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0. Foundations of Medicine > Pathology - Circulation > Flashcards

Pathology - Circulation Flashcards

1
Q

What lines the lumen of blood vessels?

A

endothelium

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2
Q

What is around the basal lamina of blood vessels?

A

smooth muscle

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3
Q

What is around the smooth muscle in blood vessels?

A

interstitial collagen fibres

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4
Q

What does the lumen of blood vessels contains?

A
  • red blood cells
  • white blood cells
  • platelets
  • plasma
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5
Q

What does plasma consist of?

A

water, proteins, other solutes

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6
Q

What does plasma contain?

A

clotting factors

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7
Q

Where are many clotting factors mainly produced?

A

in the liver but also by endothelial cells

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8
Q

What are clotting factors?

A

an amplification system, resulting in thrombin production

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9
Q

What does thrombin do?

A

converts soluble fibrinogen into insoluble fibrin

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10
Q

What does fibrin do?

A

forms a mesh of strands

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11
Q

Simplified clotting cascade

A

damage → TF + prothrombin → thrombin + fibrinogen → fibrin

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12
Q

What is meant by initial damage in the clotting cascade?

A

one obvious is trauma

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13
Q

What does trauma lead to?

A
  1. exposure of interstitial collagens (collagens in connective tissue between structures)
  2. exposure of a molecule called tissue factor (TF)
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14
Q

What is tissue factor released from?

A

smooth muscle

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15
Q

What does “many clotting factors are serine proteases” mean?

A

that clotting factors have a serine amino acid in them and they cleave other clotting factors to form the active molecule

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16
Q

Where are platelets produced?

A

in bone marrow from a cell called megakaryocyte

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17
Q

What is a megakaryocyte?

A

large cell with many nuclei

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18
Q

How do platelets work

A

trauma to vessel → exposure of platelets to interstitial collagen → platelets adhere together and try to form bridge to close gap

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19
Q

What is coagulation

A

Solidification of blood (clotting)

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20
Q

What are the 2 types of coagulation

A
  1. Thrombus formation

2. Clot formation

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21
Q

Where does thrombus formation occur

A

In flowing blood

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22
Q

Pure thrombus

A
  • Pale cream coloured

- Consists of platelets and a mesh like network of fibrin strands

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23
Q

What is thrombosis

A

The process of thrombus formation

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24
Q

Why does a thrombus of platelets and fibrin occur in flowing blood?

A

platelets have molecules on their surfaces which allows adherence to interstitial collagen ever when blood is flowing past them

  • the clotting cascade deposits factor VIII which enhances this further
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25
Q

Where does clot formation occur?

A

Blood leaks out of a vessel and becomes stationary (stagnant)

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26
Q

Describe clot formation

A

Wishing the stagnant blood, sitting next to interstitial collagen, the clotting cascade is activated

A clot consists of a network of fibrin strands and red blood cells

27
Q

What is haemostasis

A

Stopping bleeding

28
Q

What is the role of vasoconstriction in bleeding

A

Helps reduce bleeding

29
Q

How is thrombus removed?

A

A blood protein called plasminogen converts to plasmin, and plasmin cuts up fibrin into smaller fragments as a way of removing fibrin.

In a thrombus this is sometimes called thrombolysis

30
Q

What does the fibrinolytic system depend on?

A
  • Plasma protein called plasminogen being converted to plasmin
  • Plasmin cuts up fibrin into fibrin degradation products
31
Q

What are the 3 main causes of thrombosis (virchow’s triad)

A
  1. venous stasis
  2. activation of blood coagulation
  3. vein damage
32
Q

Example of pathological thrombosis -coronary artery thrombosis

A
  • coronary arteries are the main arteries in the heart and supply the heart muscle
  • smoking cigarettes increases the stickiness of platelets (find it easier to aggregate)
  • stickier platelet makes it more likely that a thrombosis will occur
  • this alteration in the properties of blood is a change in blood constituents which is part of Virchow’s triad
  • cigarette smoking can also predispose to atheroma in the coronary arteries
  • atheroma can occur and slowed blood flow predisposes to fibrin and platelet clumping
  • this is an example of a change in the pattern of blood flow which is part of Virchow’s triad
  • lipid can also rupture through the intimal surface which is a change in the intimal surface, also part of Virchow’s triad
33
Q

What is atheroma?

