Erythrocyte deformability
Encyclopedia
Erythrocyte deformability refers to the cellular
properties of erythrocytes (red blood cells) which determine the degree of shape change under a given level of applied force
. Erythrocytes change their shape extensively under the influence of applied forces in fluid flow or while passing through microcirculation
. The extent and geometry
of this shape change is determined by both the mechanical properties of erythrocytes, the magnitude of the applied forces and the orientation of erythrocytes with the applied forces. Deformability is an intrinsic property of erythrocytes determined by geometric and material properties of this unique cell . No other cells of mammalian organism have deformability comparable with erythrocytes. Furthermore, erythrocyte deformability is a mammalian property and non-mammalian erythrocytes are not deformable to an extent comparable with mammalian erythrocytes.
Shape change of erythrocytes under applied forces (i.e., shear forces in blood flow) is reversible and the biconcave-discoid shape, which is normal for most mammals, is maintained after the removal of the deforming forces. In other words, erythrocytes behave like elastic
bodies, while they also resist to shape change under deforming forces. This viscoelastic behavior of erythrocytes is determined by the following three properties : 1) Geometry of erythrocytes; the biconcave-discoid shape provides an extra surface area for the cell, enabling shape change without increasing surface area. This type of shape change requires significantly smaller forces than those required for shape change with surface area expansion. 2) Cytolasmic viscosity; reflecting the cytoplasmic hemoglobin
concentration of erythrocytes. 3) Visco-elastic properties of erythrocyte membrane, mainly determined by the special membrane skeletal network of erythrocytes.
Erythrocyte deformability is an important determinant of blood viscosity, hence blood flow resistance in the vascular system . It affects blood flow in large blood vessels, due to the increased frictional resistance between fluid laminae under laminar flow conditions. It also affects the microcirculatory blood flow significantly, where erythrocytes are forced to pass through blood vessels with diameters smaller than their size.
Erythrocyte deformability is altered under various pathophysiological conditions. Sickle-cell disease
is characterized by extensive impairment in erythrocyte deformability, being dependent on the oxygen
partial pressure
. Erythrocyte deformability has also been demonstrated to be impaired in diabetes, peripheral vascular
diseases, sepsis
and a variety of other diseases.
Erythocyte deformability is a measurable property. Ektacytometry based on laser diffraction analysis
is the preferred method for measuring deformability .
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
properties of erythrocytes (red blood cells) which determine the degree of shape change under a given level of applied force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
. Erythrocytes change their shape extensively under the influence of applied forces in fluid flow or while passing through microcirculation
Microcirculation
The microcirculation is a term used to describe the small vessels in the vasculature which are embedded within organs and are responsible for the distribution of blood within tissues; as opposed to larger vessels in the macrocirculation which transport blood to and from the organs...
. The extent and geometry
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....
of this shape change is determined by both the mechanical properties of erythrocytes, the magnitude of the applied forces and the orientation of erythrocytes with the applied forces. Deformability is an intrinsic property of erythrocytes determined by geometric and material properties of this unique cell . No other cells of mammalian organism have deformability comparable with erythrocytes. Furthermore, erythrocyte deformability is a mammalian property and non-mammalian erythrocytes are not deformable to an extent comparable with mammalian erythrocytes.
Shape change of erythrocytes under applied forces (i.e., shear forces in blood flow) is reversible and the biconcave-discoid shape, which is normal for most mammals, is maintained after the removal of the deforming forces. In other words, erythrocytes behave like elastic
Elasticity
Elasticity may refer to:*Elasticity , continuum mechanics of bodies that deform reversibly under stressNumerous uses are derived from this physical sense of the term, which is inherently mathematical, such as used in Engineering, Chemistry, Construction and variously in Economics:*Elasticity , the...
bodies, while they also resist to shape change under deforming forces. This viscoelastic behavior of erythrocytes is determined by the following three properties : 1) Geometry of erythrocytes; the biconcave-discoid shape provides an extra surface area for the cell, enabling shape change without increasing surface area. This type of shape change requires significantly smaller forces than those required for shape change with surface area expansion. 2) Cytolasmic viscosity; reflecting the cytoplasmic hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
concentration of erythrocytes. 3) Visco-elastic properties of erythrocyte membrane, mainly determined by the special membrane skeletal network of erythrocytes.
Erythrocyte deformability is an important determinant of blood viscosity, hence blood flow resistance in the vascular system . It affects blood flow in large blood vessels, due to the increased frictional resistance between fluid laminae under laminar flow conditions. It also affects the microcirculatory blood flow significantly, where erythrocytes are forced to pass through blood vessels with diameters smaller than their size.
Erythrocyte deformability is altered under various pathophysiological conditions. Sickle-cell disease
Sickle-cell disease
Sickle-cell disease , or sickle-cell anaemia or drepanocytosis, is an autosomal recessive genetic blood disorder with overdominance, characterized by red blood cells that assume an abnormal, rigid, sickle shape. Sickling decreases the cells' flexibility and results in a risk of various...
is characterized by extensive impairment in erythrocyte deformability, being dependent on the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
partial pressure
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
. Erythrocyte deformability has also been demonstrated to be impaired in diabetes, peripheral vascular
Vascular
Vascular in zoology and medicine means "related to blood vessels", which are part of the circulatory system. An organ or tissue that is vascularized is heavily endowed with blood vessels and thus richly supplied with blood....
diseases, sepsis
Sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
and a variety of other diseases.
Erythocyte deformability is a measurable property. Ektacytometry based on laser diffraction analysis
Laser diffraction analysis
Laser diffraction analysis or laser diffraction spectroscopy is a scientific technique which utilizes properties of the diffraction patterns of a laser beam passed through a substance, to measure the size of its particles...
is the preferred method for measuring deformability .