Human physiology / by William Furneaux.

  • William Samuel Furneaux
Date:
1909
Catalogue details

Licence: In copyright

Credit: Human physiology / by William Furneaux. Source: Wellcome Collection.

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    notice the thinness and irregularity of its walls. We are now enabled to look down into the cavity of the left ventricle, which resembles the right in that a membranous valve lies Ijetween it and the auricle. This valve is called the mitral valve from its supposed resemblance to a bishop’s mitre : it is also called the bicuspid valve, Ixiing composed of two cusps or flaps. As the left ventricle is as yet uncut, we may easily study the action of the valve as follows ; - Pour a little water into the ventricle, close the aorta which leads from it, and then squeeze the ventricle between the fingers and the thumb. Each time we do so, we notice that the cusps of the valve float up on the surface of the water, till they partially or entirely close the ventricle. If we remove the right auricle with its vessels (the venae cavee), we shall find that its structure is much like that of the left auricle. Again, by cutting through the walls of the left ventricle, we notice that this cavity closely Fig. 120.—The Base of the Heart. The auricles have been cut away, and the valves are closed. The pericardium has also been removed to expose the muscular fibres. 1 and I , right ventricle; 2, left ventricle; 3, wall of right auricle ; 4, wall of left auricle; 5, 5', and 5, the tricuspid valve ; 6 and 6', the mitral valve ; 7, pulmonary artery ; 8, aorta ; 9 and 9'. coronary arteries. resembles the ventricle already dissected, but that its walls are very much thicker. Lastly, lay open the aorta as we did the pulmonary arteries, and here, at the origin of this great arbery, we shall notice another set of semilunar valves, which are also arranged so as to prevent the blood from flowing back to the heart. If instead of laying open the aorta, we cut it short immediately above the semilunars, we may fill the three little pouches with water, thus illustrating their action, i.e. their tendency to close the passage from the aorta into the ventricle when acted on by a pressure from above. Just outside the semilunars of the aorta may be seen two small openings. These are the origins of the coronary arteries, by which the heart itself is supplied with blood for its nourishment. This blood is afterwards collected up by the coronary veins; and branches of both the coronary arteries and the coronary
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