Red blood cells or also known as erythrocytes derived from the Greek, which means red and kytos erythros which means sheath / cell).
red blood cells
Vertebrate erythrocytesFrom left to right: erythrocytes, platelets, and leukocytes
Erythrocytes is generally composed of hemoglobin, a complex metalloprotein containing heme groups, which in the heme group, iron atom will be temporarily connected with molecular oxygen (O2) in the lungs and gills, and then the oxygen molecules will be off to the entire the body. Oxygen can easily diffuse through the membrane of red blood cells. Hemoglobin in erythrocytes also carries some waste products such as CO2 from tissues throughout the body. Almost the entire molecule of CO2 is carried in the form of bicarbonate in the blood plasma. Myoglobin, a compound related to hemoglobin, acts as a carrier of oxygen in muscle tissue.
The color of erythrocytes derived from the heme group found in hemoglobin. While his own blood plasma fluid brownish yellow, but the erythrocytes will change color depending on the condition of hemoglobin. When bound to oxygen, erythrocytes will be colored bright red when oxygen is removed and then the color will be darker in color erirosit, and will cause a bluish discoloration of the blood vessels and skin. Oximetry pressure method have benefited from this by measuring the color change in arterial blood oxygen saturation using colorimetric techniques.
Reducing the number of oxygen carrying proteins in some specific cell (rather than dissolve in body fluids) is an important stage in the evolution of living things vertebrates (vertebratae). This process causes the formation of red blood cells that have a low viscosity, with higher oxygen levels, and better diffusion of oxygen from the blood cells to tissues. Erythrocytes of different sizes in each species of vertebrates. Erythrocyte width approximately 25% larger than the diameter of capillaries and have concluded that this increases the oxygen transfer from erythrocytes and tissues.
Vertebrate erythrocytes is known to have no fish from the families Channichthyidae. Fish from Channichtyidae families living in cold water environments containing high levels of oxygen and oxygen freely dissolved in their blood . Although they did not use hemoglobin anymore, remnants of hemoglobin can be found in their genomes.
platelets and leukocytes
Nuclei
In mammals, mature erythrocytes lack a nucleus in it (called anukleat), except in non-mammalian vertebrates such as salamanders of the genus Batrachoseps. Konsentransi ascorbic acid in the cytoplasm of erythrocytes anukleat not differ with the concentration of vitamin C present in the plasma of blood. This is in contrast with the blood cells are equipped with cell nuclei or cell networks, which have concentrations of ascorbic acid is much higher in the cytoplasm.
Low capacity of erythrocytes caused by disappearance of ascorbic acid transporter SVCT2 when eritoblas started to move up into erythrocytes. However, erythrocytes have a high power to perceive through the transporter GLUT1 DHA and reduce it to ascorbic acid.
Other functions
When erythrocytes are in tension in narrow vessels, erythrocyte would release ATP, which will cause the walls to relax and widen the network.
Also releases erythrocyte S-nitrosothiol compounds when deoxygenated hemoglobin, which also serves to dilate blood vessels and smooth flow of blood into the blood so that oxygen-deficient areas of the body.
Erythrocytes also play a role in the immune system. When red blood cells undergo a process of lysis by pathogens or bacteria, then the hemoglobin in red blood cells will release free radicals that will destroy the cell walls and membranes of pathogens, and kill him.
Mammalian erythrocytes
At the beginning of its formation, mammalian erythrocytes have nuclei, but nuclei will slowly disappear due to the pressure when the erythrocytes mature to give room to the hemoglobin. Mammalian erythrocytes also lose the other cell organelles such as mitochondria. Thus, erythrocyte never wear oxygen they deliver, but it tends to produce the energy carrier ATP through the fermentation process held by the process of glycolysis to glucose followed by lactic acid production. Further that the erythrocytes do not have insulin receptors and glucose uptake in erythrocytes is not controlled by insulin. Because of the lack nuclei and other organelles, mature erythrocytes do not contain DNA and can not synthesize RNA, and this makes red cells can not divide or repair themselves.
Mammalian erythrocytes bikonkaf shaped pieces are flattened and given the pressure in the middle, with a shape like a "barbell" when viewed in cross section. This form (after the nuclei and organelles omitted) will optimize the cell in the process of oxygen exchange with the surrounding tissue. The form is very flexible so that the load cell when it enters into the small capillaries. Erythrocytes are usually round, except in erythrocytes in the family Camelidae (camels), oval-shaped.
In a large network of blood, erythrocytes sometimes appear in the stack, arranged side by side. This formation is commonly called roleaux formation, and will show up more when elevated levels of serum proteins, such as instances when inflammation occurs.
The spleen acts as a reservoir erythrocytes, but it is limited in the human body. In some mammals, such as dogs and horses, the spleen reduces the erythrocytes in large numbers, which will be disposed in a pressure situation, where this process will result in higher oxygen transport capacity.
In human erythrocytes
Pieces of human erythrocytes have a diameter of about 6-8 μm and a thickness of 2 μm, smaller than the other cells found in the human body. [13] normal erythrocytes have a volume of about 9 fL (9 femtoliter) About a third of the volume filled by hemoglobin, a total of 270 million hemoglobin molecules, each molecule carrying four heme groups.
Adults have 2-3 × 1013 red blood cells every time (women have 4-5 million erythrocytes per microliter of blood and male has 5-6 million. While the people who live in the highlands who have low levels of oxygen which then tend to have red blood cells more). Erythrocytes contained in the blood in high amounts compared with other blood particles, such as white blood cells which only has about 4000-11000 white blood cells and platelets that have only 150000-400000 in each microliter of human blood.
In humans, hemoglobin in red blood cells have a role to deliver more than 98% oxygen throughout the body, while the remaining dissolved in the blood plasma.
Erythrocytes in the human body is about 2.5 grams of iron stores, representing about 65% iron content in the human body.
Life cycle
The process by which erythrocytes are produced is called erythropoiesis. Constantly, the erythrocytes are produced in red bone marrow, with a production rate of about 2 million erythrocytes per second (In embryos, the liver acts as the main production center erythrocytes). Production can be stimulated by the hormone erythropoietin (EPO) is synthesized by the kidneys. This hormone is commonly used as doping in sports activities. When before and after leaving the spinal cord, cells that develop is named reticulocytes and the number is about 1% of all circulating blood.
Erythrocytes developed from stem cells through reticulocytes to mature erythrocytes in about 7 days and mature erythrocytes will live for 100-120 days.
read more : http://id.wikipedia.org/wiki/Sel_darah_merah
0 comments:
Post a Comment