The walls of the left atrium are slightly thicker than the walls of the right atrium. Oxygen-rich blood from the lungs enters the left atrium through the pulmonary vein. The blood is then pumped into the left ventricle chamber of the heart through the mitral valve.From there, the blood is ready to be pumped into the body to deliver oxygen-rich blood to all bodily tissues.he blood is then pumped into the left ventricle chamber of the heart through the mitral valve. From there, the blood is ready to be pumped into the body to deliver oxygen-rich blood to all bodily tissues.
The IRS will begin accepting 2016 tax returns on Jan. 23, and this yearâs deadline is April 18 â not 15 â because the deadline arrives on a weekend and is followed by the Emancipation Day holiday in Washington.
The IRS typically issues refunds within 21 calendar days from the date that a tax return is accepted. Some tax returns may require an additional review period and take longer to process. Those who have filed their taxes can use the IRS's Where's My Refund?