Body Fluids- Intracellular Fluid Vs Extracellular Fluid: Aqueous solutions are the medium in which life’s chemical reactions take place. Solutes are substances dissolved in a solution. In the body, solutes vary depending on the part of the body but can include proteins that transport lipids, carbohydrates, and, very importantly, electrolytes. It is common in medicine to refer to a mineral dissociated from a salt that has an electrical charge (an ion) as an electrolyte. Sodium ions (Na+) and chloride ions (Cl–) are commonly referred to as electrolytes.

Osmosis is the process of water moving between compartments in the body by passing through semipermeable membranes of cells. Water diffuses from regions of higher concentration to regions of lower concentration along an osmotic gradient across a semi-permeable membrane by osmosis. Consequently, water will move into and out of cells and tissues based on the relative concentrations of water and solutes found there. Maintaining a balance of solutes inside and outside of cells is necessary to ensure normal cell function.

Body Water Content

A silhouette of a human body with various organs highlighted is depicted in this illustration. Each organ contains a specific percentage of water. There is typically 80% to 85% water in the brain, teeth contain 8% to 10% water, a single lung contains 75% to 80% water, the heart contains 75% to 80% water, the bones contain 20% to 25% water, the liver contains 70% to 75% water, the kidneys contain 80% to 85% water, the skin contains 70% to 75% water, and the muscles also contain 70% to 75% water.

Water Content Varies In Different Body Organs And Tissues, From As Little As 8 Percent In The Teeth To As Much As 85 Percent In The Brain.
Water Content Varies In Different Body Organs And Tissues, From As Little As 8 Percent In The Teeth To As Much As 85 Percent In The Brain.

Human beings are mainly composed of water, ranging from about 75 percent of body mass in infants to about 50–60 percent in adult men and women, and as low as 45 percent in those over 65 years of age. A person’s percent of body water changes as he or she develops, since the proportions of each organ, muscle, fat, bone, and other tissue change from infancy to adulthood. The brain and kidneys have the highest proportion of water, which makes up 80-85 percent of their mass. Teeth, on the other hand, contain the least amount of water, at 8–10 percent.

Fluid Compartments: Intracellular And Extracellular Fluid

There are several cells surrounding a small blood vessel in this diagram. There is fluid between each cell of the body called interstitial fluid (IF), which is a type of extracellular fluid (ECF). Extracellular fluid can also be found in blood vessels. ICF, or intracellular fluid, is the fluid that resides in the cytoplasm of each body cell.

Fluid within cells is known as intracellular fluid (ICF). Interstitial fluid (IF) is part of the extracellular fluid (ECF) between cells. Blood plasma is the second component of the ECF. The IF is responsible for transporting materials between the plasma and the cells.

The Intracellular Fluid (Icf) Is The Fluid Within Cells.
The Intracellular Fluid (Icf) Is The Fluid Within Cells.

We can talk about body fluids in terms of their specific compartments, which are largely separated from one another by some sort of physical barrier. The intracellular fluid compartment (ICF) refers to all fluid enclosed within cells by their plasma membranes.

The extracellular fluid (ECF) surrounds all cells in the body. Specifically, extracellular fluid consists of two components: the fluid component of the blood (called plasma) and the interstitial fluid (IF), which surrounds all cells and is not in the bloodstream.

Intracellular Fluid

A major component of the cytosol/cytoplasm is the ICF, which is found within cells. The ICF contains 60 percent of the body’s total water, and in an average-sized adult male, it accounts for about 25 liters (seven gallons) of fluid.

As the amount of water within living cells is tightly regulated, the fluid volume tends to be very stable. When the amount of water inside a cell falls below a certain level, the cytosol becomes too concentrated with solutes to carry on normal cellular activities; if too much water enters a cell, the cell may burst and die.

Most Of The Water In The Body Is Intracellular Fluid. The Second Largest Volume Is The Interstitial Fluid, Which Surrounds Cells That Are Not Blood Cells.
Most Of The Water In The Body Is Intracellular Fluid. The Second Largest Volume Is The Interstitial Fluid, Which Surrounds Cells That Are Not Blood Cells.

