Blood vessel - wikipedia Blood vessel `` Vascular '' redirects here. For information about plants, see Vascular plant. Blood vessel Simple diagram of the human circulatory system Details Identifiers Latin vas sanguineum TA A12. 0.00. 001 FMA 63183 Anatomical terminology ( edit on Wikidata ) The blood vessels are the part of the circulatory system, and microcirculation, 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. A few structures ( such as cartilage and the lens of the eye ) do not contain blood vessels and are labeled. Contents 1 Structure 1.1 Types 2 Physiology 2.1 Factors affecting blood flow resistance 3 Disease 4 References Structure 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 do n'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. Types 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 : Arteries Elastic arteries Distributing arteries Arterioles Capillaries ( the smallest blood vessels ) Venules Veins Large collecting vessels, such as the subclavian vein, the jugular vein, the renal vein and the iliac vein. Venae cavae ( the two largest veins, carry blood into the heart ). 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 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 Main article : Vascular resistance 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. 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. ). 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. 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. Disease Main article : Vascular disease Blood vessels play a huge role in virtually every medical condition. Cancer, for example, can not 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. Vasculitis is inflammation of the vessel wall, due to autoimmune disease or infection. References Jump up ^ `` Blood Vessels -- Heart and Blood Vessel Disorders -- Merck Manuals Consumer Version ''. Merck Manuals Consumer Version. Retrieved 2016 - 12 - 22. ^ Jump up to : Anatomy Physiology : The Unity of Form and Function, Saladin, McGraw Hill, 2012 Jump up ^ `` Factors that Affect Blood Pressure '' ( PDF ). Retrieved 6 Dec 2014. Jump up ^ `` Nerves and blood vessels ''. 420evaluationsonline. Retrieved 2 August 2016. Jump up ^ Multiphase Flow and Fluidization, Gidaspow et al., Academic Press, 1992 Arteries and veins Vessels Arteries Nutrient artery Arteriole Metarteriole Capillaries Types Continuous Fenestrated Sinusoidal Precapillary sphincter Precapillary resistance Veins Vena comitans Superficial vein Deep vein Emissary veins Venous plexus Venule Lymph Lymphatic vessel Lymph Lymph capillary Circulatory system Systemic Left heart → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava → ( Right heart ) Pulmonary Right heart → Pulmonary arteries → Lungs → Pulmonary vein → Left heart Microanatomy Tunica intima Endothelium Internal elastic lamina Tunica media Tunica externa Vasa vasorum Vasa nervorum Vascular nerves Rete mirabile Circulatory anastomosis Arteries in the human body Arteries of the head and neck CC EC sup. thyroid superior laryngeal sternocleidomastoid branch infrahyoid branch cricothyroid branch glandular branches asc. pharyngeal posterior meningeal pharyngeal branches inferior tympanic lingual suprahyoid dorsal lingual deep lingual sublingual facial cervical branches ( ascending palatine, tonsillar, submental, glandular ) facial branches ( inferior labial superior labial / nasal septum lateral nasal angular ) occipital sternocleidomastoid meningeal occipital auricular descending post. auricular stylomastoid stapedial auricular occipital Parotid sup. temporal transverse facial middle temporal ( zygomatico - orbital ) anterior auricular frontal parietal maxillary 1st part / mandibular anterior tympanic deep auricular middle meningeal ( superior tympanic, petrosal ) accessory meningeal inferior alveolar 2nd part / pterygoid to muscles of mastication ( deep temporal, pterygoid, masseteric ) buccal 3rd part / pterygopalatine posterior superior alveolar infraorbital ( anterior superior alveolar ) descending palatine ( greater palatine, lesser palatine ) artery of the pterygoid canal sphenopalatine ( posterior septal branches, posterior lateral nasal ) pharyngeal IC cervical carotid sinus petrous Vidian caroticotympanic cavernous / ophthalmic orbital group : anterior ethmoidal posterior ethmoidal lacrimal ( lateral palpebral ) medial palpebral terminal ( supraorbital, supratrochlear, dorsal nasal ) ocular group : central retinal ciliary ( short posterior, long posterior, anterior ) Circulus arteriosus major hypophysial ( superior, inferior ) brain Circle of Willis ACA ( anterior communicating, medial striate, Orbitofrontal artery ) MCA ( anterolateral central, Prefrontal artery, Superior terminal branch, Inferior terminal branch, Anterior temporal branch ) posterior communicating anterior choroidal SC vertebral artery meningeal spinal ( posterior, anterior ) basilar : pontine labyrinthine cerebellar ( AICA, SCA, PICA ) cerebral ( PCA ) thyrocervical trunk inferior thyroid inferior laryngeal tracheal esophageal ascending cervical pharyngeal glandular branches transverse cervical superficial branch deep branch / dorsal scapular scapular anastomosis suprascapular acromial branch scapular anastomosis costocervical trunk deep cervical Supreme Intercostal artery Arteries of the torso and chest Lungs Pulmonary artery Right Left ( Ligamentum arteriosum ) Heart Coronary circulation Right coronary : SA nodal AV nodal Atrial Right marginal Posterior interventricular Left coronary : Anterior interventricular Left circumflex ( Left marginal ) Aorta