Essay Sample on Differences Between Intracellular Fluids and Extracellular Fluids

Published: 2023-03-15
Essay Sample on Differences Between Intracellular Fluids and Extracellular Fluids
Type of paper:  Essay
Categories:  Knowledge Biology Anatomy
Pages: 5
Wordcount: 1329 words
12 min read

The intracellular fluid is the principal component of the cytoplasm or the cytosol and is located in the cells. The fluid consists of approximately 60% of the human body's water (Kim et al., 2017). In a normal size adult male, the fluid can account for more than 25 liters of water. Moreover, the volume of the ICF is always stable because there is close regulation of the total amount of water found in the living cells. Therefore, if the cells have a low amount of water, more solutes will be concentrated in the cytoplasm to enable normal cellular functions. Thus, if a cell is more concentrated with water, the cells will always be destroyed as they will burst.

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On the other hand, the remaining one-third of the water content of the body is accounted for by the extracellular fluids. More than 20% of the extracellular fluid is located in the plasma (Kim et al., 2017), which travels through various parts of the body in blood vessels and transports numerous materials such as wastes, gases, nutrients, electrolytes, proteins such as antibodies and clotting factors, as well as blood cells. Nevertheless, waste materials, nutrients, and gases travel between the cells and capillaries through the ECF. A semi-permeable cell membrane separates cells from the ECF which assists in regulating the transfer of materials between the cell's interior and the extracellular fluid. (Hahn et al., 2016).

The intracellular fluid or the cytosol is made up of both large and small water-soluble molecules, dissolved ions, and water. There are always various immense enzymes that are involved in the metabolism of the cells which makes the combination of small particles found in the ICF to be extraordinarily complex. The depicted proteins are always included in different biochemical procedures that deactivate or activate toxins and sustain the cells. The intracellular fluid mostly comprises of water that takes approximately 70% of a cell's total volume (Hahn et al., 2016).

The cytosol's pH is 7.4, and it is separated from the ECF by the cell membrane. However, the ICF can pass through the same cell membrane via pumps and specialized channels during active and passive transport (Kim et al., 2017). The ion concentration in the intracellular fluid of the cytosol is often slightly different from the ion concentration in the ECF. The ICF is made up of macromolecules that are in a higher amount, such as nucleic acids and proteins, than the ones located outside the cell. In contrast to the ECF, the ICF has low sodium ion concentration and high potassium ion concentration. The reason is that Na+/K ATPase pumps which control and monitor active transportation of sodium and potassium. Ions are transported against their gradient of absorption by the depicted pumps to maintain the ion composition in the intracellular fluid.

On the other hand, the ECF mainly consists of anions and cations (Kim et al., 2017). The anions include hydrogen carbonate and chloride, while the cations include calcium, potassium, and sodium, which are significant for water transport in the entire body. More than 90% of plasma consists of water as well as dissolved proteins, carbon dioxide, hormones, mineral ions, clotting factors, and glucose as it is the primary transportation medium for excretory products. The depicted dissolved substances help in physiological processes such as the distribution of drugs in the entire body, the functioning of the immune system, and gas exchange (Kim et al., 2017).

Ways in Which Sodium and Potassium Participate in Electrolyte Balance in the Body


Both potassium and sodium are significant in the human body. When potassium works along with sodium, it regulates the balance of acid-base and water in the tissues and blood. Potassium penetrates through a human's cell more readily as opposed to sodium and instigates the short exchange of sodium-potassium across the involved cell membranes (Brahma et al., 2019). As they move through the nerve cells, the electric potential is generated by the flux of sodium-potassium which assists in nerve impulses conduction. The potassium then alters its membrane potential as it leaves the cell to allow the progression of the nerve impulses (Cheng & Jusof, 2018).

The depicted gradient of the electrical potential, established by the pump of sodium-potassium, assists in the generation of muscle contraction as well as regulating the heartbeat. Also, the pump prevents cell swelling such that if potassium is removed, it might lead to the accumulation of water in the cells making the cells grow and burst (Cheng & Jusof, 2018).


Sodium helps with electrical signals in the body, allowing the human brain to function effectively as well as muscles to fire. In most cases, at the cellular level, half of the electrical pump maintains sodium in the plasma of a human body and potassium in the cells (Brahma et al., 2019). Moreover, sodium helps in energy metabolism and specific cellular biochemical reactions such that it is involved in protein synthesis from the amino acids found in the cell. Thus, sodium assists in building muscles and healthy growth (Cheng & Jusof, 2018).

Ways that Homeostasis May be Disrupted

When the volume of the fluids found in the body decreases, there will be increased osmolality due to increased sodium concentration in the blood, which will, in turn, lead to stimulation of the hypothalamus. The hypothalamus gets construed as an osmoreceptor that reacts to any osmotic pressure change and often has numerous impacts on the pituitary gland. In response, the antidiuretic hormone will then be released into the bloodstream by the posterior pituitary gland resulting in the retention of more water by the kidney. The action will then lead to increased returned water to the extracellular fluid as well as concentrated urine creating depletion of the volume (Hahn et al., 2016).

When the concentration of sodium decreases in the blood, the adrenal cortex stimulates into secreting the aldosterone hormone that commands the kidney's distal nephrons to retain a lot of sodium (Brahma et al., 2019). When the ECF has normal sodium levels, it will always maintain and attract the optimum water amount. Moreover, when the aldosterone hormone is released, the sensors will always detect heart atria stretching that depicts increased venous return or excessive return of the ECF volume. The extracellular fluid prevents the secretion of the aldosterone that results in high water excretion via renal filtration (Brahma et al., 2019).

Solutions to Return the Body to Homeostasis

To attain the right balance of the intracellular fluid and the extracellular fluid, one must consume the right amount of fluids. They should take in the right concentration of different ions required by the body, such as magnesium, potassium, and sodium. However, if there is too little or too much of the depicted minerals, it can result in different complications such as cardiac arrhythmias that are often triggered by low levels of magnesium and potassium (Hahn et al., 2016).

Also, patients might require therapies of electrolyte and fluid replacement, where, in most cases, nurses are the ones responsible for monitoring and delivering. For instance, crystalloid fluid might be recommended because they are isotonic and retained longer in the extracellular fluids. Thus, they often match the tonicity of the blood (Brahma et al., 2019).


Brahma, S. K., Mukherjee, M., Chandra, D., Bhattacharya, D., & Bhattacharya, S. B. (2019). The effects of balanced versus saline-based colloid and crystalloid solutions on acid-base and electrolyte balance in gastrointestinal surgery. Anaesthesia, Pain & Intensive Care, 159-165. Retrieved from

Cheng, H. M., & Jusof, F. (2018). Sodium and Potassium Balance. In Defining Physiology: Principles, Themes, Concepts (pp. 153-164). Springer, Singapore. Doi: 10.1007/978-981-13-0499-6_13

Hahn, R. G., Nyberg Isacson, M., Fagerstrom, T., Rosvall, J., & Nyman, C. R. (2016). Isotonic saline in elderly men: an open-labeled controlled infusion study of electrolyte balance, urine flow, and kidney function. Anaesthesia, 71(2), 155-162. Doi: 10.1111/anae.13301

Kim, E. J., Choi, M. J., Lee, J. H., Oh, J. E., Seo, J. W., Lee, Y. K., ... & Koo, J. R. (2017). Extracellular fluid/intracellular fluid volume ratio as a novel risk indicator for all-cause mortality and cardiovascular disease in hemodialysis patients. PLoS One, 12(1), e0170272. Doi: 10.1371/journal.pone.0170272

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