called erythrocytes shaped blood elements capable by hemoglobin to transport oxygen to the tissues, and carbon dioxide - to the lungs.This is a simple cell structure, which has great importance for the life of mammals and other animals.Erythrocytes are the most numerous cell type of the body: about a quarter of all cells of the body - it's red blood cells.
General regularities of existence
erythrocyte red blood cell - cell occurred from the red germ hematopoiesis.The day these cells produced about 2.4 million, they enter the bloodstream and begin to carry out their functions.During the experiments, it is determined that the adult erythrocytes, whose structure is considerably simplified compared with other cells of the body live 100-120 days.
All vertebrates (with a few exceptions) from the respiratory organs to the tissues of oxygen carried by the hemoglobin of red blood cells.There are exceptions: all members of the family "white-blooded" fish there without hemoglobin, although they can synthesize it.Since the temperature of their environment oxygen is highly soluble in water, and the blood plasma, the more massive of its carriers, which are the red blood cells, these fish are not required.
Erythrocytes chordates
In such a cell, as the erythrocyte, a different structure depending on the class of chordates.For example, fish, birds, amphibians and morphology of these cells is similar.They differ only in size.The shape of red blood cells, the volume, size and the absence of some mammalian cell organelles differ from others who have the rest of chordates.There and its regularity: the mammalian red blood cells do not contain unnecessary organelles and cell nucleus.They are much smaller, but have a greater contact surface.
Considering the structure of the red blood cells of frog and man, common features can be identified immediately.Both cells contain hemoglobin and are involved in oxygen transport.However, human cells are smaller, they are oval and have two concave surfaces.Frog erythrocytes (also birds, fish and amphibians, except salamanders) spherical, they have a nucleus and cellular organelles, which can be activated if necessary.
in human red blood cells, like red blood cells of higher mammals, no nuclei and organelles.Size goat erythrocytes - 3-4 microns person - 6,2-8,2 m.In amfiumy (tailed amphibians) cell size of 70 microns.Obviously, the size is an important factor.Human erythrocyte albeit smaller, but has a large surface area due to the two concavities.
small size of the cells and their large number will greatly increase the ability of the blood to bind oxygen, which is now not depend on external conditions.And these structural features of human red blood cells are important because they allow you to feel comfortable in a certain habitat.It is a measure of adaptation to life on land, which has started to develop in amphibians and fish (unfortunately, not all the fish in the evolution of an opportunity to settle the land), and reached its peak of development in higher mammals.
structure of human erythrocytes
structure of blood cells depends on the functions assigned to them.It is described from three perspectives:
- Features of the external structure.
- Component composition of erythrocyte.
- internal morphology.
Externally, in profile, looks like erythrocyte biconcave disk, and from the front - like a round cage.Diameter normally 6,2-8,2 m.
Most serum contains cells with slight differences in size.With a lack of iron reduces the run, and a blood smear is recognized anisocytosis (many cells of different sizes and diameters).At deficiency of folic acid or vitamin B12 increases the red blood cell to megaloblasts.Its size is about 10-12 microns.The amount of normal cells (normocytes) 76-110 cubic meters.m.
structure of red blood cells in the blood - is not the only feature of these cells.More importantly their number.Small dimensions allowed to increase their number and thus the area of the contact surface.Oxygen is increasingly captured by human erythrocytes than a frog.And it is most easily given in the tissues of the human red blood cells.
number of really important.In particular, in an adult per cubic millimeter contains 4.5-5.5 million cells.In goats about 13 million red blood cells per milliliter, while the reptiles - only 0.5-1.6 million fish 0,09-0,13 million per milliliter.A newborn baby red blood cells is about 6 million per milliliter, and the elderly - less than 4 million per milliliter.
functions
erythrocytes Red blood cells - red blood cells, the amount, structure, functions and features of which are described in this publication, it is very important for humans.They realize some very important functions:
- transport oxygen to tissues;
- carry carbon dioxide from the tissues to the lungs;
- bind toxic substances (glycated hemoglobin);
- involved in immune responses (immune to viruses and by reactive oxygen species capable of detrimental effect on blood infections);
- able to tolerate certain drugs;
- involved in the implementation of hemostasis.
