strong then the right atrium but not as strong as the left ventricle because the left atrium deals with a higher pressure in comparison to the right atrium.
The walls of the posterior left atrium are smooth, this part receives the 4 pulmonary veins
The wall of the anterior left atrium contain musculi pectinati, small ridges in the wall
Unlike in the right atrium there is no definitive division between the two
Some terminology first: The upper chambers = atria (singular atrium) The lower chambers = ventricles The atria are responsible for receiving blood: the right atrium receives deoxygenated blood from the body and the left atrium receives oxygenated blood from the lungs. The atria only pump this blood into the ventricles and therefore do not need particularly thick muscular walls. The ventricles on the other hand are responsible for pumping the blood received from the atria to the body. The right ventricle pumps the deoxygenated blood it receives from the right atrium out of the heart and into the lungs. On the other hand, the left ventricle is responsible for pumping the oxygenated blood received by the left atrium to the rest of the body. It is because of the this that the walls on the side of left ventricle are the thickest. The left ventricle requires "more muscle" than the right ventricle as the distance it has to pump the blood is far greater. So, SHORT ANSWER: The walls of the lower chambers/ventricles are thicker and more muscular than the walls of the upper chambers/atria because they have to pump blood out of the heart and to the body as opposed to the atria which only receive blood from the body and then pump into the ventricles.
Some terminology first: The upper chambers = atria (singular atrium) The lower chambers = ventricles The atria are responsible for receiving blood: the right atrium receives deoxygenated blood from the body and the left atrium receives oxygenated blood from the lungs. The atria only pump this blood into the ventricles and therefore do not need particularly thick muscular walls. The ventricles on the other hand are responsible for pumping the blood received from the atria to the body. The right ventricle pumps the deoxygenated blood it receives from the right atrium out of the heart and into the lungs. On the other hand, the left ventricle is responsible for pumping the oxygenated blood received by the left atrium to the rest of the body. It is because of the this that the walls on the side of left ventricle are the thickest. The left ventricle requires "more muscle" than the right ventricle as the distance it has to pump the blood is far greater. So, SHORT ANSWER: The walls of the lower chambers/ventricles are thicker and more muscular than the walls of the upper chambers/atria because they have to pump blood out of the heart and to the body as opposed to the atria which only receive blood from the body and then pump into the ventricles.
The wall of the ventricle is thicker than the walls of the atria because the ventricle pumps blood throughout the body, and the wall of the ventricle needs to be thick snd muscular in order to do so.
Arterial walls contain thick, muscular tissue to pump blood throughout the body. Veins have thinner walls.
Circumflex
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Atrium
A ventricle's walls are thicker than those of the atrium because it needs to generate higher pressure. This higher pressure is needed to push blood into the circulation, while the atrium only needs to push blood into the ventricle.
They have thin walls and they collect blood before it enters the ventricles.
Vein
The walls of the ventricles of the heart aren't thinner than the atria, they are thicker. This is because they require more power as they pump blood around the body, while the atria only pump blood the short distance into the ventricles. More muscular walls are therefore needed to provide this power which is why they are thicker. The left ventricle is even thicker than the right ventricle as it requires a lot more power to pump blood all around the body. The right ventricle only pumps blood to the lungs.
Vasodilation means the widening of blood vessels that results from relaxation of the muscular walls of the vessels.