The above scenario confirms that these are simple columnar epithelial tissue because columnar cells are tall, narrow and nucleus in the tall column like cells located at the basal end of the cells. Columnar epithelial tissue are responsible for absorption and secretion of molecules. These are present at some part of digestive tract, female reproductive tract, and respiratory system.
While exercising, the muscles need additional energy as the breathing rate and volume of each breath increases to bring more oxygen into the body and remove the carbon dioxide produced. The heart rate increases to supply the muscles with extra oxygen and remove the carbon dioxide produced.
Because the interior of the phospholipid bilayer is occupied by hydrophobic fatty acid chains, the membrane is impermeable to water-soluble molecules, including ions and most biological molecules.
