenestrated capillaries.
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Has holes punched in cells to allow exchange of material into lumen. Holes (windows) are called fenestrations. In cross section looks like holes in wall. Has basal lamina.
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What is a diaphragm.
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Non cellular boundary across window that acts like a sieve or screen to control size of items passing thru
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What is missing in capillaries?
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Missing tunica media and tunica adventitia.
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Where are continuous found?
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exocrine, nervous, muscle, lung
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Where is fenestrated found?
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Places requiring protein molecule access to capillaries. Endocrine, kidney and gut.
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Describe discontinuous (sinusoidal) capillaries.
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Instead of just windows in sheet of cell, big segments (holes) in endothelial barrier. Basal lamina is also discontinuou. Allows entire cells to pass through. Macrophages often found near sinusoids.
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Where are sinusoidal caps found?
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Bone marrow, spleen, liver, places requiring migration. Most rare type.
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What component controls if the capillary gets blood?
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The metarterial which branches off artery.
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How do we bypass a capillary bed avoid pressure increases?
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Bypass channels are available when a capillary bed is closed down, these arterial anastomosis open up.
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What does anastomosis mean?
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A passage connecting 2 places (like vein to artery in bypassing caps)
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What are typical portal systems?
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Connects arteriole to cap bed to venule without having to go through heart.
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What is an arterial portal system?
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Connecting an afferent arteriole with a efferent arteriole to a venule (like in kidney)
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What is a venous portal system?
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arteriole to capillary to venule to 2nd capillary to venule. Example hepatic system. Primary bed is in gut, 2nd in liver.
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What is the general function of a portal system?
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To concentrate absorbed material and transport it without moving it to the general body. Ex hepatic picks up stuff from gut, filters, cleans, etc before it all goes out to body.
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What are veins
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Return side, low pressure side
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What are post capillary venuoles?
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They receive blood from capillaries. Permeable to macromolecules, site of leukocyte movement into extravasc space. Pericytes surround- pericytic venule.
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Describe large veins.
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Large volume of blood, low pressure, 3 tunics, tunica intima has very little subendothelial, media is thinner than that of artery of same size, adventitia is relatively larger than in artery, valves to prevent reflux.
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What are valves in veins?
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They prevent reflux of blood, these are projections of Tunica intima with elastic fibers in subendothelial space into the lumen as semi lunar valves. Passive valve regulated by simple mechanics.
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Why called semilunar valves?
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Each looks like half moon.
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What are lymphatic vessels?
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Lymphatic capillaries form a network in tissue spaces and they drain tissue fluid (lymph). May look like blood vessel but you won't see and RBC). Looks like big void, but has visible lining.
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What are 2 big lymph ducts?
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Thoracic and right lymphatic duct.
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What are characteristics of lymphatic vessels.
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arise as dilated tubes with closed ends, sparse or incomplete basement membrane, permeable, few smooth muscle cells, ill defined T. Adventitia, numerous semi lunar valves, depends on compression of muscle for mvmt of lymph fluid,
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What is heart?
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Modified vessel with 3 layers, call them something different. Endocardium, myocardium, epicardium.
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Describe Endocardium.
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Tunica intima- Endothelium, subendothelial CT.
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Describe Myocardium.
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Tunica media- Cardia muscle, purkinge fibers ( to allow beat from bottom up), connective tissue.
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Describe Epicardium
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Tunica Adventitia- loose CT, mesothelium
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How is the heart an endocrine gland?
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It releases ANF (atrial natiuretic factor to regulate blood flow in kidney glomerulus.
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What is cardiac fibrous skeleton?
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Connective tissue, serves as an anchor for cardiac muscle, valves
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What are specialized impulse generating and conduction cells?
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SA node, AV node, bundles of his, AV bundle, Purkinje cells.
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Describe purkinje fibers?
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Comprised of large cells with high glycogen content and low myofibril content.
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What are the visible differences in the layers of the veins as compared to the arteries?
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Veins have little or no endothelial connective tissue (T. Intima), T. Media is thinner , T. Adventitia is thicker and has lots of elastic fibers and longitudinal muscle.
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What are the purpose of valves in veins and how do they accomplish this?
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To avoid blood reflux. Veins have a projection of the T. intima with elastic fibers that project into the lumen as semilunar valves.
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Why is there little or no blood found in a fixed sample of an artery?
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Muscle cells of T. Media contract upon fixation and this expels blood from lumen.
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Describe two ways that new blood vessels are formed.
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Vasculogenesis- generation of new blood vessel from mesenchymal cell, Angiogenesis- formation from an existing blood cell.
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What is VEGF? What are characteristics of it?
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Vascular Endothelial Growth Factor is a mediator of development, organogenesis and homeostasis. Recruits and expands vessels during bone formation, maintains capillary beds, made by white blood cells, mediates tumor growth
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How is the heart an endocrine gland?
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Produces Atrial Natiuretic Factor to increase blood flow to kidney glomerulus.
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What supports the heart?
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A cardiac fibrous skeleton of connective tissue that anchors cardiac muscle and valves.
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Name some impulse generating and conducting cells of heart.
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SA node, AV node, Bundle of his, AV bundle, Purkinje cells.
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What are purkinje cells?
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Modified cardiac muscle cells specialized to conduct impulses that regulate cardiac muscle activity. These are found in the subendocardial space.
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What are purkinje fibers made of?
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Large cells with high glycogen content and low myofibril content.
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What is the epicardium?
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A thin layer of mesothelium (simple squamous) supported by a thin layer of connective tissue that covers the heart externally.
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