Blood Vessels Histology PDF

HISTOLOGY of BLOOD VESSELS Assoc. Prof. Özlem Tuğçe Çilingir-Kaya Dept. of Histology and Embryolgy 1 CVS System 1. The heart 2. Blood vessels  O2 and CO2  Nutrients  Metabolic breakdown products  Cells of immune and other systems  Chemical m...

HISTOLOGY of BLOOD VESSELS Assoc. Prof. Özlem Tuğçe Çilingir-Kaya Dept. of Histology and Embryolgy 1 CVS System 1. The heart 2. Blood vessels  O2 and CO2  Nutrients  Metabolic breakdown products  Cells of immune and other systems  Chemical messengers  Hormones  Many other important substances  e.g. clotting factors 2 3 Cardiovascular System (CVS)  The CVS circuits consist of 1. Arteries:  Heart  Tissues - High pressure, thick muscle layer. 2. Veins:  Tissues  Heart - Very low pressure, thin muscle layer. 3. Capillaries:  Thin-walled vessels with the smallest diameter. 6 7 The relationship between sympathetic stimulation and blood vessel diameter. MAIN PULSE POINTS 8 General Structure of Blood Vessels 9 1-Tunica Intima iN which layer do we typically see internal elatic laimina ? 1. Simple squamous epithelium:  Long axes  In the direction of blood flow.  Function in secreting von Willebrand factor.  They also bind lipoprotein lipase, the enzyme that degrades lipoproteins  Role in blood homeostasis! 2. The basement membrane:  It is composed of loose CT and a few scattered smooth muscle cells, both arranged longitudinally. 3. Subendothelial layer:  Loose CT with occasional smooth muscle cells  In arteries and arterioles  Internal elastic membrane/lamina 10  Avessel has lost its ability to produce coagulation fctors and can no longer mge its permiablity or secrete vasodilators which layer of the blood is dameged 11 2-Tunica Media  Usually the thickest and middle layer of the vessel wall  Composed of helically disposed layers of smooth muscle cells  Elastic fibers, type III collagen, and proteoglycans  Larger muscular arteries have an external elastic membrane/lamina  More delicate than the internal elastic lamina  Separates the t.media from the overlying t.adventitia  Very well developed in elastic arteries.  Capillaries and postcapillary venules do not have a tunica media;  In these small vessels, pericytes replace the tunica media. 12 3-Tunica Adventitia  It consists of  a simple squamous epithelium,  basement membrane,  connective tissue,  a few elastic fibers,  blood vessels, and  sometimes smooth muscle cells. In large arteries and veins, The wall is quite thick  Needs its own blood supply Vasa vasorum (vessels of the vessels) 13 Vasa Vasorum  Small arteries that enter the vessel walls and branch profusely to serve the cells located primarily in the t.adventitia.  In the larger vessels, it nourishes the cells.  Compared with arteries, veins have more cells that cannot be supplied with O2 and nutrients by diffusion, because venous blood contains less O2 and nutrients than arterial blood.  The vasa vasorum are more prevalent in the walls of veins than arteries. 14 General Histology of ARTERIES  The efferent vessels  Transport blood away from the heart to the capillary beds. 16 Classification of Arteries 1. Elastic arteries (conducting, large-sized) 2. Muscular arteries (distributing, medium-sized) 3. Small arteries and arterioles 17  On the basis of size and characteristics of the tunica media. 18 1-Elastic Arteries 1. Tunica intima:  Endothelium: 10 to 15 μm wide and 25 to 50 μm long.  Plasma membranes contain small vesicles to transport of water, macromolecules, and electrolytes.  Weibel-Palade bodies  Internal elastic lamina We usllay see a counyous 2. Tunica media:  The thickest internal lamina in elastic arteies. False  Fenestrated elastin membranes  Circular smooth muscle cells  External elastic lamina 3. Tunica adventitia:  Loose fibroelastic CT  Fibroblasts and macrophages We see both internal elsatic  Vasa vasorum and nerves lamila and external elastic lamina 19 2-Muscular Arteries 1. T. intima:  Thinner than the elastic arteries  Subendothelial layer;  A few smooth muscle cells  Internal elastic lamina 2. T. media:  Relatively thick  Almost entirely SM  A few fine elastic fibers among SM cells, most numerous in large We see fibroblasts in t. Adventitis of muscular arteries elastic Arteries not muscualr arteries  Larger arteries, 30 or more layers; smallest peripheral arteries: 2-3 layers  External elastic lamina  Several layers of thin elastic sheets  Identifiable in larger arteries 3. T.adventitia:  Elastic and collagen fibers 21 22 Muscular arteries have more SM and less elastin in the t.media than do elastic arteries! Thinner t.intima Elastic artery Muscular artery 23 3-Arterioles  Smallest branches of