336 



COLLEGE ZOOLOGY 



Carotid arch- 

 Truncus 



•Carotid gtand 

 -Aortic arch 



Right anterior vena cava- 

 Left anterior vena cava 

 'ulmonary veins 

 ^71 



5^— Pulmocutaneous 

 arch •>{ 



Entrance of 



pulmonary 



veins 



Entrance of 

 M ^ ^ ■ W sinus venosus 

 r . . y /aV:/ V'.:] 1 Spiral valve ,:■ • 

 •■ '.\.' A [.' ■ ^.j I Left atrium — Br 

 ^•/^^•''r' '-v / '^'g^^ atrium—^ 



■^-^Conus 

 arteriosus 

 Sinus venosus 

 interatrial 

 septum 



Atrioventricular 

 valves 



Semilunar valve 

 •Ventricle 

 Posterior vena cava 



Right atrium 



Ventral view dissected 



Dorsal viev/ 



Figure 220. Heart of the frog. The arrows indicate the direction in which the blood flows. 

 In ventral view, unlabeled opening is to pulmocutaneous arch. 



other on the left; a thick-walled tube, the 

 conus arteriosus, which arises from the base 

 of the ventricle; and a thin-walled triangu- 

 lar sac, the sinus venosus, on the dorsal side. 



The arteries (Fig. 221) carry blood away 

 from the heart. The conus arteriosus divides 

 near the anterior border of the atria into two 

 vessels as shown in Fig. 220. Each branch is 

 called a truncus arteriosus, and each gives 

 rise to the following three arteries: 1. The 

 common carotid divides into the external 

 carotid (lingual), which supplies the tongue 

 and neighboring parts, and the internal 

 carotid, which gives off the palatine artery 

 to the roof of the mouth, the cerebral 

 carotid to the brain, and the ophthalmic 

 artery to the eye. Where the common 

 carotid branches is a swelling called the 

 carotid gland; this body serves to equalize 

 the blood flow, especially in the internal 

 carotid artery. 



2. The pulmocutaneous artery branches, 

 forming the pulmonary artery, which passes 



to the lungs and the cutaneous artery. The 

 latter gives off the auricularis, which is dis- 

 tributed to the lower jaw and neighboring 

 parts, the dorsalis, which supplies the skin 

 of the back, and the lateralis, which supplies 

 the skin of the sides. Most of these branches 

 carry blood to the respiratory organs— lungs, 

 skin, and mouth. 



3. The aortic (systemic) arches, after 

 passing outward and around the digestive 

 tract, unite to form the dorsal aorta. Be- 

 fore the union of the two aortic arches, 

 several branches are given off, two of which 

 are: (a) the occipitovertebral artery, which 

 gives off branches dorsally that supply the 

 backbone and posterior part of the skull; 

 (b) the subclavian artery, located just pos- 

 terior to the occipitovertebral, arising at 

 about the level of the shoulder and extend- 

 ing into the forelimbs as the brachial artery. 

 The dorsal aorta gives off the coeliacomeseu- 

 teric artery; this divides, forming the coeliac, 

 which supplies the stomach, pancreas, and 



