digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

"Vascular" redirects here. For information about plants, see Vascular plant.
Blood vessel
Circulatory System en.svg
Simple diagram of the human circulatory system
Latin vas sanguineum
Anatomical terminology

The blood vessels are the part of the circulatory system that transports blood throughout the human body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from the capillaries back toward the heart. The word vascular, meaning relating to the blood vessels, is derived from the Latin vas, meaning vessel. Avascular refers to being without (blood) vessels.

Structure[edit]

The arteries and veins have three layers, but the middle layer is thicker in the arteries than it is in the veins:

  • Tunica intima (the thinnest layer): a single layer of simple squamous endothelial cells glued by a polysaccharide intercellular matrix, surrounded by a thin layer of subendothelial connective tissue interlaced with a number of circularly arranged elastic bands called the internal elastic lamina.
  • Tunica media (the thickest layer in arteries): circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may (especially in arteries) be rich in vascular smooth muscle, which controls the caliber of the vessel.
  • Tunica adventitia: (the thickest layer in veins) entirely made of connective tissue. It also contains nerves that supply the vessel as well as nutrient capillaries (vasa vasorum) in the larger blood vessels.

Capillaries consist of little more than a layer of endothelium and occasional connective tissue.

When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis (pl. anastomoses). Anastomoses provide critical alternative routes for blood to flow in case of blockages.

There is a layer of muscle surrounding the arteries and the veins which help contract and expand the vessels. This creates enough pressure for blood to be pumped around the body. Blood vessels are part of the circulatory system, together with the heart and the blood.

Diagram of blood vessel structures.

Types[edit]

Blood vessel with an erythrocyte (red blood cell, E) within its lumen, endothelial cells forming its tunica intima (inner layer), and pericytes forming its tunica adventitia (outer layer)

There are various kinds of blood vessels:

They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart. The term "arterial blood" is nevertheless used to indicate blood high in oxygen, although the pulmonary artery carries "venous blood" and blood flowing in the pulmonary vein is rich in oxygen. This is because they are carrying the blood to and from the lungs, respectively, to be oxygenated.

Physiology[edit]

Blood vessels do not actively engage in the transport of blood (they have no appreciable peristalsis), but arteries—and veins to a degree—can regulate their inner diameter by contraction of the muscular layer. This changes the blood flow to downstream organs, and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are also used antagonistically as methods of thermoregulation.

Oxygen (bound to hemoglobin in red blood cells) is the most critical nutrient carried by the blood. In all arteries apart from the pulmonary artery, hemoglobin is highly saturated (95-100%) with oxygen. In all veins apart from the pulmonary vein, the hemoglobin is desaturated at about 75%. (The values are reversed in the pulmonary circulation.)

The blood pressure in blood vessels is traditionally expressed in millimetres of mercury (1 mmHg = 133 Pa). In the arterial system, this is usually around 120 mmHg systolic (high pressure wave due to contraction of the heart) and 80 mmHg diastolic (low pressure wave). In contrast, pressures in the venous system are constant and rarely exceed 10 mmHg.

Vasoconstriction is the constriction of blood vessels (narrowing, becoming smaller in cross-sectional area) by contracting the vascular smooth muscle in the vessel walls. It is regulated by vasoconstrictors (agents that cause vasoconstriction). These include paracrine factors (e.g. prostaglandins), a number of hormones (e.g. vasopressin and angiotensin) and neurotransmitters (e.g. epinephrine) from the nervous system.

Vasodilation is a similar process mediated by antagonistically acting mediators. The most prominent vasodilator is nitric oxide (termed endothelium-derived relaxing factor for this reason).

Permeability of the endothelium is pivotal in the release of nutrients to the tissue. It is also increased in inflammation in response to histamine, prostaglandins and interleukins, which leads to most of the symptoms of inflammation (swelling, redness, warmth and pain).

Disease[edit]

Main article: Vascular disease

Blood vessels play a huge role in virtually every medical condition. Cancer, for example, cannot progress unless the tumor causes angiogenesis (formation of new blood vessels) to supply the malignant cells' metabolic demand. Atherosclerosis, the formation of lipid lumps (atheromas) in the blood vessel wall, is the most common cardiovascular disease, the main cause of death in the Western world.

Blood vessel permeability is increased in inflammation. Damage, due to trauma or spontaneously, may lead to hemorrhage due to mechanical damage to the vessel endothelium. In contrast, occlusion of the blood vessel by atherosclerotic plaque, by an embolised blood clot or a foreign body leads to downstream ischemia (insufficient blood supply) and possibly necrosis. Vessel occlusion tends to be a positive feedback system; an occluded vessel creates eddies in the normally laminar flow or plug flow blood currents. These eddies create abnormal fluid velocity gradients which push blood elements such as cholesterol or chylomicron bodies to the endothelium. These deposit onto the arterial walls which are already partially occluded and build upon the blockage.[1]

Vasculitis is inflammation of the vessel wall, due to autoimmune disease or infection.

