pressure gradients, blood flow and peripheral resistance

Question 1

what are arteries

Answer 1

low resistance vessels conducting blood to the various organs with little loss in pressure
act as pressure resevoirs for maintaining blood flow between ventricular contractions

Question 2

what are arterioles (basic)

Answer 2

major sites of resistance to blood flow
responsible for the pattern of blood flow distribution
participate in the regulation of arterial blood pressure

Question 3

what are capillaries

Answer 3

site of exchange between blood and tissues

Question 4

what are veins

Answer 4

low resistance vessels for blood to flow back to the heart
their capacity for blood is adjusted to facilitate flow

Question 5

what are the components of vessels

Answer 5

adventitial layer - connective tissue
medial layer - smooth muscle cells
intimal layer - endothelial cells

Question 6

what is the composition of the elastic artery wall

Answer 6

5% endothelium
25% smooth muscle
40% elastic tissue
30% connective tissue

Question 7

what is the composition of the arteriole wall

Answer 7

10% endothelium
60% smooth muscle
10% elastic tissue
20% connective tissue

Question 8

what is the composition of the capillary wall

Answer 8

95% endothelium
5% connective tissue

Question 9

what is the composition of the venule wall

Answer 9

20% endothelium
20% smooth muscle
60% connective tissue

Question 10

measurements of the aorta

Answer 10

internal radius = 12mm
wall thickness = 2mm

Question 11

measurements of medium artery

Answer 11

internal radius = 2mm
wall thickness = 1mm

Question 12

measurements of arteriole

Answer 12

internal radius = 15µm
wall thickness = 20µm

Question 13

measurements of true capillary

Answer 13

internal radius = 3µm
wall thickness = 1µm

Question 14

measurement of vein

Answer 14

internal radius = 2.5mm
wall thickness = 0.5mm

Question 14

measurement of venule

Answer 14

internal radius = 10µm
wall thickness = 2µm

Question 15

measurement of vena cava

Answer 15

internal radius = 15mm
wall thickness = 1.5mm

Question 16

features of arteries

Answer 16

several hundred
thick, highly elastic walls
large radii
passageway from heart to organs
serve as pressure resevoirs

Question 17

features of arterioles

Answer 17

half a million
highly muscular, well-innervated walls
small radii
primary resistance vessels
determine distribution of cardiac output

Question 18

features of capillaries

Answer 18

ten billion
thin walled
large total cross-sectional area
site of exchange
determine distribution of extracellular fluid between plasma and interstitial fluid

Question 19

features of veins

Answer 19

several hundred
thin walled
highly distensible
large radii
passageway to heart from organs
serve as blood resevoir

Question 20

what is haemodynamics; pressure, flow and resistance

Answer 20

throughout the vascular system blood flow (F) is always from a region of higher pressure to one of lower pressure

Question 21

what is hydrostatic pressure

Answer 21

the pressure exerted by a fluid

Question 22

what is the units of flow

Answer 22

volume per unit time
L/min or ml/min

Question 23

what is the units of pressure difference

Answer 23

ΔP
drives the floe
mmHg

Question 24

what is flow rate

Answer 24

to work out; the pressure difference between two points (ΔP) and the resistance (R) to flow

Question 25

what is resistance (basic)

Answer 25

a measure of how difficult it is for blood to flow between two points at any given pressure difference a measure of the friction impeding flow

Question 26

what is blood flow

Answer 26

blood flow through vessels depends upon the pressure gradient and vascular resistance blood flows through 'tubes' the driving force is the pressure generated by contractions of the heart F = ΔP/R flow is directly proportional to ΔP flow rate depends on the pressure difference NOT the absolute pressure

Question 27

what is resistance

Answer 27

a measure of the friction impeding flow depends upon 3 factors; 1. viscosity of the blood 2. vessel length 3. vessel radius - major determinant of resistance to flow, a slight change in radius brings about a notable change in flow > resistance is directly proportional to 1/r^4, flow is directly proportional to r^4

Question 28

what is the poiseuille equation

Answer 28

INSERT IMAGE

Question 29

what is arterial pressure

Answer 29

fluctuates in relation to ventricular systole and diastole mean arterial pressure = diastolic pressure + 1/3pulse pressure

Question 30

what are arterioles

Answer 30

the major resistance vessels the small radius of arterioles offers considerable resistance to blood flow this high arteriolar resistance causes a marked drop in mean pressure as blood flows through arterioles this pressure gradient helps drive blood from the heart to the tissue capillary beds arteriolar resistance also converts pulsatile arterial pressure into non-fluctuating capillary pressure

Question 31

what is smooth muscle in the vasculature

Answer 31

arteriolar walls include a thick layer of smooth muscle that is richly innervated by nerves of the sympathetic nervous system - this smooth muscle is also sensitive to many local chemical changes and certain circulating hormones the smooth muscle runs circularly around the arteriole

Question 32

what is smooth muscle contraction of arterioles

Answer 32

⬇️ radius, ⬆️ resistance ⬇️ local blood flow vasoconstriction

Question 33

what is smooth muscle relaxation of arterioles

Answer 33

⬆️ radius, ⬇️ resistance ⬆️ local blood flow vasodilation

Question 34

what is vasoconstriction

Answer 34

increase contraction of smooth muscle increase resistance decrease of flow through the vessel

Question 35

what is vasodilation

Answer 35

decrease contraction of smooth muscle decrease resistance increase flow through the vessel

Question 36

hat a