Blood •Warning •please, do not manipulate the microscope, • •they are prepared for your study of blood smears after presentation, • •you will get instructions, how to study blood smears. Blood Plasma & Blood cells blood Composition of plasma •Water – 90 % •Proteins – 7 % (albumins, globulins, fibrinogen) •Other components – 3 % (blood gasses, nutrients, hormones, enzymes, vitamins, electrolytes) • Hematocrit: the volume of blood cells per unit volume of blood fig2 Blood Hematocrit ♂ 42 – 52 % ♀ 37 – 47 % http://ajurvedske-lazne.cz/sites/default/files/obrazky/plazma.png 55 % plasma 90 % H2O 7 % plasma proteins 3 % -AMAs, saccharids, lipids -hormones -electrolytes 45 % blood corpuscles Blood cells (formed elements) •Red blood cells – erythrocytes •White blood cells – leukocytes •Platelets – thrombocytes wbc_ident CE087600FG0010 LEUKOCYTES GRANULOCYTES (polymorphonuclears) AGRANULOCYTES (mononuclears) neutrophilic 10 - 12 mm eosinophilic 12 - 14 mm basophilic 8 - 10 mm lymphocytes 6 - 8 / 10 -12 mm monocytes 12-20 mm Neutrophil.png Eosinophil 1.png Basophil.png Lymphocyte.png Monocyte.png THROMBOCYTES ERYTHROCYTES BLOOD CORPUSCLES Výsledek obrázku pro erytrocyt 7,2 - 7,6 mm trombocyt trombocyt trombocyt 2 – 4 mm REMEMBER forever! • • •Erythrocytes: 4 – 6 millions/ 1 ml of blood •Leukocytes: 5,000 – 9,000 / 1 ml •Thrombocytes: 150,000 – 250,000/ 1 ml • •NEVER FORGET ! ERYTHROCYTES •4 – 6 million/μl •Shape: biconcave disc, • dumble-shaped (cross section) •Size: 7.4 μm in diameter (= normocyte) •Structure: plasmalemma, cytoplasm + hemoglobin 33 % absence! of the nucleus and cell organelles •Lifespan: 120 days • blood_01 CRIB_blood_cells rbcm2 wbc_ident pgps3fs 746px-A_red_blood_cell_in_a_capillary,_pancreatic_tissue_-_TEM Hemoglobin •a conjugated protein: 4 polypeptide chains + heme groups = protoporphyrin ring with ferrous iron (Fe2+ ) •Hb F (fetal) •Hb A (adult) •normochromatic ery: 32±2 picogramms (hyper-, hypo-) • hemoglobin •Polyglobulia – an increased number of ery •Anemia – a decreased number of ery • •Poikilocytosis – an occurrence of different shaped ery (spherocytes, elliptocytes, drepanocytes = sickle cells, etc.) •Anisocytosis – an occurrence of different sized ery (microcytes, macrocytes) Anisocytosis • • • •Microcytes Æ < 6.5 mm •Normocytes • Æ ± 7.4 mm •Macrocytes Æ > 8 mm • 4 Reticulocytes •Immature ery are released from the bone marrow into the peripheral blood (0.5 – 1.5 %) •They contain the rests of organelles – ribosomes, mitochondria – substantia reticulofilamentosa (brilantcresyl blue staining is used for detection) • maturation into ery – during 24 hours • Polychromatic_erythrocyte retic Functions of ery • •transport of oxygen from the lungs •transport of carbon dioxide from the tissues ERYTHROCYTES polyglobulia - polycythaemia / anemia / anisocytosis / poikilocytosis Eos Ery Ery Erytrocyty (Ery), eosinofilní granulocyt (Eos). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X Polyglobulia, anemia, anisocytosis, poikilocytosis. ERYTHROCYTES Erytrocyty (REM). ERYTHROCYTE Erytrocyt ve fenestrované kapiláře (TEM). RETICULOCYTE substantia reticulofilamentosa Retikulocyt (šipky. Nátěr periferní krve, brilantní kresylová modř, imerze, CZV: 1000X LEUKOCYTES •Granulocytes: • - neutrophils • - eosinophils • - basophils •General characteristic •Polymorphonuclears with •acidophilic cytoplasm and •Specific + azurophilic granules •Agranulocytes • - lymphocytes • - monocytes • •General characteristic •Mononuclears with •basophilic cytoplasm and •azurophilic granules • Granulocytes2 Lymphocyte Monocyte Granulocytes •General charcteristic: -polymorphonuclears – different shape of nuclei - - • band segmented with chromatin bridges -acidophilic cytoplasm – bright-pink -specific granules – with special enzymes -azurophilic granules – with lysosomal enzymes -all granulocytes are able to migrate from the vessels and by diapedesis invade a site of inflamation Granulocytes neutrophils – eosinophils - basophils • band • • 12-14 mm • •10-12 mm • 10 mm • • • • segment Neutrophil granulocytes (neutrophils) •71 % of all white blood cells (DWCC) •Æ 10 – 12 