Atria
The atria (singular atrium) are the upper chambers in the heart, delvering blood to the ventricles. The right atrium receives deoxygenated blood from around the body through the superior and inferior vena cavae, whereas the left atrium receives oxygenated blood from the lungs through the pulmonary veins.[1]
They have thin walls compared to ventricles, as the blood is only moving a short distance down to the ventricles, therefore little muscle is needed compared to ventricles which pump the blood over larger distances.[2] Atria are involved in the first stages of the cardiovascular cycle mediated by the Sinoatrial Node (SAN). A wave of depolarization sweeps over the the atria causing them to contract, which forces blood from the atria into the ventricles. The SAN acts a pacemaker whereby it could generate action potential to control heart rate[3]. This is essential as it marks the start of the electrical conduction of the heart[3].
References
- ↑ http://www.ivyroses.com/HumanBody/Blood/Heart_Structure.php
- ↑ Pocock G., Richards C. (2006) Human Physiology: The Basis of Medicine, 3rd Edition, Oxford University Press
- ↑ 3.0 3.1 Quain, Jones. (1908) Quain's Elements of Anantomy, 4. London: Longmans, Green and Co.