The 1628 treatise 'Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus' (1628)
William Harvey's book demonstrating the circulation of the blood
Science · Medicine & the body
The human heart
Described by Harvey, 1628
Medicine — cardiovascular anatomy and physiology
The muscular four-chambered pump at the centre of the circulatory system, lying in the mediastinum behind the sternum and tilted to the left. Deoxygenated blood returns to the right atrium, is pushed through the right ventricle to the lungs, comes back to the left atrium and is driven round the body by the thick-walled left ventricle. Its rhythm is set not by the brain but by its own pacemaker tissue, and its function was only correctly described in 1628, when William Harvey showed that blood circulates rather than being continuously consumed.
How to spot them
- ▸Four chambers: two atria above, two ventricles below, divided by the septum
- ▸Four valves: tricuspid and mitral between chambers, pulmonary and aortic on the way out
- ▸Its own electrical pacemaker in the wall of the right atrium, not a nerve from the brain
- ▸Questions about the 1628 book that overturned Galen, or about Cape Town in December 1967
- ▸The left ventricle is much thicker-walled than the right — it pumps to the whole body, not just the lungs
Key facts
A small patch of tissue in the wall of the right atrium that sets the pace of the whole organ
The sinoatrial node, the natural pacemaker
The tricuspid, mitral, pulmonary and aortic structures that stop backflow
The four valves; the mitral is also called the bicuspid
The bundle of His and the Purkinje fibres
The conducting system that spreads the impulse through the ventricles
Christiaan Barnard's operation at Groote Schuur Hospital, 3 December 1967 (1967)
The first human-to-human transplant of this organ; the recipient was Louis Washkansky
Willem Einthoven's string galvanometer and the P, QRS and T waves (1924)
The electrocardiogram, which won Einthoven the 1924 Nobel Prize in Physiology or Medicine
The 'lub-dub' sounds picked up through a stethoscope
The closing of the atrioventricular valves, then of the semilunar valves
The law, named for a German and a Briton, that the more the muscle is stretched by filling, the harder it contracts
The Frank–Starling law
Key ideas
- It is a double pump: the right side serves the pulmonary circulation, the left the systemic circulation, and the two beat in step.
- Cardiac muscle is myogenic — it contracts spontaneously without nervous stimulation, which is why an isolated heart can keep beating.
- Harvey's argument was quantitative: the volume pumped in an hour vastly exceeds the blood the body could possibly make, so it must be recirculated.
Quick-fire facts
- •Four chambers: right atrium, right ventricle, left atrium, left ventricle, separated by the interatrial and interventricular septa
- •The four valves are the tricuspid (right AV), mitral or bicuspid (left AV), pulmonary and aortic
- •The sinoatrial node in the right atrium is the natural pacemaker; the atrioventricular node delays the impulse before the bundle of His
- •William Harvey's 'De Motu Cordis' (1628) overturned Galen's idea that blood was made in the liver and consumed in the tissues
- •The pulmonary artery is the only artery carrying deoxygenated blood; the pulmonary veins the only veins carrying oxygenated blood
- •The muscle wall is the myocardium, lined inside by endocardium and enclosed in the fibrous pericardium
- •It is fed by the left and right coronary arteries, which branch off the aorta just above the aortic valve
- •Christiaan Barnard performed the first human-to-human transplant in Cape Town on 3 December 1967; Louis Washkansky lived 18 days
- •Willem Einthoven won the 1924 Nobel Prize in Physiology or Medicine for the electrocardiogram
- •In the foetus the foramen ovale and ductus arteriosus bypass the lungs; both normally close soon after birth
- •The apex beat is normally felt in the fifth intercostal space in the midclavicular line
Drill it — 8 cards
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Sources
- British Heart Foundation — How a healthy heart works
- OpenStax, Rice University — Anatomy and Physiology 2e — Heart Anatomy