Page 334 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Cardiovascular System / 319

(A)
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Atrial contraction Ventricular contraction
(B)

Aorta

Ventricle Ventricle
relaxed contracted

Semilunar valve
Figure 17-5. Cardiac valves. (A) Function of A‐V valves. During relaxation of the ventricle (left), the
valve leaflets open to allow blood to flow from the atrium into the ventricle (arrow). During ventricular
contraction (right), valve leaflets are forced closed. The chordae tendineae prevent the margins of the
valve from everting back into the atrium. (B) A semilunar valve. Viewed from above, the valve consists of
three cuplike leaflets. During relaxation of the ventricle, the greater pressure within the vessel closes the
valve. When the ventricle contracts, leaflets part and blood flows through the valve (arrow).

and aorta; the pulmonary valve is at the trunk, from which it is divided by the pul-
junction of the right ventricle and pul- monary valve.
monary trunk. Just distal to the pulmonary valve, the
Blood returning to the heart from the pulmonary trunk divides into right and left
systemic circulation is delivered to the pulmonary arteries, carrying deoxygen-
right atrium by the cranial and caudal ated blood to the respective lungs.
venae cavae (singular vena cava). From A variable number of pulmonary veins
the right atrium, this deoxygenated blood return blood from the lungs to the left
passes through the right A‐V valve into the atrium. From the left atrium, blood passes
right ventricle. From the right side, the through the left A‐V valve into the thick‐
right ventricle wraps around the cranial walled left ventricle. The left ventricle
side of the heart and terminates as the fun- pumps the blood past the aortic valve into
nel‐shaped conus arteriosus. The conus the aorta. The aorta and its branches carry
arteriosus is the origin of the pulmonary oxygenated blood to all parts of the body.