Sections Ascending aorta Aortic arch Descending aorta Thoracic aorta Abdominal aorta Aortic body Aortic arch Brachiocephalic Thyreoidea ima Right subclavian Right common carotid Left common carotid External carotid Internal carotid Carotid body Carotid sinus Carotid bifurcation Left subclavian Internal thoracic : Anterior intercostal Thymic Pericardiacophrenic Perforating branches terminal ( Musculophrenic, superior epigastric ) Costocervical trunk : Highest intercostal ( Posterior intercostal 1 -- 2 ) Deep cervical Descending aorta visceral : Bronchial Esophageal Mediastinal parietal : Posterior intercostal 3 -- 11 Subcostal Superior phrenic Arteries of the abdomen and pelvis Abdominal aorta Celiac Left gastric Esophageal branches Common hepatic Proper hepatic cystic Right gastric Gastroduodenal right gastroepiploic superior pancreaticoduodenal supraduodenal Splenic Pancreatic branches greater dorsal Short gastrics Left gastroepiploic Superior mesenteric Inferior pancreaticoduodenal Intestinal jejunal ileal arcades vasa recta Ileocolic colic anterior cecal posterior cecal ileal branch appendicular Right colic Middle colic Marginal Suprarenal Middle suprarenal Renal Inferior suprarenal Ureteral Gonadal Testicular artery Ovarian artery Lumbar Lumbar arteries Inferior mesenteric Left colic Marginal Sigmoid Superior rectal Common iliac Internal iliac Posterior surface Iliolumbar Lumbar branch Iliac branch Anterior surface Superior vesical artery Umbilical artery Medial umbilical ligament to ductus deferens Obturator Anterior branch Pubic branch Posterior branch Acetabular branch Cruciate anastomosis Corona mortis Middle rectal Vaginal branch ♀ / Prostatic branch ♂ Uterine ♀ Arcuate Vaginal branches Ovarian branches Tubal branches Spiral Vaginal ♀ / Inferior vesical ♂ Inferior gluteal Accompanying of sciatic nerve Cruciate anastomosis Internal pudendal Inferior rectal Perineal posterior scrotal posterior labial Bulb of penis / vestibule Urethral Deep artery of the penis helicine Deep artery of clitoris Dorsal of the penis Dorsal of the clitoris External iliac Inferior epigastric Corona mortis Deep circumflex iliac Femoral see arteries of lower limbs Median sacral Coccygeal glomus Arteries of the human arm Axillary Shoulder ( before teres minor ) 1st part Superior thoracic artery 2nd part Thoracoacromial artery pectoral branch acromial branch clavicular branch deltoid branch Lateral thoracic artery 3rd part Subscapular artery scapular anastomosis circumflex scapular artery thoracodorsal artery anterior humeral circumflex artery posterior humeral circumflex artery Brachial Forearm ( before cubital fossa ) profunda brachii radial collateral medial collateral ulnar collateral superior inferior Radial artery forearm radial recurrent wrist / carpus Dorsal carpal branch dorsal carpal arch Palmar carpal branch deep palmar arch hand Superficial palmar branch princeps pollicis radialis indicis artery superficial palmar arch Median artery median artery Ulnar artery forearm ulnar recurrent anterior posterior common interosseous anterior posterior interosseous recurrent wrist / carpus Dorsal carpal branch dorsal carpal arch Palmar carpal branch superficial palmar arch Arterial Arches Dorsal carpal arch dorsal metacarpal dorsal digital Palmar carpal arch superficial palmar arch common palmar digital proper palmar digital deep palmar arch palmar metacarpal Arteries of the human leg Inferior epigastric cremasteric ♂ / round ligament ♀ Deep circumflex iliac no major branches Femoral In femoral canal superficial epigastric superficial circumflex iliac superficial external pudendal deep external pudendal ( anterior scrotal ♂ Descending genicular saphenous branch articular branches Profunda femoris medial circumflex femoral ascending descending superficial deep acetabular lateral circumflex femoral descending transverse ascending perforating Cruciate anastomosis Trochanteric anastomosis Popliteal Genicular superior genicular ( medial, lateral ) middle genicular inferior genicular ( medial, lateral ) Sural no major branches Anterior tibial tibial recurrent posterior anterior ) anterior malleolar medial lateral dorsalis pedis : tarsal ( medial, lateral ) Tibial - fibular ( Tibial - peroneal ) trunk Posterior tibial circumflex fibular medial plantar lateral plantar fibular ( peroneal ) Arches arcuate dorsal metatarsal first dorsal metatarsal deep plantar dorsal digital arteries plantar arch plantar metatarsal common plantar digital proper plantar digital NDL : 00565488 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Blood_vessel&oldid=803552099 '' Categories : Angiology Soft tissue Talk Contents About Wikipedia Afrikaans አማርኛ অসমীয়া Bân - lâm - gú Беларуская Български Bosanski Català Čeština ChiShona Cymraeg Dansk Deutsch ދިވެހިބަސް Eesti Ελληνικά Español Esperanto Euskara فارسی Français Frysk Gaeilge Galego 한국어 Հայերեն हिन्दी Hrvatski Ido Bahasa Indonesia Interlingua IsiXhosa Íslenska Italiano עברית Basa Jawa ქართული Қазақша Kiswahili Kurdî Latina Latviešu Lietuvių Limburgs Lingála Magyar Македонски Bahasa Melayu Nederlands नेपाली नेपाल भाषा 日本 語 Norsk Norsk nynorsk ਪੰਜਾਬੀ Plattdüütsch Polski Português Ripoarisch Română Runa Simi Русский Scots Shqip Simple English Slovenčina Slovenščina کوردی Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Tagalog தமிழ் తెలుగు ไทย Тоҷикӣ Türkçe Українська Tiếng Việt Võro ייִדיש 粵語 中文 Edit links This page was last edited on 3 October 2017, at 05 : 55. 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Question: what is the muscular layer of a blood vessel
Answer: Tunica intima