In this pie chart, you can see that about 55% of water in the human body is intracellular fluid. The interstitial fluid makes up about 30% of the human body’s water. The remaining 15% of water consists mostly of plasma, along with a small percentage labeled “other fluid”.

Extracellular Fluid Composition Or Consists Of

One-third of body water is provided by the extracellular fluid (ECF). Twenty percent of the ECF is found in the plasma. Blood vessels carry plasma through the body, which carries a variety of materials, including blood cells, proteins (including clotting factors and antibodies), electrolytes, nutrients, gases, and waste products.

The Graph Shows The Composition Of The ICF, If, And Plasma. The Compositions Of Plasma And If Are Similar To One Another But Are Quite Different From The Composition Of The ICf.
The Graph Shows The Composition Of The ICF, If, And Plasma. The Compositions Of Plasma And If Are Similar To One Another But Are Quite Different From The Composition Of The ICf.

Through the IF, gases, nutrients, and waste materials travel between capillaries and cells. IF and the interior of cells is separated by a selectively permeable cell membrane. This membrane regulates the passage of materials between the IF and the interior of the cell.

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Other water-based ECF are present in the body. They include the cerebrospinal fluid that bathes the brain and spinal cord, lymph, the synovial fluid in joints, the pleural fluid in the pleural cavities, the pericardial fluid in the cardiac sac, the peritoneal fluid in the peritoneal cavity, and the aqueous humor of the eye. Since these fluids are outside cells, they are also considered components of the ECF compartment.

Extracellular compartments consist of interstitial, intravascular, and transcellular compartments. Approximately one-third of the body’s water is found in its extracellular fluid (ECF).

The Sodium-potassium Pump Is Powered By Atp To Transfer Sodium Out Of The Cytoplasm And Into The Ecf.
The Sodium-potassium Pump Is Powered By Atp To Transfer Sodium Out Of The Cytoplasm And Into The Ecf.

Types And Examples Of Extracellular Fluid

Intravascular compartment

Mammals’ intravascular fluid is blood, a complex mixture of suspension (blood cells), colloid (globulins), and solutes (glucose and ions). Blood is made up of two compartments: the intracellular compartment (the fluid inside the blood cells) and the extracellular compartment (the plasma in the blood).

The average male (70 kilograms or 150 pounds) has a plasma volume of approximately 3.5 liters (0.77 imp gal; 0.92 U.S. gal). A large part of the volume of the intravascular compartment is controlled by hydrostatic pressure gradients, as well as by reabsorption by the kidneys.

Interstitial compartment

The interstitial compartment (also called “tissue space”) surrounds the cells of a tissue. It is filled with interstitial fluid, which includes lymph. In addition to allowing ions, proteins, and nutrients to cross the cell membrane, the interstitial fluid provides an immediate microenvironment.

Blood capillaries continuously refresh and lymphatic capillaries continually collect this fluid. The interstitial space of a man (70 kilograms or 150 pounds) contains approximately 10.5 liters (2.3 imperial gallons; 2.8 gallons) of fluid.

Transcellular compartment

The third extracellular compartment, known as the transcellular compartment, is comprised of spaces in the body where fluid does not normally accumulate in large amounts, or where any significant fluid accumulation is physiologically counterproductive. An example of a transcellular space is the eye, the central nervous system, the peritoneal and pleural cavities, and the joint capsules.

It is normal for such spaces to contain a small amount of fluid, called transcellular fluid. The aqueous humor, the vitreous humor, the cerebrospinal fluid, the serous fluid produced by the serous membranes, and the synovial fluid produced by the synovial membranes are all transcellular fluids. All of them are important, yet there is not much of each.

There is only about 150 milliliters of cerebrospinal fluid in the entire central nervous system at any one time (5.3 imp fl oz; 5.1 U.S. fl oz).

The above fluids are produced by active cellular processes using blood plasma as the raw material, and they are more or less similar to blood plasma except for a few modifications tailored to their functions. Various cells of the CNS, mostly the ependymal cells, produce cerebrospinal fluid from blood plasma, for example.

