Cardio Vessels

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Arteries

Elastic - conducting arteries (large)

muscular distributing 

Anastomoses - interconnections between arteries allow alternate blood flow pathways

end arteries do not anatomose

Function - low resistance conduits

carry blood from heart to organs

large lumens - little resistance 

pressure remains constant

stretch during systole - elastic recoiling diastole

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Major Arteries and Arterioles

Major Arteries - coronary - Arch of Aorta

Thoracic Aorta - abdominal Aorta, 

Luac arteries

Arteriolioles - little artery carries blood form areteries to capillaries

regulates mean arterial pressure

contract in response to sympathetic nerves or hormones - pressure rises

Control blood distribution

flow regulated by areteriolar diameter

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Triple responses

1. red line - appears 3-15seconds - due to vasodilation caused by direct mechanical stimulation of arterioles

2. Red flares - appears 15-20 s - caused by axon reflex, stimulates, sensory nerves (dendrites) generate action potentials- vasodilation of arteries

3. Weal - develops 3-5 mins caused by increased permeability in capillaries

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Control of Arteriolar diameter

increases and decreases blood flow in specific organs for their metabolic requirements

Active HYPERAEMIA - mediate vasodilation - decreased O2 - rise in CO, H or K levels, adenosine

Inadequate - blood flow (Ischaemia)

metabolites produced by tissues are not removed

Remove arm from water (reactive Hyperaemia) - red arm

compensates blood deprivation

enables excessive metabolites to be washed away

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Capillaries

capillary bed, network of small blood vessel allow blood-- tissue exchange through diffuses

metarterides - vessel emerging from an arteriole, passes through capillary network into venule

Precapillary sptincter contract in response to high O2

Capillary pore (intercellular clefts)

space between endothial cells

plasma filters out of capillary

atriovenous anastomoses

connects artreioles with venules

allow blood to pass capillary bed

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Routes of exchange

O2 and nutrients out of blood into interstital fluid

CO2 and waste into blood

Endothiatial membrane, small molecules diffuse or active transport

Pinocytotic vesicles - allow passage through endothitial cells

fenestration - allow passage of large molecules

Mechanisms of exchange 

diffusions, bulk flow, filtration, absorption, vesicular transport, endocytosis, exocytosis

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Veins

one way valves to prevent back flow

venous tissues sinuses, enlarged venous channels

Venules- drain blood from capillaries to vein

Veins carry deoxygenated blood from organs and heart

Large lumens - little resistance

Major veins - great veins, head and upper extremities

Azygos system - Hepatic portal system

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Skeletal muscle pump and Respiratory pump

Skeletal pump - contracts, thicken and bulge and press on adjacent vessels

squeezed by contraction and relaxtion, blood always moves to heart, important for veins in legs

Respiratory pump - Inspiration - thoracic cavity pressure drops and abdominal pressure rises

blood from ab. veins into thoracic veins

backflow prevented by valves

Expiration - intrathoracic pressure rises and intradominal pressures falls

increased pressure rises squeezes from veins

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Coronary Arteries and Arterioles

Left Coronary arterys - supplies wall of the left ventricle with oxygenated blood

Right coronary artery - supplies right ventricles and portion of left ventriole - drains via coronary sirius to right atrium

Coronary arterioles - divisions of autonomic nervouse system

BF through cornoary system

Body at rest - blood flow is increased when O2 is required - exercise

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