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Blood Vessels, part 1 - Form and Function: Crash Course A&P #27
Blood Vessels, part 1 - Form and Function: Crash Course A&P #27
Published: 2015/07/20
Channel: CrashCourse
Blood Vessel Lecture
Blood Vessel Lecture
Published: 2012/06/23
Channel: Morley603
POPPED A BLOOD VESSEL! IM NEVER PLAYING WITH A BROWN SHIRT AGAIN! NBA 2k18 Playground
POPPED A BLOOD VESSEL! IM NEVER PLAYING WITH A BROWN SHIRT AGAIN! NBA 2k18 Playground
Published: 2017/09/17
Channel: CashNasty
8.7.2 Blood Vessel Structure and Function
8.7.2 Blood Vessel Structure and Function
Published: 2011/08/26
Channel: braingenie
Broken Vessels (Amazing Grace) [Official Lyric Video] - Hillsong Worship
Broken Vessels (Amazing Grace) [Official Lyric Video] - Hillsong Worship
Published: 2014/08/15
Channel: Hillsong Worship
Layers of a blood vessel | Circulatory system physiology | NCLEX-RN | Khan Academy
Layers of a blood vessel | Circulatory system physiology | NCLEX-RN | Khan Academy
Published: 2012/09/13
Channel: khanacademymedicine
Types of Blood Vessels
Types of Blood Vessels
Published: 2009/08/12
Channel: eMedTV
Anatomy and Physiology of Blood Vessels
Anatomy and Physiology of Blood Vessels
Published: 2015/11/23
Channel: New Anatomy and Physiology Video
Blood Vessel Man Model
Blood Vessel Man Model
Published: 2012/11/14
Channel: Meeko Carrillo
The Heart and Major Vessels - PART 1 - Anatomy Tutorial
The Heart and Major Vessels - PART 1 - Anatomy Tutorial
Published: 2011/11/15
Channel: AnatomyZone
Blood Vessels
Blood Vessels
Published: 2015/01/14
Channel: Robert Baker
Family Guy - Stewie breaks a blood vessel
Family Guy - Stewie breaks a blood vessel
Published: 2010/04/16
Channel: SpliffdeBrownsville
Blood Vessels, part 2: Crash Course A&P #28
Blood Vessels, part 2: Crash Course A&P #28
Published: 2015/07/27
Channel: CrashCourse
Fetal Pig Blood Vessels
Fetal Pig Blood Vessels
Published: 2013/07/23
Channel: Mark Eberle
Heart and Blood vessel
Heart and Blood vessel
Published: 2009/10/31
Channel: beyondmedic
Human Blood Vessels Anatomy
Human Blood Vessels Anatomy
Published: 2009/11/06
Channel: mommyime Sprute
Layers of a blood vessel
Layers of a blood vessel
Published: 2012/09/10
Channel: Khan Academy
Arteries, Arterioles, Venules, and Veins
Arteries, Arterioles, Venules, and Veins
Published: 2013/03/16
Channel: khanacademymedicine
10 Suprfoods To Clean Your Blood Vessels(Artery) Naturally | Educational  Health Tips
10 Suprfoods To Clean Your Blood Vessels(Artery) Naturally | Educational Health Tips
Published: 2015/06/02
Channel: Freez Frame Films
THE BLOOD VESSEL Strikes Again!!
THE BLOOD VESSEL Strikes Again!!
Published: 2017/02/17
Channel: Tim Wells Bow Hunter
3D Blood Vessel Flow
3D Blood Vessel Flow
Published: 2014/12/23
Channel: Muhammad ElHadidi
Anatomy and Physiology 232 Lab - Blood Vessel Practical
Anatomy and Physiology 232 Lab - Blood Vessel Practical
Published: 2014/05/20
Channel: Amie Duff
27 Days Healing Time Lapse: Broken Blood Vessel in Eye (Subconjunctival Hemorrhage)
27 Days Healing Time Lapse: Broken Blood Vessel in Eye (Subconjunctival Hemorrhage)
Published: 2014/09/09
Channel: Wen Lim
Mosquito Finds Blood Vessel
Mosquito Finds Blood Vessel
Published: 2016/03/03
Channel: ONE WORLD
Blood Vessel Histology Model
Blood Vessel Histology Model
Published: 2014/09/10
Channel: Dr. Elizabeth Granier, St. Louis Community College
Mosquito finds blood vessel
Mosquito finds blood vessel
Published: 2013/08/06
Channel: edyong209
How to Improve Blood Circulation - This Drink will Clean Your Blood Vessels
How to Improve Blood Circulation - This Drink will Clean Your Blood Vessels
Published: 2017/04/23
Channel: Natural Life Hacks
Blood Vessels Development Animation
Blood Vessels Development Animation
Published: 2014/03/08
Channel: anas abuassi
Blood Vessels – Arteries and Veins
Blood Vessels – Arteries and Veins
Published: 2015/06/13
Channel: Flexiguru
Angiogenesis   Formation of new blood vessels
Angiogenesis Formation of new blood vessels
Published: 2016/07/06
Channel: Hoffman Dental
Blood Vessels- Life Processes 2 Class 10 Science I Class X Science
Blood Vessels- Life Processes 2 Class 10 Science I Class X Science
Published: 2014/08/18
Channel: Dronstudy.com
Chapter 19 Blood Vessels Part 1
Chapter 19 Blood Vessels Part 1
Published: 2014/07/03
Channel: Chet Cooper
Blood Vessel Model
Blood Vessel Model
Published: 2014/12/09
Channel: Mr B's Anatomy
3D Printed Blood Vessels
3D Printed Blood Vessels
Published: 2014/06/03
Channel: GeoBeats News
Argh I Broke A Damn Blood Vessel
Argh I Broke A Damn Blood Vessel
Published: 2010/07/18
Channel: Mike Usher
Buster Bloodvessel and Bad Manners.
Buster Bloodvessel and Bad Manners.
Published: 2015/09/01
Channel: Simon Baldock
blood vessels - medical technology
blood vessels - medical technology
Published: 2011/11/23
Channel: Roman Konyzhev
Blood Vessel Elasticity
Blood Vessel Elasticity
Published: 2012/10/22
Channel: Craig Koniver, MD
Blood Vessel Lecture part 1 Dr. Parker
Blood Vessel Lecture part 1 Dr. Parker's A&P II
Published: 2013/11/05
Channel: Mandi Parker
3D-printed Blood Vessel Working Well in Monkey Trial
3D-printed Blood Vessel Working Well in Monkey Trial
Published: 2016/12/09
Channel: CCTV+
Lymphatic and Blood Vessels – Vascular Medicine (Angiology) | Medical Education Videos
Lymphatic and Blood Vessels – Vascular Medicine (Angiology) | Medical Education Videos
Published: 2015/08/27
Channel: Lecturio Medical Videos
Blood Vessels, Arteries in Urdu   Sabaq Foundation
Blood Vessels, Arteries in Urdu Sabaq Foundation
Published: 2017/01/28
Channel: himayat ullah
Nanobots Flowing Through a Blood Vessel
Nanobots Flowing Through a Blood Vessel
Published: 2007/05/20
Channel: CG4TV
Blood Vessels : Blood Vessel Reaction to Heat
Blood Vessels : Blood Vessel Reaction to Heat
Published: 2009/02/21
Channel: ehowhealth
Anatomy and Physiology Lab: Blood Vessels Part 1: Arteries
Anatomy and Physiology Lab: Blood Vessels Part 1: Arteries
Published: 2015/02/21
Channel: TeachMeAandP
Blood Vessels and Nerves of the Leg
Blood Vessels and Nerves of the Leg
Published: 2008/11/14
Channel: lochness128
Cardiovascular System, Heart and major blood vessels
Cardiovascular System, Heart and major blood vessels
Published: 2015/12/21
Channel: Dr. John Campbell
stewie pops a blood vessel
stewie pops a blood vessel
Published: 2009/08/10
Channel: brianshimafan4ever
Breast cancer cell invades artificial blood vessel
Breast cancer cell invades artificial blood vessel
Published: 2014/11/05
Channel: INBT Johns Hopkins
Lower Limb Blood Vessels
Lower Limb Blood Vessels
Published: 2014/09/30
Channel: David Bastedo
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WIKIPEDIA ARTICLE