arterial tree  30 µm – 400 µm (0.4 mm) 1. Tunica intima:  Endothelium  Basal lamina (type 3 collagen, elastic fibers) Which one of below is correct about an artry  fine internal elastic lamina in larger arterioles Thed smooth muscle layer in elatic amd muscular arteris is 2. Tunica media: seen in tunica intima With cicular arrangments  1-2 layers of smooth muscle cells Both elatic and. Muscular arterir have a clear external  Do not have an external elastic lamina! and internal lamina Tunica intima in muscular 3. Tunica adventitia: arteries is the thickest We do not see external lamina  Insignificant in arteriols Control the blood flow to capillary networks by contraction of the smooth muscle cells. 24 Clinical Correlation - Aneurysm  A sac-like dilation of the wall of an artery or less often of a vein  Results from weakness in the vessel wall and is usually age related  The most common type; abdominal aortic aneurysm. 25  Wall shear stress distribution of 20 cerebral aneurysms during cardiac cycle Geers AJ, Larrabide I, Morales HG, Frangi AF. Approximating hemodynamics of cerebral aneurysms with steady flow simulations. Journal of Biomechanics, 47(1):178–185, 2014. 26 27 Metarterioles  Arteries that supply blood to capillary beds. i. The smooth muscle layer is not continuous ii. Rather, the individual muscle cells are spaced apart iii. Each encircles the endothelium  It is believed that this arrangement permits these smooth muscle cells to function as a sphincter upon contraction. 28 Specialized Sensory Structures in Arteries 1. Carotid sinuses  Baroreceptor, located in the internal carotid artery 2. Carotid bodies  Chemoreceptor, located at the bifurcation of the common carotid artery 1. Glomus cells 2. Sheath cells 3. Aortic bodies  Structure and function are similar to those of carotid body.  Nerve endings monitor blood pressure and composition  Control the heartbeat, respiration and blood pressure 29 30  10 minutes 31 Capillaries  Arises from the terminal ends of the arterioles  The smallest vessels (5-10 µm), often smaller than erythrocyte  Form capillary bed by branching and anastomosing  Specialized for diffusion of substances  Major site of gaseous exchange  Thinnest wall of all BVs  Endothelial cells,  BL  secreted by endothelial cells,  Occasional scattered cells (pericytes) 32 General Structure of Capillaries  A single layer of squamous endothelial cells rolled into a tube  Long axis of the cells lie in same direction as blood flow!!  Cytoplasm,  Golgi complex  A few mitochondria  RER and free ribosomes  Desmin and vimentin  Characteristic feature  «Pinocytotic vesicles»  Associated with the entire plasmalemma  Not all of capillary beds are open at any one time!  Increased demand initiates opening of more beds  Increase blood flow. 33  Which of of the sentances below is correct about Pericytes pericytes  Located along outside of capillaries & small venules  Long primary processes are located along the long axis of capillary.  Secondary processes arise from primary ones wrap around capillary, forming a few gap junctions with endothelial cells  Share the basal lamina of endothelial cells  Contractile cells: Regulate blood flow  Tropomyosin  Isomyosin  Protein kinase  After injury may undergo differentiation to become smooth muscle cells and endothelial cells! 34 Classification of Capillaries 1. Continuous  No pores & fenestrations  Fasciae occludentes  Pinocytic vesicles  Muscle, nervous and connective tissue 2. Fenestrated  60-80nm in diameter pores covered diaphragm  Numerous pinocytic vesicles  Pancreas, intestines, glomerulus, endocrine gl. 3. Sinusoidal / Discontinious  30 to 40 μm  Many large fenestrae that lack diaphragms  Lack of pinocytic vesicles  BL permits enhanced exchange between the blood and the tissues  BM, liver, spleen, lymphoid organs, and certain of the endocrine glands 35 36  Arrows indicate fenestrae closed by diaphragms. In this cell the nucleus (N), Golgi complex (G), and centrioles (C ) can be seen. Note the continuous basal lamina on the outer surface of the endothelial cell (double arrows). Junqueira, LC and Carneiro, J, Basic Histology, 11th ed., McGraw-Hill, New York, 2005. p. 216. Endothelial cells of continuous capillaries are joined by tight junctions. They contain pinocytotic vesicles (arrows). There is a continuous basal lamina. Fawcett DW, The Cell: An Atlas of Fine Structure, WB Saunders, Philadelphia, 1966, p. 403. Liver sinusoid in cross section (rat). Open fenestrae are evident in the endothelial cell cytoplasm. Cormack, D.H. Ham’s Histology, 9th ed., Lippincott, Philadelphia, 1987, p. 531. SYSTEMIC CAPILLARY LEAK SYNDROME 38 VEINS  Return