CVS Theme 1

What are the features of conduit arteries?

Large proportion of elastic tissue allowing stretch/recoil, relatively large diameter of 1.5cm

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What are the features of resistance arteries?

Smaller diameter (60mm) and large proportion of smooth muscle in their thick walls (providing a large resistance to flow, slowing it so arterioles not damaged)

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What are the features of arterioles?

Small lumen (37um), have 1-2 layers of smooth muscle cells

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What are the features of capillaries?

Extremely small (diameter 9um, one cell layer thick so short diffusion distance)

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What are the features of venules?

20um in diameter, comprised of range of tissues

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What are the features of veins?

Large lumen (smallest 5mm), walls more fibrous than elastic as blood flows at lower pressure, valves to prevent backflow

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How does the heart change during development?

Starts as midline structure, shifts so left becomes posterior and right anterior (meaning right chambers predominate sternocostal surface and left chambers predominate the posterior surface)

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How is it ensured the left and right pumps of the heart have matched output? Why is this important?

Elastic recoil of arteries averages the heart's contractions over a dozen beats (Starling's law, when elastic energy stored in the walls fuels recoil) so pressure is reduced in venous system (matching output to pulmonary, so doesn't empty).

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Why is the inferior vena cava prone to damage?

Thinner walls (than the superior), prone to tearing during trauma

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What calculations can be used to measure flow rate?

Ohms law where F=Diff P/R (also states I=V/R). More accurately (as involves more parameters) is Poisuelle's law, states F=Pi x Diff P x r^4/8 x viscosity x length. Can be simplified to F directly proportional to r (as varies most).

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What is the fossa ovalis?

Present in the right atrium, depression previously open before birth (where aorta was connected to it as oxygenated blood came from mother)

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How is inversion of the atrioventricular valves prevented?

Papillary muscles contract just before heart so valves already tensed; chordae tendinae stretch from these, exact length so valves can just close

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What is the role of the coronary sinus?

Opening in the right ventricle just inferior to the AV node, no mucle in its wall, drains 70% deoxygenated blood from the heart via the small, middle and great cardiac veins

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Describe the pericardium

Fibrous pericardium most external (remains rigid), then parietal serous before visceral serous (innermost). Functions to separate heart movement from thorax and act as a barrier to infection.

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What is the cause of cardiac tamponade?

When pericardial space (between parietal and visceral, enough pericardial fluid within to allow movement without losing surface tension) fills with blood/fluid from infection; heart is compressed and prevented from beating due to rigid fibrous layer

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What is the extrinsic innervation to the SAN?

Preganglionic parasympathetic from cardiac branches of vagus (decreases bpm), postganglionic sympathetic from cardiac branches of sympathetic chain (increases bpm and contraction force to make up for decreased filling time)

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What is the moderator band?

Right AV bundle as it moderates the degree of opening of the right AV vlave (left AV bundle does same but not seen as thicker walls)

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What are the features of the cardiac vessels (coronary arteries and cardiac veins)?

Blind end vessels with no anastomoses or valves, so their blockage can lead to infarction/independant beating of the heart's chambers (so systems dysregulated, causing death)

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When does oxygenated blood enter the coronary arteries?

When it is pushed into the pockets formed by the leaflets of the aortic SL valve

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Describe the anatomy of the left coronary artery

Runs down the anterior interventricular groove, gives rise to the circumflex branch and the anterior interventricular artery

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Describe the anatomy of the right coronary artery

Runs in the anterior atrioventricular groove, gives rise to posterior interventricular artery and right marginal artery

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What is the role of the anterior cardiac vein?

Drains the remaining 30% of deoxygenated blood directly into the right ventricle

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What is the atrial ventricular septa?

Connective tissue separating the atria and ventricles which maintains muscular continuity so they still operate as one muscle/contract simultaneously

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What is the fibrous skeleton?

Comprised of dense fibrous tissue separating the two atria and two ventricles. Cusps of the AV and SL valves are embedded in it, supporting/anchoring them and preventing inversion. Electrally isolates sides of the heart (so don't contract together).

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What is the mediastinum?

Central compartment of the thoracic cavity, surrounded by loose connective tissue

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What are the features of the superior mediastinum?

Where thorax and neck meet above sternal angle. Anterior = sternothyroid, sternohyoid, thymus, sup VC and brachiocephalic V. Intermediate = aortic arch, phrenic and vagus. Posterior = oesophagus, trachea, thoracic duct and left recurrent laryngeal N.

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What are the features of the inferior mediastinum?

Below sternal angle; anterior part is anterior to pericardium, middle part is pericardium itself, posterior part (containing descending aorta, vagus nerve, sympathetic chain, oesophagus and thoracic duct) is behind it

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How is ischemic heart disease (through coronary artery burst/blockage) managed?

Injecting clot-busting drugs, coronary bypass (vein from legs/chest stiched to create a diversion) or coronary cateterisation (tubes run from pelvis to heart and stent placed; less invasive and rapid)

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What are the symptoms of ischemic heart disease?

Frequent/unprompted fainting, referred toothache, jaw/arm pain on left.

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Why should lidocaine injections be avoided in pateints with ischemic heart disease?

Administered with adrenaline which causes vasoconstriction (reducing blood to heart further)

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What is the cause of hypertensive heart disease?

High blood pressure increasing the workload of the heart (though hypertension may also be a symptom)

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What is the cause of rheumatic heart disease?

Highly exaggerated autoimmune response to bacteria so heart valves damaged

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What is cor pulmonale?

Secondary heart disease due to a lung condition (as heart must work harder to pump blood around the body at lower oxygen saturations)

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What are the causes of non-cyanotic congential heart disease (where blood is still able to flow around the body)?

Septal defect (hole in heart so blood from LA to RA), patent ductus arteriolus (foetal channel from pulmonary artery to aorta doesn't close), valve stenosis (narrowing of SL valves makes stiff) or coarction (aortic lumen narrowed by fibrous tissue)

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What are the features of cyanotic congential heart disease?

Severely reduced blood flow to the body (in 80% through Fallot's tertraology); causes cyanosis, finger clubbing, dysnopea (breathlessness) and foetal termination

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What occurs in Fallot's tetraology?

Pulmonary stenosis (narrowing of pulmonary SL valve), RV hytrophy (increase in thickness as pulmonary stenosis increases workload), overriding aorta (recieves blood from RV as well as LV) and a septal defect (so flow between ventricles)

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How can the thyroid cause heart disease?

Overactive so increased release of thyroxine increases heart rate, straining the heart

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What is the cause of cyanosis? Where does it occur?

Decrease in Hb conc by >5g/100ml, causing blue discoulouration of skin/mucous membranes. Central = tongue and lips as pulmonary oxygenation inadequate. Peripheral = tips of fingers/toes as slow systemic circulation

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What is the cause of finger clubbing?

Finger ends enlarged/nails gain longitudinal curvature due to cyanotic congential heart disease or endocarditis (inflammation of endocardium)

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How else may heart disease be identified?

Prominent neck veins in semi-supine position (as increased external jugular vein pressure), hypertrophy identified by an x ray/apex heartbeat or pitting oedema (as hydrostatic pressure reduced, ankle impression for more than 10s)

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CVS Theme 1

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