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Blood vessel
Circulatory System en.svg
Simple diagram of the human circulatory system
Details
Identifiers
Latin vas sanguineum
TA A12.0.00.001
FMA 63183
Anatomical terminology

The blood vessels are the part of the circulatory system, and microcirculation, that transports blood throughout the human body.[1] 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. A few structures (such as cartilage and the lens of the eye) do not contain blood vessels and are labeled.

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. Veins don't have the external elastic lamina, but only an internal one.
  • 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).

Factors affecting blood flow resistance[edit]

Vascular resistance occurs where the vessels away from the heart oppose the flow of blood. Resistance is an accumulation of three different factors: blood viscosity, blood vessel length, and vessel radius.[2]

Blood viscosity is the thickness of the blood and its resistance to flow as a result of the different components of the blood. Blood is 92% water by weight and the rest of blood is composed of protein, nutrients, electrolytes, wastes, and dissolved gases. Depending on the health of an individual, the blood viscosity can vary (i.e. anemia causing relatively lower concentrations of protein, high blood pressure an increase in dissolved salts or lipids, etc.).[2]

Vessel length is the total length of the vessel measured as the distance away from the heart. As the total length of the vessel increases, the total resistance as a result of friction will increase.[2]

Vessel radius also affects the total resistance as a result of contact with the vessel wall. As the radius of the wall gets smaller, the proportion of the blood making contact with the wall will increase. The greater amount of contact with the wall will increase the total resistance against the blood flow.[3]

Disease[edit]

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.[4]

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.[5]

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

References[edit]

  1. ^ "Blood Vessels - Heart and Blood Vessel Disorders - Merck Manuals Consumer Version". Merck Manuals Consumer Version. Retrieved 2016-12-22. 
  2. ^ a b c Anatomy Physiology: The Unity of Form and Function, Saladin, McGraw Hill, 2012
  3. ^ "Factors that Affect Blood Pressure" (PDF). Retrieved 6 Dec 2014. 
  4. ^ "Nerves and blood vessels". 420evaluationsonline. Retrieved 2 August 2016. 
  5. ^ Multiphase Flow and Fluidization, Gidaspow et al., Academic Press, 1992

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