PBL 1: Eric Sands: Cardiovascular Flashcards
Passage of a blood cell through the heart/lungs
unoxygenated blood enters via the IVC and SVC → RA → Tricuspid Valve → RV → Pulmonary Artery → L/R Pulmonary Arteries → L/R lungs → Pulmonary Vein → LA → Bicuspid Valve → LV → Oxygenated blood to body via Aorta
Where do the right and left coronary arteries arise?
Above two cusps of the aortic valve
Right Coronary Artery
- Supplied RA/RV and braches posteriorly to give tise to posterior interventricular artery that supplied posterior left ventricular wall and septum.
Left Coronary Artery
Branches to give the anterior interventricular artery which supplies anterior septum and anterior LV wall, the circumflex branch supplies LA/LV
Layers of the Arteries
- Tunica Externa
- External Elastic Lamina
- Tunica Media
- Internal Elastic Lamina
- Subendothelial Layer
- Endothelium
- Tunica Intima
Layers of the veins
- Tunica Externa
- Tunica Media
- Subendothelial Layer
- Endothelium
- Tunica Intima
HAS VALVES
NO ELASTIC
How do we calculate blood pressure?
BP = CO * TPR
How do we calculate cardiac output?
CO = HR * SV
How do we calculate TPR?
TPR = 1/r4
How do we calculate Ventricular Wall Stress?
VWS = PxR / 2h
P: Interventricular Pressure
r: Ventricular Radius
h: Ventricular Wall Thickness
What factors determine the work done by the heart and thus its demand for oxygen?
- Ventricular Wall Stress; the force acting tengentially to the myocardial fibres. Increase = increased oxygen
- Heart Rate. The contraction of the myocardium measured in BPM. Increases in BPM required more contractions per minute, each contraction requires more energy = more o2 needed for ATP
- Contractility: Measure of strength of myocardial contraction. Increasing the strength or force requires more energy, more atp = more demand for o2
What 3 factors determine coronary blood supply?
- Oxygen content
- Perfusion Pressure
- Vascular Resistance
How does oxygen content affect coronary blood supply?
[Hb] affects O2 content, the more Hb, the more O2 can be bound and transported. Anemia, Haemorrhage and decreased [Hb] decrease O2 supply to the heart.
Decreased oxygen saturation (CO poisoning, high altitude) may also affect O2 supply
How does perfusion pressure affect coronary blood supply?
- Myocardium recieves blood during diastole
- Changes in diastolic pressure will alter perfusion pressure of coronary arteries
- Hypotension lowers perfusion pressure for the myocardium which results in decreased perfusion and therefore O2 supply
How does vascular resistance affect coronary blood supply?
Vascular resistance affect coronary blood flow. It is affected by external comppression during systole as well as intrinsic controls.
Intrinsic controls include neural controls (a receptor causing vasoconstriction, b2 receptor vasocilation)
Metabolic factors (H2O2, H+, CO2, Lactate, Adenoine cause vasodilation
Endothelial factors: NO, EDHF, Prostacyclin cause vasodilation, Endothelin 1 causes vasoconstriction
Q = pressure/resistance
What is Ischaemic heart disease?
Inadequate blood/O2 supply to the myocardium resulting in myocardial hypoxia. The muscle resorts to anaerobic metabolism to meet energy demands which produces exxcessive metabolic by-products including adenosine, lactate and serotonin which activate nociceptors.
What causes ischaemia and list common examples.
Anything that causes an imbalance of O2 supply/demand can cause ischaemia
Examples: Anaemia, Exercise, Atherosclerosis, Vasospasm
Causes of Atherosclerosis?
- Fibrous plaque build-up within the intima of the artery
- Usually occur at areas of bifurcation where flow is turbulen causing increased mechanical stress on the endothelium
- Unregulated lipid levels cause increased lipid deposit within the intima increasing risk of atheroma formation
- Atheroma decreases radius of lumen
Consequences of atherosclerosis
- Increased risk of thrombus
- Decreased lumen radius
- Decreased ability to vasodilate
Decreased ability to supply or increase supply of O2
List risk factors for Heart Disease
- Age
- Sex
- Smoking
- Hypertension
- Dyslipidaemia
- Diabetes Mellitus
- Obesity
- Physical Inactivity
- Family History
