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)

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