Circulation pathology

Question 1

what is the origin of platelets

Answer 1

platelets from a cell called megakaryocyte platelets bud off as cytoplasmic extensions and end up in blood

Question 2

role of platelets in relation to trauma or tissue damage

Answer 2

platelets try to close the gap that tissue factors made during trauma or damage. platelets have molecules on their surfaces that allow adherence to interstitial collagen which is how they close the gap

Question 3

main site of production of key clotting factors

Answer 3

liver or endothelial cells

Question 4

mechanism of action of key clotting functions

Answer 4

amplification system (clotting cascade) that results in thrombin production- damage leads to release of tissue factor which produces thrombin from prothrombin which leads to production of fibrin from fibrinogen

Question 5

production of fibrin in producing clots and thrombi

Answer 5

thrombin converts soluble fibrinogen into insoluble fibrin which forms a mesh of strands

Question 6

difference between clot formation and thrombus formation

Answer 6

thrombus occurs in flowing blood, it is pale cream coloured, uses fibrin and platelets.
clots form in stagnant blood, fibrin and red blood cells, red in colour

Question 7

what happens in thrombolysis

Answer 7

removal of fibrin in thrombus by plasminogen converting to plasmin and then cutting up fibrin into smaller fragments

Question 8

what happens in a wound due to trauma

Answer 8

vasoconstriction reduces bleeding, clot formation occurs in space around vessel and may fill void, thrombus forms in flowing blood and stops bleeding from gaps on vessels

Question 9

causes of thrombosis

Answer 9

changes in intimal surface of vessel, changes in pattern of blood flow, changes in blood constituents (virchows triad)

Question 10

haemostasis

Answer 10

stopping of bleeding

Question 11

example of changes in intimal surface of vessel

Answer 11

atheroma lipid coming onto surface. lipid and collagen can rupture intimal surface. platelets and fibrin now exposed to abnormal substance and turbulent flow and are deposited as thrombus

Question 12

example of changes in pattern of blood flow

Answer 12

smoking can predispose to atheroma in coronary arteries (narrow down the lumen) so decreased blood flow so build up of fibrin and platelets

Question 13

example of changes in blood constituents

Answer 13

smoking increases stickiness of platelets so makes more likely to clot

Question 14

ischaemia

Answer 14

poor blood flow. if severe then this leads to hypoxia

Question 15

hypoxia

Answer 15

low oxygenation of tissue

Question 16

necrosis

Answer 16

tissue death

Question 17

infarction

Answer 17

necrosis as a result of ischaemia

Question 18

embolism

Answer 18

mass of material moving in the vascular system and able to become lodged in the vessel and block it

Question 19

pulmonary embolism

Answer 19

sluggish flow in leg veins leads to thrombosis and clot formation, part of this breaks off and embolises, this embolus passes into inferior vena cava then to right heart then pulmonary trunk and lodges in pulmonary artery branch which leads to pulmonary infarct (lung)

Question 20

thromboembolism

Answer 20

blockage that is broken off from a thrombus or clot and blocks further down in circulation

Question 21

what is circulatory shock

Answer 21

profound circulatory failure causing poor perfusion of vital organs. low blood pressure and its physiological consequences. happens if low blood pressure combined with fast pulse

Question 22

3 major types of circulatory shock

Answer 22

hypovolaemic, septic (generalised vasodilation), cardiogenic

Question 23

a physiological mechanism that tries to maintain blood pressure in shock

Answer 23

cartotid sinuses sense if blood pressure drops and then respond by sending nerve cells to the brain stem. the brain stem in turn tells the heart to pump harder and faster

Question 24

2 organs that can be damaged by shock

Answer 24

brain- reversible then permanent, ischaemic infarction, kidneys- reversible then severe

Question 25

example of hypovolaemic shock

Answer 25

ruptured spleen- blood flows out of spleen so less blood in vessels so they collapse so inferior vena cava collapses so venous pressure flows to virtually zero. low volume of blood

Question 26

signs of circulatory shock

Answer 26

low blood pressure, high pulse rate