An artery is a blood vessel in humans, and most other animals that takes blood away from the heart to one or more parts of the body. Most arteries carry oxygenated blood; the two exceptions are the pulmonary and the umbilical arteries, which carry deoxygenated blood to the organs that oxygenate it. The effective arterial blood volume is that extracellular fluid which fills the arterial system.
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.
Veins are blood vessels in humans, and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. In contrast to veins, arteries carry blood away from the heart.
A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. 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 cross capillaries include water, oxygen, carbon dioxide, urea, glucose, uric acid, lactic acid and creatinine. Lymph capillaries connect with larger lymph vessels to drain lymphatic fluid collected in the microcirculation.
The portal vein or hepatic portal vein (HPV) is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents. Approximately 75% of total liver blood flow is through the portal vein, with the remainder coming from the hepatic artery proper. The blood leaves the liver to the heart in the hepatic veins.
Hypertensive retinopathy is damage to the retina and retinal circulation due to high blood pressure.
Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously monitors and adjusts to conditions in the body and its environment. Hemodynamics explains the physical laws that govern the flow of blood in the blood vessels.
The microcirculation is the circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within organ tissues. The microvessels include terminal arterioles, metarterioles, capillaries, and venules. Arterioles carry oxygenated blood to the capillaries, and blood flows out of the capillaries through venules into veins.
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.
A venule is a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to drain into the larger blood vessels, the veins. Venules range from 7μm to 1mm in diameter. Veins contain approximately 70% of total blood volume, 25% of which is contained in the venules. Many venules unite to form a vein.
The glomerulus is a network of small blood vessels (capillaries) known as a tuft, located at the beginning of a nephron in the kidney. Each of the two kidneys contains about one million nephrons. The tuft is structurally supported by the mesangium, composed of intraglomerular mesangial cells. The blood is filtered across the capillary walls of this tuft through the glomerular filtration barrier, which yields its filtrate of water and soluble substances to a cup-like sac known as Bowman's capsule. The filtrate then enters the renal tubule of the nephron.
The conjunctiva is a tissue that lines the inside of the eyelids and covers the sclera. It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epithelium and stratified cuboidal epithelium. The conjunctiva is highly vascularised, with many microvessels easily accessible for imaging studies.
The renal circulation supplies the blood to the kidneys via the renal arteries, left and right, which branch directly from the abdominal aorta. Despite their relatively small size, the kidneys receive approximately 20% of the cardiac output.
The vasa recta of the kidney, are the straight arterioles, and the straight venules of the kidney, – a series of blood vessels in the blood supply of the kidney that enter the medulla as the straight arterioles, and leave the medulla to ascend to the cortex as the straight venules.. They lie parallel to the loop of Henle.
Congestive hepatopathy, is liver dysfunction due to venous congestion, usually due to congestive heart failure. The gross pathological appearance of a liver affected by chronic passive congestion is "speckled" like a grated nutmeg kernel; the dark spots represent the dilated and congested hepatic venules and small hepatic veins. The paler areas are unaffected surrounding liver tissue. When severe and longstanding, hepatic congestion can lead to fibrosis; if congestion is due to right heart failure, it is called cardiac cirrhosis.
The lobules of liver, or hepatic lobules, are small divisions of the liver defined at the microscopic (histological) scale. The hepatic lobule is a building block of the liver tissue, consisting of a portal triad, hepatocytes arranged in linear cords between a capillary network, and a central vein.
Cerebral vasculitis is vasculitis involving the brain and occasionally the spinal cord. It affects all of the vessels: very small blood vessels (capillaries), medium-size blood vessels, or large blood vessels. If blood flow in a vessel with vasculitis is reduced or stopped, the parts of the body that receive blood from that vessel begins to die. It may produce a wide range of neurological symptoms, such as headache, skin rashes, feeling very tired, joint pains, difficulty moving or coordinating part of the body, changes in sensation, and alterations in perception, thought or behavior, as well as the phenomena of a mass lesion in the brain leading to coma and herniation. Some of its signs and symptoms may resemble multiple sclerosis. 10% have associated bleeding in the brain.
Salus's sign is a clinical sign in which deflection of retinal venules can be seen on fundoscopy occurring in patients with hypertensive retinopathy. Arteriosclerosis causes shortening or lengthening of arterioles, which causes venules to be moved at points where arterioles and venules cross over. This is seen at right-angle crossing points, where the venule crosses the arteriole in a horseshoe shape.
The internal elastic lamina or internal elastic lamella is a layer of elastic tissue that forms the outermost part of the tunica intima of blood vessels. It separates tunica intima from tunica media.
Sickle cell retinopathy can be defined as retinal changes due to blood vessel damage in the eye of a person with a background of sickle cell disease. It can likely progress to loss of vision in late stages due to vitreous hemorrhage or retinal detachment. Sickle cell disease is a structural red blood cell disorder leading to consequences in multiple systems. It is characterized by chronic red blood cell destruction, vascular injury, and tissue ischemia causing damage to the brain, eyes, heart, lungs, kidneys, spleen, and musculoskeletal system.