Composition of Body Fluids: Intracellular And Extracellular Fluid

There are more similarities between the plasma and IF components of the ECF than either has to the ICF. Protein, sodium, chloride, and bicarbonate are highly concentrated in blood plasma. Protein concentrations in the IF are relatively low, but sodium, chloride, and bicarbonate concentrations are high. Conversely, potassium, phosphate, magnesium, and protein are more abundant in the ICF. Overall, the ICF contains high concentrations of potassium and phosphate \(mathbf{HP{O_4}^{-2}}\), whereas both plasma and the ECF contain high concentrations of sodium and chloride.

The bar graph shows the concentration of several ions and proteins in intracellular fluid, interstitial fluid, and plasma. On the X-axis, ions and proteins are categorized. The Y-axis shows the concentration in milliequivalents per liter, ranging from 0 to 160. On the X-axis, three different colored bars are shown above each compound. The first bar represents intracellular fluid (ICF), the second bar represents interstitial fluid (IF, which is part of ECF), and the third bar represents plasma (ECF).

High concentrations of K plus and HPO four two minus are present in the intracellular fluid. The level of MG two-plus and protein is lower, and the amount of the other compounds is negligible. The interstitial fluid contains high concentrations of NA plus and CL minus, along with smaller amounts of HCO 3 minus, and very small amounts of the other compounds. Plasma contains large concentrations of NA plus and CL minus, with smaller concentrations of HCO 3 minus and protein, and negligible amounts of the others.

Function Of Intracellular Fluid

Fluid Movement Between Compartments

Fluids move between compartments as a result of hydrostatic pressure, the force exerted by a fluid against a wall. The hydrostatic pressure of blood can be defined as the force exerted by blood against the walls of the blood vessels by the pumping action of the heart. At the arteriolar end of capillaries, hydrostatic pressure (also known as capillary blood pressure) is higher than the opposing colloid osmotic pressure in blood-a “constant” pressure primarily caused by circulating albumin.

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Plasma and nutrients are forced out of capillaries and into surrounding tissues by this pressure. Fluids and cellular wastes enter the capillaries from the venule end, where hydrostatic pressure is less than osmotic pressure. The filtration pressure squeezes the plasma from the blood into the IF around the tissue cells. Surplus fluid in the interstitial space that is not returned directly to the capillaries is drained from tissues by the lymphatic system, which then reenters the vascular system at the subclavian veins.

Net Filtration Occurs Near The Arterial End Of The Capillary Since Capillary Hydrostatic Pressure (Chp) Is Greater Than Blood Colloidal Osmotic Pressure (Bcop).
Net Filtration Occurs Near The Arterial End Of The Capillary Since Capillary Hydrostatic Pressure (Chp) Is Greater Than Blood Colloidal Osmotic Pressure (Bcop).

Near the arterial end of the capillary, net filtration occurs because capillary hydrostatic pressure (CHP) is greater than blood colloidal osmotic pressure (BCOP). Since CHP = BCOP, there is no net movement of fluid near the midpoint of the capillary. In the capillary, net reabsorption occurs near the venous end since BCOP is greater than CHP.

Solute Movement Between Compartments

The movement of some solutes between compartments requires energy and is an active transport process, whereas the movement of other solutes is passive. Cells utilize active transport to move specific substances against concentration gradients through membrane proteins, requiring energy in the form of ATP. The sodium-potassium pump, for example, uses active transport to pump sodium out of cells and potassium into cells, with both substances moving against their concentration gradients.

Glucose Molecules Use Facilitated Diffusion To Move Down A Concentration Gradient Through The Carrier Protein Channels In The Membrane.
Glucose Molecules Use Facilitated Diffusion To Move Down A Concentration Gradient Through The Carrier Protein Channels In The Membrane.

The diagram shows a carrier protein embedded in the plasma membrane between the cytoplasm and extracellular fluid. The extracellular fluid contains several glucose molecules. The carrier protein reacts with the extracellular fluid in the first step and with the cytosol in the second step. A glucose molecule travels from the extracellular fluid into the carrier protein.

