1. Circulatory system Shiping Ding ( 丁世萍 ), Ph. D School of Medicine, Zhejiang University

2. Learning Objectives To be familiar with the type of capillary. To be familiar with the type of artery and vein. To distinguish with all the types of blood vessels.

3. Concepts of organs and systems  Organ: composed of four kinds of the tissues in a particular way Types Hollow organs: studied from inside to outside Substantial organs:  System: composed of many organs which have relationship with each other in structure and function. parenchyma interstitium

4. General outline Blood vascular system (cardiovascular system) Lymphatic vascular system ---Closed tubular system According to the circulating fluid in the tubes, blood or lymph:

5. Cardiovascular System The histological study of the cardiovascular system includes two major components Heart – mainly functions as a pump to move blood (and all the things blood carries) through the body. Blood vessels – are the tubes that distribute the blood to the cells and then back to the heart.

6. The blood vessels include three major divisions: Arteries – deliver blood from heart to capillaries Capillaries – the smallest blood vessels and closest to body cells, the interchanges between blood and tissues occur there Veins – carry blood from body to the heart

7. Histological Structure of Blood Vessels

8. Structural feature of Arteries and Veins: Tunica intimae 1. Endothelium 2. Subendothelial layer 3. Internal elastic membrane Tunica media Mainly smooth muscle Tunica adventitia external elastic membrane Mainly connective tissue medium-sized A

9. Artery  transport blood from heart to capillaries  according to their size, structure and function Large artery Medium-sized artery D>1mm Small artery D>0.3~1mm Arteriole D<0.3mm are classified

10. The wall of Arteries consist of three layers or “coats” often referred to as tunics. – Tunica intimae – is the inner coat – Tunica media – is the middle layer – Tunica adventitia or tunica externa is the outer layer of the wall of the blood vessel Layers of arteries wall differ in different size blood vessels. The structure and function of arteries change as their diameter decreases. Structure features of artery

11. Tunica intimae is the inner coat and it consists of 1)inner endothelial layer 2)subendothelial layer: a layer of loose connective tissue 3)internal elastic membrane (often very distinct) This layer is relatively constant within different size arteries.

12. Tunica media This layer makes up the greatest part of the wall of the artery. It is comprised primarily of smooth muscle. In small arteries or arterioles it may be only 1-3 cells thick but in larger arteries may comprise hundreds of layers of muscle cells. In large arteries, there in increased amounts of elastin fibers.

13. Tunica adventitia This is the outer layer of the wall of the artery. It consists primarily of connective tissue and serves to attach the blood vessel into the surrounding connective tissue. Often contains adipose tissue and often contains blood vessels (vasa vasorum) that supply the walls of the blood vessels.

14. Medium-sized artery (Muscular artery): diameter larger than 1mm  muscular artery: diameter larger than 1mm Tunica intima Endothelium Subendothelial layer: LCT Internal elastic lamina: clear Tunica media: contain 10~40 layers of circular smooth muscle smooth muscle Tunica adventitia External elastic lamina LCT: contain vasa vasorum

15. TunicaAdventitiaTunicaMediaTunicaintima Medium-sized artery

16. Classic muscular artery- elastic stain

17. Large (elastic) artery:  contains aorta, the pulmonary trunk and their main branches  With a large lumen relative to wall thickness  subendothelial layer is thicker with a few smooth muscles  tunica media is thick, contains a 40-70 concentrically-arranged elastic lamina  internal and external elastic lamina are not distinguished  tunica adventitia are thinner, abundant vasa vasorum PT stain

18. Elastic artery Muscular artery

19. Small artery:   muscular artery and peripheral resistance vessel  internal elastic lamina is clear, while external elastic lamina is not distinguished  the tunica media contains 3~9 layers of smooth muscles

21. Arterioles: Less than 0.3mm in diameter. Have similar and simpler structure as that of muscular artery. Less than 0.3mm in diameter. Have similar and simpler structure as that of muscular artery. Several layers of smooth muscle in tunica media. Several layers of smooth muscle in tunica media. Responsible for the presence of blood pressure. Responsible for the presence of blood pressure.

22. Vein   large lumen, thin wall, irregular  internal and external elastic lamina are not clear  tunica media is thin, with a few elastic fibers and smooth muscles  tunica adventitia is thick (best-developed)  some veins have valves

23. Large veins D>10mm

24. Medium-sized vein D=2~9mm

26. Vein valves: Bag-like protrusion of tunica intima, which prevents the blood flow from running to opposite direction. Exists only in the vein that has low position or far away from heart.

