Anatomy and Physiology
Anatomy and physiology supplies the reasoning behind clinical nursing: normal values, organ relationships and direction of blood flow. Expect labelling-style recall plus applied items such as asking which vessel carries deoxygenated blood.
Direction of flow
- Systemic: left ventricle to aorta to tissues to vena cava to right atrium. Pulmonary: right ventricle to pulmonary artery to lungs to pulmonary veins to left atrium. The pulmonary artery carries deoxygenated blood and the pulmonary vein oxygenated blood, the reverse of every other vessel.
- Coronary arteries arise from the aorta just above the aortic valve; the right coronary artery supplies the SA and AV nodes in most people, and the SA node lies in the right atrium.
Values worth memorising
- Cardiac output 4–8 L/min; stroke volume 60–100 mL; heart rate 60–100/min.
- Blood pH 7.35–7.45; PaO₂ 80–100 mmHg; PaCO₂ 35–45 mmHg; bicarbonate 22–26 mEq/L.
- Haemoglobin 13–17 g/dL in men and 12–15 g/dL in women; RBC 4.5–5.5 million/µL; WBC 4000–11,000/µL; platelets 150,000–400,000/µL.
Worked example
A patient has a heart rate of 80 beats/min and stroke volume of 70 mL. Cardiac output = 80 × 70 = 5600 mL/min, about 5.6 L/min, which is normal. If tachycardia raises the rate to 160 while stroke volume falls to 40 mL because filling time shortens, output becomes 6.4 L/min but coronary perfusion falls. Reasoning: output is a product, so rate alone never tells the whole story; diastolic filling determines coronary flow.
Quick regional points
The nephron begins at the glomerulus in the cortex and loops into the medulla; the left lung has two lobes and the right three; the portal triad is portal vein, hepatic artery and bile duct; the brachial plexus arises from C5 to T1.
Traps
Reversing pulmonary artery and vein, forgetting that the SA node lies in the right atrium, and mixing preload with afterload.