Chapter 20: The Cardiovascular System: Vessels and Circulation

blood pressure

force blood exerts against the inside of wall of a vessel

Explain how veins serve as a blood reservoir for the cardiovascular system.

-At rest majority of blood in systemic circulation -blood can be shifted away from veins via vein vasoconstriction (when blood needed for physical exertion) - or shifted to veins via vein vasodilation when less blood is needed (at rest)

Explain the difference between an intercellular cleft and a fenestrations.

-Glucose, ions, and larger molecules may leave the blood through intercellular clefts of continuous capillaries -Larger molecules can pass through the pores of fenestrated capillaries, and even large plasma proteins can pass through the great gaps in the fenestrated and sinusoid capillaries

define atherosclerosis

hardening of elastic and muscular arteries caused by build up of plaque

Describe the hormones that regulate blood pressure.

hormonal regulation alters resistance and blood volume -renin-angiotensin system -atrial natriuretic peptide

explain hydrostatic pressure

hydrostatic pressure: force exerted by blood against the walls - pushes fluid out of blood in capillary into the interstitial space (pressure is higher inside the capillary, driving fluid out)

how are capillaries classified

based on how permeable they are -continuous, fenestrated and sinusoid

fenestrated capillaries

basement membrane and lining of endothelial cells is complete -intercellular clefts between endothelial cells *same as continuous but contains fenestrations: pores in endothelia -allows passage of plasma and smaller plasma proteins, does not allow formed elements to pass -located where there is major fluid transport between blood and ISF (small intestine, kidney)

continuous capillary

basement membrane and lining of endothelial cells is complete -intercellular clefts between endothelial cells -allows plasma and some leukocytes to pass through vessel wall -located in most capillaries (muscle and skin)

capillary bed as sphincters are contracted

blood bypasses capillary bed and enters in venous circulation, sparing blood for other tissue

define local blood flow and name the factors that determine it

blood delivered to the capillaries of a specific tissue degree of vascularity myogenic response local regulatory factors total blood flow

capillary bed as sphincters are relaxed

blood flows into capillary bed allowing for capillary exchange

explain how vascularization of tissue may change over time

angiogenesis: formation of new blood vessels in a tissue, when more blood is needed in tissue regression: loss of blood vessels, when less blood is needed in tissue

Define mean arterial pressure.

average pressure exerted by blood on arteries MAP= CO x TPR to control MAP, the body can alter CO and/or TPR

respiratory pump

pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand 2 steps: -inspiration (breathe in): diaphragm contracts, increased abdominal pressure, decreased thoracic pressure, compresses abdominal veins and blood moves to thoracic veins -expiration (breathe out): diaphragm relaxes, increased thoracic pressure, decreases abdominal pressure, compresses thoracic veins, blood moves to heart

autoregulation

process by which a tissue regulates its local blood flow in response to metabolic demand *relationship between local regulatory factors, metabolism and perfusion

How does the body achieve long-term versus short-term regulation of blood pressure?

short term: Nervous system regulation (alters: CO, Resistance, Blood Volume) baroreceptors long term: hormonal (endocrine) regulation (alters: Resistance and Blood Volume)

which type of capillary would allow the passage of formed elements and large plasma proteins

sinous capillaries

Describe the general anatomic structure and function of capillaries.

site of exchange between blood and tissue -connect arteriole and venule -composed of basement membrane and endothelium and precapillary sphincters

tunica media

smooth muscle and elastic fibers - vasoconstriction (narrow)and vasodilation (widen) of vessel lumen

blood flow of veins and arteries (sizes)

veins: large vein --> small to medium sized vein --> venule--> capillary bed arteries: elastic artery --> ,muscular artery --> arteriole--> capillary bed

factors affecting total peripheral resistance, which then affect total blood flow

vessel radius (increase diameter = decrease TPR) vessel length (longer=higher TPR) blood viscosity (higher viscosity=higher TPR)

vasa vasorum

"vessels of vessels" network of small arteries and veins that nourish outer region of very large vessels, found in externa

Explain the effects of vasomotor center activation on peripheral resistance and the distribution of blood volume throughout the body.

