The Vascular System Flashcards
Describe arteries:
Wide lumen
elastic wall
maintains pressure
Describe arterioles:
- Narrow lumen
- Contractile wall
- Controls resistance and pressure of blood by altering lumen size
Describe capillaries:
- Narrow lumen
- Thin walls
- Site of exchange of nutrient, oxygen and metabolic waste
Describe venues and veins:
- Wide lumen
- Compliant wall
- Low resistances
- Blood reservoir
- Valves to prevent back flow
There are 3 major types of capillaries; continuous,
fenestrated and sinusoidal. Which of the following best
describes fenestrated capillaries?
Select one: A. Located in the bone, liver and endocrine glands, very permeable allowing larger molecules such as plasma proteins between blood and interstitial space B. Located in specialist areas of the body, highly permeable, contains ‘windows’ allowing small peptides C. Located in most regions of the body, semi-permeable allowing H2O and small solutes
B
What are continues capillaries?
Supplies most of the body - allows small solutes and H2O to cross
What adaptions do continuous capillaries have?
Blood-brain barrier, whereby gap junctions between endothelial cells
prevent movement between the blood and interstitial space
What are fenestrated capillaries?
Contain pores – allows much greater movement between blood and
interstitial space; including that of small peptides
Where are fenestrated capillaries located?
Specialised areas
-Endocrine, intestines and glomerulus
What are sinusoidal capillaries?
Resemble fenestrated capillaries but more ‘pores’ allowing larger molecules such as plasm proteins to cross
Where are sinusoidal capillaries located?
Bone, liver and other endocrine organs
What are three different types of capillaries?
- Continuos capillaries
- Fenestrated capillaries
- Sinusoidal capillaries
What three factors determine how blood travels through blood vessels?
- Pressure
- Flow
- Resistance
What is pressure in relation to blood flow?
The driving force behind blood flow, generated by the heart. Blood flows
from high to low pressure regions
What is flow in relation it blood flow?
Volume per unit time (L/min; Q). Blood flow is determined by ΔP (starting point vs endpoint) and
resistance to flow
What is resistance in relation to blood flow?
An impediment to flow; high
resistance means a higher ΔP is needed to achieve the same flow
What is the equation for blood flow?
Change in pressure / resistance
What factors does resistance to blood flow depend on?
- Blood viscosity
- Vessel length
- Vessel radius
How does blood viscosity affect resistance to blood flow?
The thicker the blood, the higher the resistance to flow
How does vessel length affect resistance to blood flow?
The longer the vessel, the higher the resistance to flow
How does vessel radius affect resistance to blood flow?
The narrower a vessel is, the higher the resistance to flow
What is the equation for resistance?
(8 x blood viscosity x blood length) / ( π x vessel radius^4)
What is the function of the cardiovascular system?
Delivery of oxygen and nutrients to tissue and removal of waste products
What does the cardiovascular system consist of?
Pump (heart), pipes (blood vessels) and a carrier (blood)
Do we have a singular or double circulation is the cardiovascular system?
Double circulation
What is the double circulation in the cardiovascular system?
- Pulmonary circulation
- Systematic circulation
What is the pulmonary circulation?
Specialised circulation that is relatively short, simple and operates at a lower pressure than systematic circulation
Is there a difference in cardiac output in two circulations of the cardiovascular system?
No - equal
Is there a difference in resistance to flow in two circulations of the cardiovascular system?
Pulmonary - short
Systematic - high
Is there a difference in pressure in two circulations of the cardiovascular system?
Pulmonary - short
Systematic - high
What is the normal pressure in the pulmonary circulation?
25/10 mmHg
What is the normal pressure in the systematic circulation?
120/80 mmHg
What is the major determination of blood pressure and flow?
Resistance determined by radius of blood vessels
What does mmHg stand for?
millimeters mercury
What is another name for mean arterial blood pressure?
Blood pressure
How do you calculate the mean arterial blood pressure?
2(diastolic) + systolic / 3
How many times longer is the diastole to systole at rest?
Twice
How does a dicrotic notch occur?
- Left ventricle contracts
- Blood forced into aorta
- Aortic valve closes rapidly
- Sends pressure wave within the aorta
Where is the biggest drop in pressure in the circulation?
Arterioles
Why is the biggest drop in pressure in the arterioles?
Due to their small radius and high resistances
What blood vessel holds the largest share of blood in the whole circulation?
Veins
What is the word for the veins having the largest share of blood?
Capacitance
How is mean arterial blood pressure determined by?
- Cardiac output
- Total peripheral resistances
- Blood volume
How does cardiac output affect the mean material blood pressure?
Heart rate and stroke volume
How does total peripheral resistance affect the mean material blood pressure?
Constriction or dilating muscular arteries and arterioles
How does blood volume affect the mean material blood pressure?