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After that, the protein changes shape, closing at both ends. In this way, the glucose is pushed closer to the cytosol end of the carrier protein. Afterward, the protein opens on the cytosol side and closes on the extracellular side, allowing glucose to enter the cytosol.

As a molecule or ion passes through a membrane, it is dependent on the presence of a concentration gradient that allows the molecules to diffuse from an area of high concentration to an area of low concentration. Molecules such as gases, lipids, and water (which also uses water channels in the membrane called aquaporins) pass fairly easily through the cell membrane; others, including polar molecules such as glucose, amino acids, and ions, do not. 

By moving down a concentration gradient through specific protein channels in the membrane, some of these molecules enter and exit cells using facilitated transport. Energy is not required for this process. Transporters that use facilitated transport, for example, transport glucose into cells.

The Major Intracellular And Extracellular Electrolytes: Sodium, Potassium, And Chloride

An electrolyte is a substance that dissociates in solution and can conduct an electric current. Electrolytes are found in the extracellular and intracellular fluids. In extracellular fluid, sodium is the most abundant cation and chloride is the most abundant anion. Potassium is the most abundant cation in intracellular fluid. The electrolytes play a crucial role in maintaining homeostasis.

Similarities Between Intracellular and Extracellular Fluid

  • Total body fluids consist of both intracellular and extracellular fluids.
  • Cell membranes allow materials to exchange between intracellular fluid and extracellular fluid.
  • Both intracellular and extracellular fluids serve to nourish the body’s cells and lubricate its cavities.

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Intracellular Fluid Vs Extracellular Fluid Percentage

  • Definition
    • Intracellular Fluid: The intracellular fluid is a fluid found in the cell membrane, containing dissolved ions and other components, which are crucial to cellular functions.
    • Extracellular Fluid: Extracellular fluid is a fluid that surrounds a particular cell, aiding it in its function.
  • Significance
    • Intracellular Fluid: The intracellular fluid is found within the cell.
    • Extracellular Fluid: The extracellular fluid is located outside of the cell.
  • Components
    • Intracellular Fluid: The cytosol is part of the intracellular fluid.
    • Extracellular Fluid: Extracellular fluid is composed of blood plasma, tissue fluid, and transcellular fluid.
  • Sodium and Potassium Ion Concentration
    • Intracellular Fluid: In intracellular fluid, the concentration of sodium ions is low and the concentration of potassium ions is high.
    • Extracellular Fluid: The concentration of sodium ions in the extracellular fluid is high and the concentration of potassium ions is low.
  • Water
    • Intracellular Fluid: 55% of the body’s water is found in the intracellular fluid.
    • Extracellular Fluid: About 45 percent of the body is made up of extracellular fluid.
  • Body Weight
    • Intracellular Fluid: The intracellular fluid comprises 33% of total body weight.
    • Extracellular Fluid: The extracellular fluid comprises 27% of total body weight.
  • Volume
    • Intracellular Fluid: The intracellular fluid comprises 19 L of total body fluids.
    • Extracellular Fluid: The extracellular fluid comprises 23 L of total body fluids.

Disorders Or Diseases From The Fluid Imbalance: Edema

Edema is the accumulation of excess water in the tissues. This most commonly occurs in the soft tissues of the extremities. Water leakage from blood capillaries is one of the physiological causes of edema. Almost always, edema is caused by an underlying medical condition, by the use of certain drugs, by pregnancy, by localized injury, or by an allergic reaction.

Symptoms of edema in the limbs include swelling of subcutaneous tissues, an increase in the size of the limb, and tightened skin. A finger pressed into a suspected area will confirm whether there is subcutaneous edema there. Edema may occur if the depression persists for several seconds after the finger is removed (a condition known as “pitting”).

An Allergic Reaction Can Cause Capillaries In The Hand To Leak Excess Fluid That Accumulates In The Tissues.
An Allergic Reaction Can Cause Capillaries In The Hand To Leak Excess Fluid That Accumulates In The Tissues.

In addition to being a symptom of heart and kidney failure, pulmonary edema occurs when excess fluid accumulates in the air sacs of the lungs. The symptoms of pulmonary edema may include chest pain and difficulty breathing. Any person with symptoms of pulmonary edema should seek immediate medical attention since it compromises gas exchange in the lungs.

