. A laboratory manual and text-book of embryology. Embryology. EARLY DEVELOPMENT OF THE HEART AND PAIRED BLOOD-VESSELS 259 between the atria and the bulbo-ventricular part of the heart is the coronary sulcus. As the bulbo-ventricular region increases in size, the duplication of the wall between the two limbs lags behind in development and finally disappears (Fig. 252 a, b), leaving the proximal portion of the bulb and the ventricular limb to form a single chamber, the primitive ventricle. In an embryo of 5 mm. the heart is thus composed of three undivided chambers: (1) the sinus venosus openin
. A laboratory manual and text-book of embryology. Embryology. EARLY DEVELOPMENT OF THE HEART AND PAIRED BLOOD-VESSELS 259 between the atria and the bulbo-ventricular part of the heart is the coronary sulcus. As the bulbo-ventricular region increases in size, the duplication of the wall between the two limbs lags behind in development and finally disappears (Fig. 252 a, b), leaving the proximal portion of the bulb and the ventricular limb to form a single chamber, the primitive ventricle. In an embryo of 5 mm. the heart is thus composed of three undivided chambers: (1) the sinus venosus opening dorsad into the right dilation of the atrium; (2) the bilaterally dilated atrium opening by the single transverse atrial canal into (3) the primitive undivided ven- tricle. The three-chambered heart is persistent in adult fishes, but in birds and mammals a four-chambered heart is developed in which circulates venous blood on the right and arterial blood on the left. The important changes leading to the formation of the four-chambered heart. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Prentiss, Charles William, 1874-1915. Philadelphia, London, W. B. Saunders
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectembryology, bookyear1
