Anatomy (Histology) of the Circulatory System

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1 Anatomy (Histology) of the Circulatory System

2 Blood Vessels 1. Histology a. Terms: (1) lumen – cavity
(2) tunica intima – simple squamous epithelium (3) tunica media – elastic connective tissue and smooth muscle (4) tunica externa (adventitia) – fibrous connective tissue

3 (5) vasa vasorum – vessel of a vessel

4 artery

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7 b. Types of blood vessels
(1) Elastic Arteries (a) contain much elastic connective tissue in walls (b) act to smooth-out blood flow (c) act to divert blood flow from inactive tissues to active tissues

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9 Tunic means cloth or layers

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11 (2) Muscular Arteries (a) contain much smooth muscle in walls (b) innervated by autonomic motorneurons

12 We have 60,000 miles of blood vessels and we only have 5-6 liters of blood

13 Muscular Artery

14 Muscular Artery

15 Microscopic Structure of Blood Vessels

16 a. vein b. large artery – elastic artery c. arteriole (small artery) – contain more smooth muscles

17 Vein

18 Large Artery (Elastic Artery)

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22 (3) Capillary Bed – anastomose or interconnections of capillaries
(a) there are about 60,000 miles of capillaries in the body (b) nutrients diffuse out of capillaries, while tissue waste products diffuse into capillaries (c) metarteriole (capillary bed by-pass) – (thoroughfare channel) (d) precapillary sphincters – muscular valves that regulate blood flow

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26 Vasoconstriction – when arteries constrict
Venoconstriction – when veins constrict

27 (4) Venules – small veins

28 Capillary Bed picture

29 Venule Picture

30 Cross section of an artery and vein

31 Cross section of blood vessels

32 (5) Veins (a) thinner-walled than arteries (b) no elastic connective tissue in walls - visceral smooth muscle (c) innervated by autonomic motorneurons (d) possess semi-lunar valves to prevent the back-flow of blood

33 Semi-lunar valves

34 (6) venous sinuses – very thin wall; no tunica media
(a) veins with no elastic connective tissue or smooth muscle (b) examples: cranial venous sinuses coronary sinus hepatic sinuses

35 Cranial venous sinuses

36 2. Pathologies & Disorders of Blood Vessels
a. Arteriosclerosis b. Atherosclerosis (1) plaque formation (2) results in (a) coronary artery disease (CAD) (b) hypertension (increased BP)

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38 (c) aneurysms: (1) weak spot in wall of vessel (2) diagnosed with angiogram (d) Phlebitis (1) inflammation of veins (2) thrombophlebitis

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41 (e) Embolism (1) dislodged blood clot (2) Examples: cerebral embolism; pulmonary embolism

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43 f. Varicose veins (1) veins distended with blood due to deficient valves (2) examples: Great Saphenous Vein; Hemorrhoidal Veins

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45 (3) factors: (1) genetic (2) posture (3) pregnancy/obesity