As a result of heart failure, pulmonary edema occurs when excessive amounts of fluid accumulate in the pulmonary capillaries of the lungs because the left ventricle of the heart is unable to pump sufficient blood into the systemic circulation.

Whenever the left side of the heart is unable to pump out its normal volume of blood, the blood in the pulmonary circulation gets “backed up,” first in the left atrium, then in the pulmonary veins, and finally in the pulmonary capillaries. Fluid is pushed out of the pulmonary capillaries and into the lung tissues due to the increased hydrostatic pressure within them as blood continues to flow into them from the pulmonary arteries.

In chronic and severe liver disease, where the liver is unable to manufacture plasma proteins, edema may also be caused by damage to blood vessels and lymphatic vessels, or by a decrease in osmotic pressure. In capillaries, a decrease in plasma proteins results in a decrease in colloid osmotic pressure (which counterbalances the hydrostatic pressure). In this process, water is lost from the blood to the surrounding tissues, causing edema.

Presented here are the dorsal surfaces of a person’s right and left hands. There are several blood vessels visible under the left hand’s skin. However, the top of the right hand is swollen and there are no visible blood vessels.

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 case of a toll collector or a supermarket cashier. In the lower limbs, deep veins rely on skeletal muscle contractions to push against the veins and return blood to the heart. As a result, venous blood pools in the lower limbs and can leak into the surrounding tissues.

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Among the medications that can cause edema are vasodilators, calcium channel blockers used to treat hypertension, non-steroidal anti-inflammatory drugs, estrogen therapies, and some diabetes medications. Medical conditions that can cause edema include congestive heart failure, kidney damage and kidney disease, disorders of the veins of the legs, and cirrhosis.

Edema is usually treated by eliminating the underlying cause. Exercises that help keep the blood and lymph flowing through the affected areas can reduce the effects of the condition. 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.

Conclusion

Water makes up most of your body. Fluids in the body are aqueous solutions containing varying concentrations of solutes. To maintain cellular function, an appropriate balance of water and solute concentrations must be maintained. The cytosol becomes too concentrated due to water loss, which compromises cell function. Cell membranes can be damaged, and the cell can burst if the cytosol becomes too dilute due to water intake by cells.

Hydrostatic pressure is the force exerted by a fluid against a wall and causes a fluid to move between compartments. Additionally, fluid can move between compartments along an osmotic gradient. Some solutes need ATP to move across concentration gradients between compartments during active transport processes. The passive transport of a molecule or ion is determined by its ability to pass through the membrane as well as the presence of a gradient of high to low concentration.

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FAQs

What is the difference between intracellular and extracellular fluid?

What is the difference between Intracellular and Extracellular Fluid? Intracellular fluid is inside the cell while extracellular fluid is outside the cell.

What is the difference between ICF and ECF?

Intracellular fluid (ICF) is the cytosol within the cell. Extracellular fluid (ECF) surrounds the cells serves as a circulating reservoir. The ECF is divided into the interstitial fluid which bathes the outside of the cells and intravascular fluid (i.e., plasma, lymph, and cerebral spinal fluid).

What is the difference between intracellular and interstitial fluids?

  • Intracellular fluid: The liquid found inside cells, between the endomembrane and the membrane-bound organelles.
  • Interstitial fluid: A solution that bathes and surrounds the cells of multicellular animals; also called tissue fluid.

What is only found in the intracellular fluid?

The intracellular fluid contains water and dissolved solutes and proteins. The solutes are electrolytes, which help keep our body functioning properly. There are a lot of electrolytes inside the cell, but potassium, magnesium, and phosphate have the greatest concentrations.

What is meant by extracellular fluid?

Extracellular fluid, in biology, is body fluid that is not contained in cells. It is found in blood, in lymph, in body cavities lined with serous (moisture-exuding) membrane, in the cavities and channels of the brain and spinal cord, and in muscular and other body tissues.

Is intracellular fluid hypertonic?

The difference in total charge between the inside and outside of the cell is called the membrane potential.