The nucleus contains the chromosomes of the cell. The main genome of the organism is found in the nucleus. In humans, the nucleus holds 46 chromosomes, which contains about 25,000 genes. However, mitochondria have DNA of their own.The human mitochondrion has DNA in the form of plasmids, which are circular pieces of DNA. Mitochondrial genes encode for 13 proteins and 24 RNA molecules that are only found in the mitochondrion.he nucleus contains the chromosomes of the cell. The main genome of the organism is found in the nucleus. In humans, the nucleus holds 46 chromosomes, which contains about 25,000 genes. However, mitochondria have DNA of their own.
Print. The heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood out of your heart.The heart valves, which keep blood flowing in the right direction, are gates at the chamber openings.he heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood.
The main parts of the heart are the chambers, the valves, and the electrical nodes. Heart Chambers: There are two different types of heart chambers. The first is the atrium (plural is atria), which receives blood returning to the heart through the veins. The right atrium pumps blood to the right ventricle, and the left atrium pumps blood into the left ventricle. This blood is then pumped from the atrium into the second chamber called the ventricle.