1. Blood Vessels
PART 1

2. Blood Vessels 3 major types of blood vessels:
Arteries – carries blood away from the heart
Capillaries – The functional vessels which actually delivers nutrients to cells
Veins – return blood to the heart

3. Structure of Blood Vessels
Composed of three layers (tunics)
Tunica intima – composed of simple squamous epithelium
Tunica media – sheets of smooth muscle
Contraction – vasoconstriction
Relaxation – vasodilation
Tunica externa – composed of connective tissue
Lumen
Central blood-filled space of a vessel

4. Generalized structure of arteries, veins, and capillaries.
Tunica intima
Artery
Endothelium
Vein
Subendothelial layer
Internal elastic membrane
Tunica media (smooth muscle and elastic fibers)
External elastic membrane
Tunica externa (collagen fibers)
Vasa vasorum
Valve
Capillary network
Lumen
Lumen
Basement membrane
Capillary
Endothelial cells

5. Structure of Arteries, Veins, and Capillaries
Figure 19.1a

6. Types of Arteries Elastic arteries – the largest arteries
Diameters range from 2.5 cm to 1 cm
Includes the aorta and its major branches
Sometimes called conducting arteries
High elastin content dampens surge of blood pressure
Figure 19.2a

7. Unique features Types of Arteries Muscular (distributing) arteries
Lie distal to elastic arteries
Diameters range from 1 cm to 0.3 mm
Includes most named arteries
Tunica media is thick
Unique features
Internal and external elastic laminae
Figure 19.2b

8. Types of Arteries Arterioles Smallest arteries
Diameters range from 0.3 mm to 10 µm
Larger arterioles possess all three tunics
Diameter of arterioles controlled by
Local factors in the tissues
Sympathetic nervous system
Figure 19.2c

9. Capillaries Smallest blood vessels Diameter from 8–10 µm
Red blood cells pass through single file
Types of Capillaries:
Continuous – most common – diffusion and intercellular clefts for larger molecules
Fenestrated – “windows” has holes – found in kidneys, intestines and endocrine glands
Sinusoids – wide, leaky capillaries. Follows a twisted path and has wide and narrow areas. Useful when exchange of large materials is necessary such as in the bone marrow and spleen

10. RBCs in a Capillary
Figure 19.3

11. Capillary Beds Network of capillaries running through tissues
Precapillary sphincters
Regulate the flow of blood to tissues
Tendons and ligaments – poorly vascularized
Epithelia and cartilage – avascular
Receive nutrients from nearby CT

12. Capillary Beds
Figure 19.4a

13. Capillary Beds
Figure 19.4b

14. Capillary Permeabillity
Endothelial cells – held together by tight junctions and desmosomes
4 Routes of molecules:
1. Direct Diffusion through endothelial membrane
2. Intercellular clefts – unjoined areas of cell membrane to allow passage of large molecules
3. Pinocytotic vesicles – vesicles invaginate from the plasma membrane and migrate across the endothelial cell transporting dissolved gasses, nutrients and wast products
4. fenestrations – pores in the endothelial cells allow passage of many small molecules

15. Structure of Capillaries – Cross Section
A vesicle within an endothelial cell to transport liquid from blood to tissues
Figure 19.5a

16. Structure of Capillaries – Cross Section
In kidneys
Figure 19.5b

17. Routes of Capillary Permeability
Four routes into and out of capillaries
Direct diffusion – across capillary wall (endothelial cell membrane)
Through intercellular clefts – most
Through cytoplasmic vesicles
Through fenestrations - kidneys

18. Low Permeability Capillaries
Blood-brain barrier
Capillaries have complete tight junctions
No intercellular clefts are present
Vital molecules pass through
Highly selective transport mechanisms
Not a barrier against
Oxygen, carbon dioxide, and some anesthetics

19. Sinusoids Wide, leaky capillaries found in some organs
Usually fenestrated
Intercellular clefts are wide open
Occur in bone marrow and spleen
Sinusoids have a large diameter and twisted course

20. Sinusoids
Figure 19.5c

21. Veins Conduct blood from capillaries toward the heart
Blood pressure is much lower than in arteries
Smallest veins – called venules
Diameters from 8 – 100 µm
Smallest venules – called postcapillary venules
Venules join to form veins
Tunica externa is the thickest tunic in veins

22. Mechanisms to Counteract Low Venous Pressure
Valves in some veins
Particularly in limbs
Skeletal muscle pump
Muscles press against thin-walled veins
Figure 19.6

23. Vascular Anastomoses Vessels interconnect to form vascular anastomoses
Organs receive blood from more than one arterial source
Neighboring arteries form arterial anastomoses
Provide collateral channels
Veins anastomose more frequently than arteries

24. Vasa Vasorum Tunica externa of large vessels have
Tiny arteries, capillaries, and veins
Vasa vasorum vessels of vessels
Nourish outer region of large vessels such as the aorta, brachiocephalic a., common iliac a.
Inner half of large vessels receive nutrients from luminal blood
It’s how the cells of the large vessels receive nutrients

25. Pulmonary Circulation
Pulmonary trunk leaves the right ventricle
Divides into right and left pulmonary arteries
Superior and inferior pulmonary veins
Carry oxygenated blood into the left atrium

