Cardiovascular System - Lec 5-6 Flashcards
Explain the functions of the lymphatic system
Some water moves from capillaries to tissues every day and must be removed, therefore, the lymphatic system functions to drain the extra interstitial fluid from the tissues and drain proteins from tissue to return to blood
Drainage begins with a series of tiny capillaries with lymph fluid (lymphatic vessels) that form a meshlike network throughout tissues. These vessels have very low pressure and so can be occluded.
NOT CIRCULATION, Lymph nodes are distributed around body and so are specific to a tissue region
They respond to infection by increasing immune activity, thus, enlarging themselves.
So lymphatic system gets rid of infectious causing factors like Metastases are removed from the lymph at lymph nodes that are specific and these lymp nodes will enlarge as they carry infectious substances of the infection
LYMPH NODES ARE COMMON SITES AT WHICH TUMOURS CAN BEGIN THE SPREAD
Explain what affects flow of the lymp through the vessels
Flow of lymp is usually occurs under low pressure but this can be further affected by
- Muscle and respiratory pumps (compressing vessels causes pushing fluid through the narrowed vessels )
- tone in ducts (lymphatic ducts have tiny bit of muscles in the walls, so we are referring to the contraction of this muscle to constrict)
- Pressuure of IF
If drainage stops working, IF will stop being removed from the tissues and can lead to swelling of the tissues ie. bandage too tight causing swelling as flow has been cut off at the lymphatic drainage
Explain what happens if there’s an increase in IF
Causes an oedema, swelling
This can be caused by:
- heart failure
- inflammation
- peripheral venous insufficiency (valves not working properly)
- hypoalbuminaemia (low levels of albumin protein in blood)
- reduces lymphatic drainage (common after cancer surgery)
- standing for long periods (gravity prev3nts flow of lymph back into vascular system ejacular vein)
What does the formation of an oedema depend on?
rate at which IF volume increases
RATE AT WHICH THE IF is drained away
Explain how oedema formation can depend on the rate at which the IF volume increase
An icrease in IF volume will cause the following which maximises odeama formation:
characteristics of capillaries: inflammation causes them to become leaky
balance of forces acting on the fluid
- force 1 = that favours movement out of capillary.
This occurs because the blood pressure in capillary pushes water out (thus pushing out force)
The osmotic pressure is the interstitial space allows for the sucking of water out of capillary
- force 2 = opposes movement out of capillary.
This occurs due to possibly the fluid pressure in the iterstital space (due to too much IF in space not allowing more).
The osmotic pressure of the blood will also prevent IF movement out of capillary (this may be due to the fact that things like protein in blood leech on to the water)
Explain what’s atherosclerosis and it’s pathogenesis
Cholesterol plays an essential role In its pathogenesis
Fatty streaks appear in subendothelial (tissue under wall) space
- LDLs (low density lipoprotein) penetrate endothelium (interior layer of vessels) causing thickening of the walls due to fat accumulation and makes blood flow disrupted
- inflammation occurs
- fats are oxidised and ingested by macrophages (eat up dead tissue) (causing fatty streak)
Forms plaque (abnormal tissue on walls of artery) and Calcification of the plaque is common. This is bad as it affects the functions of the artery as the plaque isn’t elastic and isn’t smooth due to the accumulation of smooth muscle and collagen.
As walls gets thr
What’re the risk factors of atherosclerosis
Age (can occur in old to young)
Smoking
Diabetes (usually type 2 as it associated with obesity)
Hyperlipidaemia (a lot of fat in blood)
Hypertension (high blood pressure: push more fat from blood into arteries)
Explain the atherosclerosis that is classified as ischaemic disease and myocardial infarction
Ischameic disease and myocardial infraction (heart attack)
Blood supply to the heart is very important, so if it’s demands aren’t reached, the heart can switch to anaerobic energy production which causes significant pain (angina) (75% narrowing of vessel)
So the plaques of atherosclerosis pathogenesis can narrow blood vessels and the plaque can be disrupted eventually causing a blood clot within the vessel. HENCE, that region of the heart can die and other areas might be damaged
If the damaged areas are large, the heart won’t be able to act as effective pump, depolarisation disrupted SND THE DAMAGED REGIONS CAN BECOME ECOTOPIC PACEMAKERS
This can be detected due to poor pumping, low blood pressure, high heart rate, pain, severe chest pain, left arm pain, ECG abnormalities and loss of viable myocardium or a regional wall abnormality
Can be confused for ingestion
How can you analyse ischaemic disease?
Stress scintigraphy - radioactive isotopes are taken up by active heart muscle and we can see areas that are getting less blood flow as less isotopes are taken in that region
Stress echocardiography - gives images of abnormal wall motion
Coronary arteriography - contrast media are injected to allow direct visualisation of coronary arteries
Coronary artery calcium CT - high negative predictive value; very little disease in absence of calcium
Why do we attempt to increase the heart rate during imaging sometimes?
You’d want to slow down heart rate to take good images sometimes right by using beta blockers to reduce SNS activty
But sometimes you want to do the opposite, and increase heart rate by using drugs like:
Pharmecutical agents like adenosine and doubtamine
- adenosine dilates coronary vessels which increase flow rate in vessels and less of a response in stenotic vessels
- doubtamine is a synthetic catecholamine increases heart rate, blood pressure, and myocardial contractibility
Explain the atherosclerosis that is classified as an aneurysm
A localised area of widening of the vessel wall, with destruction to the elastic tissue which causes a decrease in strength of walls (no longer able to withstand the high blood pressure of blood)
CAN OCCUR DUE TO TRAUMA
Usually affects the aorta (this is fatal), usually occurs at the region of divide
Associated with an increased risk of vessel rupture which can can a fatal haemorrhage or in the Brain it can cause a haemorrhagic stroke
How are aneurysms analysed?
Plain radiogroahs - May appear as a large soft tissue mass with calcification
US - shows enlargement of the vessel
CT - shows location and extent and some evidence of risk of rupture
Explain the atherosclerosis that is classified as claudication
Peripheral arterial disease causes severe muscle pain on exercise
Not getting enough blood delivered to muscle, thus lack of oxygen and therefore experience pain.
Arteries narrowing, so blood flow decreased,
How is claudication analysed?
Can use non imaging and imaging techniques
- Doppler ULtrasonography
- angiography
Explain the atherosclerosis that is classified as a cerebrovascualr accident
Occurs in the brain, injury to blood vessels of brain
Usually called a stroke, where blood flow is affected causing death of brain cells. FIX AS SOON AS POSSIBLE. there’s two types of strokes but they show same symptoms, but treating them use differnt mechanics:
- Ischaemic stroke - clot of vessel due to plaque buildup in Brain which kills the brain cells due to blood flow disruption. Can use drugs to dissolve clot and allow for blood flow
- Haemorrhagic stroke - it’s an aneurysm in the brain (bleeding in the brain).
