CLASS REPTILIA 



409 



Vein 



Trachea 



Carotid 



Esophagus 



Ventral cervical 



Vertebral 



Right aortic arch 



Lung 



Anterior vena cava 

 Innominate 

 Sinus venosus 

 Posterior vena cava 

 Right atrium 



Liver 



Gall bladder 

 Ventricle 



Posterior vena cava 



Pancreas 



Small intestine 



Spleen 



Anterior mesenteric 



Large intestine 



Abdominal 



Bladder 



Pelvic 



Lorynx 



External jugular 



nternal jugular 



Subclavian 



Left aortic arch 



Brachial 



Axillary 



Pulmonary 



Hepatic 



Left atrium 



Liver 



Hepatic portal 



Stomach 



Gastric 



Coeliac 



Oviduct 



Dorsal aorta 



Kidney 

 -Renal 

 Ovary 



Femoral 

 Renal portal 



Accessory bladder 



Cloaca 



Cloacal opening 



Figure 276. The internal structure of a turtle. 



a mixture of oxygenated blood from the left 

 atrium and venous blood from the right 

 atrium. 



Certain species of turtles have a well-de- 

 veloped renal portal system; the hepatic 

 portal system shows an advance in develop- 

 ment over the condition as described in the 

 frog. 



Respiratory system 



Turtles breathe by means of lungs. Air 

 enters the mouth cavity by way of the nasal 

 passages. The glottis opens into the larynx, 

 through which the air passes into the trachea 

 or windpipe. The trachea divides, sending 



one bronchus to each lung. The lungs are 

 more complicated than those of the am- 

 phibians. The bronchi branch out a num- 

 ber of times, and the lung cavity is broken 

 up into many spaces so that the respiratory 

 surface is greatly increased. 



The presence of a hard rigid shell, in tur- 

 tles, makes general expansion and contrac- 

 tion of the body impossible. Turtle respira- 

 tion, therefore, presents some unusual prob- 

 lems. It was formerly thought that it had a 

 breathing mechanism similar to amphibians, 

 but this is not the case; the turtle has its 

 own unique method of breathing. Inspira- 

 tion is accomplished by two flank muscles 

 which serve the same function as the mam- 