mm •Cytoplasm: bright pink (eosinophilic = acidophilic ) •Specific granules: neutrophilic (Æ 0.3 mm) (alcaline phosphatase, kolagenase, lysozyme, …) •Nucleus: band-shaped (4 %) or segmented (67 %) (2-5 segments) • S96538-163-f004 mo103le nh%20band%20x100a band1 HEME001 Neutrophil-EM_copy_small Functions of Neutrophils •a central role in inflammatory processes – Neu invade, by diapedesis from the vessels, sites of infection in response to factors (e.g. cytokines) released by cells which reside at an infection site. •cell membrane receptors allow Neu to recognise foreign bodies (bacteria, tissue debris), which they begin to phagocytose and destroy. • • The Neu die once their supply of granules has been • exhausted. Their lifespan is only about • one week. Dead neutrophils and tissue debris are the • major components of pus. Eosinophil granulocytes (eosinophils) •1– 4 % of all white blood cells (DWCC) •Æ 12 – 14 mm •Cytoplasm: bright pink (eosinophilic = acidophilic ) •Specific granules: eosinophilic (Æ 0.5 – 1 mm) (enzymes: acid phosphatase, peroxidase,histaminase, arylsufatase …) •Nucleus: dumb-belt, (2 segments) chromatin bridge Fig1 7290350f8 eo104le Eosinophil_small Functions of Eosinophils •phagocytosis of antibody-antigen complexes and prevention of the immune system from "overreacting„ •eos are involved in the response of the body against parasitic infections, which are accompanied by an increase in the number of eosinophils. Basophil granulocytes (basophils) •up to 1 % of all white blood cells (DWCC) •Æ up to 10 mm •Cytoplasm: bright violet-pink (lightly basophilic ) •Specific granules: (Æ 2 mm) (heparin, histamin, …) •Nucleus: „shape of dick S“ ba103le HEME005 basophil_small Functions of Basophils •heparin and histamine are vasoactive substances. They dilate the blood vessels, make vessel walls more permeable and prevent blood coagulation. They facilitate the access of heparinocyte in a site of infection. •antibodies produced by plasma cells (activated B-lymphocytes) bind to the receptors on the plasma membrane of basophils. If these antibodies come into contact with antigens, they induce the release of the contents of the basophil granules. Agranulocytes •General charcteristic: -mononuclears – shape of nuclei is spherical, oval or bean-shaped • • -basophilic cytoplasm – blue -NO specific granules -azurophilic granules – with lysosomal enzymes • ly106le Neu-B Neu-S NEUTROPHILIC GRANULOCYTES - bands, segments - Neutofilní granulocyt – tyčka (Neu-T), segment (Neu-S); trombocyty (šipka). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X NEUTROPHILIC GRANULOCYTE „BAND“ Neutrofilní granulocyt – tyčka. Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X NEUTROPHILIC GRANULOCYTE „SEGMENT“ Neutrofilní granulocyt – segment Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X Eos Neu EOSINOPHILIC GRANULOCYTE Eosinofilní granulocyt (Eos), neutrofilní granulocyty (Neu). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X EOSINOPHILIC GRANULOCYTE Eosinofilní granulocyt (Eos). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X EOSINOPHILIC GRANULOCYTE Eosinofilní granulocyt (TEM). BASOPHILIC GRANULOCYTE Basofilní granulocyt. Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X LYMPHOCYTES •Classification: • - according to origin – T-Ly (thymus), B-Ly • (bone marrow @ bursa of Fabricius in birds) • - according to the size – small (Æ 8 mm), • medium (Æ 10-12 mm), large (Æ 16-18 mm), • - according to the function – natural killer cells, • helper cells, memmory cells, supressor cells, • - according to life-span Lymphocytes - structure •20 % of all white blood cells (DWCC) • • • •small, medium-sized, large Ly •cytoplasm – dark blue, contains non-specific azurophilic granules with lysosomal enzymes (hydrolases) and numerous ribosomes •nucleus – round, hyperchromatic – coarse grains of heterochromatin (dark violet colour) • Fialová motanina Fialová motanina lymphocyte_small ly100le blood5 Functions of Lymphocytes •B-lymphocytes differentiate into antibody producing plasma cells and so they represent "humoral immunity" •T-lymphocytes represent the "cellular immunity" and may attack foreign cells, cancer cells and cells infected by e.g. a virus LYMPHOCYTE Lymfocyt. Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X LYMPHOCYTE Lymfocyt (TEM). MONOCYTES •5 % (DWC), Æ 15 – 20 mm •cytoplasm – voluminous, bright blue, contains non-specific azurophilic granules with lysosomal enzymes (hydrolases) and numerous ribosomes •nucleus – oval to bean-shaped, finely dispersed chromatin mo105le monocyte_small Functions of Monocytes •monocytes enter the connective tissue they differentiate into macrophages. At sites of infection macrophages are the dominant cell type after the death of the invading neutrophils. •macrophages phagocyte microorganisms, tissue debris and the dead neutrophils. • •mono also give rise to osteoclasts, which are able to distroy bone. They are of importance in bone remodelling. Mono Ly MONOCYTE and LYMPHOCYTE Monocyt (Mono), lymfocyt (Ly). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X Mono Neu MONOCYTE and „NEUTROPHIL“ Monocyt (Mono), Neutrofilní granulocyt - segment (Neu). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X fagosomes MONOCYTE Monocyt (TEM). THROMBOCYTES (blood platelets) •150,000 – 300,000 / 1 ml of blood •thrombocytosis X thrombocytopenia •- are not cells, but cytoplasmic fragments of large cell (megakaryocyte) in bone marrow •shape: spindle-shaped discoid plate •size: 2 – 4 mm •cytoplasm – basophilic (bright violet-blue), contains microtubules and a,d and l granules: • alpha granules – fibrinogen, … • delta granules – serotonin, Ca ions, ATP and ADP,… • lambda granules – are small lysosomes Platelet structure •Hyaloplasm contains microtubules (on the periphery of platelet) • •Granuloplasm contains granules • • Functions of thrombocytes •Platelets assist in haemostasis, the arrest of bleeding. •Serotonin is a vasoconstrictor. Its release from thrombocytes, adhering to the walls of a damaged vessels, is sufficient to close even small arteries. Platelets, which come into contact with collagenous fibers in the walls of the vessel, swell, become "sticky" and activate other platelets to undergo the same transformation. This cascade of events results in the formation of a platelet plug (or platelet thrombus). Finally, activating substances are released from the damaged vessel walls and from the platelets. These substances mediate the conversion of the plasma protein prothrombin into thrombin. Thrombin catalyzes the conversion of fibrinogen into fibrin, which polymerizes into fibrils and forms a fibrous net in the arising blood clot. Platelets captured in the fibrin net contract leading to clot retraction, which further assists in haemostasis. Ly Neu THROMBOCYTES BLOOD PLATELETES Trombocyt (šipky), nutrofilní granulocyt – segment (Neu), lymfocyt (Ly). Nátěr periferní krve, panoptické barvení (Pappenheim), imerze, CZV: 1000X th100le loadBinary loadBinary How to prepare blood smear? • • Blood type test How to prepare blood smear - I •Smears of peripheral blood must be made immediately. •Step 1. Place drop of blood about 1cm from the frosted end of a clean slide. bloodsmear1 How to prepare blood smear - II •Step 2. hold the end of a second slide (“spreader”) against the surface of the first slide at an angle of 30-45 degrees. bloodsmear3 How to prepare blood smear - III •Step 3. draw it back to contact the drop of blood. Allow the blood to spread and fill the angle between the two slides. • bloodsmear4 How to prepare blood smear - IV •Step 4. Push the “spreader” slide at a moderate speed forward until all of the blood has been spread into a moderately thin film. bloodsmear5 How to prepare blood smear - V •prepared smear for fixation (methyl alcohol, 3-5 minutes) and staining (special panoptic method according to Pappenheim can be used) wcd%20PBS%20slide Light microscope manipulation • •DO NOT USE TODAY •Course adjustment knob •ONLY •Fine adjustment knob •YOU CAN USE TODAY • Olympus04B Light microscope manipulation •focuse a picture in LM and look at it with both eyes •regulate a distance between the eyepices so, you can see one focused circular field • • • bad