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89 terms

Cardiovascular system- Blood vessels

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Arteries
muscular, elastic vessels, carry blood away from the heart, thick-walled vessels with thick tunica media(muscle)
Arterioles
smaller branches of arteries
capillaries
tiny, thin-walled vessels, site of exchange of substances between blood and tissues, reduce to endothelial layer + basement membrane, exchange vessels
venules
small branches which merge to form veins, carry blood from capillaries to veins, very thin-walled near capillaries- site of some exchange, muscle and connective tissue in walls increases as they get farther from capillaries
veins
large, relatively thin-walled vessels, carry blood to the heart
vasa vasorum
vasculature of large vessels
systemic circuit
arteries carry oxygenated blood away from heart, veins carry deoxygenated blood to the heart
pulmonary circuit
arteries carry deoxygenated blood away from the heart, veins carry oxygenated blood to the heart
anatomy of blood vessels
3 layers (tunics): tunica interna, tunica media, tunica externa
tunica interna
(intima) inner layer
tunica interna is made up of?
endothelium- simple squamous epithelium
tunic media
middle layer
tunic media is made up of?
circular smooth muscle and elastic fibers
tunica externa
(adventitia) outer layer
tunica externa is made up of?
fibrous connective tissue
types of arteries
elastic arteries, muscular arteries, arterioles
elastic arteries
largest diameter, closet to heart.
(aorta and it main branches, pulmonary trunk and arteries)
have higher proportion of elastic fivers and less muscle
stretch to accommodate surge of blood from heart, the recoil to pump blood along vessels
muscular arteries
smaller diameter branches off aorta and pulmonary arteries, higher proportion of muscle, diameter controlled by ANS-regulate blood flow to different body regions
arterioles
tiny branches within tissues, deliver blood to capillaries, walls get thinner as they get smaller, resistance vessels
resistance vessels
control resistance (opposition to blood flow) by changing diameter (smaller vessel=greater resistance), vasoconstriction and vasodilation
vasoconstriction
decreased diameter
vasodilation
increased diameter, diameter regulated by ANS (maintains blood pressure)
exchange vessels
site of diffusion of materials between blood and tissues found in most tissues; number depends on metabolic needs of tissue, capillary bed
capillary bed
10-100 capillaries supplying a tissue region, precapillary sphincters
precapillary sphincters
regulate blood flow into capillaries alternately open and close based on needs of tissue
capillary permeability
continuous capillaries, fenestrated capillaries, sinusoids
continuous capillaries
found in most tissues, water, small solutes, lipid-soluble materials can cross through
fenestrated capillaries
found at sites of filtration, absorption, and secretion (kidneys, ventricles of brain, ciliary body of eye,small intestine, endocrine glands)
sinusoids
found at sites of protein and cellular exchange (red bone marrow, spleen, liver) very permeable- allow blood cells and plasma proteins to cross
veins in depth
large thin-walled vessels (collapse when empty)
tunica media(muscle) much reduced, stretch readily; may be damaged by high pressure
venoconstrict or venodilate to regulate blood volume returning to the heart
valves, skeletal muscle, respiratory pump
valves in the veins
one-way cusps that prevent backflow of blood, pressure in veins is too low to keep blood flowing against gravity
skeletal muscle pump
contraction of limb muscles compresses veins, helps return blood to heart
respiratory pump
pressure changes in the thoracic cavity during breathing help return blood to the heart
collateral circulation
alternate pathway for blood flow in a region if one vessel becomes blocked, anastamoses, end artery
anastamoses
connections between arteries/arterioles supplying adjacent regions (also occur in veins and venules)
end artery
artery that doesn't anastamoses, infarction
infarction
death of tissue due to blockage of an end artery
hemodynamics
forces involved in circulating blood
total blood flow=cardiac output(CO)
factors affecting blood flow: blood pressure, vascular resistance
blood pressure
greater pressure=greater force
vascular resistance
greater resistance=less flow
vascular resistance(R)
opposition to flow due to friction between blood and vessel wall
vascular resistance depends on?
