Third Day. 



Vascular System (continued). 

 A. Venous System. 



1. Note :— 



(a) The heart lying in the thin pericardium, the two auricles, the single 



ventricle, the truncus arteriosus which divides into two branches. 

 Remove the pericardium from the heart, and tilt the apex of 

 the heart forwards, noting the sinus venosus into which the right 

 and the left superior vena? cava? (or precavals) and the single inferior 

 vena cava (or postcaval) open. 



(b) The veins passing from each side of the sinus venosus. Each superior 



vena cava is joined by the following branches : — 



(i) The external jugular vein from the region of the tongue and 

 the mandible. 



(ii) The internal jugular vein from the head and a thick subscapular 

 vein from the shoulder. These veins join the superior vena 

 cava independently of each other so that there is no innominate 

 vein as in the Frog, 

 (hi) The subclavian vein, made up of a brachial vein from the arm, 

 a cutaneous vein from the skin, and a muscular vein from the 

 abdominal muscles. The cutaneous and the muscular veins 

 are separate veins so that there is no single musculo-cutaneous 

 vein. 

 [In the Frog the superior vena cava is joined by the folloiving branches : — 



(i) The external jugular vein, formed by the union of a lingual vein 

 from the tongue and a mandibular vein from the margin of the 

 lower jaw. 



(ii) The internal jugular vein from the head and the subscapular vein 

 from the back of the arm and shoulder, both joining the superior 

 vena, cava by a common vein, the innominate. 



(Hi) The subclavian vein, formed by the brachial vein from the fore- 

 limb and a musculo-cutaneous vein from the muscles of the body 

 and from the skin.~\ 



(c) The hypoglossal and the glossopharyngeal nerves, both running 



alongside of the lingual artery. 

 Make an enlarged drawing showing the above parts (a) and (b). 



2. Note the inferior vena cava, receiving the renal veins from the kidneys, 

 the hepatic veins from the liver, and opening into the sinus venosus. 



3. Trace back the abdominal vein, and note that it is formed by the 

 union of the two pelvic veins, which pass along the bases of the legs. The 

 pelvic veins occur deep down in the body under the posterior part of the 

 pelvic girdle, which should be cut through in order to see them. At the 

 union of the pelvic veins to form the abdominal vein a small rectal vein, 

 passing along the ventral surface of the rectum, joins the abdominal vein. 



14 



