Although water forms the large majority of the cytosol, it mainly functions as a fluid medium for intracellular signaling signal transduction within the cell, and plays a role in determining cell size and shape.
The concentrations of ions, such as sodium and potassium, are generally lower in the cytosol compared to the extracellular fluid; these differences in ion levels are important in processes such as osmoregulation and signal transduction. The cytosol also contains large amounts of macromolecules that can alter how molecules behave, through macromolecular crowding. The extracellular fluid can be divided into two major subcompartments: interstitial fluid and blood plasma.
The extracellular fluid also includes the transcellular fluid; this makes up only about 2. In humans, the normal glucose concentration of extracellular fluid that is regulated by homeostasis is approximately 5 mm. The pH of extracellular fluid is tightly regulated by buffers and maintained around 7.
Extracellular matrix : Spatial relationship between the blood vessels, basement membranes, and interstitial space between structures. It is the intravascular fluid part of the extracellular fluid. It plays a vital role in intravascular osmotic effects that keep electrolyte levels balanced and protects the body from infection and other blood disorders.
Interstitial fluid or tissue fluid is a solution that bathes and surrounds the cells of multicellular animals. The interstitial fluid is found in the interstitial spaces, also known as the tissue spaces. On average, a person has about 11 liters 2. The majority of the interstitial space functions as an ECM, a fluid space consisting of cell-excreted molecules that lies between the basement membranes of the interstitial spaces. The interstitial ECM contains a great deal of connective tissue and proteins such as collagen that are involved in blood clotting and wound healing.
Transcellular fluid is the portion of total body water contained within the epithelial-lined spaces. It is the smallest component of extracellular fluid, which also includes interstitial fluid and plasma.
It is often not calculated as a fraction of the extracellular fluid, but it is about 2. Examples of this fluid are cerebrospinal fluid, ocular fluid, joint fluid, and the pleaural cavity that contains fluid that is only found in their respective epithelium-lined spaces. The function of transcellular fluid is mainly lubrication of these cavities, and sometimes electrolyte transport.
The composition of tissue fluid depends upon the exchanges between the cells in the biological tissue and the blood. This means that fluid composition varies between body compartments. The cytosol or intracellular fluid consists mostly of water, dissolved ions, small molecules, and large, water-soluble molecules such as proteins. This mixture of small molecules is extraordinarily complex, as the variety of enzymes that are involved in cellular metabolism is immense.
These enzymes are involved in the biochemical processes that sustain cells and activate or deactivate toxins. The pH of the intracellular fluid is 7. The cell membrane separates cytosol from extracellular fluid, but can pass through the membrane via specialized channels and pumps during passive and active transport.
The concentrations of the other ions in cytosol or intracellular fluid are quite different from those in extracellular fluid. The cytosol also contains much higher amounts of charged macromolecules, such as proteins and nucleic acids, than the outside of the cell. In contrast to extracellular fluid, cytosol has a high concentration of potassium ions and a low concentration of sodium ions.
These pumps transport ions against their concentration gradients to maintain the cytosol fluid composition of the ions. The extracellular fluid is mainly cations and anions. These ions are important for water transport throughout the body.
These dissolved substances are involved in many varied physiological processes, such as gas exchange, immune system function, and drug distribution throughout the body. Due to the varying locations of transcellular fluid, the composition changes dramatically. Some of the electrolytes present in the transcellular fluid are sodium ions, chloride ions, and bicarbonate ions. Cerebrospinal fluid is similar in composition to blood plasma, but lacks most proteins, such as albumins, because they are too large to pass through the blood—brain barrier.
Ocular fluid in the eyes contrasts with cerebrospinal fluid by containing high concentrations of proteins, including antibodies. Extracellular fluid is separated among the various compartments of the body by membranes. These membranes are hydrophobic and repel water; however, there a few ways that fluids can move between body compartments.
There are small gaps in membranes, such as the tight junctions, that allow fluids and some of their contents to pass through membranes by way of pressure gradients. Hydrostatic pressure is generated by the contractions of the heart during systole.
