3. Circulatory system includes cardiovascular system and lymphatic vascular system. The cardiovascular system includes heart, arteries, capillaries and veins. There are three layers in the wall of the vascular: tunica intima, tunica media and tunica adventitia.

4. Fig 1 Medium-sized artery and vien(HE stain,low mag.) medium-sized vien medium-sized artery

5. Fig 2 Medium-sized artery Tunica media Internal elastic membrane external elastic membrane endotheliun adventitia

6. Tunica adventitia Fig 3 medium-sized vien(HE stain,high mag.) Tunica intima Tunica media

7. Valve of vien Fig 4 vein(HE stain,high mag.),showing valve of vein

8. Fig 5 Large artery(HE stain,low mag.) lumen Tunica intima Tunica media

9. Fig 6 Large artery(HE stain,high mag.) Tunica adventitia Tunica intima

10. Elastic membrane in tunica media of large artery Fig 7 Large artery(special stain,high mag.)

11. Tunica media Fig 8 Large vein (HE stain,low mag.) Tunica adventiti a A bundle of smooth muscle

12. Tunica media Fig 9 Large vein (HE stain,high mag.) Tunica adventitia Tunica intima

13. A bundle of smooth muscle in tunica adventitia of large artery Fig 10 The adventitia of large vein (HE stain,high mag.)

14. Fig 11 Small artery and small vein (HE stain, high mag.) Small vein Small artery

15. capillarie s Fig 12 Section of connective tissue arteriole venule

16. The wall of heart is organized in three layers: endocardiun, myocardium and epicardium. Endocardiun includes endothelium, subendothelial layer and subendocardial layer.

17. endocardium Fig 13 Ventricle wall (HE stain,high mag.) Purkinje fiber myocardium

18. Fig14 Epicardium of ventricle wall mesothelium

19. Lymphatic vascular system includes lymphatic capillaries, lymphatic vessels and lymphatic ducts.

20. Fig 13 lymphatic vessel lymphatic valve