Blood Clotting + Atherosclerosis Flashcards
Give two reasons for blood clotting.
- Limits blood loss
- Prevents entry of pathogens through open wounds
Describe the blood clotting process (6)
- Platelets and damaged blood vessel tissue release thromboplastin.
-Presence of calcium ions, protein factors and Vitamin K in blood plasma activates thromboplastin - The enzyme catalyses conversion of prothrombin to thrombin
- Thrombin enzyme catalyses conversion of fibrinogen to fibrin
- Fibrin fibres form a mesh
- Traps red blood
cells and platelets to form a blood clot
What is prothrombin?
A soluble protein
What are both thrombin and thromboplastin?
Enzymes
What is fibrinogen?
A soluble globular protein
What is fibrin?
Solid insoluble fibres - a fibrous protein
What’s needed for thromboplastin to catalyse the reaction of prothrombin to thrombin? 3
- Calcium ions
- Vitamin K
- Protein factors
What 3 diseases are caused by the formation of blood clots?
- Heart attack/myocardial infarction
- Stroke
- Deep Vein Thrombosis
What are the symptoms of a heart attack? 3
- Pain in chest and upper body
- Shortness in breath
- Sweating
How does blood clotting cause heart attacks? 3
- Coronary arteries carrying blood with oxygen to heart muscle is blocked
- Heart muscle not receiving any oxygen so cannot respire
- Causes damage and death to heart muscle cells
What is a stroke?
Rapid loss of brain function due to disruption of blood supply to brain
How does a blood clot cause a stroke?
- Blood clot blocks artery leading to brain
- Reduces amount of blood and therefore oxygen reaching brain for respiration
What is deep vein thrombosis [DVT]?
Formation of a blood clot in a vein deep inside the body e.g leg vein
What can DVT be caused by?
Prolonged inactivity e.g long flights
What link is there between age and DVT?
Risk of DVT increases with age
Define “atherosclerosis”
The hardening of arteries leading to heart disease and stroke
Define “thrombosis”
Fatty deposits increase chance of blockage by a blood clot
Describe the steps of atheroma formation 6
- Damage to the endothelium of arteries
- Causes an inflammatory response
- White blood cells migrate to the area
- WBCs and lipids from blood clump together to form fatty streaks
- Over time, more WBCs, lipids, fiborous tissue and calcium salts build up
- Harden to form a fibrous plaque - an atheroma
What does an atheroma cause?
Blood pressure increase
How does an atheroma lead to blood pressure increase?
- Artery becomes less elastic
- Lumen of artery narrows
- Restricts blood flow
What is atherosclerosis an example of?
Positive feedback
How is atherosclerosis an example of positive feedback?
- Atheromas forming makes further formation of atheromas more likely
- Atheromas make damage more likely
- As they rupture the wall of the endothelium
