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CARDIOVASCULAR SYSTEM BLOOD VESSELS. General Organization Arteries Large (Elastic) Arteries Muscular (Distributing) Arteries Arterioles (Small) Arteries Precapillary (Terminal) Arterioles Capillaries Veins Venules Medium Veins Large Veins Lymphatics. General Organization.
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CARDIOVASCULAR SYSTEMBLOOD VESSELS • General Organization • Arteries • Large (Elastic) Arteries • Muscular (Distributing) Arteries • Arterioles (Small) Arteries • Precapillary (Terminal) Arterioles • Capillaries • Veins • Venules • Medium Veins • Large Veins • Lymphatics
General Organization • Blood Vascular System • Portal System • Lymph Vascular System
Tissue Components • Endothelium • Elastic elements • Muscular elements • Connective tissue elements
Arteries - General Structural Plan • Tunica Intima • Tunica Media • Tunica Adventitia • Arteriosclerosis
Tunica Intima • Endothelium • Basement membrane • Subendothelial connective tissue • Internal elastic lamina (IEL)
Tunica Media • Smooth muscle • Elastic fibers/lamina
Tunica Adventitia • External elastic lamina (EEL) • Connective tissue • Vasa vasorum • Sympathetic nerves
Arteriosclerosis - “Hardening of Art.” • Atherosclerosis • Monckeberg’s Medical Calcific Sclerosis • Arteriolosclerosis
Myointimal Cells • Intimal smooth muscle cells • Potential of fibroblasts, macrophages & SM • Foam cells (lipophages)
BV CLASSIFICATIONS • Arteries • Large (Elastic) • Medium (Muscular) • Small (Arterioles) • Capillaries • Continuous • Sinusoids • Lymphatics • Veins • Small (Venules) • Medium • Large (Cava)
Large (Elastic) Arteries • Tunica intima • thicker subendothelial c.t. • poorly defined IEL • Tunica media - thickest, largely elastic • Tunica adventitia • EEL poorly defined • vasa vasorum
Muscular (Distributing) Arteries • Tunica intima - thin with prominent IEL • Tunica media - largely smooth muscle • Tunica adventitia • thick with prominent EEL • vasa vasorum, lymphatics, nerves
Arterioles (Small Arteries) • Tunica intima - absence of IEL • Tunica media - gradual reduction in layers • Tunica adventitia - no EEL
Precapillary (Terminal) Arterioles • Metarterioles • no IEL • 1-2 smooth muscle cells • serve as AV shunts • true capillaries are branches • Precapillary Sphincters • guard openings of true capillaries
Capillaries - General Structural Plan • Endothelium • Basement Memb. • Pericytes • Other Cells
Endothelium • Cells elongated along capillary axis • Attached by both occluding (tight) and communicating (gap) junctions • Oval or elongated nucleus (bulges into lumen) • Contractile - cytoplasmic filaments • Pinocytotic vesicles and vacuoles
Basement Membranes • Continuous in blood vascular system (prominent in brain as BBB) • Discontinuous in sinusoids and lymphatics • Collagen Type IV • Elastic fibers
Pericytes • Enclosed in own basement membrane • Discontinuous and irregularly spaced • Particularly numerous in brain (BBB) • Nucleus bulges away from lumen
Other Cells • Fixed macrophages • Mast cells - secrete heparin • Rare nerve fibers
Capillary Function • Barrier • Endocapillary layer • Endothelium • Basal lamina and pericytes • Adventitia • Exchange Forces • Hydrostatic • Osmotic • Concentration
Capillaries - Structural Types • True Capillaries • Continuous capillaries • Fenestrated capillaries with diaphragms • Fenestrated capillaries without diaphragms • Sinusoids • Lymphatic Capillaries
Venules (Small Veins) • Tunica intima - endothelial tube • Tunica media • Pericytes • Isolated smooth muscle cells • Tunica Adventitia - minimal
Medium Veins • Tunica intima - thin, forms valves • Tunica media - scattered smooth muscle • Inner layer longitudinally arranged in large veins • Tunica adventitia - thick with longitudinal
Large Veins • Tunica intima - slightly thicker than medium • Tunica media - sparse smooth muscle cells • Tunica adventitia - thick with longitudinal bundles of smooth muscle cells
Lymphatics • Tunica intima & adventitia only • Discontinuous basement membrane • Very frequent valves • Anchoring filaments • Extensive vasa vasorum • Lymphangion • Interposed lymph node filters • Drain into veins
BV CLASSIFICATIONS • Arteries • Large Elastic lamina • Medium >10 SM layers • Small (Arterioles) <5 SM layers • Capillaries • Continuous (Fenestrated & Non-Fenestrated) • Sinusoids (Liver, spleen, lymph nodes, BM) • Lymphatics (Everywhere) • Veins • Small (Venules) Thin wall, large lumen • Medium Few layers of SM, “ • Large (Cava) Long. SM in Adv.