blood vessels

Question 1

define systemic vessels and pulmonary vessels

Answer 1

SYSTEMIC VESSELS: transport blood through most body parts from the left ventricle and back to the right atrium

PULMONARY VESSELS: transport blood from the right ventricle through lungs and back to left atrium

Question 2

name the 5 types of capillaries, describe and give examples

Answer 2

1. continuous - no gaps between endothelial cells, less permeable to large capillary types, eg, muscle, nervous tissue
2. fenestrated - have pores and are where cytoplasm is absent and plasma membrane is thin, eg, intestinal villi, glomeruli or kidney
3. sinusoidal - large diameter with large capillaries, eg, endocrine glands.
4. sinusoids - large diameter sinusoidal capillaries, eg, liver, bone marrow.
5. veneous sinuses - small in structure, eg, spleen

Question 3

list the layers of a blood vessel wall and state the function of each

Answer 3

TUNICA INTIMA - endothelial, basement membrane, internal elastic membrane, fenestrated layer of elasrtic fibres

TUNICA MEDIA - allows for vasodilation and vasoconstriction

TUNICA EXTERNA - connetive tissue, merges with surrounding C.T.

Question 4

describe muscular and elastic artery

Answer 4

elastic artery -
largest diameters, pressure high and flucatuates between systolic and diastolic. eg, tunica intima and thin tunica externa

muscular artery - smooth muscle allows to regulate blood supply by constricting or dilating. distributes to different regions of the body.

Question 5

define arterioles and state its function

Answer 5

transport blood from small arteries to capillaries

smallest arteries where three tunics can be differentiated

like small arteries, capable of vasoconstriction and dilation

Question 6

define venules and small veins

Answer 6

VENULES - drain capillary network, Endothelial cells and basement membrane with a few smooth muscle cells. As the diameter of venules increases, the amount of smooth muscle increases.

SMALL VEINS - Smooth muscle cells form a continuous layer. Addition of tunica adventitia made of collagenous connective tissue

Question 7

define vasa vasorum

Answer 7

blood vessels that supply the walls of arteries and veins. Penetrate the vessel walls from the exterior. Branches of arteries.

Question 8

define portal veins

Answer 8

veins that begin in a primary capillary network, extend some distance and end in a secondary capillary network without a pumping mechanism, such as the heart, between (eg hepatic portal vein).

Question 9

define the neural innervation of blood vessels

Answer 9

Unmyelinated sympathetic nerve fibers form plexi in tunica adventitia: vasoconstriction

Small arteries and arterioles innervated to greatest extent

Vessels of penis and clitoris innervated by parasympathetic

Some blood vessels innervated by myelinated fibers and act as baroreceptors that monitor stretch and detect changes in blood pressure

Question 10

define vasoconstriction and vasodiation

Answer 10

vasoconstriction - Vasoconstriction is narrowing or constriction of the blood vessels. It happens when smooth muscles in blood vessel walls tighten.

vasodilation - the widening of blood vessels, happens naturally in your body when an increase in blood flow to tissues in your body is needed.

Question 11

what are some of the arterial changes that occur with age?

Answer 11

arteriosclerosis - General term for degeneration changes in arteries making them less elastic

atherosclerosis - Deposition of plaque on walls

Question 12

what does pulmonary circulation do?

Answer 12

moves blood to and from the lungs

includes:
PULMONARY TRUNK - arises from right ventricle

PULMONARY ARTERIES - branches of pulmonary trunk which project to lungs

PULMONARY VEINS - exit each lung and enter left atrium

Question 13

what is systemic circulation and what does it include?

Answer 13

all arteries:
AORTA:
- from which all arteries are derived either directly or indirectly
- branches into ascending, descending, thoracic, abdominal.

CORONARY ARTERIES
- supply the heart

Question 14

give examples of where baroreceptors are located?

Answer 14

carotid arteries

aorta

and other larger arteries in the neck

Question 15

what is blood pressure and how is it measured?

Answer 15

measure of the force exerted by blood against the vessel wall.

measured by listening (auscultation) for Korotkoff sounds produced by turbulent flow in arteries as pressure is released from a blood pressure cuff

Question 16

what is laminar flow ?

Answer 16

a streamlined blood flow; interior of blood vessel is smooth and of equal diameter along its length
Outermost layer moving slowest and centre moving fastest

Question 17

what is turbulent flow?

