WordNet

invest with or as with a body; give body to (同)personify
the external structure of a vehicle; "the body of the car was badly rusted"
the main mass of a thing
a natural object consisting of a dead animal or person; "they found the body in the lake" (同)dead body
the entire structure of an organism (an animal, plant, or human being); "he felt as if his whole body were on fire" (同)organic structure, physical structure
a collection of particulars considered as a system; "a body of law"; "a body of doctrine"; "a body of precedents"
a group of persons associated by some common tie or occupation and regarded as an entity; "the whole body filed out of the auditorium"; "the student body"; "administrative body"
an individual 3-dimensional object that has mass and that is distinguishable from other objects; "heavenly body"
the central message of a communication; "the body of the message was short"
of or relating to either of the two major arteries supplying blood to the head and neck

PrepTutorEJDIC

〈C〉『身体』,肉体 / 〈C〉(人・動物の)『胴体』 / 〈C〉)物の)『主要部』,本体《+『of』+『名』》 / 〈C〉(…の)『団体』,群れ:(…のたくさんの)集まり《+『of』+『名』》 / 〈C〉物体,…体 / 〈U〉実質;(酒・味などの)こく / 〈C〉《話》人
頚(けい)動脈 / 頚動脈の
《英話》人;(特に)男

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/04/15 04:52:43」(JST)

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The carotid body (carotid glomus or glomus caroticum) is a small cluster of chemoreceptors and supporting cells located near the fork (bifurcation) of the carotid artery (which runs along both sides of the throat).

The carotid body detects changes in the composition of arterial blood flowing through it, mainly the partial pressure of oxygen, but also of carbon dioxide. Furthermore, it is also sensitive to changes in pH and temperature.

Structure

The carotid body is made up of two types of cells, called glomus cells: glomus type I (chief) cells, and glomus type II (sustentacular) cells.

Glomus type I/chief cells are derived from neural crest,^[1] which, in turn are derived from neuroectoderm. They release a variety of neurotransmitters, including acetylcholine, ATP, and dopamine that trigger EPSPs in synapsed neurons leading to the respiratory center.

Glomus type II/sustentacular cells resemble glia, express the glial marker S100 and act as supporting cells.

The carotid body contains the most vascularized tissue in the human body^{[citation needed]}. The thyroid gland is very vascular, but not quite as much as the carotid body.

Function

The carotid body functions as a sensor: it responds to a stimulus, primarily O₂ partial pressure, which is detected by the type I (glomus) cells, and triggers an action potential through the afferent fibers of the glossopharyngeal nerve, which relays the information to the central nervous system.

Stimulus

While the central chemoreceptors in the brainstem are highly sensitive to CO₂ the carotid body is a peripheral chemoreceptor that mainly provides afferent input to the respiratory center that is highly O₂ dependent. However, the carotid body also senses increases in CO₂ partial pressure and decreases in arterial pH, but to a lesser degree than for O₂

The output of the carotid bodies is low at an oxygen partial pressure above about 100mmHg (13,3 kPa) (at normal physiological pH), but below 60mmHg the activity of the type I (glomus) cells increases rapidly due to a decrease in hemoglobin-oxygen saturation below 90%.

Detection

The mechanism for detecting reductions in PO₂ has yet to be identified, there may be multiple mechanisms^[2] and could vary between species. Hypoxia detection has been shown to depend upon increased Hydrogen sulfide generation produced by cystathionine gamma-lyase as hypoxia detection is reduced in mice in which this enzyme is knocked out or pharmacologically inhibited. The process of detection involves the interaction of cystathionine gamma-lyase with hemeoxygenase-2 and the production of carbon monoxide.^[3] Yet, some studies show that physiologic concentration of Hydrogen Sulfide may not be strong enough to trigger such responses.

Other theories suggest it may involve mitochondrial oxygen sensors and the haem-containing cytochromes that undergo reversible one-electron reduction during oxidative-phosphorylation. Haem reversibly binds O₂ with an affinity similar to that of the carotid body, suggesting that haem containing proteins may have a role in O₂, potentially this could be one of the complexes involved in oxidative-phosphorylation. This leads to increases in reactive oxygen species and rises in intracellular Ca²⁺. However, whether hypoxia leads to an increase or decrease in reactive oxygen species is unknown. The role of reactive oxygen species in hypoxia sensing is also under question.^[4]

The oxygen dependent enzyme haem-oxidase has also been put forward as a hypoxia sensor. In normoxia, haem-oxygenase generates carbon monoxide (CO), CO activates the large conductance calcium-activated potassium channel, BK. Falls in CO that occur as a consequence of hypoxia would lead to closure of this potassium channel and this would lead to membrane depolarisation and consequence activation of the carotid body.^[5] A role for the "energy sensor" AMP-activated protein kinase (AMPK) has also been proposed in hypoxia sensing. This enzyme is activated during times of net energy usage and metabolic stress, including hypoxia. AMPK has a number of targets and it appears that, in the carotid body, when AMPK is activated by hypoxia, it leads to downstream potassium channel closure of both O₂-sentive TASK-like and BK channels^[6]