correct • Olympus06.gif (5474 bytes) Light microscope manipulation •Look at the slide only through the right eyepiece and focuse some point in the picture. •Without refocusing, look at the left eyepiece. •In doing so, screw the ring below the left eyepiece to focuse the same point. •So, the dioptric correction is set up. • • • • • • • • • •Now, you can start to study blood •smear in your LM J Olympus07.gif (4519 bytes) Fialová motanina Fialová motanina Fialová motanina 50% Ery 7.4 mm Neu – band Neu – segment Eos 12-14 mm Baso 10 mm 10 – 12 mm Platelet 2 – 4 mm Lymfo 8 mm Mono 15 – 20 mm How to study blood smear in LM? •Lens of immersion objective /magnifying 100x/ is immersed into drop of immersion oil and blood smear is prepared for study. • •Swich on the microscope and check the picture in the microscope. • •If the image is not sharp, focus it using microscrew! If it is not possible, contact your teacher. • How to count leukocytes in blood smear? •blood smear have to be systematicaly viewed (for fear to count some cells several-times) • • • or • • • How to count leukocytes in blood smear? •differential white cell count (DWCC) is an important hematologic sreening which helps to diagnose •leukocytes percentage is the result of this investigation •100 white cells must be count and registered in the table prepared for all types of leukocytes (Neu-bands, Neu-segments, Eos, Baso, Ly, Mono) •arithmetic sum of each type of leukocytes represents their percentage (%) Table 1 2 Neu bands / Neu segments //// // /// Eos / Baso Ly // //// Mono // 10 cells 10 cells 9 10 results norm // 4 % //// / /// 67 % / // 3 % / 1 % / //// 20 % 5 % 10 cells 10 cells 100% 100 % Differential white cell count (DWCC) •Total number of leukocytes: normal values • Neutrophils - bands 4 % - segments 67 % Eosinophils 3 % Basophils 1 % Lymphocytes 20 % Monocytes 5 % ∑ = 100 % remember Anomalies of DWCC • * sum total of bands and segments has to be compared with norm; • normal value is 71 % (4 % bans + 67 % segments) é Increased number ê Decreased number Neutrophils* neutrophil granulocytosis neutrophil granulocytopenia Eosinophils eosinophil granulocytosis eosinophil granulocytopenia Basophils basoophil granulocytosis basoophil granulocytopenia Lymphocytes lymphocytosis lymphocytopenia Monocytes monocytosis monocytopenia Normal ratio of neutrophil bands and segments •(B : S) is 4 % : 68 % = 1 : 17 •Turn to the left – bands are increased •Turn to the right – segments are increased in peripheral blood • • • • turn turn •to the left to the right • • • • • • • • turn turn • to the left to the right B 2S 3S 4S 5S BLOOD Slide Peripheral blood smear, panoptic staining (method of Pappenheim), immersion oil, magnif. 1000x Blood vessels are categorized by function : •Arteries conduct blood away from the heart and have proportionately more smooth muscle and elastic tissue than veins of comparable size. •Arteries are commonly sub-categorized into elastic arteries (the largest one), muscular arteries (middle-sized), and arterioles. •Veins return blood to the heart. •The composition of the wall varies among arteries and veins. Bloodstream organization • arteries arterioles precapillaries capillaries postcapillaries venules veins beating heart animation Structure of blood vessel wall •tunica interna (intima) •endothelium + subendothelial connective tissue •________membrana elastica interna__________ •tunica media •smooth muscle tissue – circularly oriented •________membrana elastica externa__________ •tunica externa (adventitia) •loose connective tissue + nerves + vasa vasorum •(+ longitudinal smooth muscle – only in veins) • •is a specialized form of mesenchyme-derived epithelium •simple squamous epithelium – 1 layer of flattened cells forms a thin, waterproof and antithrombogenic lining of all blood vessels, heart and lymphatic vessels • Endothelium Function of endothelium •the control of blood pressure by vasoconstriction and vasodilation, •blood clotting, •formation of new blood vessels (angiogenesis), •control of the passage of materials and the transit of white blood cells into and out of the