It pushes water out of the small tight junctions in the capillaries. The water potential is created due to the ability of the small solutes to pass through the walls of capillaries. This buildup of solutes induces osmosis. The water passes from a high concentration of water outside of the vessels to a low concentration inside of the vessels, in an attempt to reach an equilibrium. Gas, oil, antifreeze and windshield wiper fluid all serve a role in helping our cars function properly.
Below is a list of bodily fluids and the role each one plays in keeping our bodies healthy and running on all cylinders. Bodily fluids are liquids that come from inside human bodies and help transport nutrients and expel waste from human cells.
A short list of bodily fluids includes:. A decrease in the normal levels of plasma proteins results in a decrease of colloid osmotic pressure which counterbalances the hydrostatic pressure in the capillaries. This process causes loss of water from the blood to the surrounding tissues, resulting in edema.
Mild, transient edema of the feet and legs may be caused by sitting or standing in the same position for long periods of time, as in the work of a toll collector or a supermarket cashier.
Otherwise, the venous blood pools in the lower limbs and can leak into surrounding tissues. Medications that can result in edema include vasodilators, calcium channel blockers used to treat hypertension, non-steroidal anti-inflammatory drugs, estrogen therapies, and some diabetes medications. Underlying medical conditions that can contribute to edema include congestive heart failure, kidney damage and kidney disease, disorders that affect the veins of the legs, and cirrhosis and other liver disorders.
Therapy for edema usually focuses on elimination of the cause. Activities that can reduce the effects of the condition include appropriate exercises to keep the blood and lymph flowing through the affected areas.
Other therapies include elevation of the affected part to assist drainage, massage and compression of the areas to move the fluid out of the tissues, and decreased salt intake to decrease sodium and water retention. Your body is mostly water.
Body fluids are aqueous solutions with differing concentrations of materials, called solutes. An appropriate balance of water and solute concentrations must be maintained to ensure cellular functions. If the cytosol becomes too concentrated due to water loss, cell functions deteriorate. If the cytosol becomes too dilute due to water intake by cells, cell membranes can be damaged, and the cell can burst.
Hydrostatic pressure is the force exerted by a fluid against a wall and causes movement of fluid between compartments.
Fluid can also move between compartments along an osmotic gradient. Active transport processes require ATP to move some solutes against their concentration gradients between compartments.
Passive transport of a molecule or ion depends on its ability to pass easily through the membrane, as well as the existence of a high to low concentration gradient. What happens in tissues when capillary blood pressure is less than osmotic pressure? Plasma contains more sodium than chloride. How can this be if individual ions of sodium and chloride exactly balance each other out, and plasma is electrically neutral?
Skip to content Learning Objectives By the end of this section, you will be able to: Explain the importance of water in the body Contrast the composition of the intracellular fluid with that of the extracellular fluid Explain the importance of protein channels in the movement of solutes Identify the causes and symptoms of edema. External Website. Disorders of the… Fluid Balance: Edema. Edema is the accumulation of excess water in the tissues.
It is most common in the soft tissues of the extremities. The physiological causes of edema include water leakage from blood capillaries. Edema is almost always caused by an underlying medical condition, by the use of certain therapeutic drugs, by pregnancy, by localized injury, or by an allergic reaction. In the limbs, the symptoms of edema include swelling of the subcutaneous tissues, an increase in the normal size of the limb, and stretched, tight skin.
One quick way to check for subcutaneous edema localized in a limb is to press a finger into the suspected area. Chapter Review Your body is mostly water. Interactive Link Questions Watch this video to learn more about body fluids, fluid compartments, and electrolytes.
Fluid enters the capillaries from interstitial spaces. Review Questions. Critical Thinking Questions 1. How is fluid moved from compartment to compartment? Glossary extracellular fluid ECF fluid exterior to cells; includes the interstitial fluid, blood plasma, and fluids found in other reservoirs in the body fluid compartment fluid inside all cells of the body constitutes a compartment system that is largely segregated from other systems hydrostatic pressure pressure exerted by a fluid against a wall, caused by its own weight or pumping force interstitial fluid IF fluid in the small spaces between cells not contained within blood vessels intracellular fluid ICF fluid in the cytosol of cells.
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