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Aquaporins are "the plumbing system for cells". Water moves through cells in an organized way, most rapidly in tissues that have aquaporin water channels. [28] For many years, scientists assumed that water leaked through the cell membrane, and some water does. However, this did not explain how water could move so quickly through some cells. [28]
Paracellular transport refers to the transfer of substances across an epithelium by passing through the intercellular space between the cells. [1] It is in contrast to transcellular transport, where the substances travel through the cell, passing through both the apical membrane and basolateral membrane. [2] [3]
For example, water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal. Deficits to body water result in volume contraction and dehydration. Diarrhea is a threat to both body water volume and electrolyte levels, which is why diseases that cause diarrhea are great threats to fluid balance.
The constrained intracellular pathway exacted by the tight junction barrier system allows precise control over which substances can pass through a particular tissue (e.g. the blood–brain barrier). At the present time, it is still unclear whether the control is active or passive and how these pathways are formed.
Thermodynamically the flow of substances from one compartment to another can occur in the direction of a concentration or electrochemical gradient or against it. If the exchange of substances occurs in the direction of the gradient, that is, in the direction of decreasing potential, there is no requirement for an input of energy from outside the system; if, however, the transport is against ...
The diving reflex is a set of physiological responses that occur in response to cold water immersion, particularly when the face or body is exposed to cold water. It is an evolutionary adaptation that helps mammals, including humans, manage the challenges of being submerged in cold water.
Osmosis is important in regulating the balance of water and salt within cells, thus it plays a critical role in maintaining homeostasis. [15] Aquaporins are integral membrane proteins that allow for the rapid passage of water and glycerol through membranes. The aquaporin monomers consist of six transmembrane alpha-helix domains and these ...
Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the hyponome, created by a fold in the mantle. Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by ...