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23 Cards in this Set
- Front
- Back
General layers of the heart and vessels |
Heart- endocardium, myocardium, epicardium Vessels- Tunica intima, tunica media, tunica adventitia |
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Layers of the heart |
Endocardium- made up of a layer of endothelial cells and a sub endothelial layer of connective tissue (containing nerves, veins and Purkinje fibres) Myocardium- highly vascularised, made up of cardiac muscles Epicardium- Made up of fibroelastic connective tissue, containing blood vessels, lymphatics, nerves and adipose tissue, covered by a layer of simple squamous epithelium |
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Features of cardiac muscle |
Branched Striated Involuntary Centrally placed nucleus Adjacent cardiac muscles form a syncytium to act in a coordinated contraction through intercalated discs (allows rapid transmission of electrical impulses, consists of three cell to cell junctions- gap, adhering and desmosomes) |
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Purkinje fibres features |
Found in endocardium (specifically sub-endocardium) Specialised cardiac muscle cells, generates and conducts impulses to created synchronised contraction Larger, has more glycogen and mitochondria, fewer myofibrils, no t-tubules and no intercalated discs (only desmosomes and gap junctions) compared to cardiac muscle |
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features of the tunica intimate (general) |
Innermost layer One layer of simple squamous epithelium- known as endothelial Encircled by a layer of sub endothelial- made up of loose connective tissue Internal elastic lamina, a fenestrated sheet of elastic fibres, separates intima from tunica media
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Role of endothelial |
(found in tunica intimate) regulates transport of substances from lumen to vessel wall controls local clotting through secretion of soluble factors enables migration of WBCs from blood to tissue |
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Tunica media |
middle layer consists of circularly arranged smooth muscle contraction of this regulates blood flow if muscles are weakened, walls become dilated, causing aneurysms Matrix consists of elastic and collagen fibres external elastic lamina separates tunica media from the outer tunica adventitia |
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tunica adventitia |
outermost layer connective tissue layer- many collagen and elastin fibres blends in with surrounding connective tissue, providing anchoring contains vasa vasorum, small nutrient arteries and veins providing blood supply to walls of larger vessels |
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types of arteries |
elastic, mucular, arterioles |
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elastic arteries |
also known as large/conducting arteries transports blood away from heart tunica intima is thick, made up of endothelium with thick loose connective tissue sublayer tunica media made up of 50 - 70 concentrically arranged fenestrated elastic membranes (laminae) with smooth muscle cells and collagen fibres between them (internal and external lamina not readily visible) |
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Why do elastic arteries need to be elastic |
large diameter, yet walls are very thin undergo expansion with each systole have to recoil during diastole to maintain BP and continue to move blood |
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Muscular artery |
also known as medium or distributing, as it distributes blood to various parts of the body thick wall (25% of diameter) tunica intima consists of endothelium and flattened sub endothelial layer of collagen and elastic fibres tunica media is the major identifying characteristic- thick smooth muscular layer with 10-40 layers of smooth muscle, w/ much less elastic fibres, external elastic lamina readily recognisable in larger elastic arteries tunica adventitia is well developed, contains mainly collagen, elastin and vasa vasorum |
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Features of arterioles |
small arteries, 0.004 - 0.4mm in diameter delivers blood to capillaries retain general features of muscular arteries regulates blood flow to capillaries by met arterioles, which connect small arterioles to capillaries- junctions are surrounded by a ring of smooth muscle, which act as a pre capillary sphincters and can cause arteriovenous shunting (important in thermoregulation) Tunica intima- very thin sub endothelial layer of loose connective tissue tunica media- 1 - 3 layers of smooth muscle (key feature!) tunica adventitia- fairly prominent |
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capillaries |
usually 7 - 9 um in diameter walls consist of a single layer of endothelium, surrounded by a basement membrane pericytes found between basement membrane and endothelium Capillaries allow passive diffusion + pinocytosis of nutrients and wastes WBCs can move through intercellular junctions (diapedesis)
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Types of capillaries |
Continuous Fenestrated Discontinuous |
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continuous capillaries |
most common, found in muscle, fat, connective tissue, lungs, brain no pores or spaces between cells in walls, tight junctions between cells in walls continuous basement membrane cells can move in.out by diapedesis macromolecules can pass through endothelial cells by pinocytotic vesicles
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fenestrated capillaries |
found in tissues where rapid exchange occurs (glomeruli of kidney, villi of intestinal wall) have pores which penetrate endothelial cells, covered by a thin diaphragm (not found in glomeruli) have a continuous basement membrane |
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discontinuous capillaries |
aka sinusoids larger, more irregularly shaped found in liver/haematopoietic organs (spleen, bone marrow) gaps between adjacent endothelial cells lacks basement membrane no continuous lining between lumen and surrounding tissue- not a barrier to blood constituents phagocytic cells are present (kupffer in liver) |
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Types of veins |
venules, medium + large |
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venules |
formed by the confluence of capillaries tunica intima lacks subendothelial layer tunica media consists of 1 -2 layers of muscle fibre, increases with size tunica adventitia fuses with surrounding connective tissue |
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medium and large veins |
all three tunica present intima- well developed, but thin, folds in endothelium forms valves media- thin, muscular, can regulate diameter (useful due to low BP) adventitia- predominant layer, thickest and best developed, spirally arranged collagen and elastic fibres, longitudinal smooth muscle and more vasa vasorum than arteries |
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Lymphatic capillaries |
thin endothelial lined tubes that... - drain interstitial fluid -resemble blood capillaries, but begin as blind-ending vessels, have incomplete.absent basement membranes, lack pericytes, have larger irregular lames, lack tight junctions, have anchoring filaments which contract to allow fluid to enter and lacks RBCs |
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medium/large lymphatic vessels |
resemble veins, consist of three basic laters containing much less smooth muscle.elastic or collagen fibres have valves (but still lacks RBCs) |