diameter of vessel lumen, blood viscosity, blood vessel length
1. diameter of vessel lumen
smaller diameter=more resistance, regulated by vasoconstriction and vasodilation
2. blood viscosity
thicker blood=more resistance, depends mainly on ratio of blood cells to plasma
3. blood vessel length
longer blood vessel=more resistance
Blood pressure in depth
hydrostatic pressure of blood on the walls of an artery, pressure delivering blood to tissue capillaries, systolic pressure, diastolic pressure, pulse, sphygmomanometer
sphygmomanometer
used to measure systemic blood pressure
systolic pressure
highest arterial pressure, produced by left ventricular systole
diastolic pressure
lowest arterial pressure, during ventricular diastole; maintained by elastic rebound in arteries and resistance in arterioles
pulse
palpable change in artery diameter during systole and diastole, pulse pressure
pulse pressure
=systolic BP - diastolic BP
capillary exchange
exchange of solutes between blood and tissues, diffusion, bulk flow, net filtration pressure
diffusion
solutes exchanged from high concentration to low concentration, from blood into cells-oxygen, nutrients, hormones. from cells into blood- carbon dioxide, wastes, hormones (plasma proteins and blood cells only diffuse through sinusoid capillaries)
bulk flow
pressure driven movement of fluid across a membrane (water and solutes small enough to fit through pores in membrane) filtration, reabsorption
filtration
bulk flow from blood -> interstitial fluid, driven by capillary blood pressure (CBP)
reabsorption
bulk flow from interstitial fluid -> blood, driven by blood osmotic pressure (BOP) due mainly to plasma proteins in blood
net filtration pressure (NFP)
indicates net fluid movement, NFP= CBP-BOP, positive NFP, negative NFP
positive NFP
filtration occurs (at beginning of capillaries)
negative NFP
reabsorption occurs (at end of capillaries)
85% of filtered fluid is reabsorbed
excess returned to blood by lymphatic system
edema
excess fluid accumulation in tissues
regulation of blood pressure and blood flow
tissue perfusion, blood pressure depends on, autoregulation of capillary beds, neural regulation, hormonal regulation, shock
tissue perfusion
amount of blood being supplied to tissues; must supply needs of tissues for oxygen and nutrients, and removal of wastes
blood pressure depends on?
cardiac output: heart rate and stroke volume, vascular resistance
autoregulation of capillary beds
based on needs of tissues, local factors cause dilation or constriction of arterioles and precapillary sphincters, vasodilators (low oxygen, high carbon dioxide, lactic acid, inflammatory chemicals) vasoconstrictors- various clotting factors
neural regulation
cardiovascular center
cardiovascular center
medulla oblongata inputs, baroreceptors and chemoreceptors, vasomotor center
baroreceptors
in aorta and carotid arteries, detect blood pressure (and volume)
chemoreceptors
in aorta and carotid arteries, detect blood O2, CO2, and pH
vasomotor center
regulates vascular resistance, sympathetic vasomotor neurons
sympathetic vasomotor neurons
cause vascular constriction, vasoconstriction in arteries (> blood pressure) and cause venoconstriction - increases venous return to heart > preload = > CO = > BP
hormonal regulation
RAA system, ADH, erythropoietin, adrenal medulla
1. RAA system
stimulated by decreased blood flow to kidneys, angiotensin II, aldosterone, increases BP
angiotensin II
vasoconstriction (thirst, >CO)
aldosterone
kidneys retain sodium and water, increased blood volume
2. ADH
stimulated by dehydration, vasoconstriction, kidneys retain water (less urine) - increases blood volume, increases BP
3. erythropoietin
stimulated by hypoxia (low O2) or <BP, increases formation of RBCs = increases blood volume, increases BP
4. adrenal medulla
sympathetic response, increases CO and vascular constriction
shock
cardiovascular system fails to deliver adequate oxygen and nutrients to meet cellular needs throughout body
4 types of shock
hypovolemic, cardiogenic, vascular, obstructive
hypovolemic shock
low blood volume, hemorrhage, dehydration- diarrhea, vomiting, sweating, diabetes - excessive urine production
cardiogenic shock
poor heart function, heart disease or damage, valve problems, arrhythmias
vascular shock
decreased vascular resistance, anaphylactic shock, neurogenic shock, septic shock
anaphylactic shock
allergy vasodilators
neurogenic shock
CV center dysfunction (head trauma)
septic shock
bacterial toxins
obstructive shock
blockage of blood flow, pulmonary thromboembolism
signs and symptoms of shock
low BP, rapid HR, weak, rapid pulse, cool, pale skin and nausea(sympathetic effects) impaired mental state, reduced urination and increased thirst, acidosis (low plasma pH)