26. Pulmonary Circulation
Figure 19.7

27. Systemic Circulation Systemic Arteries
Carry oxygenated blood away from the heart
Aorta – largest artery in the body

28. Major Arteries
Figure 19.8a

29. The Aorta Ascending aorta – arises from the left ventricle
Branches – coronary arteries
Aortic arch – lies posterior to the manubrium
Branches
Brachiocephalic trunk
Left common carotid
Left subclavian arteries

30. The Aorta
Figure 19.9

31. The Aorta Descending aorta – continues from the aortic arch
Thoracic aorta – in the region of T5–T12
Abdominal aorta – ends at L4
Divides into right and left common iliac arteries

32. Arteries of the Head and Neck
Figure 19.10a

33. Major Arteries Serving the Brain
Cerebral arterial circle – Circle of Willis
Figure 19.10c

34. Arteries of the Upper Limb and Thorax
Figure 19.11

35. Arteries of the Abdominal Aorta
Inferior phrenic arteries
Celiac trunk
Superior mesenteric artery
Suprarenal arteries
Renal arteries
Gonadal (testicular or ovarian) arteries
Inferior mesenteric artery
Common iliac arteries

36. Arteries of the Abdominal Aorta
Figure 19.12

37. The Celiac Trunk and Main Branches
Figure 19.13

38. Distribution of the Superior and Inferior Mesenteric Arteries
Figure 19.14

39. Arteries of the Pelvis and Lower Limbs
Internal iliac arteries
External iliac artery
Femoral artery
Popliteal artery
Anterior tibial artery
Posterior tibial artery

40. Internal Iliac Artery
Figure 19.15b

41. Arteries of the Pelvis and Lower Limbs
Figure 19.16a

42. Arteries of the Pelvis and Lower Limbs
Figure 19.16b

43. Figure 19.17

44. Systemic Veins Three major veins enter the right atrium
Superficial veins lie just beneath the skin
Multivein bundles – venous plexuses
Unusual patterns of venous drainage
Dural sinuses
Hepatic portal system

45. Venae Cavae and Tributaries
Superior vena cava
Returns blood from body regions superior to the diaphragm
Inferior vena cava
Returns blood from body regions inferior to the diaphragm
Superior and inferior vena cava
Join the right atrium

46. Abdominal Cavity Showing Vasculature
Figure 19.19

47. Major Veins of the Systemic Circulation
Figure 19.18

48. Veins of the Head and Neck
Dural Sinuses
Superior and inferior sagittal sinuses
Straight sinus
Transverse sinuses
Sigmoid sinus
Figure 19.20b

49. Veins of the Head and Neck
Venous drainage
Internal jugular veins
External jugular veins
Vertebral veins
Figure 19.20a

50. Veins of the Upper Limbs
Deep Veins
Follow the paths of companion arteries
Have the same names as the companion arteries
Superficial veins
Visible beneath the skin
Cephalic vein
Basilic vein
Median cubital vein
Median vein of the forearm

51. Figure 19.21a

52. Antecubital Fossa Form anastomese frequently
Median cubital vein is used to obtain blood or administer IV fluids
Figure 19.22

53. Veins of the Thorax Azygos vein Hemiazygos vein
Accessory hemiazygos vein
Figure 19.21b

54. Veins of the Abdomen Lumbar veins
Gonadal (testicular or ovarian) veins
Renal veins
Suprarenal veins
Hepatic veins

55. Tributaries of the Inferior Vena Cava
Figure 19.23

56. The Hepatic Portal System
A specialized part of the vascular circuit
Picks up digested nutrients
Delivers nutrients to the liver for processing

57. The Basic Scheme of the Hepatic Portal System
Figure 19.24

58. Veins of the Hepatic Portal System
Figure 19.25

59. Veins of the Pelvis and Lower Limbs
Deep veins
Share the name of the accompanying artery
Superficial veins
Great saphenous vein empties into the femoral vein
Small saphenous vein empties into the popliteal vein

60. Veins of the Right Lower Limb and Pelvis
Figure 19.26a

61. Figure 19.26b

62. Figure 19.27

63. Disorders of the Blood Vessels
Aneurysm – a ballooning out of a major artery such as the aorta
Deep vein thrombosis of the lower limb – formation of clots in the veins of the leg or thigh. The clot may detach and travel to the heart and pulmonary trunk, blocking a branch of the pulmonary artery which may be fatal
Venous disease – inadequate drainage of venous blood from the limb. Tissues become ischemic and vulnerable to damage and ulceration. Caused by the failure of valves so blood pools and causes swelling of legs.
Arteriovenous malformation – a congenital condition in which capillaries fail to develop in a certain location so that an artery continues directly into a vein. The high pressure entering a vein cause an aneurysm which can compress nearby tissues or burst and cause a stroke. Normally occurs in the brain
Atherosclerosis – arterial walls become thick and stiff from hypertension, chemicals or viral or bacterial infections. Irritation of the endothelium prompts inflammatory response. LDL is attracted, cholesterol follows.
Microangiopathy of diabetes – complication of diabetes. Elevated blood sugar lead to deposit of glycoproteins in the basement membrane of capillaries diminishing the efficiency of the capillary. Organs most vulnerable are: kidneys, retina, periheral nerves and feet.