1. THE CIRCULATORY SYSTEM Heart and Vessels

2. Basic Structure of Circulatory System Tunica intima –Endothelium supported by basement membrane and delicate collagenous tissue. Tunica media –Muscle and CT Tunica adventitia –CT

3. Layers of Artery The usual histologic preparations cause the layers to appear thicker than those shown here; the drawing is actually similar to the in vivo architecture of the vessel. At the moment of death, the artery experiences an intense contraction; consequently, the lumen is reduced, the internal elastic membrane undulates, and the muscular tunica thickens. A medium sized muscular artery, showing its layers.

4. Types of Vessels Elastic artery Muscular artery Arteriole Capillary Muscular venule, small vein Vein Muscular vein

5. Layers of Aorta Tunica intima –Endothelium –Collagenous fibers, elastic fibers & elastin sheets Tunica media –Extremely elastic (sheets of elastin), smooth muscle Tunica adventitia –Collagenous, elastic fibers

6. AORTA: Elastic Artery (x4)

7. Aorta: Tunica Media (x20)

8. ELASTIC ARTERY: AORTA

9. Tunica Media: H&E stain

10. Muscular Artery Tunica intima –Endothelium –Fine collagenous fibers, smooth muscle –Internal elastic lamina clearly evident Tunica media –Smooth muscle –Collagenous, reticular, elastic fibers –External elastic lamina clearly evident Tunica adventitia –Thick collagenous, elastic tissue

11. Muscular Artery (x4)

12. Muscular Artery x10

14. Muscular Artery (L) vs Elastic Artery (R)

15. Arteriole Tunica intima –Endothelium –Some CT –Internal elastic lamina may be present Tunica media –Muscle layer several layers thick –External elastic lamina may be present Tunica adventitia –Collagenous, elastic CT as thick as tunica media

16. Arteriole Large Small

17. Venules

18. Veins Tunica intima –Endothelium –Scant CT Tunica media –Thin muscle layer –Collagen, elastic fibers Tunica adventitia –Bulk of vessel wall

19. Vein x10

21. Muscular Vein

22. Artery, Vein

24. HEART Epicardium –(Tunica adventitia) Myocardium –(Tunica media) Endocardium –(Tunica intima) Surrounded by pericardium

26. BLOOD VESSEL

27. HEART

28. Myocardium and Endocardium Endocardium consists of endothelium which is supported by a delicate layer of collagenous tissue beneath which lies a fibro-elastic layer. Endo Myo

29. HEART

30. Epicardium Mesolthelium (single layer of epithelium) surrounds think layer of fibro-elastic tissue. Adipose tissue connects epicardium to Myocardium.