In order to answer why the cell would need aquaporins when the plasma membrane is permeable to water, we need to understand the make-up of water and the cell membrane. The water molecule is polar with its H+ and OH- ions. Cell membranes are selectively permeable.
Anatomy of the Auricle. The auricle or pinna is a relatively large appendage on the side of the head. It is prominent in most people and plays a very important role in hearing â it directs sound waves into the ear canal. The auricle is composed of cartilage which is covered by skin.
a ridgelike structure. carina traÂ´cheae a downward and backward projection of the lowest tracheal cartilage, forming a ridge between the openings of the right and left principal bronchi. carina urethraÂ´lis vagiÂ´nae the column of rugae in the lower anterior wall of the vagina, immediately below the urethra.