組織學 Historlogy 台北醫學大學 / 解剖學科教授 : 邱瑞珍分機號碼 :3261. 電子郵件信箱

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1 組織學 Historlogy 台北醫學大學 / 解剖學科教授 : 邱瑞珍分機號碼 :3261 電子郵件信箱 :rueijen@tmu.edu.tw 1

2 The Circulatory System 台北醫學大學 / 解剖學科教授 : 邱瑞珍分機號碼 :3261 電子郵件信箱 :rueijen@tmu.edu.tw 2

3 學習目的 The structure of the arteries The structure of the veins The structure of the lymphatic vessels 3

4 參考資料 Junqueira's Basic Histology, twelfth edition, text and atlas, Anthony L. Mescher, McGraw-Hill Companies 4

5 Summary HEART STRUCTURAL PALN OF BLOOD VESSELS LYMPHATIC VASCULAR SYSTEM 5

6 Circulatory system: blood & lymphatic vascular systems Blood vascular system: composed heart : pump blood arteries: efferent vessels, carry blood with nutrients & oxygen tissue capillaries: smallest blood vessels, interchange veins: convergence of capillaries, convey blood heart 6

7 Lymphatic vascular system: begin with lymphatic capillaries closed-ended tubules larger vessels blood vascular system return fluid of tissue space blood 7

8 Internal surface: endothelium Circulatory system: macrovasculature: vessels more than 0.1mm in diameter large arterioles, muscular & elastic arteries, muscular veins microvasculature: arterioles, capillaries, post-capillary venules functional important: site of interchange 8

9 HEART A muscular organ contract rhythmically, pumping blood R & L ventricles: blood lung & rest of body R& L atria: receive blood from body & lung Walls of heart: internal endocardium middle mycardium external epicardium 9

10 Endocardium A single layer of squamous endothelial cells Thin layer of loose connective tissue: elastic & collagen fibers & smooth muscle cells Subendocardial layer: veins & nerves, branch of impulse-conducting system 10

11 Myocardium Thickest, consist of cardiac muscle cells Arranged in layers: surround heart chambers complex spiral Ventricles thicker than atria Epicardium Simple squamous epithelium (mesothelium) support by a thin layer of connective tissue Subepicardial layer: veins, nerves, adipocytes 11

12 Heart valves: central core: dense fibrous connective tissue (containing elastic & collagen fibers) both sides: endothelial layers bases: attach to strong fibrous rings part of fibrous skeleton site of origin & insertion of cardiac muscle fibers 12

13 Heart: specialized system generate a rhythmic stimulus for contraction Consist: 2 nodes located in right atrium: sinoatrial (SA) node: pacemaker atrioventricular (AV) node Atrioventricular bundle (of His) 13

14 SA node: a small mass of modified cardiac muscle cells fusiform, smaller & fewer myofibrils AV node: similar to SA node cytoplasmic projections branch in various directions AV bundle: originate from node pass along interventricular septum split into L & R bundles branches to both ventricles 14

15 Distal fibers of AV bundles: larger than ordinary cardiac muscle fibers conducting myofibers or Prukinje fibers 1 or 2 nuclei cytoplasm: rich in mitochondria, glycogen myofibrils: sparse, restricted to periphery Both parasympathetic & sympathetic neural components heart Ganglionic nerve cells & nerve fibers: present close to SA & AV nodes affect heart rate & rhythm 15

16 Parasympathetic: slow heartbeat Sympathetic: accelerate rhythm Between muscle fibers: afferent free nerve endings sensibility & pain Partial obstruction of coronary arteries: reduce supply of oxygen cause pain (angina pectoris) 16

17 STRUCTURAL PALN OF BLOOD VESSELS 3 layers of vascular wall: Tunica intima One layer of squamous epithelial cells Subendothelial layer: loose connective tissue smooth muscle found in In arteries: internal elastic lamina most external component of intima composed of elastin holes (fenestrated) allow diffusion 17

18 Tunica media Middle layer Concentric layers of helically arranged smooth muscle cells Among smooth muscle cells: elastic fibers & lamellae, reticular fibers, proteoglycans, glycoprotein In arteries: external elastic lamina separate from adventitia 18

19 Tunica adventitia (tunica externa) Consist of type I collagen & elastic fibers Continuous with stromal connective tissue of organs Large vessels: vasa vasorum consist of arterioles, capillaries, venules in tunica adventitia & outer part of media provide metabolites to cells of those layers large vessels: walls too thick to be nourished by diffusion from lumen 19

20 Larger vessels: supplied with sympathetic nerve fibers norepinephrine vasoconstriction nerve not enter media of arteries: neurotransmitter diffusion smooth muscle : gap junctions Thinner walled veins: nerve ending: in adventitia & media overall density : less than encountered arteries 20

21 In skeletal muscle: arteries: also receive cholinergic vasodilator nerve supply Acetylcholine: act on endothelium produce nitric oxide diffuse to smooth muscle cells muscle relax lumen dilated 21

