Circulation 1

Question 1

What is the precursor cell of platelets?

Answer 1

Megakaryocytes

Question 2

What causes the maturation of megakaryocytes?

Answer 2

Erythropoietin

Question 3

Where are clotting factors produced?

Answer 3

Mainly in the liver but also in endothelial cells.

Question 4

Briefly describe the clotting factor cascade.

Answer 4

Damage caused interstitial collagen to be exposed and tissue factor to be released.
TF(factor III) reacts with clotting factor VIII
Interstitial collagen exposure/ plasma contact with subendothelial tissue causes a series of reactions.
The products (of these two pathways) then react and cause prothrombin (factor II) to convert to thrombin.
This causes fibrinogen(factor I) to convert to fibrin.

Question 5

Are platelets involved in thrombus or clot formation?

Answer 5

Thrombus formation

Question 6

What are the main differences between clot and thrombus formation?

Answer 6

Clots form in stagnant blood and contain RBC and fibrin

Thrombi form in flowing blood (at the side) and contain platelets and fibrin.

Question 7

What is the difference between a clot and an embolus?

Answer 7

Embolus can be made out of many different materials, clots are always formed by fibrin and red blood cells.
Emboli move from where they originate, through the bloodstream and cause a clot somewhere else.
Clots for a blockage, where they are formed.

Question 8

What are the components of Virchow’s triad?

Answer 8

Change in the intimal surface of a vessel
Change in the pattern of flow of blood
Change in the constituents of blood

Question 9

What does any element of Virchow’s triad cause?

Answer 9

An thrombus to form

Question 10

Define ischaemia

Answer 10

An insufficient supply of blood to a tissue

Question 11

Define Hypoxia

Answer 11

severe lack of oxygen supply to the tissue

Question 12

Define anoxia

Answer 12

Absence of oxygen supply to an organ/tissue

Question 13

Define Necrosis

Answer 13

dead or dying tissue

Question 14

Define infarct

Answer 14

Necrosis as a result of ischaemia

Question 15

What are some reversible effects of ischaemia? (e.g. in the hand)

Answer 15

Numbness
Temperature drop
Change in colour
Tingling

Question 16

Irreversible effects of ischaemia

Answer 16

Infarct, stroke, “heart attack” (myocardial infarct)

Question 17

Define embolism

Answer 17

An obstruction in a blood vessel due to a blood clot or other foreign matter that gets stuck while travelling through the bloodstream.

Question 18

What is the most common embolism?

Answer 18

Pulmonary thromboembolism

Question 19

How does a pulmonary thromboembolism occur?

Answer 19

Usually a thrombus and clot will form in a leg vein due to slow blood flow, some of this breaks off and travels up the vein, in to the inferior vena cava, then in to the right heart, then the pulmonary trunk and lodges in a pulmonary artery

Question 20

What does a pulmonary thromboembolism often cause?

Answer 20

A pulmonary infarct.

Question 21

Define circulatory shock

Answer 21

Profound circulatory failure causing poor perfusion of vital organs

Question 22

What are the classic clinical signs of shock?

Answer 22

Low blood pressure (e.g. 60/40)

fast (and weak) heart rate/pulse (>100 bpm)

Question 23

What components does blood pressure rely on?

Answer 23

Enough blood in the system
Smooth muscle in vessels having a certain tone
Heart pumping blood effectively

Question 24

What will happen if there is not enough blood in the system?

Answer 24

Vessels will collapse

Question 25

What happens if the tone of the smooth muscle decreases?

Answer 25

The vessel will dilate and therefore the blood pressure will decrease

Question 26

What part of the body can detect blood pressure and changes in it?

Answer 26

Carotid bodies at the bifurcation of the carotid arteries sense blood passing them and can detect the partial pressure of oxygen in the blood. In oxygen partial pressure decreases then BP will decrease

Question 27

What happens in blood pressure drops?

Answer 27

The carotid arteries sense this and send signals to the brain stem. The brain stem will then tell the heart to pump faster, it will also cause the vascular tone to increase in the limbs and abdomen. This forces blood back towards the chest and head, so that vital organs have enough blood. The brain stem also stimulates adrenaline secretion form the adrenal gland, so the heart will pump even faster and harder.

Question 28

Name the 3 types of shock

Answer 28

Septic (infection) Hypovolaemic Cardiogenic

Question 29

What causes Hypovolaemic shock, what happens and what is the treatment?

Answer 29

the total volume of blood in the circulatory system falls significantly, (e.g. due to haemorrhage or dehydration) Vessel start to collapse, then not enough blood is getting to vital organs. ( venous pressure would be low or 0) Treatment-Transfuse blood through an IV cannula very quickly and try to stop/slow the bleeding.

Question 30

What is cardiogenic shock and what is its treatment?

Answer 30

Heart is failing to pump effectively or consistently (e.g. due to a heart attack). Venous pressure would be normal. Treatment- drugs to increase heart function

Question 31

What is septic shock?

Answer 31

when large quantities of bacteria and their toxins begin to circulate in the bloodstream, due to and untreated or inadequately treated infection. The foreign molecules in the blood cause vasodilation, so blood will pool in veins, so not enough blood will be getting back to the heart. Venous pressure will be low, the right side of the heart will not be filling much.

Question 32

Explain the 2 main examples of organ damage which occurs in shock

Answer 32

Brain injury- due to decreased perfusion to the brain (initially reversible), so then infarct occurs. Renal injury( e.g. decrease renal function)- decreased perfusion of kidneys, which leads to necrosis of the kidney tubules.