Answer 17

Interrupted flow
Rate of flow exceeds critical velocity
Fluid passes a constriction, sharp turn, rough surface
Partially responsible for heart sounds
Sounds due to turbulence not normal in arteries and is probably due to some constriction

Question 18

list the factors that are involved in the dynamics of blood flow

Answer 18

Rate of flow through a tube is expressed as the volume that passes a specific point per unit of time. E.g.; cardiac output at rest is 5L/min, thus blood flow through the aorta is 5L/min

Flow = (P1 – P2/R)

P1 and P2 are pressures in the vessel at points one and two; R is the resistance to flow

Directly proportional to pressure differences, inversely proportional to resistance

Question 19

define poiseuille’s law

Answer 19

flow decreases when resistance increases and vice versa.

eg, during exercise, the heart beats with greater force, increasing the blood pressure in the aorta. capillaries located in skeletal muscles increase in diameter, decreasing resistance and increasing flow. Flow in the aorta can increase from 5L/min to 25L/min.

Question 20

define viscocity

Answer 20

the measure of resistance of liquid to flow eg, a lid sliding on top of a container of water, which will make the water move as it is in direct contact.

as viscocity increases, pressure required to flow increases. eg, water has low viscocity, honey has higher.

viscosity greatly influenced by hematocrit (% of composition of red blood cells). eg, dehydration of RBS will increase viscosity

Question 21

define laplace’s law

Answer 21

force acting on blood vessel wall is proportional to diameter of the vessel x blood pressure

F = D x P, thus a diameter of a vessel increase, force on the wall increases. weakened part of a vessel wall bulges out and is an aneurysm.

Question 22

what is vascular compliance?

Answer 22

the tendency for blood vessel volume to increase as blood pressure increases.

eg, venous system has a large compliance and acts as a blood reservoir.

Question 23

what is the systemic circulation determined by?

Answer 23

• anatomy of circulatory system
• dynamics of blood flow
• regulatory mechanisms that control heart and blood vessels

Question 24

what is the difference between systolic and diastolic pressures?

Answer 24

systolic - the amount of pressure in your arteries during the contraction of your heart muscle.

diastolic - refers to your blood pressure when your heart muscle is between beats. This is called diastolic pressure

Increases when stroke volume increases or vascular compliance decreases. . Compliance tends to decrease with age (arteriosclerosis) and pressure rises.

Question 25

what is capillary exchange?

Answer 25

the movement of substances into and out of capillaries

DIFFUSION
Lipid soluble cross capillary walls diffusing through plasma membrane. E.g., O2, CO2, steroid hormones, fatty acids.
Water soluble diffuse through intercellular spaces or through fenestrations of capillaries. E.g., glucose, amino acids.

Question 26

what is net filtration pressure (NFP), in fluid exchange across capillary walls

Answer 26

force responsible for moving fluid across capillary walls. two forces affect pressure:

• hydrostatic pressure
• osmotic pressure

Question 27

what is oedema?

Answer 27

fluid retention in the body.

if capillaries become more permeable, proteins can leak into the IF increasing ICOP (interstitial fluid colloid osmotic pressure). more fluid moves from the capillaries into the IF (interstitial fluid).

Question 28

what is venous tone?

Answer 28

continual state of partial contraction of the veins as a result of sympathetic stimulation.

Question 29

describe blood pressure and the effect of gravity

Answer 29

In a standing position, hydrostatic pressure caused by gravity increases blood pressure below the heart and decreases pressure above the heart.

Muscular movement improves venous return.

Question 30

what is Vasomotion?

Answer 30

periodic contraction and regulation of precapillary sphincters. autoregulation.

long term local control:capillaries become more dense in a region that regularly has an increased metabolic rate.

Question 31

how is blood pressure regulated short term?

Answer 31

baroreceptor reflexes - change peripheral resistance, heart rate, and stroke volume in response to changes in blood pressure

chemoreceptor reflexes - sensory receptors sensitive to oxygen, carbon dioxide, and pH levels of blood

central nervous system ischemic response - results from high carbon dioxide or low pH levels in medulla and increases peripheral resistance

Question 32

list the long term regulation of blood pressure mechanisms

Answer 32

Renin-angiotensin-aldosterone mechanism

Vasopressin (ADH) mechanism

Atrial natriuretic mechanism - released from cardiac muscle cells when atrial blood pressure increases, stimulating an increase in urine production, thus decreasing blood volume and pressure.

Fluid shift mechanism - movement of fluid from interstitial spaces into capillaries in response to decrease in blood pressure.

Stress-relaxation response - when blood volume suddenly declines and pressure drops, smooth muscles contract and vice versa.

Question 33

what is pulse pressure?

Answer 33

Pulse pressure can be used to take a pulse to determine heart rate and rhythmicity
Most frequent site used to measure pulse rate is in the carpus with the radial artery- the radial pulse.

Question 34

state the three stages of how shock can affect blood flow

Answer 34

Compensated: Blood pressure decreases only a moderate amount and mechanisms are able to reestablish normal blood pressure and flow
Progressive: Compensatory mechanisms inadequate and positive feedback cycle develops; cycle proceeds to next stage or medical treatment and reestablishes adequate blood flow to tissues
Irreversible: Leads to death, regardless of medical treatment