It is called the Rugae.
Rugae is a term used in anatomy to refer to a series of ridges produced by folding of the wall of an organ. For example the gastric rugae which allows for expansion of the stomach after the consumption of foods and drinks. The rugae of the vagina are the transverse ridges on the mucous membrane lining the vagina. They allow the vagina to stretch during childbirth.
The respiratory system works directly with the circulatory system to provide oxygen to the body. Oxygen taken in from the respiratory system moves into blood vessels that then circulate oxygen-rich blood to tissues and cells.
The air that is inside a ship is much less dense than water. That's what keeps it floating! ... As a ship is set in water, it pushes down and displaces an amount of water equal to its weight
