Left atrium

Left atrium

Infobox Anatomy
Name = PAGENAME
Latin = atrium sinistrum
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Caption = Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow.


Caption2 = Computer rendering of a human left atrium.
Precursor =
System =
Artery = circumflex branch of left coronary artery
Vein = oblique vein of the left atrium
Nerve =
Lymph =
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DorlandsPre = a_71
DorlandsSuf = 12167887
The left atrium is one of the four chambers in the human heart. It receives oxygenated blood from the pulmonary veins, and pumps it into the left ventricle, via the bicuspid valve.

tructure

Blood is pumped through the left atrioventricular orifice, which contains the bicuspid or mitral valve. A normal left atrium may be up to 5.5cm in maximum diameter; any larger than this is a sign of cardiac failure. This may occur in cases of mitral regurgitation.

The left atrium of a human faces more or less posteriorly. It is named 'left' based on the chamber's embryological and (putative) evolutionary origin. The term 'base' of the heart sometimes refers to the left atrium, though 'base' is an ambiguous term.

Attached to the left atrium is the left auricular appendix (auricle). This auricle is a common site for formation of thrombi, which may embolise causing stroke or ischemic gut. Atrial fibrillation makes this more likely.

Foramen ovale

There is a foramen ovale (oval hole) between the right and left atrium in the fetus. After birth, this should close over and become the fossa ovale. If it does not, this is an atrial septal defect (hole in the heart). In the fetus, the right atrium pumps blood into the left atrium, bypassing the pulmonary circulation (which is useless in a fetus). In an adult, a septal defect would result in flow in the reverse direction - from the left atrium to the right - which will reduce cardiac output, potentially cause cardiac failure and in severe or untreated cases, death.

Blood supply

The left atrium is supplied mainly by the left circumflex coronary artery, though the branches are too small to be identified in a cadaveric human heart and are not named.

The oblique vein of the left atrium is partly responsible for venous drainage; it derives from the embryonic left superior vena cava.

Animals

Many other animals, including mammals, also have four-chambered hearts, and have a left atrium. The function in these animals is similar. Some animals (amphibians, reptiles) have a three-chambered heart, in which the blood from each atrium is mixed in the single ventricle before being pumped to the aorta. In these animals, the left atrium still serves the purpose of collecting blood from pulmonary veins.


=Additional

ee also

* Right atrium



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Look at other dictionaries:

  • left atrium — noun the left upper chamber of the heart that receives blood from the pulmonary veins • Syn: ↑left atrium of the heart, ↑atrium sinistrum • Hypernyms: ↑atrium cordis, ↑atrium of the heart …   Useful english dictionary

  • left atrium of the heart — noun the left upper chamber of the heart that receives blood from the pulmonary veins • Syn: ↑left atrium, ↑atrium sinistrum • Hypernyms: ↑atrium cordis, ↑atrium of the heart …   Useful english dictionary

  • left atrium — noun One of the chambers of the heart in humans and other mammals, receives oxygenated blood from the lungs via the pulmonary veins, and pumps it into the left ventricle …   Wiktionary

  • Oblique vein of the left atrium — Vein: Oblique vein of the left atrium Base and diaphragmatic surface of heart. (Oblique vein of the left atrium labeled at center left.) Latin vena obliqua atrii sinistri …   Wikipedia

  • oblique vein of the left atrium — n a small vein that passes obliquely down the posterior surface of the left atrium, empties into the coronary sinus, and is a remnant of the left duct of Cuvier called also oblique vein, oblique vein of left atrium, oblique vein of Marshall …   Medical dictionary

  • oblique vein of the left atrium — noun a tributary of the coronary sinus; on the posterior wall of the left atrium • Syn: ↑vena obliqua atrii sinistri • Hypernyms: ↑vein, ↑vena, ↑venous blood vessel …   Useful english dictionary

  • left atrium of heart — a. cordis sinistrum …   Medical dictionary

  • Left atrial myxoma — is a benign tumor located in the left upper chamber of the heart (atrium) on the wall that separates the left chamber from the right (the atrial septum). . Right atrial myxomas are sometimes associated with tricuspid stenosis and atrial… …   Wikipedia

  • Left margin of heart — Sternocostal surface of heart. Heart seen from above …   Wikipedia

  • Left heart — is a term used to refer collectively to the left atrium and left ventricle of the heart; occasionally, this term is intended to reference the left atrium, left ventricle, and the aorta collectively.The left atrium receives oxygenated pulmonic… …   Wikipedia

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