Circulation Disturbances Flashcards
What causes increased blood in tissues?
Hyperaemia
Congestion
What causes decreased blood in tissues?
Ischaemia
Infarction
Describe hyperaemia…
Causes increased blood in terminal vascular bed
- Reserve capillaries are filled
- Increased erythrocytes in vessels causes redness
- Active process
- Well oxygenated blood
- Can be physiological i.e. blush
- Can be pathological
Describe congestion…
Causes increased blood in the terminal vascular bed
- impeded blood flow out of tissue
- Physical obstruction of vessels by compression or blockage
OR…
- Failure of forward blood flow
- Poorly oxygenated venous blood
What are the 3 types of congestion?
- Localised
- Generalised
- Hypostatic
What are the effects of congestion?
Depends on how quickly the congestion develops
- If there is gradual onset of congestion collateral circulation develops
What is development of collateral circulation?
When redundant capillaries develop new blood flow routes
What may chronic congestion lead to?
- Oedema
- Hypoxia
- Diapedesis/ haemorrhage
What is diapedesis?
The passage of blood cells through intact walls of capillaries
- Low volume loss of blood
- Pulmonary congestion - heart failure cells
- Hepatic congestion - Nutmeg liver
Describe what heart failure cells look like…
Alveolar macrophages contain brown/gold haemosiderin pigment due to phagocytosis and breakdown of RBCs
- When the left ventricle doesn’t pump very well and the pressure dams back into the lungs
- lung capillaries fill up with RBCs and some get pushed into alveolar macrophages and they eat the macrophages
What does nutmeg liver look like?
Does this when the right ventricle starts to fail
- Pressure builds up
- Lots of organs congested but the liver shows it most markedly
What is ischaemia?
Inadequate blood supply of a tissue relative to its needs
Leads to…
- Hypoxia
- Malnutrition
- Build up of waste products
What are some causes of ischaemia?
- Cardiac Arrest
- Arterial Obstruction
- Venous obstruction
- Capillary Damage
- Hypovolaemia
- Severe vasodilation
What can cause arterial obstructions?
- Thrombosis
- Embolism
- Arterial spasm
- Arteritis
What causes a heart attack?
When atherosclerotic plaques in the coronary vessels cause clots to form
- These block the blood supply to the cardiac muscle which causes an infarct
What is an embolism?
Lodging of a blood clot, fat globule, gas bubble or foreign body in a blood vessel
- affects part of the body distanced from the site of origin
Describe arteritis…
Inflammation of the walls of arteries due to infection or autoimmune response
What are the modifying factors of ischaemia consequences?
- The specific tissue that is involved
i. e. brain vs. fibrous tissue - The duration and the speed of the onset
i. e. sudden is more severe - Oxygenation state of the blood
i. e. severity is increased in anaemic animals - Temperature of the tissue
i. e. this lowers metabolic rate (enzymes)
What is an infarct?
A localised area of necrotic tissue
Is a consequence of ischaemia
Describe the appearance of a recent infarct..
There are gross changes when an infarct starts to develop
- This can tell you how old an infarct is
- Redness and swelling
- Wedge-shaped area affected
- Degeneration and Necrosis of ischaemic tissue
Describe the appearance of an older infarct..
- Tissue lightens in colour (du to RBC breakdown)
- Swelling resolves
- There is a line of hyperaemia
- Removal of necrotic tissue as fibroblasts start to grow into the tissue
- Scarring
What are some examples of infarcts?
Generally found in organs that don’t have a dual blood supply
- Kidney, brain, spleen, limbs, intestines etc
What is a sterile infarct?
An infarct in which the cause is sterile
What is a septic infarct?
An infarct in which the cause is bacterial etc.
