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BIOL10002 > 20. Circulation Of Blood Around The Body > Flashcards

20. Circulation Of Blood Around The Body Flashcards

1
Q

What pressure must arteries and arterioles withstand?

A

Carry blood away from the heart so must withstand high pressure

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2
Q

What is the function of the aorta?

A

Expands during contraction phase of cardiac cycle and contracts elastically (elastic recoil) between contractions WINDKESSEL EFFECT

  • Reduces pressure fluctuations between beats
  • Help to propel blood into the aorta and prevent back flow
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3
Q

What is the function of the arteries and arterioles?

A

They adjust their diameter (and therefore their resistance to flow) and so change the amount f blood flowing through them
- Called resistance vessels because they control blood flow to specific tissues

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4
Q

What does the tunica adventita consist of?

A
  • Connective tissue

- External elastic lamina

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5
Q

What does the tunica intima consist of?

A
  • Internal elastic lamina, connective tissue

- Endothelium

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6
Q

What does the tunica media consist of?

A

smooth muscle

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7
Q

How do arteries and arterioles maintain high pressure?

A

They have many collagen and elastic fibres in the tunica adventita which strengthen the vessel wall

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8
Q

What enables the aorta to expand and recoil between contractions

A

Elastin fibres

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9
Q

What enables the arteries and arterioles to adjust their diameter (and therefore the resistance to flow)?

A

Smooth muscle in tunica media contracts to case vasoconstriction (narrowing of artery diameter)

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10
Q

What do the endothelial cells in the tunica intima do?

A

They produce factors that cause vasodilation or vasoconstriction (widening or narrowing of artery diameter)

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11
Q

What is the purpose of veins?

A

They drain blood from capillary beds under very low pressure (not sufficient to propel blood to the heart)

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12
Q

Why are venules and veins called capitance vessels?

A

Because of their ability to stretch and store blood

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13
Q

What is the structure of an artery?

A

Same as a vein but with a valve in the centre

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14
Q

How do veins expand/contract?

A
  • Vein walls are expandable because they have little muscles or less collagen in the adventitia
  • Smooth muscle contracts to help return blood to the heart under low pressure
  • The smooth muscle layer is thin but there is a large blood volume in the veins which means that a small contraction pushes lots of blood towards the heart
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15
Q

How is backflow in veins prevented?

A

One way valves

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16
Q

How does venous return work?

A
  • Gravity affects venous return
  • Larger veins have smooth muscle which contracts to assist venous return
  • Skeletal muscles contract in surrounding muscles
17
Q

What is deep vein thrombosis?

A
  • Formation of a blood clot (thrombus) in a deep vein
  • In a person sitting upright, gravity causes blood to accumulate in the veins of the lower body
  • Decreased flow rate of blood due to immobility can lead to venous thrombosis
18
Q

What is the function of capillaries?

A
  • They receive high pressure blood from the arterioles and allow exchange of materials between blood and interstitial fluid
  • Gas exchange: O2 delivered to tissues and CO2 removed
  • Nutrient delivery: glucose, ions, water etc to the tissues
  • Waste removal: metabolites removed from tissue
  • Production of tissue fluid: extracellular fluid
19
Q

How does the structure of capillaries enable their funciton?

A
  • They are very narrow
  • Single layer of endothelial cells called the endothelium which improves diffusion and osmosis
  • Have tiny holes called fenestrations
  • Allows water, some ions, solutes like glucose and very small proteins to leak out
20
Q

What happens to pressure and velocity when blood enters the large area of the capillary beds?

A

Pressure and velocity are lost

21
Q

Why do arterioles have such extensive branching?

A

This hugely increases the overall cross sectional area

  • Extensive branching reduces pressure and flow
  • Enough pressure remains for water and solutes to be squeezed through capillaries and into interstitial spaces
22
Q

What are starling’s forces?

A

Two opposing forecasts that maintain water balance in the capillaries.

23
Q

What are the two starling’s forces?

A
  • Blood pressure (hydrostatic): tends to force water and small molecules out
  • Osmotic pressure: tends t draw water back into capillaries. Osmotic pressure is due to large protein molecules that cannot leave the capillaries
24
Q

What is oedema?

A

An imbalance between blood pressure, osmotic pressure and lymphatic draining

25
Q

What happens in coronary heart disease?

A

A narrowing of the small blood vessels that supply blood and oxygen to the heart.

This can lead to heart attacks and strokes

26
Q

What is atherosclerosis?

A

Where a clot forms inside the artery.

  • Healthy arteries have a smooth endothelial lining
  • Atherosceloris begins with damage to endothelial cells
  • Because of the inflammatory response, deposits of plaque form
  • Smooth muscle cells migrate towards the lumen and attract lipids (cholesterol) so plaque becomes fatty
  • Smooth muscles cells produce fibrous connective tissue hardening the artery which narrows it
27
Q

Where is blood supplied to the heart from?

A
  • The two main coronary arteries which branch off the base of the aorta
  • The right coronary artery and the left coronary artery
28
Q

What does a heart attack involve?

A

If they become blocked the heart muscle can become damaged or stop beating

29
Q

How does aspirin treat coronary heart disease?

A

Help prevents blood clots from forming in the arteries and reduces the risk of having a heart attack

30
Q

How do calcium channel blockers help treat chronic heart disease?

A

To relax arteries, lower blood pressure, and reduce strain on the heart

31
Q

How do nitrates help treat chronic heart disease?

A

They stop chest pain and improve blood supply to the heart

32
Q

How do statins treat chronic heart disease?

A

Lower cholesterol

33
Q

What are the main differences between arteries and veins

A
  • Arteries have more elastin, more smooth muscle, and more fibrous collagen in tunica adventitia
  • Veins have less collagen and elastin less smooth muscle and valves

BIOL10002 (28 decks)

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