Reduction or increases affects cardiac output
What is the equation for blood pressure?
Cardiac output x total peripheral resistance
How is blood pressure regulated?
- Neurological
- Humoral
How is blood pressure regulated humorally?
- Aldosterone, adrenaline, ADG, ANP and BNP etc
- Short and long term
- Influences vascular resistance and blood volume
How is blood pressure regulated?
- Autonomic nervous system
- Short term regulation
- Influences cardiac output and vascular resistance
Where are arterial baroreceptors located?
Aortic arc AND carotid sinus
What do arterial baroreceptors do?
-Continuously monitor atrial blood pressure
-Input to cardiovascular
centre in medulla oblongata
-Output is autonomic
nervous system response
-Responsible for rapid,
short-term control of blood
pressure
What is the frequency of arterial baroreceptors dependent on?
Arterial blood pressure
Do the frequencies of the arterial baroreceptors increase or decrease when lower material pressure?
Decrease
Do the frequencies of the arterial baroreceptors increase or decrease when higher material pressure?
Increase
Describe how baroreceptors control of increased blood pressure:
- Baroreceptors detect stretch in vessels walls
- Aortic arch and carotid artery increase firing rate
- Carotid baroreceptors send information up through glossopharyngeal nerve
- Aortic arch sends information through Vegas nerve to CV centre within medulla oblongata
- Response though parasympathetic nerve and vagus nerve efferent
- Increasing activity of parasympathetic output to Sino-artial node
- Sympathetic output decreases to sino martial node
- Decreasing the activity of B1 receptors
- Decrease in heart rate and cardiac output
- Vasoconstriction decreases and resistances
- Blood pressure falls
What are the five main blood vessels?
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
What is the general three layer in vessel structure?
- Tunica interna
- Tunica media
- Tunica externa
What is tunica interna in relation to the layers of the blood vessels?
- Innermost
- Endothelial Cells
- Basement Membrane (‘anchor’)
- Connective Tissue
What is tunica media in relation to the layers of the blood vessels?
-Middle
-Boundary marked by internal and
external elastic lamina (sheet)
-Smooth muscle cells (encircle vessel)
-Elastin and collagen
What is tunica externa in relation to the layers of the blood vessels?
- Outer
- Connective tissue
- Nerves, blood vessels
- Collagen and elastin
What is the average wall to lumen thickness of an aorta?
2mm/25mm
What is the average wall to lumen thickness of muscular artery?
1mm/4mm
What is the average wall to lumen thickness of arteriole?
30 micrometer to 30 micrometer
Fill in the gap the sentence:
Vessel structure is … to suit function
modified
What varies between blood vessels?
Wall thickness and diameter of lumen
What doe large arteries buffer?
Systolic rise in pressure, convert
intermittent flow to continuous flow and maintain blood flow
and pressure during diastole
What does a thick media of an artery contain?
-Lots of elastin fibres that allow stretching during systole and rebound during diastole
What does a wide lumen in an artery provide?
Low resistances allowing pressure and velocity to drop
What do large arteries absorption and return helping to propel blood during diastole?
Energy
What do muscular arteries do?
Distribute flow, resist collapse at joints and adjust blood flow to tissue/organs
Why do muscular arteries have thick smooth muscle media?
Degree of vasoconstriction and dilation to adjust blood flow
Why do muscular arteries have thick tunica externa?
Loose structure and longitudinal collagen fibres prevent retraction when cut
Why do arterioles have abundant sympathetic nerve endings?
Allow extensive vasoconstriction and vasodilation
What is arteriolar vasoconstriction?
Increases upstream arterial blood pressure, but reduces downstream blood flow to tissue
How do arterioles regulate blood flow to tissues?
vasoconstrict/dilatate rapidly and extensively allows them to adjust blood flow to tissues according to metabolic demand
What do capillaries provide?
Large cross-section for gaseous/nutrient exchange
Where is there a higher abundance of capillaries?
Metabolically active tissue
What is the equation for velocity?
Blood flow/cross-sectional areas
Finish the sentence:
The larger the cross-sectional area of capillaries slow velocity meaning…
Gaseous and nutrients exchange more affectivity
What is the fluid exchange between capillaries and surrounding tissue fluid determine by?
- Hydrostatic pressure
- Osmotic pressure
What is hydrostatic pressure?
- determined by flow and vessel resistance (i.e. blood
pressure) - force that ‘pushes’ water out of blood vessels
What is osmotic pressure?
-determined mainly
by charged proteins in the blood
-‘pulls’ water into blood vessels
How are excess fluid returned to the circulation
via lymphatic system
What aids venous return from lower half of the body?
Skeletal muscle pump and respiratory pump
What is a venoconstriction?
Shunts blood from peripheral to central vessels to increase stroke volume
