2. CIRCULATORY SYSTEM Dr Iram Tassaduq

3. OVERVIEW Transport of nutrients, hormones, gases, & other vital materials requires highly controlled flow. Body has 2 circulatory systems. Blood vascular system Lymph vascular system

4. BLOOD VASCULAR SYSTEM The heart, which is a pump for propelling the fluid. The arteries which are tubes for conveying the blood toward the organs & tissues. The capillaries, which are anastomosing channels of small caliber with thin walls providing for much of the interchange of substances between the blood & tissue fluids. The veins, which in their initial segment also provide for blood-tissue fluid interchange but in addition serve for the return of blood to the heart.

6. LYMPH VASCULAR SYSTEM Consists of lymphatic capillaries & various sized lymphatic vessels which ultimately drain into main trunks, the thoracic duct & the right lymphatic duct, which empty into large veins in the neck.

7. VESSEL WALLS TUNICA INTIMA TUNIC A MEDIA TUNICA ADVENTITI A

8. ELASTIC ARTERY (AORTA) Also called conducting arteries. Diameter: >1cm Intima :  Endothelium  Connective tissue  Smooth muscles 1 - Tunica intima 2 - Tunica media 3 - Tunica externa Stained with orsein

9. TUNICA MEDIA  Smooth muscles  Elastic lamellae

10. TUNICA ADVENTITIA  Thinner than tunica media  Connective tissue  Elastic fibers

13. MUSCULAR ARTERY 2-10 mm in diameter Intima:  Endothelium  Connective tissue  Smooth muscle  Internal elastic membrane

14. MUSCULAR ARTERY Media:  25-40 layers of Smooth muscle fibers  Collagen fibers  Elastic tissue

15. MUSCULAR ARTERY Adventitia:  Thinner than media  Connective tissue  Some elastic fibers

16. MUSCULAR ARTERY

17. SMALL ARTERY 0.1-2 mm in diameter Internal elastic membrane present 8-10 layers of smooth muscles. Very thin tunica adventitia

18. SMALL ARTERY LOW POWER VIEW OF SMALL ARTERY HIGH POWER VIEW OF SMALL ARTERY & ARTERIOLE

19. ARTERIOLE Arterioles can be differentiated from arteries by the numbers of layers of smooth muscle. No more than 6 layers. A “precapillary arteriole” ( 1-2 layers )

20. VEINS Veins are distinguished by their thinner wall, valves, collapsed state. The tunica media does not look as well organized as that in the artery or arteriole.

21. VENULE MUSCULAR VENULE:  50-100 µm in diameter  1-2 layers of smooth muscles in media VA N

22. SMALL SIZE VEIN 0.1-1 mm in diameter 2-3 layers of smooth muscles in tunica media Thicker adventitia

23. MEDIUM VEIN 1-10 mm in diameter Media is considerably thinner Adventitia is well developed & forms bulk of the wall.

24. LARGE VEIN

25. >1mm in diameter 2-15 layers of smooth muscles Much thicker adventitia containing connective tissue & some elastic fibers.

26. CAPILLARIES Thin walled tubules with an average diameter of about 4-10 µm. Branch extensively without much change in caliber, & the branches anastomose to form networks which vary in density & pattern in different tissues & organs. The tissues with the highest metabolic activity have networks of elaborately branched & closely packed capillaries.

27. TYPES OF CAPILLARIES

28. MICROSCOPIC VIEW

30. MEDIUM SIZE ARTERY AND VEIN

31. ARTERIOLE & VENULE ARTERIOLE & VENULES SMALL ARTERY & VEIN