27. Vein with valve

28. A Comparison of a Typical Artery and a Typical Vein

29. elastic tissue is colored dark purple, cytoplasm (in smooth muscle and nerve) is lighter purple, and collagen is pale pink. Artery, vein, nerve, elastin stain

30. elastic tissue is colored dark brown, collagen is pale pink and cytoplasm (in smooth muscle and nerve) is purple.

31. Artery, vein, nerve, trichrome stain collagen is colored blue and smooth muscle is red. Red blood cells in the venous lumen are brighter red.

32. Capillaries Capillaries are the site where materials carried in the blood are unloaded and other materials are loaded into the blood. In many organs the capillaries form a network. Consist of a single layer of simple squamous epithelium. the average diameter about 8um.

33. Capillaries 1) L/M: A single layer of endothelial cells Pericyte A basement membrane Pericyte: long cytoplasmic processes have a contractile function, participating in the repair process

34. Capillary - pericyte

35. The types of Capillaries Continuous C. Fenestrated C. Sinusoid E/M  E/M

36. Continuous capillary Fenestrated capillarySinusoid Structure  endothelial cell: large number of pinocytotic vesicles  cell junctions between the endothelia (tight junction)  no pores, no gaps  basement membrane: integrity  endothelial cells: present abundant perforated pores (60- 80nm in D, with 4-6 nm diaphragm)  have or haven’t diaphragm on them  basement membrane: continuous  a greatly enlarged diameter (30~40um)  endothelial cell: intercellular clefts are large between cells, many pores without diaphragm  absence of a continuous basement membrane  macrophages are located either among or outside the cells of the endothelium Location distributed in muscle tissue, brain, lung and connective tissue, etc. distributed in tissues where rapid interchange of substances occurs between the tissue and the blood, as in the kidney glomerulus, mucosa of gastrointestine, some endocrine glands distributed in tissues where interchange of substance in big size occurs, as in the liver, spleen, and some endocrine glands The types of Capillaries

38. Continuous capillary Fenestrated capillary Sinusoid

39. Heart  a hollow muscular organ that contracts rhythmically  pump blood through the circulatory system

40. The wall of heart endocardium  endocardium  myocardium epicardium  epicardium

41. The wall of heart E SE subendocardial layer endocardium myocardium epicardium Purkinje fibers

42. endocardium Endothelium Subendothelial layer: fined CT Subendocardial layer: LCT, blood vessels, nerves and the impulse-conducting system of the heart

43. 闰盘线粒体 myocardium  thickest layer, consists of cardiac muscle, is richly supplied with capillaries  three layers are divided roughly, cardiac muscle arrange spirally.

44. Cardiac muscle:HE×100

45. 构成心包脏层 心包受损 影响心脏功能 epicardium LCT: contain adipose cells, blood vessels and nervesMethothelium

46. Conducting System components: sinoatrial node (SA node): the primary pacemaker of the heart located in epicardium of right atrium atrioventricular node( AV node) bundles( AV bundles) located in subendocardial layer. network of Purkinje fiber

47. Impulse generating and conducting system of the heart: Pacemarker cell Transitional cell Purkinje cell LocationSA / AVSA / AV /AV bundle AV bundle / branches Structure small, fusiform or polygonal in shaped less myofibril thinner and shorter than caridac muscle more myofibril than P cell shorter, boarder than caridac muscle, with 1-2 centrally located nuclei rich in mitochondria, glycogen, less myofibril well-developed intercalated disks Function heartbeat generating transmit impulse transmit impulse Transmit impulse into the ventricle quickly

48. transitional cellPurkinje cell

49. Cardiac cell Purkinje cells both broader and shorter than ordinary cardiac muscle fibers, rich in sarcoplasm, two nuclei can be found,well- developedintercalateddisks. Purkinje cells both broader and shorter than ordinary cardiac muscle fibers, rich in sarcoplasm, two nuclei can be found, well- developed intercalated disks.

50. Purkinje fiber

51. Purkinje fibers

52. cardic valve The core of dense connective tissue endothelium prevent the back flow of blood

53. Question 1. To describe the difference between large artery and medium-sized artery. 2. To describe the types of capillary.

54. Good-bye!

55. Thank you for your attention!