Carbon dioxide can be transported through the blood via three methods. It is dissolved directly in the blood, bound to plasma proteins or hemoglobin, or converted into bicarbonate.
The majority of carbon dioxide is transported as part of the bicarbonate system. Carbon dioxide diffuses into red blood cells. Inside, carbonic anhydrase converts carbon dioxide into carbonic acid (H2CO3), which is subsequently hydrolyzed into bicarbonate (HCO3−) and H+. The H+ ion binds to hemoglobin in red blood cells, and bicarbonate is transported out of the red blood cells in exchange for a chloride ion. This is called the chloride shift.
Bicarbonate leaves the red blood cells and enters the blood plasma. In the lungs, bicarbonate is transported back into the red blood cells in exchange for chloride. The H+ dissociates from hemoglobin and combines with bicarbonate to form carbonic acid with the help of carbonic anhydrase, which further catalyzes the reaction to convert carbonic acid back into carbon dioxide and water. The carbon dioxide is then expelled from the lungs.
Blood vessels visible in the posterior view of the heart include the Superior and inferior vena cava and the pulmonary veins. The superior vena cava and the inferior vena cava drain systemic venous blood into the posterior wall of the right atrium. The pulmonary veins transport blood from the lungs back to the heart and are best seen in posterior view of the heart. Other features visible in the posterior view include, right and left atrium, right and left ventricle, aorta, aortic arch, pulmonary veins and arteries, coronary sinus, coronary artery and posterior interventricular artery.
Roots and stems
Explanation: the cork of mature roots and woody stems is perforatedby nonsuberized pores called lenticels.