-vessels constrict: increased peripheral resistance -redistribute blood from venous reservoir: increased blood volume -more blood to skeletal muscle and heart, less blood to other tissues: redistribution of blood flow

name the type of capillary exchange: 1.) fluid moves from blood to interstitial fluid based on blood osmolarity and pressure 2.) insulin is transported through endothelia by a series of endocytosis and exocytosis 3.) glucose moves down its concentration gradient from the blood to the interstitial fluid by passing from through intercellular clefts

1.) bulk flow 2.) vesicular transport 3.) diffusion

renin-angiotensin system role in hormonal regulation of BP

1.) kidneys detect low blood pressure 2.) kidneys release renin, liver continuously releases angiotensinogen 3.) renin converts angiotensinogen to angiotensin 1 4.) angiotensin converting enzyme converts angiotensin 1 to angiotensin 2 5.) effect mediated by angiotensin 2: powerful vasoconstriction, increase fluid intake in thirst center and decrease urine formation via kidneys overall effect: increase in blood pressure

Atrial natriuretic peptide (ANP) role in hormonal regulation of BP

1.) stretch of atrial walls, increase blood volume and increase venous return stimulate cellular response 2.) cells of atrial wall release ANP 3.) effect mediated by ANP: vasodilation (decrease in resistance), increase in urine output (decrease blood volume) overall effect: decrease blood pressure

Explain the mechanisms that help the venous system combat the low pressure gradient in veins to return blood to the heart

1.) valves: ensue one way blood flow 2.) pumps: pressure changes caused by the movement of muscle throughout the body move blood - two types of venous return pumps: skeletal muscle pump and respiratory pump

name the local regulator factors

2 types of vasoactive chemicals: vasodilator and vasoconstrictor

tunica externa

CT, elastic and collagen fibers - anchors vessels to surrounding structures - contains vasa vasorum

Compare the speed of blood flow in arteries, veins and capillaries (blood flow velocity)

The rate, or velocity, of blood flow varies inversely with the total cross-sectional area of the blood vessels. As the total cross-sectional area of the vessels increases, the velocity of flow decreases. -Blood flow is slowest in the capillaries, which allows time for exchange of gases and nutrients.

to increase blood flow to tissue, precapillary sphincters will ______

When the surrounding tissues need oxygen and have excess waste products, the precapillary sphincters open, allowing blood to flow through and exchange to occur before closing once more -if sphincters are open, the blood will flow into the associated branches of the capillary bed. -If sphincters are closed, then the blood will flow directly from the arteriole to the venule through the thoroughfare channel. -At any given moment, only about 5-10 percent of our capillary beds actually have blood flowing through them.

define total blood flow

amount of blood transported through entire vasculature (all vessels) total blood flow directly related to cardiac output (CO)

name the types of blood vessels

artery- transfer blood away from heart veins- transport blood to the heart capillaries- site of gas exchange

skeletal muscle pump

as skeletal muscle contract, veins are squeezed, propelling blood toward the heart

lymphatic systems role in fluid reabsorption

at the venous end of the capillary 85% of fluid is reabsorbed -15% of fluid not reabsorbed by capillary during bulk flow is absorbed by the lymphatic system and eventually is returned to venous system

vasoconstrictor

chemicals that cause contraction of smooth muscle in arterioles and precapillary sphincters caused by increased oxygen and/ or nutrients; decreased CO2 and H+, lactase decreased metabolism = decreased perfusion

vasodilator

chemicals that cause the relaxation of smooth muscle in arterioles and precapillary sphincters causes by decreased oxygen and/ or nutrients; increased CO2 and H+, lactase increased metabolism = increased perfusion

compare and contrast filtration and absorption processes of bulk flow

filtration: blood plasma containing nutrients is filtered out of capillary at the arterial end of capillary bed -positive NFP absorption: tissue fluid containing waste is reabsorbed back into the capillary at the venous end -negatove NFP

explain colloid osmotic pressure

colloid osmotic pressure: pull of fluid back into the blood in capillary due to the tissues concentration of proteins -the blood contains more solutes (meaning it contains less water than the interstitial space) which drives water to flow into capillary -fluid moves toward the area of lower protein and H2O concentration (blood)

myogenic response

contraction or relaxation of smooth muscle in blood vessel in response to stretch of vessel wall -maintain homeostatic blood flow by vasoconstriction and vasodilation

define vasomotion

cyclical opening and closing of capillary sphincters - regulates amount of blood entering capillary bed, there is not enough blood on the body to feed every capillary bed at the same time, helps re-direct blood to other areas

