1. Blood Vessels and Circulation

2. 2 Some embryology first  There are at first six pairs of aortic arches  In fish these are connected to the gills  They undergo a transformation in mammals  Birds use the right arch of the fourth pair  Mammals use the left arch of the fourth pair

3. 3 Ventral (anterior) view Full set of arches develops, but not all present at the same time; (before transformation) Transformation : 4 th through 7 th weeks: some persist, some atrophy

4. 4 Right common carotid a ------------------------------. Right subclavian a. -------------------------- Brachiocephalic trunk----------------------------------- 4 th arches become: Left side: aortic arch Right side: brachiocephalic trunk

5. 5 What the aortic arches become… Right common carotid a ---------------------------. Right subclavian a. --------------------------- Brachiocephalic trunk-------------------------------

6. 6 What the aortic arches become… Right common carotid a ---------------------------. Right subclavian a. --------------------------- Brachiocephalic trunk-------------------------------

7. 7 What the aortic arches become… Right common carotid a ---------------------------. Right subclavian a. --------------------------- Brachiocephalic trunk-------------------------------

8. 8 What the aortic arches become… Right common carotid a ---------------------------. Right subclavian a. --------------------------- Brachiocephalic trunk-------------------------------

9. 9 What the aortic arches become… Right common carotid a ---------------------------. Right subclavian a. --------------------------- Brachiocephalic trunk-------------------------------

10. 10 What the aortic arches become… Right common carotid a ---------------------------. Right subclavian a. --------------------------- Brachiocephalic trunk-------------------------------

11. 11 3 Major types of blood vessels  Body  RA  RV  Lungs  LA  LV  Boby 1.Arteries 2.Capillaries 3.Veins Arteries carry blood away from the heart -”branch,” “diverge” or “fork” Veins carry blood toward the heart -”join”, “merge,” “converge”

12. 12 General characteristics of vessels  Three layers (except for the smallest) 1.Tunica intima - AKA intima 2.Tunica media – smooth muscle 3.Tunica externa - AKA adventitia  Lumen is the central blood filled space

13. 13  Intima is endothelium (simple squamous epithelium)  Tunica media: layers of circular smooth muscles  Lamina (layers) of elastin and collagen internal and external  Thicker in arteries than veins (maintain blood pressure) Smooth muscle contraction: - vasoconstriction Smooth muscle relaxation: - vasodilation

14. 14  Adventitia (t. externa) – longitudinally running collagen and elastin for strength and recoil

15. 15 “muscular” middle sized artery

16. 16 Arteries  Carry blood away from the heart  From biggest to smallest, these are the categories: 1. Elastic 2. Muscular 3. Arterioles (then these to capillaries)  Pressure diminishes along the route 1.Elastic arteries: act as conduits  2.5-1 cm diameter  Expand with surge of blood from heart contraction  Recoil from heart relaxation, which aids movement of blood  Elastin is thick in media: dampens the surge of blood pressure  Aorta and its branches

17. 17 Arteries continued 2. Muscular arteries: act as distributing arteries  Middle sized.3mm-1cm  Changes diameter to differentially regulate flow to organs as needed  Internal as well as external elastic lamina  Most of what we see as “arteries”  From these we measure blood pressure Tunica media larger in proportion to the lumen, thus “muscular”

18. 18 Arteries continued 3. Arterioles  Smallest:.3mm-10um  Only larger ones have all 3 layers  Send blood into capillaries Tunica media has only a few layers of smooth muscle cells

19. 19 Capillaries Heart  arteries  capillaries  veins  heart  Capillaries are smallest blood vessel  8-10um  Just big enough for a single file of erythrocytes (RBCs)  Composed of:  single layer of endothelial cells surrounded by a membrane  General Function  Oxygen and nutrient delivery to tissues  CO2 and nitrogenous waste (protein break-down product) removal

21. 21

22. Types of Capillaries 1.Continuous – has virtually no “gaps” open in its walls (e.g., blood-brain barrier) 2.Fenestrated – numerous “pores” in the endothelium (e.g., intestinal lining, kidneys, endocrine glands) 3.Sinusoids – modified “leaky” capillaries (e.g., liver, spleen, bone marrow)