An increased pCO₂ is detected because the CO₂ diffuses into the cell, where it increases the concentration of carbonic acid and thus protons. The precise mechanism of CO₂ sensing is unknown, however it has been demonstrated that CO₂ and low pH inhibit a TASK-like potassium conductance, reducing potassium current. This leads to depolarisation of the cell membrane which leads to Ca²⁺ entry, excitation of glomus cells and consequent neurotransmitter release.^[7]

Arterial acidosis (either metabolic or from altered PCO₂) inhibits acid-base transporters (e.g. Na⁺-H⁺) which raise intracellular pH, and activates transporters (e.g. Cl⁻-HCO₃⁻) which decrease it. Changes in proton concentration caused by acidosis (or the opposite from alkalosis) inside the cell stimulates the same pathways involved in PCO₂ sensing.

Another mechanism is through oxygen sensitive potassium channels. A drop in dissolved oxygen lead to closing of these channels which results in depolarization. This leads to release of the neurotransmitter dopamine in the glossopharengeal and vagus afferente to the vasomotor area.

Action potential

The type I (glomus) cells in the carotid (and aortic bodies) are derived from neuroectoderm and are thus electrically excitable. A decrease in oxygen partial pressure, an increase in carbon dioxide partial pressure, and a decrease in arterial pH can all cause depolarization of the cell membrane, and they affect this by blocking potassium currents. This reduction in the membrane potential opens voltage-gated calcium channels, which causes a rise in intracellular calcium concentration. This causes exocytosis of vesicles containing a variety of neurotransmitters, including acetylcholine, noradrenaline, dopamine, adenosine, ATP, substance P, and met-enkephalin. These act on receptors on the afferent nerve fibres which lie in apposition to the glomus cell to cause an action potential.

Relay

The feedback from the carotid body is sent to the cardiorespiratory centers in the medulla oblongata via the afferent branches of the Glossopharyngeal nerve. The afferent fibres of the aortic body chemoreceptors are relayed by the Vagus nerve. These centers, in turn, regulate breathing and blood pressure, with hypoxia causing an increase in ventilation.

Clinical significance

Micrograph of a carotid body tumor.

Paraganglioma

A paraganglioma is a tumor that may involve the carotid body and is usually benign. Rarely, a malignant neuroblastoma may originate from the carotid body.

References

^ Gonzalez C, Almaraz L, Obeso A, Rigual R (1994). "Carotid body chemoreceptors: from natural stimuli to sensory discharges". Physiol. Rev. 74 (4): 829–98. PMID 7938227.
^ Ward JP (2008). "Oxygen sensors in context.". Biochim Biophys Acta. 1777 (1): 1–14. doi:10.1016/j.bbabio.2007.10.010. PMID 18036551.
^ Peng Y-J, Nanduri J, Raghuraman G, Souvannakitti D, Gadalla M.M, Kumar GK, Snyder SH, Prabhakar NR. (2010). H2S mediates O2 sensing in the carotid body PNAS 107 (23) 10719-10724. doi:10.1073/pnas.1005866107
^ Gonzalez C, Sanz-Alfayate G, Agapito MT, Gomez-Niño A, Rocher A, Obeso A (2002). "Oxygen sensors in context.". Respir Physiol Neurobiol. 132 (1): 17–41. doi:10.1016/S1569-9048(02)00047-2. PMID 12126693.
^ Williams SE, Wootton P, Mason HS, Bould J, Iles DE, Riccardi D, Peers C, Kemp PJ (2004). "Hemoxygenase-2 is an oxygen sensor for a calcium-sensitive potassium channel". Science 306 (5704): 2093–7. doi:10.1126/science.1105010. PMID 15528406.
^ Wyatt CN, Mustard KJ, Pearson SA, Dallas ML, Atkinson L, Kumar P, Peers C, Hardie DG, Evans AM (2007). "AMP-ACTIVATED PROTEIN KINASE MEDIATES CAROTID BODY EXCITATION BY HYPOXIA". J Biol Chem. 282 (11): 8092–8. doi:10.1074/jbc.M608742200. PMC 1832262. PMID 17179156.
^ Buckler KJ, Williams BA, Honore E (2000). "An oxygen-, acid- and anaesthetic-sensitive TASK-like background potassium channel in rat arterial chemoreceptor cells". J. Physiol. 525 (1): 135–142. doi:10.1111/j.1469-7793.2000.00135.x. PMC 2269923. PMID 10811732.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 換気調節 control of ventilation
2. 傍神経節腫：疫学、臨床症状、診断、および組織学的検査 paragangliomas epidemiology clinical presentation diagnosis and histology
3. 換気調節障害 disorders of ventilatory control
4. 頚部腫瘤の評価 evaluation of a neck mass
5. 傍神経節腫：限局性疾患の治療 paragangliomas treatment of locoregional disease

English Journal

Role of platelet-derived growth factor in cerebral vasospasm after subarachnoid hemorrhage in rats.

