Water Management

Water Management

Water management, as we just saw, is tightly tied to the management of sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function.. The waterThe universal solvent essential for life. just goes where the salt is among those fluid compartmentsDivisions of body water: intracellular, extracellular, and transcellular.. The only fluid compartment able to exchange with the outside world is the plasmaThe liquid component of blood.. The ICF is just a reservoir for water. We can take water or give water to the ICF in an effort to maintain the ECF osmolarityA measure of solute concentration in fluid; affects fluid movement between compartments.. Even if you don’t drink water during the day, you would still produce water. Even coffee flavored water is metabolized. You would generate water from metabolizing your food. You make water every time you make ATPThe energy currency of cells used for muscle contraction.!

There are way more ways to exit the body than there is to enter it when it comes to water. Expiratory respirationThe process of gas exchange, including ventilation, external and internal respiration., sweat, regular water loss through the skinThe body’s largest organ, providing protection and regulation., and fecesSolid waste material formed in the large intestine and expelled through the anus. are outputs that occur every day without choice. Obligatory water reabsorptionThe process of fluid moving back into capillaries from surrounding tissues due to colloid osmotic p happens in the descending loopThe portion of the nephron loop that is permeable to water but not solutes, leading to water reabsor of the nephronThe functional unit of the kidney that filters blood and produces urine.. This process tries to take back any water you can. If you are secreting ADH, aldosteroneA hormone that increases sodium and water reabsorption in the kidneys, helping regulate blood pressu, or angiotensin IIA powerful vasoconstrictor that increases blood pressure and stimulates aldosterone release., you can reclaim water via facultative reabsorption. You are extra lucky because you will take back even more water.

Hormonal Water Management

When talking about hormones there are three major ones that affect ECF volume and osmolarity. Consequently, blood volume and blood pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. are affected. So, why, then, do I only have ADH and aldosterone listed here on this slide? What am I missing? Angiotensin II is missing. That is because, aside from other things that angiotensin II does, it causes vasoconstrictionThe narrowing of blood vessels due to contraction of smooth muscle, increasing blood pressure and re. Angiotensin II turns on these two hormones. Both hormones act on the distal convoluted tubuleThe part of the nephron where final adjustments to ion and water balance occur under hormonal contro and the collecting ductA duct in the nephron that collects urine from multiple nephrons and adjusts water reabsorption.. Aquaporins are inserted into the cuboidal cellsThe basic structural and functional units of life. of juxtamedullaryRefers to nephrons or structures located near the boundary between the renal cortex and medulla. nephrons, allowing for more reabsorption.

ADH is a hormone that conserves water. ADH triggers thirst. It has the capacity to increase your water volume. However, you might not respond to that emotion of thirst. What it is more likely to do is affect your kidneys to create really concentrated urineThe liquid waste excreted by the kidneys.. This will conserve your blood volume. If you respond to thirst, ADH will raise your blood volume. Along with more water in the balloon comes more pressure on the vessels, and blood pressure will increase. No matter what you are decreasing your plasma osmolarity, which is probably good since we all live in dehydrationA condition in which fluid loss exceeds intake, leading to a decrease in total body water. anyway.

At the same time that ADH is turned on, aldosterone was probably triggered as well. Aldosterone acts on the DCT of the nephron to reabsorb sodium and secrete potassium(K⁺): Major ICF cation; essential for muscle and nerve function.. As sodium is reabsorbed, water comes with it. More water means more blood volume and more blood pressure. As for osmolarity, it increases it. The reabsorption of sodium far outweight the water that comes with it.

Edema and Hypoproteinemia

This is where we have to discuss edemaExcess fluid in interstitial spaces.. Many of you have seen people with edema. This is the swelling of a body area, usually the legs. Edema is not the swelling of cells. Edema is the expansion of the interstitial space or the accumulation of fluid in the interstitial fluids.

When you get a bruise, you’ve probably damaged a capillary or two. All the fluid leaks out of them. The venule doesn’t reclaim it all. This is why bruises swell. Fluid is trapped in the interstitial fluidThe fluid surrounding cells within tissues. and is not reclaimed by the lymphatic vessels in the area.

For example, blood with the right amount of plasma proteinsLarge molecules made of amino acids with various functions in the body. in it can keep fluids in the blood vessels. People with liverA large organ that produces bile, detoxifies blood, and stores nutrients. failure, and low plasma proteins are not able to reclaim the fluids from their tissues. Their blood has a low osmotic pressureThe force exerted by water moving across a membrane due to osmosis.. So do their lymph fluids. This means that water is not attracted to the blood. It doesn’t want to be reclaimed in reabsorption.

As edema progresses, you are basically bleeding out or losing fluid from the circulatory system. That’s kind of like bleeding out! But all the fluids them get trapped in the interstitial space. This creates something known as peripheral congestion. Peripheral is referring to the systemic circuitThe part of the circulatory system that carries oxygenated blood from the heart to the body and retu. The word congestion refers to the abnormally high amount of fluid in the systemic circuit. Of course, this excess fluid puts pressure on the heart and lungs and their ability to expand. As the fluid builds, the individual dies.