23. Continuous Capillaries Figure 19.3a

24. Fenestrated Capillaries Figure 19.3b

25. Sinusoids Figure 19.3c

26. Capillary Beds  A microcirculation of interwoven networks of capillaries, consisting of:  Vascular shunts – thoroughfare channel connecting an arteriole directly with a venule  True capillaries – 10 to 100 per capillary bed, capillaries branch off and return to the thoroughfare channel

27. Capillary Beds

28. Blood Flow Through Capillary Beds  Precapillary sphincter  Cuff of smooth muscle that surrounds each true capillary  Regulates blood flow into the capillary  Blood flow is regulated by vasomotor nerves and local chemical conditions

29. Capillary Beds

30. 30 Veins  From smallest to large: Capillaries  venules  veins  heart  Veins are larger than arteries  Tunica externa is thicker  But…blood pressure is lowered at capillaries, so the walls of veins are much thinner  There is less elastin

31. 31 Special features of veins  Valves  Prevent backflow  Most abundant in legs (where blood has to travel against gravity)  Muscular contraction  Aids the return of blood to heart in conjunction with valves

32. 32 Exercise helps circulation (because muscles contract and squeeze blood back to the heart)

33. 33 Vascular anastomoses (shunts)  Alternative pathways or connections between blood vessels  Protect organs from being supplied by just one route  Poor anastomoses & therefore vulnerable: central artery of retina, kidneys, spleen, bone diaphyses

34. 34 Angiogram

35. 35 Major Arteries

36. 36

37. 37 Systemic Veins  3 major vessels enter Right Atrium:  SVC (superior vena cava)  IVC (inferior vena cava)  Coronary sinus  Many veins are very superficial (unlike arteries)  Venous plexuses (networks of anastomoses and parallel veins) are very common  Head and hepatic portal systems are unusual

38. 38 Vein overview Note that unlike the arteries, the veins have a brachiocephalic on the right and left sides

39. 39

40. 40 Leg veins  Names similar to arteries  Femoral becomes external iliac after crossing under inguinal ligament  External iliac joins with internal iliac to form common iliac vein _________used for grafting in coronary artery bypass grafts: is the longest vein in the body

41. 41 Vascular System ( Blood vessels of the body)  Two circulations  Systemic  Pulmonary  Arteries and veins usually run together  Often nerves run with them  Sometimes the systems do not have bilateral symmetry  In head and limbs, most are bilaterally symmetrical

42. 42 Pulmonary Circulation  Pulmonary trunk branches  Right and left pulmonary arteries  Division into lobar arteries  3 on right  2 on left  Smaller and smaller arterioles, into capillaries surrounding alveoli  Gas exchange  Pulmonary system pressure is only 1/6 of systemic blood pressure

43. 43 Pulmonary Circulation  After gas exchange blood enters venules  Larger and larger into Superior and Inferior Pulmonary veins  Four Pulmonary Veins empty into left atrium

44. 44

45. 45 In lungs

46. 46 Systemic Circulation  Oxygenated blood to body  Leaves LV through Ascending Aorta  Only branches are the 2 coronary arteries to the heart  Aortic Arch has three arteries branching from it: 1.Brachiocephalic trunk, has 2 branches:  Right common carotid a.  Right subclavian a. 2.Left common carotid a. 3.Left subclavian a. Ligamentum arteriosum connecting to pulmonary a. remember aortic arches…

47. 47  Hepatic portal system  Picks up digested nutrients from stomach & intestines and delivers them to liver for processing and storage  Storage of nutrients  Detoxification of toxins, drugs, etc.  Two capillary beds  Route: artery to capillaries of gut to hepatic portal vein to liver’s capillaries to hepatic vein to IVC Tributaries of hepatic portal vein: - superior mesenteric vein -splenic vein -inferior mesenteric vein

48. 48 Assignment - Some Diseases  Atherosclerotic cardiovascular disease  Cerebrovascular disease  Coronary artery disease (CAD)  Peripheral vascular disease (PVD)  Affecting veins  Chronic venous insufficiency  Deep venous thrombosis (DVT)  Aneurysms  Portal hypertension  Hypertension