the smallest blood cells are platelets.They look like a nuclear-free drives.Their diameter is likely to 4 microns, and the thickness - up to 0.75 microns.Each liter of human blood platelet volume is at a level between 180 and 350 x 109.
path appearance platelet
platelets appear in the process of fragmentation of the cytoplasm.They are separated from the huge bone marrow - megakaryocytes.They, in turn, are the result of endomitosis.After separation occurs 3-5 cycles, during which the chromosomes are doubled, but the cytoplasm without divided.This process experts called incomplete division.
It is important to understand that the place of formation of platelets - a red bone marrow.From it they go out and enter the bloodstream.But a third of them immediately deposited in the spleen.This is due to the slower their movement through the tortuous splenic cords.The remaining 2/3 circulate in the blood in an average of seven days.The maximum duration of their life up to 12 days.
nucleation process plates
To understand how come the smallest blood cells, it is necessary to know not only the place of formation of platelets.It is important to clarify the process of their development.So, is the founder of megakaryoblasts.It is a large square, whose size is 20 microns with the core.It contains nucleotides.Megakaryoblasts transformed into promegakariotsit.This structure is prone to polymorphism of the nucleus, cytoplasm her grain-free, basophilic.
next stage of development is the megakaryocyte.This enormous cell in bone marrow, the diameter of which is from 60 to 120 microns.It is a rough core, which can take rather bizarre shapes.The cytoplasm it is large, it is a granular inclusions of pink and purple.
penultimate stage is the appearance of megakaryocyte trombotsitogennogo.After it has isolated itself platelets.They are separated from the cytoplasm megakaryocyte.All of this takes place in the bone marrow, is the main place of formation of platelets.
Isolation plates
Trombotsitogennye megakaryocytes in the bone marrow are at the endothelial surface, called the sinus.These cytoplasmic processes pass therethrough.Some of them penetrating into the lumen of the sine of 1-2 microns and fixed on megakaryocyte endothelium.They act as an anchor.Other processes - a long cytoplasmic tape length by up to 120 microns.They pass through the lumen of the sinus.They are called prothrombocytes.Each megakaryocyte can be from 6 to 8.
in the lumen of the sinus begins a local reduction of the cytoplasm.As a result, it is broken and there is about 1,000 individual platelets.This place platelet has not recently.This is because the bloodstream also fall prothrombocytes.They reach the lung microvasculature, there are released full platelets.That is why the pulmonary veins are more of them than in the corresponding arteries.It is remarkable that they can be formed even from 7 to 17% of the platelets passing through the bloodstream.
cell types
Experts distinguish several forms of the smallest blood cells.Separately isolated young platelets.Compared to their mature forms it has a relatively large size, sparse grit and bluish gialomer.Their formation affects bone marrow intensive work, it is often associated with a substantial loss of blood.
differ in appearance and old platelets.Photography under microscope allows to consider that they have a narrow rim, a large number of vacuoles and granules.They differ irregular contours, tight granulomerom that may occupy the entire platelet.Excessive their number indicates the appearance of a malignant tumor.
separate release form of irritation.It otshnurovaniya from megakaryocytes appear in violation of the separation process.Their presence indicates blood diseases.They often appear as small, or conversely, giant platelets in human blood.
Normally, blood should be more than 90% of the mature forms of platelets.They have a disc-like shape with clear boundaries, centrally located granulomerom, which consists of 5-20 azurophilic grains, purple gialomerom.
process of life
Appearing in the bone marrow, the cells leave the main place platelet production.By the way, their production is regulated trombotsitopoetinami.They, in turn, appear not only in bone marrow, spleen and liver.Experts identify two groups trombotsitopoetinov.They can be long or short duration.The first of these contribute to the full maturation and differentiation of megakaryocytes, and the second increase cleavage of these small plates and accelerate their penetration in the blood.
Destroyed platelets, photos of which can be seen in multiple increase, on average, a week operation.This process occurs mainly in the bone marrow, but also decompose these blood cells in the spleen and liver.The destruction takes place in the system of special cells called macrophages.
structure plates
Each mature platelet can be divided into three zones.The peripheral part is a three-layer membrane.It contains receptors for collagen, serotonin, thrombin, epinephrine, ADP.The outer portion of the membrane is special amorphous layer consisting of the factors responsible for the clotting of blood plasma.
Middle layer is a sol-gel.There are special channels with access to the outside of the membrane.Also layer comprises microfilaments responsible for disc-shaped plates.From this part of the properties of platelets it depends on how will be a retraction of a blood clot.
also highlights zone organelles.It contains glycogen and alpha-granules, dense bodies, mitochondria.
functions
learn how to appear described small particles of blood, many are beginning to wonder what makes platelets.They are intended to participate in hemostasis and help repair damaged blood vessels.This is possible thanks to the fact that they can attach to the damaged wall and restore them.These cells are necessary to prevent bleeding and the primary outlet body fluid from the bloodstream.
ensure enforcement of the properties of platelet function: adhesion and aggregation.So call them the ability to be attached to subendothelium and stick together.