Perfusion

delivery of blood per time per gram of tissue, ensures all cells un body have constant delivery of blood to provide nutrients and remove waste

name the methods of capillary exchange

diffusion vesicular transport bulk flow *diffusion and vesicular transport are used to transport studs in blood; bulk flow transports fluids

tunica interna

endothelium (simple squamous epithelium) - provides smooth surface to reduce friction -releases substances to relax or constrict vessel

edema

excess fluid build up in interstitial space -caused by an imbalance in filtration and reabsorption at capillary -blockage of lymph capillary, reason why reabsorbed is important

explain transcytocis of vesicular transportation

large, insoluble particles cannot be transported via diffusion, must use transcytosis blood --> endocytosis-->moves through endothelial cell in a membrane bound sphere --> exocytosis --> exits cell to interstitial fluid (process can be reversed)

sinous capillary

lining of endothelial cells is incomplete basement membrane is incomplete or absent -allows passage of large substances as well as plasma and plasma proteins -located in red bone marrow for formed elements to enter the blood, liver and spleen for removal of old RBC from circulation

general structure of blood vessels

lumen: inside space vessel wall: surrounds lumen, composed of tunics 3 tunics: interna, media and externa

bulk flow

movement of large amounts of fluid and their dissolved substances in one direction down a concentration gradient -two parts: filtration and absorption -two influences: hydrostatic pressure and colloid osmotic pressure filtered / pushed out via hydrostatic pressure absorbed / pulled in via colloid osmotic pressure

vesicular transport

movement of particles through the plasma membrane by the processes of exocytosis/ endocytosis -moves larger solutes and proteins 1.) endothelial cells use transcytosis to move large substances to other side of cell (can move both directions; blood to interstitial or interstitial to blood)

baroreceptors

stretch receptors that detect change in BP -located in tunica externa of aorta and carotid sinus -changes frequency of firing to signal BP changes increase BP=increase rate of signals decrease BP=decrease rate of signals stimulate the brain to stimulate the cardiac center or vasomotor center to return BP to homeostasis

Explain how norepinephrine release from neurons of the vasomotor center can cause some blood vessels to constrict and others to dilate.

sympathetic regulation of blood vessel constriction vs dilation release of NE: if NE binds to a1 receptor: vasoconstriction if NE bind to b2 receptor: vasodilation

Define compliance and describe why compliance is necessary for the normal function of healthy blood vessels

the ability of a blood vessel to stretch and recoil -an increase in volume occurs in a vessel when the pressure in that vessel is increased. -The tendency of the arteries and veins to stretch in response to pressure has a large effect on perfusion and blood pressure

blood pressure gradient

the change in blood pressure from one end of a blood vessel to the other -the driving force that moved blood through the vasculature -blood pressure in the venous system is close to zero

net filtration pressure

the difference between net hydrostatic pressure and net osmotic pressure (comparing push to pull) NET HP - NET COP postive NFP = filtration negative NFP = reabsorption

degree of vascularity

the extent of blood vessel distribution, determined by metabolism of an organ -high metabolism = high vascularization (brain and skeletal muscle) -low metabolism = low vascularization (tendons and ligaments)

diffusion

the movement of substances from high to low concentrations -moves small, dissolves solutes and gases 1.) small solutes diffuse via endothelial cells or intercellular clefts (continuous) 2.) large solutes diffuse via fenestrations (fenestrated) or gaps (sinusoid)

Explain how the cardiac center will alter cardiac output in response to changes in blood pressure.

to increase BP: cardioacceleratory center of sympathetic nervous system will release NE to increase HR and SV, and therefore CO to decrease BP: cardioinhibitory center of parasympathetic nervous system will release Ach to decrease HR and SV, and therefore CO

Describe how cardiac output establishes a blood pressure gradient and what happens to that gradient following an increase or decrease in cardiac output

total blood flow = pressure gradient (CO) / Resistance increase (steeper) pressure gradient by increasing CO = increase in total blood flow decrease pressure gradient by decreasing CO = decrease in total blood flow

Explain the relationship of both blood pressure gradients and resistance to total blood flow

total blood flow is influenced by pressure gradient (CO) and resistance CO: directly related to total blood flow -high CO, high blood flow Resistance: inversely related to total blood flow -high resistance, low blood flow

does the structure of arteries vs. veins differ

tunica media is thicker in arteries lumen is wider in veins valves exist only in veins

stimulus of a vasodilation myogenic response vs vasoconstriction myogenic response

vasodilation: stimulated by decrease blood flow, decrease stretch of vessel vasoconstriction: stimulated by increase blood flow, increase stretch of vessel