blood to the heart  Empty their contents into larger veins  Almost 70% of the total blood volume is in these vessels 1. Tunica Intima:  A thin endothelial lining 2. Tunica Media:  Contains 2-3 layers of muscle cells 3. Tunica Adventitia:  The broadest layer  Contains longitudinal collagen fibres  Vasa vasorum 40 The tunics of veins are not as distinct or well-defined as those of arteries! Classification of Veins  On the basis of their diameter and wall thickness; Valves are seen in the level of sub endotheila tissue in small and median veins 42 1-Large Veins  >10mm in diameter (Vena cavae, subclavian and portal veins)  Return venous blood directly to the heart from the extremities, head, liver, and body. 1. Tunica intima:  Endothelium with BL  Subendothelial CT with some SM cells, fibroblasts and elastic fibers  Thicker than medium-sized 2. Tunica media: Thin or absent in most large veins 3. Tunica adventitia: The thickest layer  Many elastic fibers  Abundant collagen fibers  Dispersed longitudinally arranged SM cells  Vasa vasorum 43 44 2-Medium Veins  Less than 1 cm in diameter  Drain most of the body (extremities)  Valves are characteristic 1. Tunica intima:  Endothelium with BL  Subendothelial layer with some SM  Reticular fibers 2. Tunica media:  Loosely orginized SM cells  Collagen fibers  Fibroblasts 3. Tunica adventitia:  Longitudinally arranged collagen & elastic bundles,  A few SM cells 45 46 Valves of Veins  Two leaflets composed of a thin fold of the intima projecting into the lumen.  Prevent backflow  Assist blood flow to heart  Veins in arms & legs: Valves  Also present in other medium & large veins  Number of valves depends on whether or not the vein carries blood against gravity. 47 48 3-Venules  The venule is smaller than a vein and  Similar to a vein has a much thinner tunica media than an artery or arteriole. 49 50 51  Artery, vein and nerve Small artery and vein 52  Clinical Correlations Arteriosclerosis: Hyaline or concentric thickening which is often associated with hypertension and/or diabetes. 53 Clinical Correlations  Hardening of the arteries: In the muscular arteries, deposits of collagen and proteoglycans increase in the walls, thus reducing their flexibility. o Atherosclerosis*: Distinguished by infiltrations of soft, noncellular lipid material into the intima walls; these infiltrations can reduce the luminal diameter appreciably even by age 25. However, the fibrous plaques that form in the intima of older persons are pathological. 54 55  What is the main difference between arteriosclerosis and atherosclerosis? Both conditions involve the hardening of the arteries. Atherosclerosis is a common and specific type of arteriosclerosis. Arteriosclerosis is caused by oxidative damage to elastin fibers. The damage causes breakage of elastin fibers, lowering their structured arrangement. As a result, the artery walls become stiff and hard, leading to arteriosclerosis. Atherosclerosis is caused by damage to endothelial cells. When the endothelial cells are damaged, it leads to inflammation, causing plaque development. 56  Parameters Atherosclerosis Arteriosclerosis The buildup of plaque in artery The hardening or thickening of Meaning walls causes the arteries to artery walls, restricting blood narrow flow to organs and tissues A broader term for a group of Scope A type of arteriosclerosis conditions Type of deposits Fatty deposits Calcium deposits Mild atherosclerosis shows no Occurrence of symptoms. Symptoms are usually It causes no symptoms, symptoms experienced in moderate to especially in the early stages. severe atherosclerosis. Causes Damage to endothelial cells Damage to elastin fibres 57  Clinical Correlations 58  Coronary artery blockage and myocardial infarction. 60 61  SORULAR Vasa vasorum aşağıdaki yapılardan hangisine benzer fonksiyon gösterir? A) Atrioventriküler kapaklar B) Semilunar kapaklar C) Koroner arterler D) Elastik arterler E) Metarteriyoller 63  SORULAR Aşağıdaki özelliklerden hangisi somatik kapilerleri viseral kapilerlerden esas olarak ayırır? A) Pencere bulunup bulunmadığı B) Lümen çapı C) Damar duvarı kalınlığı D) Perisit bulundurup bulundurmadığı E) Bazal laminanın kalınlığı 64  SORULAR Aşağıdakilerden hangisi belirgin bir internal elastik lamina içerir? A) Kapillerler B) Metarteriyoller C) Arteriyoller D) Müsküler arterler E) Venler 65  SORULAR Aşağıdaki ifadelerden hangisi sağlıklı ve hasar görmemiş kapillerler için en doğrudur? A) Kan basıncını kontrol ederler B) Tek katlı prizmatik epitelle döşelidirler C) Düz kas ile çevrilidirler D) Pıhtı oluşumunu inhibe ederler E) Satellit hücrelerle bazal laminalarını paylaşırlar 66  THANK YOU… 68