A

a disease of coronary arteries which results in a build up of lipids under the intimal surface

34
Q

What can atheroma result in?

A

the lipid can result in abnormal blood flow

  • can get both slow and turbulent flow
35
Q

Describe the lines of Zahn

A

arterial thrombus

  • multiple layers of thrombus and clot (pale layers of thrombus alternating with red layers of clot)
36
Q

What does complete obstruction by thrombus blocking an artery lead to?

A

No flow beyond the blockage

37
Q

What does partial obstuction by thrombus blocking an artery lead to?

A

Decreased blood flow beyond the blockage

38
Q

What is ischaemia

A

Poor blood flow

39
Q

Describe the consequences of ischaemia

A
  • If it is severe enough can lead to decreased oxygenation of tissues
  • The tissue is said to be ‘ischaemic’
  • Ischaemic heart tissue is often painful
40
Q

What is hypoxia?

A

Decreased oxygenation of tissues

41
Q

What is an infarct?

A

A localised area of dead tissue as a result of Ischaemia

42
Q

What is coronary artery thrombosis

A

Infarct in heart

43
Q

What is cerebral artery thrombosis

A

Infarct in brain

44
Q

What is an embolism

A

A mass of material moves in the vascular system and bale to become lodged in a vessel and block its lumen

45
Q

What are most emboli derived from?

A

Thrombi or clots

46
Q

What do emboli do?

A

Break off and go elsewhere in the circulation

47
Q

What is thromboemolis?

A

When thrombi/clots embolise

48
Q

How does a pulmonary embolism occur?

A
  • Sluggish flow in leg veins lead to thrombosis and clot formation
  • Part of thrombus breaks off and travels up vein
  • Embolus passes into inferior vena cava, then the right heart. then pulmonary artery bench
  • Embolism block pulmonary artery and get pulmonary infarct
49
Q

Provide an example of marrow embolism

A

fracture a leg -> marrow enters ruptures -> air embolisms to lung vessels

50
Q

Examples of air embolism

A

Knife wound to neck -> air enters vein -> marrow embolisms to lung vessels

51
Q

What is circulatory shock

A

Profound circulatory failure causing poor perfusion of vital organs

52
Q

What does shock mean in practice?

A

Low blood pressure in physiological consequences

53
Q

What does normal blood pressure rely on?

A

Enough blood in the systemSmooth muscle in vessels having a certain ‘tone’heart pumping blood

54
Q

What is normal blood pressure(arterial)

A

120/80

55
Q

What happens if smooth muscle tone is decreased?

A

The vessel will dilate, if enough vessels new affected then blood pressure may fail

56
Q

There are ____ carotid bodies and ___ carotid sinuses on either side of the neck

A

2,2

57
Q

What do the 2 carotid bodies consist of?

A

Groups of cells which sense the partial pressure of oxygen

58
Q

What do the carotid sinuses do if blood pressure drops?

A

They send nerve signals to the brain stem which then tells the heart to pump harder and faster via nerve signals

59
Q

What is the physiological response to low blood pressure?

A

Faster pulse

60
Q

In practice circulatory shock is present if:

A
  • Low blood pressure combined with fast pulse
61
Q

What are the 3 main causes of circulatory shock

A
  1. hypovolaemic
  2. septic
  3. cardogenic
62
Q

Describe hypovolaemic shock

A

Low blood pressure reflects severe reduction in amounts of blood in circulation

High pulse reflects physiological response to low blood pressure

63
Q

Describe some of the complications of shock

A
  • Decreased perfusion of brain -> initially reversible but then permanent
  • Decreased perfusion of kidneys -> initially reversible, then more severe

0. Foundations of Medicine (167 decks)

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