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Blood vessels - general structure

Blood vessels - general structure. Three major types of blood vessels are : arteries, capillaries and veins The walls of all blood vessles except capillaries are composed of three distinct layers (tunics) surrounding a space (lumen). The tunics are from inside to outside

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Blood vessels - general structure

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  1. Blood vessels - general structure • Three major types of blood vessels are : arteries, capillaries and veins • The walls of all blood vessles except capillaries are composed of three distinct layers (tunics) surrounding a space (lumen). • The tunics are from inside to outside • Tunic intima - endothelium, simple squamous epithelium • Tunica media - circulary arranged smooth muscle and elastic fibers interspersed with sheets of elastin • Tunica adventitia - collagen

  2. Arteries • Elastic arteries - conducting arteries • arterial pulse • Muscular arteries - distributing arteries • Arterioles

  3. Capillaries • Continous capillaries • Fenestrated capillaries • Sinusoids

  4. Capillary Beds • General structure - terminal arteriole ---------> metarteriole -------------> thoroughfare channel -----------------> postcapillary venule (PICTURE) • Vascular shunts • True capillaries

  5. Veins • Venules • Veins • Venous sinuses

  6. Cardiac Output CO = SV x HR SV = EDS - ESV • Therefore to regulate CO we can alter HR or SV • SV can be altered by alteruing either EDS or ESV

  7. Regulation of SV • Preload - Starling Law of the Heart • Contractility • Afterload

  8. Regulation of HR • Neuronal - sympathetic and parasympathetic (vagal) • Chemical • Hormones • ions • Other factors

  9. Definition of variables • Blood pressure- P =F/A the force exerted on wall of blood vessel per unit area • Resistance - the opposition to flow mainly in the periphery PR or TPR • Blood viscosity - opposition to flow related to the thickness of blood • Total BV length • Total BV diameter

  10. Relationships among the variables • BP = CO X TPR • Resistance • directly proportional to BV L • directly proportional to 1/r4 • Directly proportional to blood viscocity • BF = difference in BP in different parts of the vascular system / TPR

  11. Relationships among the variables • MAP = dBP + 1/3 pulse pressure • pulse pressure = SBP - DBP • BP and BF velocity in different parts of vascular system

  12. Control of BP • A Short term - 1 neural controls • Cardiovascular center • baroreceptor initiated reflexes • chemoreceoptor initiated reflexes • higher brain involvement

  13. Control of BP • 2 Hormones • adrenal medulla hormones • ANF atrail natriuretic factor • ADH antidiuretic hormone • Angiotensin II • EDF endothelium derived factors • NO nitric oxide also called endothelium derived relaxing factor EDRF

  14. Control of BP • 3 Drugs and chemicals • alcohol • inflammatory chemicals -histamine , kinins

  15. Control of BP • B Long term - 1. kidney regulation

  16. Capillary filtration

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