Shiba M, Suzuki H, Fujimoto M, Shimojo N, Imanaka-Yoshida K, Yoshida T, Kanamaru K, Matsushima S, Taki W.SourceDepartment of Neurosurgery, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan, mshiba@clin.medic.mie-u.ac.jp.
Acta neurochirurgica. Supplement.Acta Neurochir Suppl.2013;115:219-23.
Background and purpose: The role of platelet-derived growth factor (PDGF) remains unknown in cerebral vasospasm after subarachnoid hemorrhage (SAH). In this study, we examined the effects of PDGF receptor (PDGFR) inactivation on cerebral vasospasm in the endovascular perforation model of SAH in rats
PMID 22890672

Proteomic analysis of the carotid body: a preliminary study.

Giulio CD, Angelucci S, Ilio CD, Eleuterio E, Giuseppe FD, Sulpizio M, Verratti V, Pecyna M, Pokorski M.SourceDepartment of Neurosciences and Imaging, University of Chieti, Via dei Vestini 31, 66100, Chieti, Italy, digiulio@unich.it.
Advances in experimental medicine and biology.Adv Exp Med Biol.2013;756:349-53.
We present a proteomic analysis of the rat carotid body (CB) preparation by comparison between normoxia and hypoxia. Proteomic investigation would be helpful to identify the stress-induced protein during hypoxia and to know what O(2) species are being sensed by CB cells. Adult Wistar rats were used,
PMID 22836653

Japanese Journal

術中心停止を来した頸動脈小体腫瘍の1症例

小野寺美子,神田浩嗣,黒澤温 [他]
麻酔 63(1), 81-83, 2014-01
NAID 40019936390

Thrombus Removal by Acute-phase Endovascular Reperfusion Therapy to Treat Cerebral Embolism Caused by Thrombus in the Pulmonary Vein Stump after Left Upper Pulmonary Lobectomy: Case Report

Ikeda Hiroyuki,Yamana Norikazu,Murata Yoshitake,Saiki Masaaki
NMC Case Report Journal, 2014
… Cerebral angiography showed left internal carotid artery occlusion. … Thrombus removal using a retrieval device was performed and complete recanalization of the left internal carotid artery was obtained. … Although blood abnormalities or arrhythmia such as atrial fibrillation were not observed, thrombus in the left upper pulmonary vein stump was detected with contrast-enhanced computed tomography of the body trunk, which was therefore considered as the source of cerebral embolism. …
NAID 130004715772

Associations between Inflammatory Markers and Subclinical Atherosclerosis in Middle-aged White, Japanese-American and Japanese Men: The ERA-JUMP Study

Nagasawa Shin-ya,Ohkubo Takayoshi,Masaki Kamal,Barinas-Mitchell Emma,Miura Katsuyuki,Seto Todd B.,El-Saed Aiman,Kadowaki Takashi,Willcox Bradley J.,Edmundowicz Daniel,Kadota Aya,Evans Rhobert W.,Kadowaki Sayaka,Fujiyoshi Akira,Hisamatsu Takashi,Bertolet Marianne H.,Okamura Tomonori,Nakamura Yasuyuki,Kuller Lewis H.,Ueshima Hirotsugu,Sekikawa Akira,ERA-JUNP Study Group
Journal of Atherosclerosis and Thrombosis, 2014
… Aim: To examine whether the inflammatory markers C-reactive protein (CRP) and fibrinogen are associated with biomarkers of atherosclerosis [carotid intima-media thickness (IMT) and coronary artery calcification (CAC)] in the general male population, including Asians.Methods: Population-based samples of 310 Japanese, 293 Japanese-American and 297 white men 40-49 years of age without clinical cardiovascular disease underwent measurement of IMT, CAC and the CRP and fibrinogen levels as well as other conventional risk factors using standardized methods. …
NAID 130004704379

Related Pictures

★リンクテーブル★

リンク元	「頚動脈小体」「化学受容器」「glomus caroticum」
関連記事	「carotid」「body」

「頚動脈小体」

Carotid body
	Section of part of human glomus caroticum. Highly magnified. Numerous blood vessels are seen in section among the gland cells.
	Diagram showing the origins of the main branches of the carotid arteries.
Details
Latin	glomus caroticum
Identifiers
Gray's	p.1281
Dorlands; /Elsevier	g_07/12394794
TA	A12.2.04.007
FMA	50095
	Anatomical terminology