blood, •in some organs, there are highly differentiated endothelial cells to perform specialized 'filtering' functions (renal glomerulus in kidney, blood-brain barrier, placental barrier). Zonula occludens lumen Pinocytic vesicles 1 2 Endothelial cells (1,2) Pinocytic vesicles Blood capillaries Blood capillaries •diameter from about 8 µm (to 30-40 µm) •lumen is lined by 1-2 endothelial cell •reticular fibers surround the capillaries •capillary bed between arteries and veins •pericytes • •3 types of capillaries continuous • fenestrated • sinusoids nerve8.jpg (58247 bytes) Function of capillaries (1) •respiratory gasses, nutrients and waste products change between blood and tissues • Function of capillaries (2) •allow the blood cells to pass throughout their wall into the connective tissue (by diapedesis) Neutrophils microphages Eosinophils Basophils mast cells Lymphocytes plasma cells Monocytes macrophages Continuous capillaries • •The smallest: cca 8 mm •The wall: - endothelium – 1-2 cells (zonulae occludentes and nexuses) - lamina basalis - pericytes - reticular fibers •only allow small molecules, water and ions to diffuse Example of occurrence: muscle tisue, brain Fenestrated capillaries •Endothelial cells with fenestra („windows“) 70 nm Æ, diaphragm (thinner than plasma membrane) boards fenestrum •continuous basal lamina •in the organs with quic and intensive metabolism and substances change •allow small molecules and limited amounts of protein to diffuse Exampl of occurrence: intestinal villi, endocrine glands Capillaries with pores •special type of fenestrated capillaries •not fenestra with diaphragm, but opened pores are in endothelium •in glomeruli of renal corpuscles Pores capillary lumen Sinusoidal capillaries (sinusoids) •Æ from 8 to 40 mm • • •endothelium – fenestra, pores and intercellular clefts; some cells are able to phagocyte •incomplete basal lamina •reticular fibers •allow erytrhocytes and serum proteins to enter. Example of occurrence: liver, spleen, bone marrow Stavba srdce a cév - 3 Céva Endothelium Tunica interna Membrana elastica interna Tunica media Tunica externa (Membrana elastica externa) Tunica interna (intima) TI •endothelium •subendothelial connective tissue – thin layer of elastic + collagen fibers (longitudinally oriented) Tunica media TM •consists of smooth muscle cells and elastic membranes in varying proportions (circularly oriented) •is thicker in arteries than in veins • Tunica externa (adventitia) TA •fibrous connective tissue + smooth muscle cells in veins (logitudinally) •is thicker in vein; is the thickest layer in large veins [1] and veins of low limbs [2] •contains vessels and nerves (vasa et nervi vasorum) in large vessels • Stavba srdce a cév - 11 Vena 2 1 media (+ intima) adventitia Compare the wall structure of artery and vein you too can be wealthy you too can be wealthy Arterial part of bloodstream •According to diameter, morphological differences and ratio of elastic fibers and smooth muscle cells: • •Arterioles Æ < 0.5 mm •Muscular arteries (small and middle-sized) • Æ 0.5 – 1 mm •Elastic arteries (large: aorta and arteries • growing from aorta) Arteriole •Æ < 0.5 mm •The wall •TI: endothelium + subendothelium •membrana elastica int. •TM: smooth muscle cells (cca circular 5 layers) •TA: fibrocytes, reticular (+collagen) fibers • Muscular artery •TI: endothelium + subendothelium (with smooth muscle cells (longit.) •membrana elastica int. •TM: up to 40 layers of smooth muscle cells, elastic and collagen fibers •membrana elastica ext. •TA: loose connective tissue „circular“ TM+TA arrangement is spiral, but … Elastic artery •TI: endothelium + subendothelium (100 mm wide layer of connective t.) •TM: up to 40-60 layers of fenestrated elastic membranes, small amount of smooth muscle cells and reticular fibers •TA: loose connective tissue (+ vasa et nervi vasorum) Stavba srdce a cév - 7 Aorta Portal circulation: arterial or venous •two capillary systems side-by-side 1 2 3 capillaries vessel capillaries WHERE? 