Examples of endothelial cells in the following topics:
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- Venule walls have three layers: an inner endothelium composed of squamous endothelial cells that act as a membrane, a middle layer of muscle and elastic tissue, and an outer layer of fibrous connective tissue.
- Venules are extremely porous so that fluid and blood cells can move easily from the bloodstream through their walls.
- In contrast to regular venules, high-endothelial venules (HEV) are specialized post-capillary venous swellings.
- They are characterized by plump endothelial cells as opposed to the usual thinner endothelial cells found in regular venules.
- HEVs enable lymphocytes (white blood cells) circulating in the blood to directly enter a lymph node by crossing through the HEV.
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- New blood vessels are formed from endothelial stem cells, which give rise to the endothelial cells which line the vessels.
- Endothelial stem cells (ESCs) are one of three types of stem cells found in bone marrow.
- These parent stem cells, ESCs, give rise to endothelial progenitor cells (EPCs), which are intermediate stem cells that lose potency.
- ESCs will eventually produce endothelial cells (ECs), which create the thin-walled endothelium that lines the inner surface of blood vessels and lymphatic vessels.
- The former requires differentiation of endothelial cells from hemangioblasts and then the further organization into a primary capillary network.
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- Substances are transported through the endothelial cells themselves within vesicles.
- The substance to be transported is endocytosed by the endothelial cell into a lipid vesicle which moves through the cell and is then exocytosed to the other side.
- Listeria monocytogenes has been shown to enter the intestinal lumen via transcytosis across goblet cells.
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- The BBB results from the selectivity of the tight junctions between endothelial cells in CNS vessels that restrict the passage of solutes.
- At the interface between blood and the brain, endothelial cells are joined by these tight junctions, which are composed of smaller subunits, frequently biochemical dimers that are transmembrane proteins such as occludin, claudins, and junctional adhesion molecule.
- Each of these transmembrane proteins is anchored into the endothelial cells by another protein complex.
- This barrier also includes a thick basement membrane
and
astrocyte cell projections called astrocytic feet (forming the thin barrier called the glia
limitans) that surround the
endothelial cells of the BBB, providing biochemical support to those cells.
- The BBB endothelial cells restrict the passage of substances from the
bloodstream to a greater extent than endothelial cells in capillaries elsewhere in the
body.
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- Vasculogenesis is the process of blood vessel formation occurring by new production of endothelial cells.
- For example, if a monolayer of endothelial cells begins sprouting to form capillaries, angiogenesis is occurring.
- Vasculogenesis, in contrast, is when endothelial precursor cells (angioblasts) migrate and differentiate in response to local cues (such as growth factors and extracellular matrix) to form new blood vessels.
- Blood vessel with an erythrocyte (red blood cell) within its lumen, endothelial cells forming its tunica intima or inner layer, and pericytes forming its tunica adventitia (outer layer).
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- Capillaries, which form part of the micro-circulation, are the smallest of the body's blood vessels at between 5-10
μm in diameter with the endothelial vessel wall of only one cell thick.
- During embryological development, new capillaries are formed by vasculogenesis, the process of blood vessel formation occurring by de novo production of endothelial cells and their formation into vascular tubes.
- Continuous - Endothelial cells provide an uninterrupted lining, only allowing small molecules like water and ions to diffuse through tight junctions.
- Fenestrated - Fenestrated capillaries have pores in the endothelial cells (60-80 nanometers in diameter) that are spanned by a diaphragm of radially-oriented fibrils.
- Capillaries are of small diameter with the vessel wall being a single cell thick.
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- The endothelial cells of intact vessels prevent clotting by expressing a fibrinolytic heparin molecule and thrombomodulin, which prevents platelet aggregation and stops the coagulation cascade with nitric oxide and prostacyclin.
- When endothelial injury occurs, the endothelial cells stop secretion of coagulation and aggregation inhibitors and instead secrete von Willebrand factor, which causes platelet adherence during the initial formation of a clot.
- When the lining of a blood vessel breaks and endothelial cells are damaged, revealing subendothelial collagen proteins from the extracellular matrix, thromboxane causes platelets to swell, grow filaments, and start clumping together, or aggregating.
- Blood vessel with an erythrocyte (red blood cell) within its lumen, endothelial cells forming its tunica intima or inner layer, and pericytes forming its tunica adventitia (outer layer).
- Microvessel showing an erythrocyte (E), a tunica intima of endothelial cells, and a tunica adventitia of pericytes.
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- Structures called "blood islands" form in the yolk sac of an embryo by cellular differentiation of hemangioblasts into endothelial cells.
- Next, the capillary plexus forms as endothelial cells migrate outward from blood islands and form a random network of continuous strands.
- These strands then undergo a process called "lumenization," the spontaneous rearrangement of endothelial cells from a solid cord into a hollow tube.
- Angiogenesis also contributes to the complexity of the initial network; endothelial buds form by an extrusion-like process which is prompted by the expression of vascular endothelial growth factor (VEGF).
- These endothelial buds grow away from the parent vessel to form smaller, daughter vessels reaching into new territory.
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- Normally, the endothelial cells express molecules that inhibit platelet adherence and activation while platelets circulate through the blood vessels.
- These molecules include nitric oxide, prostacylcine (PGI2) and endothelial ADP-ase.
- During an injury, subendothelial collagen from the extracellular matrix beneath the endothelial cells is exposed on the epithelium as the normal epithelial cells are damaged and removed, which releases von Willebrand Factor (VWF).
- VWF causes the platelets to change form with adhesive filaments (extensions) that adhere to the subendothelial collagen on the endothelial wall.
- PDGF and VEGF are involved in angiogenesis, the growth of new blood vessels and cell cycle proliferation (division) following injury.
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- Blood is composed of plasma and three types of cells: red blood cells, white blood cells, and platelets.
- RBCs, endothelial vessel cells, and other blood cells are also marked by glycoproteins that define the different blood types.
- There are several different types of white blood cells: basophils, eosinophils, neutrophils, monocytes, natural killer cells, B- and T-cell lymphocytes, macrophages, and dendritic cells, all of which perform distinct functions.
- They result from fragmentation of large cells called megakaryocytes, which are derived from stem cells in the bone marrow.
- The sticky surface of platelets allows them to accumulate at the site of broken blood vessels to form a clot, due in part to the release of clotting factors that occurs during endothelial injury to blood vessels.