ch 4 - [1/2] BV and circulation (structure/function, capillary exhange, blood flow/pressure)

arteries

carry blood away from the heart → branch into arterioles

arterioles

branch into capillaries (smallest bvs); nutrient and waste exchange occurs

venules

combined capillaries making a small vein; thin walls compared to veins

veins

combined venules conducting blood to the heart; contains valves, larger lumens and thinner walls than arteries

summarize the BV pathway from largest to smallest

arteries → arterioles → capillaries

venules = bunches of capillaries

veins = bunches of venules

provides oxygenized blood to bodily tissues

systemic arteries of systemic circuit

returns deoxygenated blood to heart

systemic veins

leaves the heart with deoxygenated blood to bring it to the lungs for gas exchange

pulmonary arteries in the pulmonary circuit

returns freshly oxygenated blood from lungs to heart for the systemic pathway

pulmonary veins

• blood leaves the ___ side of the heart for pulmonary circulation

• blood returns to the ___ side of the heart for pulmonary circulation

• right

• left

label the arteries and veins in the pulmonary and systemic circulatory circuits

blood has higher pressure [away from / closer to] the heart

closer to the heart

compare blood pressure levels of arteries VS veins

• arteries = thicker walls, smaller lumens to maintain BP = higher blood pressure

• veins = thinner walls, wider lumens as surface area increases = lower blood pressure

purpose of valves

in veins - unidirectional bloodflow back to the heart

3 tissue layers in veins and arteries

tunics

• tunica intima

• tunica media

• tunica externa

tunica intima in artery vs vein vs capillary

• composition

regulates capillary exchange, blood flow

lined by endothelium, bound to areolar connective tissue via basal lamina

artery: has internal elastic membrane (wavy shape) for stretching/structure

vein: smooth endothelium, valves for unidirectional bloodflow connected

capillary: smooth endothelium

tunica media in artery vs vein vs capillary

• contraction vs relaxation

• composition

regulates blood pressure and flow

• contraction = vasoconstriction, increasing BP

• relaxation = vasodilation, decreasing BP

smooth muscle with connective elastic fibers, collagen fibres for flexibility

artery: thickest layer, many elastic fibers

veins: thinner than tunica externa, more collagen

capillary: does not exist

tunica externa in artery vs vein vs capillary

• composition

connective tissue with mostly collagen fibers, some elastic fibers, smooth fibres in veins)

artery: thinner than tunica media (might be thicker in some large arteries)

veins: thickest layer, contains smooth muscle cells

capillary: does not exist

capillary exchange (def)

circulates gases/nutrients/wastes to and from bodily cells using diffusion across the endothelial membranes

capillary exchange: small mlcs

use simple diffusion to pass through endothelial membranes

capillary exchange: glucose, amino acids, ions

use facilitated diffusion (channel/carrier proteins) or intercellular clefts

capillary exchange: larger mlcs

• pores of fenestrated capillaries

• exocytosis/endocytosis

• gaps of sinusoidal capillaries

capillary exchange: water

osmosis

blood pressure (def)

hydrostatic force exerted by blood on blood vessel walls

(ventricles contract, exerting pressure on blood and pushing it out into arteries)

blood pressure [drops/rises] as blood travels through smaller arteries → arterioles → capillaries → venules → veins

[drops] (wider lumens and thinner walls allowing for increased surface area, more flow with less resistance)

unit of blood pressure

mm Hg

bodily location where BP is commonly measured

systemic arteries - brachial artery of arm, mm Hg unit

ratio of 2 numbers that systemic BP is recorded in

ex: 120/80

• numerator = systolic pressure

• denominator = diastolic pressure

systolic pressure

(systole = contraction as blood is pumped out of heart)

arterial pressure causing blood to be ejected when ventricles contract

ex: 120/80

diastolic pressure

(diastole = relaxation period as blood fills heart chamber)

arterial pressure of blood during ventricular relaxation

ex: 120/80

mean arterial pressure

• value of the actual mean in most people

• condition occurring if value drops too low

avg blood pressure in arteries = 70-110 mm Hg

• ischemia (insufficient bloodflow) leading to hypoxia (low blood oxygen)

pulse pressure

difference btwn recorded systolic and diastolic pressure values

normal blood pressure for adults

systolic pressure: less than 120mm Hg

diastolic pressure: less than 80 mm Hg

pulse (def)

expansion and recoiling of elastic fibers in arteries as blood flows out of heart

artery where pulse is most readily measured

radial artery (at wrist)

identify the various arteries where pulse can be measured (9)

relationship between blood flow and blood pressure

• in the arteries (if more blood is not pumped)

• in the veins

blood flow = movement of blood through body part

blood pressure = hydrostatic force of blood against blood vessel walls

• if pressure in arteries increases (BP rises) but amt of blood pumped is the same, the flow decreases

• if pressure in veins increases, flow will also increase as veins typically have low BP

6 variables influencing blood flow & blood pressure

1. cardiac output: blood flow out of the ventricles, affected by heart rate, stroke volume

2. compliance: ability for compartment to expand and accommodate increased blood flow (ex/ the more an artery expands when BF increases, the less BP will increase)

3. blood volume: when blood volume decreases → pressure and flow decrease

4. blood viscosity: increased blood viscosity = decreased flow, increased pressure

5. blood vessel length: longer vessel → greater resistance and lower flow

6. blood vessel diameter: determined by vascular tone; increased diameter = increased flow, lower pressure

factors increasing and decreasing cardiac output (variable influencing blood flow, blood pressure)

increasing:

• epinephrine

• norepinephrine

• thyroid hormones

• increased Ca2+

decreasing:

• decreased Ca2+

• parasympathetic stimulation (rest and digest)

• increased or decreased K+

name 2 things affecting blood viscosity

• blood plasma

• formed elements

name 2 things playing significant role in regulating blood pressure

• vasodilation of arterioles

• vasoconstriction of arterioles

• name 2 physiological pumps increasing pressure in the venous system

• explain why pressure in the venous system must be greater than in the atria

1. skeletal muscle pump

2. respiratory pump

• to ensure that blood can flow back to the heart through the venules and veins, especially in the lower appendages

skeletal muscle pump

physiological pump in venous system increasing pressure to ensure blood can flow back to the heart

• skeletal muscles surrounding vein in lower appendages will contract, squeezing the vein and pushing blood upward

respiratory pump

physiological pump in venous system increasing pressure to ensure blood can flow back to the heart

• inhalation: thorax volume increases, pressure decreases

• pressure in veins of thorax decreases

• blood from veins outside thorax will flow towards it, and to the atria