1: glomerulus eferent arteriole renal tubules capillaries in KIDNEY 2: GIT organs vena portae hepatic sinusoids in LIVER 3: hypothalamus hypophyseal vein adenohypophysis in HYPOPHYSIS Venous part of bloodstream •Venules Æ 0.2 – 1 mm •Small and medium sized veins Æ 1 – 9 mm •Large veins (v. cava inf. et. sup. - the largest vein) • •Valves - pocket-like duplication of endothelium scaffolded by elastic c.t. - protection against venous reccurence Venule •Æ < 0.2 - 1 mm •The wall •TI: endothelium only •TM: smooth muscle cells (cca circular 1-3 layers) •TA: thick layer of loose connective tissue • Vein1.jpg (63203 bytes) Small and medium-sized venules •Æ 1 – 9 mm •TI: endothelium + irregular layer of subendothelium + valves •TM: irregular, thin layer of smooth muscle cells, elastic and collagen fibers •TA: thick layer of loose connective tissue with smooth muscle cells • Stavba srdce a cév - 11 Vena Vein from lower part of body Vein + artery Large veins •TI: endothelium + subendothelium (+smooth muscle cells) •TM: thin layer of connective tissue + reduced amount of smooth muscle cells •TA: longitudinal bundles of smooth muscle cells in loose connective tissue (vasa et nervi vasorum) • Stavba srdce a cév - 13 Vena cava The heart is the hardest working muscle in the human body. • • • • •Hollow muscular organ – blood pump •Rythmic contraction •Involuntary muscle • • • Pericardial sac: pericardium + epicardium PERICARDIUM Outer (parietal) layer EPICARDIUM Inner (visceral) layer Pericardial cavity Pericardial cavity - contains 15 – 50 ml of serous fluid serves as lubricans; - is lined with mesothelium • •Epicardium •Myocardium •Endocardium •------------------- • • The wall of heart Endocardium (homologous to intima of blood vessels) •Consists of: •Endothelium •Subendothelium – thin connective tissue layer •Elastic-muscular layer – dense c.t. (elastic fibers, smooth m. cells) •Subendocardium – c.t. + vessels, nerves and distal part of conducting system (ventricular bundles and Purkinje fibers) • • • Purkinje fibers ¹ Purkinje cells woman doctor writing notes in a chart. black square with neon green jagged reading of a heart monitor animated eye clipart NEXUSES Myocardium •cardiomyocytes „working“ • „conducting“ •cells in right ventricle – natriuretic factor (when intravascular volume increases, this factor is released and causes natriuresis and diuresis in kidney) •atrial myocardium is thinner than ventricular •„left heart“ myocardium is thinner than „right heart“ •cords of cardiomyocytes are ended on heart skeleton •damage of myocardium - infarction •low regeneration of myocardium – by scar (decreases function of heart muscle) Heart skeleton Trigonum fibrosum sin. Trigonum fibrosum dx. Anulus fibrosus sin. Anulus fibrosus dx. Pars membranacea interventricularis Endocardial valves Plates of dense connective tissue (continuous with heart skeleton) covered with endocardium. Epicardium Mesothelium lines pericardial space and so it covers outer surface of epicardium and inner surface of pericardiu mesothelium connective tissue subepicardial c.t. myocardium hearty thanks for your attention Muscular artery • Stavba srdce a cév - 7 Aorta Aorta Stavba srdce a cév - 11 Vena Vein from lower part of body adventitia media intima Stavba srdce a cév - 13 Vena cava intima media adventitia Vena cava Lymphatic vessells •Lymphatic vessels (often just called lymphatics) are channels which drain excess fluid ("lymph") from tissues. •In most peripheral tissues, some plasma seeps out of capillaries. A portion of this is taken back up in venules while the rest drains into terminal lymphatic channels, also called lymphatic capillaries. A shift in the balance between fluid entering and leaving tissues (e.g., increased vascular permeability due to inflammation) can result in accumulation of tissue fluid, or edema. •All lymphatic vessels eventually lead "downstream" to the thoracic duct, which empties into the vena cava (a point where blood pressure is quite low; higher pressure would impede drainage). •Lymphatic vessels resemble blood vessels with exceptionally delicate walls (and, of course, without red blood cells). Smaller lymphatic vessels consist of little more endothelium.