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HA&P 1 (BIOL2529) > M3 Topic 5: Blood Vessels > Flashcards

M3 Topic 5: Blood Vessels Flashcards

(51 cards)

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1
Q

What are the main types of blood vessels

A
  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins
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2
Q

Overview of blood vessels in cardiovascular system and roles

A
  1. Heart contracts, blood pushed from ventricles into ARTERIES (large, muscular, carry blood away from heart)
  2. These ARTERIES branch off to produce smaller ARTERIES, and eventually, ARTERIOLES
  3. ARTERIOLES carry blood into tissue and organs of body, feeding blood into branched CAPILLARIES
  4. Blood drains out of CAPILLARIES into small veins called VENULES
  5. VENULES then merge together to form progressively larger VEINS, which then return blood back to heart

Arteries = act as pressure reservoirs
Arterioles = provide variable resistance
Capillaries = where exchange takes place
Veins = act as volume reservoirs

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3
Q

Layers of blood vessels

A

Walls of most blood vessels made up of 3 layers (AKA tunics)

  • Thickness and composition of these layers vary depending on type of blood vessel, differences contributing to functions of each one

They are called the…

  • Tunica interna (or intima)
  • Tunica media
  • Tunica externa
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4
Q

Vessel lumen

A

The space within the blood vessel, where the blood travels

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5
Q

Tunica interna/intima

A

Innermost layer of blood vessel, in direct contact with blood flowing through vessel lumen

  • Innermost part of it a layer of simple squamous epithelium (lines inside of all blood vessels)
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6
Q

Endothelium role in blood vessel function

A

Can synthesise and release chemical substances that regulate functions such as constriction and dilation of blood vessels, and initiation of blood clotting

  • Supported by basement membrane and connective tissue
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7
Q

Tunica media

A

Middle layer of vessel wall, containing elastic fibres and smooth muscle cells arranged in circular manner around vessel

  • Smooth muscle in this layer allows blood vessels to change diameter in response to NS or chemicals/hormones in blood
  • Changes in diameter allow body to regulate and change amount of blood flow to different organs and tissues
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8
Q

Vasoconstriction

A

Contraction of smooth muscle in vessel wall, decreasing/narrowing vessel diameter

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9
Q

Vasodilation

A

Relaxation of smooth muscle in vessel wall, increasing/widening vessel diameter

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10
Q

Tunica externa

A

Outer layer of blood vessel wall, containing elastic fibres and connective tissue that help protect and support vessel

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11
Q

Arteries

A

Act as pressure reservoirs

  • Contain all 3 layers
  • Have largest amount of smooth muscle in their walls of any other blood vessel types

Types of arteries

  • Elastic arteries
  • Muscular arteries
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12
Q

Elastic arteries

A

Large, thick-walled arteries that are located closest to the heart

  • Thick walls help withstand high pressures generated by contraction
  • Contain large amount of protein called elastin in vessel wall, makes arteries very elastic
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13
Q

How does the elasticity of arteries help them act as pressure reservoirs?

A

Elasticity allows arteries to expand during ventricular contraction (as blood enters), and recoil during ventricular relaxation

  • Elastic recoil of arterial wall maintains arterial pressure during ventricular relaxation, helps maintain relatively constant flow of blood into circulatory system
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14
Q

Muscular arteries

A

Located distal to elastic arteries, distributing blood to organs in the body

  • Have thick muscular tunica media, but less elastin than elastic arteries
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15
Q

Names of the major arteries superior to the heart

A
  • Right/left common carotid artery
  • Right/left vertebral artery
  • Right/left subclavian artery
  • Brachiocephalic trunk
  • Aorta
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16
Q

Arterioles

A

Smallest arteries in the body

  • Responsible for regulating flow of blood into different tissues and organs of the body
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17
Q

How is blood flow regulated in arterioles?

A

Arteriole wall contains smooth muscle

  • Contraction & relaxation of smooth muscle will change diameter of arterioles and thus, the amount of blood that can flow through these arterioles into the target tissue
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18
Q

Distribution of cardiac output

A

Not distributed equally to all tissues

  • Some organs receive more than others, can change depending on circumstances
  • Control of blood flow to individual organs can be altered by NS and local control mechanisms, enabling body to alter local blood flow to meet metabolic demand
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19
Q

Effect of exercise on distribution of cardiac output

A

CO is increased during exercise, as well as the distribution

  • Ensures sufficient blood supply to the organs that need it
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20
Q

What are the 3 basic physical forces that drive the processes of blood flow?

A
  • Blood pressure
  • Blood flow
  • Resistance
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21
Q

Blood pressure

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A

Amount of force that blood exerts on vessel wall, measured in millimetres of mercury (mmHg)

  • Highest in arteries near heart, lowest in veins
  • Differences in blood pressure cause blood to move or flow through circulation
  • Blood flows from area of high pressure to area of low pressure, following pressure gradient
22
Q

Blood flow

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A

Volume of blood that is flowing through a region each minute, measured in mL/min

  • Arterioles play critical role in regulating amount of blood flow to different organs by altering resistance
23
Q