22 22

23 Large Elastic Arteries Help to stabilize blood flow Include: aorta & its large branches Fleshly: yellowish color from elastin in media Intima: thicker than muscular arteries internal elastic lamina: present may not easily discerned Media: elastic fibers & concentrically arranged elastic laminae smooth muscle cells, reticular fibers, proteoglycans, glycoproteins Adventitia: relatively underdeveloped 23

24 Muscular Arteries Control blood flow organs Intima: very thin subendothelial layer prominent internal elastic lamina Media: up to 40 layers of more prominent smooth muscle cells intermingled with elastic lamellae, reticular fibers, proteoglycans external elastic lamina: only in larger muscular arteries Adventitia: connective tissue contain lymphatic capillaries, vasa vasorum, nerves 24

25 Arterioles Muscular arteries branch repeatedly smaller and smaller 2 or 3 medial layers of muscle Arterioles: smallest arteries 1 or 2 layers of smooth muscle layers generally less than 0.5 mm in diameter lumen as wide as wall is thick subendothelial layer: very thin elastic laminae: absent media: circularly arranged smooth muscle cells adventitia: very thin & inconspicuous 25

26 Capillaries Permit different levels of metabolic exchange between blood & tissues Composed of : a single layer of endothelial cells Endothelial cells: form a tube Capillaries: 5-10 μm average diameter length: 50 μm comprise over 90% of all blood vessels total length: 96000km total diameter: 800 times larger than aorta 26

27 Velocity of blood: in aorta: 320 mm/s in capillaries: 0.3 mm/s because their thin wall & slow flow a favorable place for exchange water, solutes, macromolecules In general: endothelial cells: polygonal & elongated in the direction of blood flow nucleus: bulge into lumen junctions of tight zonula occludentes type present 27

28 Pericytes: enclosed by a basal lamina may fuse with that of endothelial cells well-developed networks of myosin, actin, tropomyosin : contractile function After tissue injuries: pericytes proliferate & differentiate form tunica media & cells with various other functions in re-establishing microvasculature & its ECM 28

29 Capillary: structural variations 3 types 1. continuous (tight) capillaries allow regular exchange of material most common type found in muscles, connective tissue, exocrine glands & nervous tissue pinocytotic vesicles : luminal & basal surface transport of material 29

30 2.Fenestrated capillaries: allow more extensive molecular exchange presence of small circular fenestrae covered by a very thin diaphragm containing heparan proteoglycans no lipid bilayer basal lamina: continuous voering fenestrae found in kidney, intestine, choroid plexus, endocrine glands 30

31 3. Sinusoid (Discontinuous) capillaries : permit maximal exchange endothelial cells: large fenestrae without diaphragm form a discontinuous layer separate from one another:wide space basal lamina: also discontinuous irregularly shaped diameter: 30-40μm found in liver, spleen, some endocrine organs, bone marrow 31

32 Venules Transition from capillaries to venules: gradually Postcapillary venules: similar structurally to capillaries with pricytes but diameter: from 15-20μm participate in exchange converge larger collecting venules 2 or 3 smooth muscle layers muscular venules 32

33 Veins Blood entering vein: very low pressure move forward heart: contraction of tunica media external compression from surrounding muscles or organs Valve: projection from tunica intima to prevent back-flow of blood Most veins: small or medium veins diameter less than 1 cm located in parallel with muscular arteries 33

34 Intima thin subendothelial layer Media small bundles of smooth muscle cells intermixed with reticular fibers & a delicate network of elastic fibers Adventitia collagenous well-developed 34

35 Big venous trunks, paired with elastic arteries: large veins Well developed intima Media: relative thin few layers of smooth muscle cells abundant connective tissue Adventitia: thick in large veins frequently contain longitudinal bundles of smooth muscle Both media & adventitia: contain elastic fibers not like those of elastic arteries 35

36 LYMPHATIC VASCULAR SYSTEM Collect excess interstitial fluid from tissue space return to blood Fluid: lymph Flow in only one direction: toward the heart Lymphatic capillaries originate in various tissue thin, closed-ended vessels a single layer of endothelium + an incomplete basal lamina held open by bundles of anchoring filaments of elastic fiber system also bind vessels to connective tissue 36

37 Lymphatic capillaries larger lymphatic vessels Interposed in path : lymph nodes Lymphatic: found in almost all organs except CNS & bone marrow Larger lymphatics: similar to veins thinner walls lack a clear-cut separation between tunics more numerous internal valves 37

38 Lymphatic vessels: dilated assumed a nodular or beaded, between valves Lymphatic circulation: aided by external forces contraction of skeletal muscles unidirectional flow: many valves contraction of smooth muscles of larger lymphatic vessels: also help to propel End up as 2 large trunk: thoracic duct & right lymphatic trunk empty lymph veins 38

39 Structure of lymphatic ducts: similar to that of large veins reinforced smooth muscle in middle layer muscle bundles: longitudinally & circularly arranged former predominating adventitia: relatively undeveloped contain vasa vasorum & neural network Lymphatic vessels: also a major distributor of lymphocytes, antibodies, immune components 39