Pore
From Free net encyclopedia
A pore, in general, is some form of opening, usually very small. Pores can be found on many organisms, such as in plants, animals, and humans.
More commonly, in talking about the skin, a pore is an opening into a sebaceous gland that secretes oil to lubricate and protect the surface of the skin.
Enlarged pores can be a cosmetic problem, especially during puberty, where pores, especially around the nose (the "T-zone") enlarge in order to cope with increased oil output. Often, after puberty ends, and the oil glands approach a regular output, the pores may consequently decrease in size too.
In plants, pores exist in leaves in order to aid in photosynthesis and respiration. In these cases, the pores are known as stoma. Many organic substances are porous (containing many pores), and they can be very light. Such substances include wood and the bones of some birds, whose porous structure enables these substances to be very light, but strong.
Cells often contain pores called aquaporins in order to facilitate the movement of water in and out of cells by means of osmosis. Ion channels contain pores to allow ions to pass through the cell's plasma membrane into or out of the cell.
In geology, pores refer to the open space within a rock. Just as a stack of oranges in the grocery store have spaces between them, so too do rocks. Pores in rock are where groundwater, oil, and natural gas are found.
Pores can also be referred to as the space between molecules. For example, when salt dissolves in water, it goes in the pores of the water.
The holes in a sponge.