Resistance

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A

Force that opposes blood flow

  • Higher resistance = lower blood flow
  • Lower resistance = higher blood flow

Determined by vessel length, blood viscosity & vessel diameter

24
Q

Vessel diameter

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A

Inversely proportional to resistance

  • Contraction of smooth muscle in arteriole wall causes vasoconstriction, increasing resistance
  • Relaxation of smooth muscle in arteriole wall causes vasodilation, decreasing resistance
25
What are the factors that influence arteriole diameter?
- ANS (primarily the sympathetic NS) - Local mediators (e.g. produced by metabolically active tissue)
26
Local regulation of blood flow via the ANS
Most arterioles have sympathetic innervation. - Activity of sympathetic NS releases noradrenaline, causes vasoconstriction - Many arterioles have basal tone (partial contraction) that can be regulated by changes in NS activity and circulating mediators
27
Local regulation of blood flow via local mediators
Locally produced mediators can alter arteriole diameter - Production of mediators often linked to metabolic activity of tissue - Circulating hormones can also alter arteriole tone and local blood flow Example - Exercising skeletal muscle = decrease oxygen, increase CO2, increase H+, causing vasodilation of arterioles
28
Capillaries
Smallest blood vessels in the body which forms branched networks known as capillary beds
29
What happens as blood flows through capillary bed?
Materials such as gases, nutrients, metabolites and waste products are exchanged between the blood and tissues
30
What is the capillary wall made of?
Single squamous cell layer (the endothelium) together with a basement membrane, making the wall of capillaries very thin - As wall very thin, exchanged materials don't have to travel far between blood and tissues, making it efficient - Also aided by gaps between endothelial cells that help make the capillary permeable
31
Where does blood enter the capillary beds from and flow out?
Enters capillary beds from the arterioles, and flows out of the capillary beds into the venules
32
How is the amount of blood that enters the capillary bed regulated?
Regulated by upstream arterioles - If arteriole dilated, more blood will flow through capillary bed, allowing for exchange of materials to occur - If arteriole constricted, blood won't flow through capillary bed
33
What determines the amount of capillaries (capillary density) in a tissue?
Depends on metabolic demand of particular tissue - Tissues with high demand (e.g. brains, muscles, liver) require more oxygen + nutrients, thus have more capillaries - Tissues with lower demand (e.g. ligaments, tendons) will have fewer capillaries => low capillary density = longer time to heal from injury
34
How is the velocity of blood flow through a vascular bed affected?
Depends on its total cross-sectional area (CSA) - High CSA = lower velocity Although diameter of individual capillaries is very small, large number of capillaries make the total CSA high - Slow velocity important, allows time for substance exchange to occur
35
Bulk flow
Movement of large amounts of fluid across the capillary wall - Fluid moves out of capillaries at arterial end and into interstitial fluid that lies in space between vessels and tissues - Re-enters into capillaries at venous end
36
What is the movement of fluid in bulk flow driven by?
Hydrostatic pressure and Osmotic pressure gradients
37
Hydrostatic pressure
Pressure generated by blood within the vessel - Drives fluid out of the capillaries - Decreases as blood moves through capillary bed
38
Osmotic pressure
Pressure generated by plasma proteins - Drives fluid into the capillaries - Remains constant as blood moves through capillary beds
39
Pressure gradient at the arterial end of the capillary bed
Hydrostatic pressure > Osmotic pressure Net movement = fluid out of capillaries
40
Pressure gradient at the venous end of the capillary bed
Osmotic pressure > Hydrostatic pressure Net movement = fluid into the capillaries
41
Lymphatic vessels
Collect excess interstitial fluid from bulk flow and return it to blood stream - Lie close to almost all blood capillaries
42
Lymph
Fluid that enters lymphatic vessels
43
Attributes of lymphatic system that are similar to circulatory system
- Capillaries have very thin walls and gaps between cells (easy movement of fluid from interstitial space into lymphatic vessel) - Smaller lymphatic vessels join to form progressively larger vessels - Lymphatic vessels contain valves that maintain one-way fluid
44
Lymphatic trunks
Joining of large lymphatic vessels that drain lymph fluid back into venous circulation
45
Unique attributes of lymphatic system compared to circulatory system
Lacks central pump (heart) - Relies on contraction of larger lymphatic vessels + external compression of vessels for fluid flow
46
What can cause oedema (tissue swelling)?
Accumulation of excess interstitial fluid - Due to blockage or obstruction in lymphatic system - Due to imbalance in blood hydrostatic pressure and colloid osmotic pressure
47
Veins
Carry blood from capillary beds back towards heart - Blood leaving capillary beds drains into small venules (which join together to form progressively larger venules and veins) - Diameter and wall thickness increases as vessels become larger
48
Layers of veins
Have the 3 layers that can be found in arterial blood vessel wall - Much less smooth muscle in veins than arteries, thus thinner walls - Lumen is larger compared to corresponding arteries
49
How do thin walls and large lumen contribute to the function of veins
Allows veins to contain large amount of blood with little resistance to blood flow - Veins are highly distensible (ability to stretch + expand), allows them to act as volume reservoirs
50
Valves within veins
Prevents blood from flowing back to capillary beds and ensure blood keeps moving back towards heart - Veins in limbs (particularly lower limbs) contain most valves (blood moves upwards against force of gravity)
51
Names of the major systemic veins of the body superior to the heart
- Right/left internal jugular vein - Right/left external jugular vein - Right/left subclavian vein - Right/left brachiocephalic vein - Superior vena cava

HA&P 1 (BIOL2529) (40 decks)

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