References[edit]

  1. ^ Multiphase Flow and Fluidization, Gidaspow et al., Academic Press, 1992

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Blood_vessel — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
937618 videos foundNext > 

Blood Vessel Lecture

Human Blood Vessels Anatomy

Recorded on November 5, 2009 using a Flip Video camcorder. South Central College Instructor: Toby Leonard For: Human Anatomy Class (Biology 220)

Types of Blood Vessels

This video describes the types of blood vessels and explains how they function in the body. For videos and more check out http://www.emedtv.com/.

8.7.2 Blood Vessel Structure and Function

http://braingenie.com/

Layers of a blood vessel

Remember the 3 key layers of a blood vessel (Tunica intima, Tunica media, and Tunica externa) and how arteries, veins, and capillaries are all different from...

Mosquito finds blood vessel

Capillary feeding by Anopheles gambiae. The proboscis is inserted along the lumen of the blood vessel. Credit: Choumet et al, PLOS 2012.

Blood Vessel Physiology: Overview of Primary Concepts

Visit: http://www.uctv.tv/) Arteries, veins, capillaries. Dr. Igor Mitrovic, Department of Physiology UCSF, explores the primary concepts and functions of t...

Blood Vessels And Their Functions

Blood Vessels and Their Functions.

Rep Rap 3D Printing Blood Vessel Networks

Bioengineers have been steadily advancing toward the goal of building lab-grown organs out of a patient's own cells, but a few major challenges remain. One o...

Red blood cells in a blood vessel in Blender 3D and Cycles tutorial, with subs

TEXT VERSION: http://www.cg-village.com/blender-3d-tutorials/48-blender-3d-cycles-tutorial-red-blood-cells-in-a-blood-vessel-with-subs.html === Hi everybody,...

937618 videos foundNext > 

1303 news items

Telegraph.co.uk

Telegraph.co.uk
Sun, 10 Aug 2014 13:04:37 -0700

A blood vessel-creating gene that could be used to combat cancer, heart disease and strokes has been identified by scientists. Piezo1, as the gene is called, allows new blood vessel networks to grow in response to changes in blood flow. Researchers say ...

MesotheliomaHelp.net (blog)

MesotheliomaHelp.net (blog)
Thu, 21 Aug 2014 00:07:30 -0700

Blood vessel networks are not already pre-constructed but emerge rather like a river system,” said Professor David Beech, of the School of Medicine at the University of Leeds, who led the research, in the press release announcing the discovery ...

Medical Daily

Medical Daily
Sun, 10 Aug 2014 09:52:30 -0700

Stem cell infusions may help promote healing in damaged brain of stroke victims. Photo courtesy of Shutterstock. Stroke patients suffer immensely. Even after their initial brain trauma they have a long road to recovery, but new stem cell research may ...

Headlines & Global News

Headlines & Global News
Sun, 27 Jul 2014 15:07:30 -0700

The study, published in a recent edition of the journal Nature, showed a molecule called focal adhesion kinase (FAK) signals the body to repair itself after chemotherapy or radiotherapy, Cancer Research U.K. reported. The Barts Cancer Institute ...
 
HealthCanal.com
Thu, 31 Jul 2014 14:22:30 -0700

As researchers have zeroed in on the characteristics of a healthy endothelium, nitric oxide has emerged as the hero. It keeps platelets from clotting, prevents inflammation and broadly regulates "blood vessel's essential missions," says Romer. But if ...
 
Xconomy
Thu, 21 Aug 2014 09:30:00 -0700

This year about 20 million patients in the U.S. will undergo a procedure in which a doctor will thread a catheter into a blood vessel to treat a cardiac ailment, say, or provide dialysis or chemotherapy. But in five percent of these “vascular-access ...
 
Nature.com
Wed, 20 Aug 2014 10:21:49 -0700

Studies in different vertebrate models have shown that these precursors, called haematopoietic stem cells, originate at least in part from the first functional intra-embryonic blood vessel, the dorsal aorta. However, the cell types and signalling ...

PBS NewsHour

PBS NewsHour
Thu, 21 Aug 2014 07:25:13 -0700

This triggers the uncontrollable bleeding for which Ebola is known, though it only happens for about 50 percent of patients and occurs mostly inside the body. In fatal cases, blood pressure plummets after blood vessel damage, and death from shock or ...
Loading

Oops, we seem to be having trouble contacting Twitter

Talk About Blood vessel

You can talk about Blood vessel with people all over the world in our discussions.

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!