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Anatomy Finals' Notes

Blood Vessels and Hemodynamics

Arteries, Capillaries and Veins
arteries --> arterioles --> capillaries --> venules --> veins Arteries = away from heart
Veins = toward heart
Only capillaries directly serve cells
Tunica Intima = inside of blood vessel. Single layer of cells similar to the lining of the heart Tunica Media = middle layer. Smooth muscle...regulates diameter of vessels Tunica Adventitia (externa) = outer layer. Collagen for sturdy, membranous coating...protection

3 Types of Arterial Vessels
Elastic Conducting Arteries. Thick-walled. Large-diameter near the heart. Highest proportion of elastin. Smooth out pressure fluctuations; recoil helps to maintain pressure and flow of blood Muscular Distributing Arteries. Deliver blood to specific organs. More smooth muscle than elastin. The consequences = if standing still, blood will pool in lower limbs...loss of blood flow to brain Arterioles. Do not need as much as elastic tissue as the others. Tunica media is primarily smooth muscle...determine which capillary beds flushed minute to minute Vasa vorum = provides blood to immediate tissue

Valves in veins to prevent back flow in lower limbs

Microcirculation and 3 types of Capillaries
Walls are only a thin tunica intima
function = exchange
Continuous Capillaries = skin and muscle; uninterrupted lining intercellular clefts allow limited passage of fluids, small solutes Fenestrated Capillaries = similar but the endothelial cells are riddled with pores (fenestrations)...increased permeability to fluids. Found in small intestine and endocrine organs and kidney Sinusoidal Capillaries = highly modified, leaky capillaries (liver, bone marrow, lymphoid tissues, endocrine organs). Large, irregular lumens and usually fenestrated; fewer tight junctions and large intercellular clefts for passage of proteins and RBCs Microcirculation = flow of blood from an arteriole to a venule through a capillary bed vascular shunt = metarteriole (central vessel for exchange) + thoroughfare channel Precapillary Sphincter = surrounds root of each capillary

Venules and Veins
Venules = post capillary venules = just endothelium and a few fibroblasts; larger venules have sparse tunica media and thin tunica adventitia Veins = 3 tunics, but walls thinner and lumens larger

relatively little elastin/ smooth muscle in tunica media; tunica adventitia is heaviest up to 65% of blood is in veins at any one time...blood reservoirs? 2 structural adaptations that promote blood return = valves and large internal diameter

Some Terms
Blood Flow = need pressure gradient for flow to happen. Can be regulated independently for various tissues and organs Blood Pressure = force per unit area exerted on the wall of a blood vessel by its contained blood (mm Hg) refers to systemic arterial blood pressure in the largest arteries near the heart F = P1 – P2 / R... (Pressure at begin – pressure at end) / Resistance Resistance is the major determinant of blood flow because a change in blood vessel radius increases resistance to the 4th power measures total of frictional forces that impede flow; flow and resistance are inversely related influenced by Blood Viscosity, Vessel Length and Vessel Diameter Blood Viscosity...due to formed elements, plasma proteins...fairly constant Vessel Length...more length = more resistance...does not vary day-to-day Vessel Diameter...can be regulated; fluid not touching walls moves faster Arterioles can regulate their diameters

greatest pressure drop at the level of the arterioles

Blood Pressure
Pulse Pressure = systolic – diastolic
indicates vigour of contraction of ventricle
provides info on elasticity of aorta and major arteries Mean Arterial Pressure = diastolic pressure + 1/3 pulse pressure pressure that...
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