por What is crenation?
crenation is a term used to describe the shape of some object or structure that has scalloped edges or the surface is irregular. Generally, the term is applied to the hematological phenomenon where red blood cells or red blood cells are subjected to a hypertonic solution. As a consequence, the cell proceeds to release the water that is inside it, causing flaccidity and could cause cell destruction.
The opposite phenomenon occurs when blood cells are exposed to a hypotonic environment, where there are fewer solutes inside the cell. In this case, the cell bursts, due to the accumulation of water, and is called hemolysis.
In addition, crenation is a term used to describe certain characteristics of red blood cells, where they exhibit a kind of projections on their surface.
In most cases, the observation of said hematological irregularities are a technical artifact, while in some patients they do represent indications of some pathology.
Definition
In biology, the concept of crenation is broad and can be applied to different scenarios. In this article we will focus on describing two of its meanings in the area of hematology: one of these is the loss of water from red blood cells and the other refers to an irregular characteristic of these cells.
Osmotic behavior of erythrocytes
The movement of water and the concentration of solutes outside and inside cells are parameters that drive the processes of osmosis and diffusion, which play a vital role in biological systems. Before describing the phenomenon of crenation, we must understand two key concepts: diffusion and osmosis.
Passive Transport Basics
Diffusion
The movement of particles from a relatively more concentrated area to a less concentrated one—down the concentration gradient—is called diffusion. For example, when carbon dioxide diffuses out of the cell or the movement of sodium ions into the cell during a nerve impulse.
Osmosis
Osmosis occurs when water is the substance that diffuses through a semi-permeable membrane —such as biological membranes— in the presence of a solute. In this case, the solute cannot diffuse across the membrane, but water can.
There are innumerable examples of osmosis. In fact, it is a phenomenon that extends to our daily lives. When we prepare a pickle of vegetables, we subject them to a very concentrated solution of salt, and they tend to lose their water and take on a wrinkled appearance.
osmosis in erythrocytes
In cells, membranes behave like a semi-permeable barrier. It is an essential component, since cells need to delimit their space and they do so with this lipid and dynamic structure.
The membrane of red blood cells or erythrocytes are semi-permeable structures and the direction of water movement will depend on the internal and external concentration of this system.
There is a terminology to refer to these parameters: when the solution is more concentrated than the interior of the cell, we say that it is hypertonic regarding the latter. In contrast, when the external concentration is lower it is a solution hypotonic If the concentration in both compartments is the same, the term isotonic.
crenation
Like the pickled vegetables in the previous example, when we put red blood cells into a hypertonic solution, water tends to flow out of the cell. Consequently, the cell wrinkles and loses its turgor. This phenomenon is called crenation.
The analogous concept of cell dehydration in plant structures is known as plasmolysis. During water loss, the cell wall remains intact, while the membrane wrinkles and organelles progressively accumulate in the center.
hemolysis
Following this logic, the reverse phenomenon of crenation occurs when we submit red blood cells to a hypotonic solution. Here, the water will enter the cell and could cause cell rupture, leading to hemolysis.
Importance of crenation and hemolysis in medicine
In many medical settings, it is necessary to provide the patient with intravenous infusions. For example, if an individual is not able to eat normally orally, it will be necessary to feed them through an intravenous nutrient solution, that is, the supply of food occurs directly into the veins.
The concentration of body fluids must be known to supply a solution of equal concentration (isotonic), to avoid crenation or hemolysis.
Crenation and the shape of erythrocytes
According to the meaning of the term crenation, it is used to describe the peculiar characteristic of red blood cells to develop numerous extensions in regular and short patterns all over their surface. When these cells present this condition, they resemble a sea urchin or a porcupine, which is why the phenomenon is also called echinocytosis.
Crenation in erythrocytes was initially evidenced by Eric Ponder, who described it as a phenomenon of transformation of the disc into a sphere with multiple projections.
Causes of crenation
There are multiple causes that can explain the phenomenon of crenation in erythrocytes. In some blood smears it is common to observe crenate cells, not only in individuals with special hematological conditions, they also appear in healthy individuals.
Artifacts in the laboratory
Crenation is usually a technical artifact, the product of a prolonged rest of the sample overnight before carrying out the procedure required for the observation of the blood in the laboratory.
They also usually appear when erythrocytes are separated from plasma and suspended in a saline solution at 9 g/l. Similarly, the presence of fat on the slide on which the sample is deposited causes the observation of crenate cells.
The use of certain chemical compounds also leads to cell crenation. It has been shown that the use of EDTA produces a marked crenation pattern.
medical conditions
In the event that the sample extension is made with fresh blood, crenation represents a medical alert that must be considered.
The phenomenon is generally observed in patients with medical conditions such as uremia (accumulation of toxic products in the blood) or in individuals undergoing extracorporeal circulation. Crenation has also been noted to be common in preterm infants following exchange transfusion.
References
Guyton, AC, & Hall, JE Compendium of Medical Physiology. Elsevier. Lewis, SM, Bain, BJ, & Bates, I. Practical Hematology. Elsevier Spain. Thibodeau, GA, Patton, KT, & Howard, K. Structure and Function. Elsevier Spain. Wintrobe, MM Wintrobe’s clinical hematology. Lippincott Williams & Wilkins.