13. Atheroma and thrombosis Flashcards
Define atherosclerosis
Degeneration of arterial walls characterised by fibrosis, lipid deposition, and inflammation, which limits blood circulation and predisposes to thrombosis
Where in the vessels is endothelial injury/atherosclerosis most likely to occur?
Where the vessels bifurcate, as this is where the blood flow is most turbulent
Less likely where the blood flow is more laminar
Why does atherosclerosis occur?
Due to chronic injury and repair of the endothelium (first step = endothelial injury)
Why is hyperlipidaemia a risk factor for atherosclerosis?
In hyperlipidaemia, lipid will accumulate in the innermost part of the vessel wall (the intima)
Monocytes (or macrophages when they are in the tissue ) will migrate into the intima due to lipid endothelial injury and ingest the lipid becoming foam cells
= FATTY STREAK
In which layer of the vessel wall does lipid accumulate at the begging of atherosclerosis?
In the intima (innermost layer)
Which type of cell ingests deposited lipid?
Monocytes (called macrophages when they are in the tissue)
After macrophages have ingested lipid, what do they become?
Foam cells
What is a fatty streak?
Early stage of atherosclerosis (first grossly visible lesion)
It is when the macrophages are ingesting lipid deposits and becoming foam cells
What do foam cells do?
They secrete chemokines, attracting more monocytes/macrophages, lymphocytes and smooth muscle cells
Foam cells secrete chemokines which attract smooth muscle cells as well as other cells. What do smooth cells do?
Proliferate and secrete connective tissue
What does an atherosclerotic plaque consist of?
Fat, extracellular material and leukocytes and smooth muscle
What is another name for a white blood cell?
A leukocyte
An atherosclerotic plaque has a specific structure. What does it consist of?
- dead central CORE
- SHOULDER region which might contain some new blood vessels
- thin CAP which might be unstable and rupture
- fibrous CAP which consists of collagen and smooth muscle
What is the sequelae of atherosclerosis?
- occlusion
- block a blood vessel
- tissue dies
- could lead to gangrene
- weakening of vessel wall
- aneurysm formation
- haemorrhage
- erosion (due to turbulence of blood e.g.)
- possible thrombus formation on top of atherosclerotic plaque
What is an embolus?
A mass of material in the vascular system able to lodge in a vessel and block it
What is the most common embolus?
A thrombus (a thromboembolus)
What is thrombosis?
Solidification of blood contents formed in the vessel during life
How is thrombosis different to a blood clot?
Different in pathogenesis and morphology
Thrombosis = within body during life, dependent on platelets, firm
Clot = stagnant blood, enzymatic process, elastic, adopts shape of vessel
Do platelets have a nucleus?
No
`What are platelets activated by?
Collagen exposed by endothelial damage
What two types of secretory granules do platelets contain?
- alpha granules
- dense granules
What do platelet alpha granules secrete?
- fibrinogen
- fibronectin
- PDGF
What do platelet dense granules secrete?
- chemotactic chemicals
Where are megakaryocytes located and what are they responsible for?
In the bone marrow
Responsible for the production of platelets
