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.
Most of the cartilage that develops in prenatal life is eventually replaced by bone. However, there are two places where cartilage is found in the adult: Extraskeletal cartilage. For example, the cartilaginous rings in the trachea and the costal cartilage connecting ribs to the sternum. Articular cartilage. This type of cartilage is found in articulating joints, where it provides a smooth, gliding surface at the ends of articulating bones.