continue the consideration of such a cell is a red blood cell, its structure is optimized to maximize the implementation of the above functions.It is as easy and mobile, has a large contact surface for gas diffusion and chemical reactions with hemoglobin, and quickly and is divided up for the loss in the peripheral blood.This highly specialized cell to replace the function of which is not yet possible.
erythrocyte membrane
In such cells are erythrocytes, the structure is very simple, it does not apply to its membrane.This 3-layer.Mass fraction of the membrane is 10% of the cell.It consists of 90% protein and only 10% of the lipids.This makes the red blood cells are special cells in the body, as in almost all other membrane lipids prevail over proteins.
volume of red blood cells by the shape of the cytoplasmic membrane fluidity may vary.Outside, there is a layer of the membrane surface proteins that have a large number of carbohydrate residues.This glycopeptides, beneath which is a bilayer of lipids, hydrophobic ends facing inwardly and outwardly of the erythrocyte.Under the membrane on the inner surface of the back layer is protein without carbohydrate moieties.
erythrocyte receptor complex
membrane function is to ensure the deformability of red blood cell, which is necessary for the capillary passage.At the same time the structure of human red blood cells provides additional capabilities - cell interaction and electrolyte current.Proteins with carbohydrate residues - a receptor molecule, due to which on erythrocytes "hunted" CD8-leukocytes and macrophages of the immune system.
Red blood cells through receptors exist and are not destroyed by their own immune systems.And when the result of multiple push through the capillaries or because of mechanical damage to the red blood cells lose some receptors, macrophages of the spleen "extract" them from the bloodstream and destroy.
internal structure of erythrocyte
What is the red blood cell?The structure of it is of no less interest than the function.This cell is like a bag of hemoglobin, a limited membrane receptors which are expressed: clusters of differentiation and a diverse group of blood (by Landsteiner, Rh, Duffy, and on the other).But inside the cell is special and very different from other cells of the body.
The differences are as follows: red blood cells in women and men do not contain the core, they do not have ribosomes and endoplasmic reticulum.These organelles are removed after filling the cell cytoplasm hemoglobin.Then organelles proved unnecessary, because to push through the capillaries needed cell with minimum dimensions.Because it contains only inside hemoglobin and several auxiliary proteins.Their role is not yet clear.But due to lack of endoplasmic reticulum, ribosomes and the nucleus it became light and compact, and most importantly, can be easily deformed with the fluid membrane.And it's the most important features of the structure of red blood cells.
Erythrocyte lifecycle
main features are the red blood cells in their short lives.They can not share and synthesize protein from the removal of the nucleus from the cell, and therefore the structural damage to their cells accumulate.As a result, red blood cells characteristic of aging.However, hemoglobin, which is captured by macrophages in the spleen red blood cell death, will always be sent to the formation of new oxygen carriers.
life cycle of red blood cell begins in the bone marrow.This body is present in the plate material: sternum, in the wings of the ilium bone of the skull base, and also in the cavity of the femur.Here, from the stem cells of blood under the influence of cytokines produced predecessor myelopoietic code (CFU-GEMM).She then division will ancestress of hematopoiesis, designated with the code (BFU-E).From it formed the predecessor of erythropoiesis, which is indicated by a code (CFU-E).
The same cells are called colony of red blood cell germ.It is sensitive to erythropoietin - hormone substance nature, excreted by the kidneys.Increasing the amount of erythropoietin (in a positive feedback in functional systems) accelerates division and production of erythrocytes.
formation of red blood cells
sequence of transformations of bone marrow cell CFU-E is as follows: it is formed from erythroblast, and from it - pronormotsit giving rise basophilic normoblasts.With the accumulation of the protein becomes polychromatic normoblasts and then oxyphilic normoblasts.After removal of the nucleus it becomes reticulocytes.Last enters the bloodstream and differentiate (mature) to normal red blood cell.
destruction of red blood cells
about 100-125 days, the cells circulating in the blood, constantly carries oxygen and remove metabolic products from the tissues.It transports associated with hemoglobin carbon dioxide and sends it back to the lungs, simultaneously filling their protein molecule oxygen.And to the extent of injury and losing the molecule phosphatidylserine receptor molecules.Because of this, the erythrocyte falls "under the scope" of the macrophage and destroyed them.A heme derived from all undigested hemoglobin again directed to the synthesis of new erythrocytes.
