The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away from the tissues. Blood vessels are needed to sustain life, because all of the body's tissues rely on their functionality.
A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter, and having a wall one endothelial cell thick. They are the smallest blood vessels in the body: they convey blood between the arterioles and venules. These microvessels are the site of exchange of many substances with the interstitial fluid surrounding them. Substances which exit include water, oxygen, and glucose; substances which enter include water, carbon dioxide, uric acid, lactic acid, urea and creatinine. Lymph capillaries connect with larger lymph vessels to drain lymphatic fluid collected in the microcirculation.
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature by processes of sprouting and splitting. Vasculogenesis is the embryonic formation of endothelial cells from mesoderm cell precursors, and from neovascularization, although discussions are not always precise. The first vessels in the developing embryo form through vasculogenesis, after which angiogenesis is responsible for most, if not all, blood vessel growth during development and in disease.
Endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels, and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. Endothelial cells form the barrier between vessels and tissue and control the flow of substances and fluid into and out of a tissue.
Cherry angiomas, also known as Campbell de Morgan spots or senile angiomas, are cherry red papules on the skin. They are a harmless benign tumour, containing an abnormal proliferation of blood vessels, and have no relationship to cancer. They are the most common kind of angioma, and increase with age, occurring in nearly all adults over 30 years.
Pericytes are multi-functional mural cells of the microcirculation that wrap around the endothelial cells that line the capillaries and venules throughout the body. Pericytes are embedded in basement membrane, where they communicate with endothelial cells of the body's smallest blood vessels by means of both direct physical contact and paracrine signaling. Pericytes help to maintain homeostatic and hemostatic functions in the brain and also sustain the blood–brain barrier. These cells are also a key component of the neurovascular unit, which includes endothelial cells, astrocytes, and neurons. Pericytes regulate capillary blood flow, the clearance and phagocytosis of cellular debris, and the permeability of the blood–brain barrier. Pericytes stabilize and monitor the maturation of endothelial cells by means of direct communication between the cell membrane as well as through paracrine signaling. A deficiency of pericytes in the central nervous system can cause the blood–brain barrier to break down.
Vascular endothelial growth factor (VEGF), originally known as vascular permeability factor (VPF), is a signal protein produced by cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors, the platelet-derived growth factor family of cystine-knot growth factors. They are important signaling proteins involved in both vasculogenesis and angiogenesis.
Granulation tissue is new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size. Examples of granulation tissue can be seen in pyogenic granulomas and pulp polyps. Its histological appearance is characterized by proliferation of fibroblasts and new thin-walled, delicate capillaries (angiogenesis), infiltrated inflammatory cells in a loose extracellular matrix.
Vasculogenesis is the process of blood vessel formation in the embryo, occurring by a de novo production of endothelial cells. It is sometimes paired with angiogenesis, as the first stage of the formation of the vascular network, closely followed by angiogenesis.
Arteriogenesis refers to an increase in the diameter of existing arterial vessels.
Intussusceptive angiogenesis also known as splitting angiogenesis, is a type of angiogenesis, the process whereby a new blood vessel is created. By intussusception a new blood vessel is created by splitting of an existing blood vessel in two. Intussusception occurs in normal development as well as in pathologic conditions involving wound healing, tissue regeneration, inflammation as colitis or myocarditis, lung fibrosis, and tumors amongst others.
Neovascularization is the natural formation of new blood vessels, usually in the form of functional microvascular networks, capable of perfusion by red blood cells, that form to serve as collateral circulation in response to local poor perfusion or ischemia.
Cytochalasin E, a member of the cytochalasin group, is an inhibitor of actin polymerization in blood platelets. It inhibits angiogenesis and tumor growth. Unlike cytochalasin A and cytochalasin B, it does not inhibit glucose transport.
A cartilage-derived angiogenesis inhibitor is an angiogenesis inhibitor produced from cartilage. Examples include the peptide troponin I and chondromodulin I. The antiangiogenic effect may be an inhibition of basement membrane degradation.
Vascular endothelial growth factor A (VEGF-A) is a protein that in humans is encoded by the VEGFA gene.
Angiogenesis is the process of forming new blood vessels from existing blood vessels. It is a highly complex process involving extensive interplay between cells, soluble factors, and the extracellular matrix (ECM). Angiogenesis is critical during normal physiological development, but it also occurs in adults during inflammation, wound healing, ischemia, and in pathological conditions such as rheumatoid arthritis, hemangioma, and tumor growth. Proteolysis has been indicated as one of the first and most sustained activities involved in the formation of new blood vessels. Numerous proteases including matrix metalloproteases (MMPs), a disintegrin and metalloprotease domain (ADAM), a disintegrin and metalloprotease domain with throbospondin motifs (ADAMTS), and cysteine and serine proteases are involved in angiogenesis. This article focuses on the important and diverse roles that these proteases play in the regulation of angiogenesis.
Remodeling is the process of improving a building.
HP59 is a pathologic angiogenesis capillary endothelial marker protein which has been identified as the receptor for the Group B Streptococcal Toxin molecule known as CM101, the etiologic agent for early-onset versus late-onset Group B Strep.
Vascular remodelling is a process which begins usually at day 22, and continues to around the tenth week of human embryogenesis, when, on day 22, an immature heart begins contracting, pushing fluid through the early vasculature. This first passage of fluid initiates a signal cascade and cell movement based on physical cues including shear stress and circumferential stress, which is necessary for the remodelling of the vascular network, arterial-venous identity, angiogenesis, and the regulation of genes through mechanotransduction. This embryonic process is necessary for the future stability of the mature vascular network.
Neuroangiogenesis is the coordinated growth of nerves and blood vessels. The nervous and blood vessel systems share guidance cues and cell-surface receptors allowing for this synchronised growth. The term neuroangiogenesis only came into use in 2002 and the process was previously known as neurovascular patterning. The combination of neurogenesis and angiogenesis is an essential part of embryonic development and early life. It is thought to have a role in pathologies such as endometriosis, brain tumors, and Alzheimer's disease.
