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.
1 Pinna (anatomy) , the outer part of the ear-also referred to as the auricle. 2  Pinna (genus) , a genus of bivalve molluscs also known as pen shells. 3  In botany the pinnae are the divisions of a compound leaf or frond; Pinnation#Plants or Frond#Pinnate fronds. 4  A part (cusp) of a crown (pinnae).