Organs or local tissues due to vascular obstruction and blood flow stophypoxiaThe necrosis that occurs is called infarction（infarction）。Infarction is generally caused by ischemia and hypoxia of local tissues caused by arterial occlusion, butveinBlockingBlood stasisIt may lead to hypoxia or infarction.
Failure to establish effective collateral circulation
The formation of infarction mainly depends on whether effectiveCollateral circulation。For the liver and lung with double blood circulation, after the blood vessel is blocked, it is not easy to have infarction through the compensation of collateral circulation.Some organs have few anastomotic branches, such as kidney, spleen, brain and arteryRapid occurrenceInfarction often occurs when occlusion occurs.
The tolerance of local tissues to ischemia and the state of systemic blood circulation.If myocardial and brain tissue are sensitive to hypoxia, transient ischemia can also cause infarction.Whole body blood circulationanemiaorCardiac insufficiencyIt can promote the occurrence of infarction.
The shape of the infarct depends on the vascular distribution of the organ.The blood vessels of most organs are conical branches, such as spleen, kidney, lung, etc., so the infarct focus is also conical, and the section is wedge-shaped, ortriangleIts tip is located at the place where the blood vessel is blocked, and its bottom is the surface of the organ.heartcoronary arteryThe branches are irregular, so the infarct is map shaped.mesenteryThe blood vessels were fan-shaped branches, so the intestinal infarction was segmental.
The infarct of heart, kidney, spleen and liver isCoagulative necrosisThe necrotic tissue is dry, hard and surface subsidence.cerebral infarctionbyLiquefactive necrosisIt is soft and loose when fresh, and can be liquefied into capsule cavity after a long time.
The color of the infarction depends on the blood content in the focus. When the blood content is low, the color is gray, which is calledAnemic infarction（anemic infarct）。When the blood content is high, the color is dark red, which is calledHemorrhagic infarction（hemorrhagic infarct）。
Infarction type
Anemic infarction of spleen
According to the amount of blood in the infarct and whether there is bacterial infection, the infarct can be divided into the following three types.[1]
1．Anemic infarction: Occurs onorganization structureDenseCollateral circulationInadequate parenchymal organs such as spleen, kidney, myocardium andBrain tissue。When the infarct focus is formed, the blood in the collateral vessels at the edge of the focus enters less necrotic tissue, and the infarct focus is grayish white, so it is called anemic infarction (also calledWhite infarct）。It occurs in the spleenRenal infarctionThe focus is conical, with the tip toward the part where the blood vessel is blocked, and the bottom near the surface of the organ,Serous membraneThe surface is often covered with a small amount of cellulosic exudate.miocardial infarctionThe focus is irregular map.In the early stage of infarction, the border between the infarct and the normal tissueinflammatory reaction A congestive bleeding zone is common, and several days laterred blood cellcovermacrophageAfter phagocytosis, it turns intoHemosiderinAnd become yellowish brown.In the late stage, the surface of the lesion subsided, the texture became firm, and the yellowish brown bleeding zone disappearedgranulation tissue And scar tissue.Microscopicallyischemia natureCoagulative necrosisChange, visible in early infarctionNuclear pyknosis, nuclear fragmentation, nuclear lysis and other changes, the cytoplasm was uniform red, and the outline of the tissue structure was preserved (such as renal infarction).In the late stage, the lesions showed a homogeneous structure with red staining, and granulation tissue and scar tissue formed at the edge.In addition, cerebral infarction is generallyAnemic infarctionThe necrotic tissue often becomes soft and liquefied, without structure.
2．Hemorrhagic infarction：Commonly seen in lungs, intestines, etc., with dualblood circulation, loose tissue structure with severeCongestionIn case of massive hemorrhage in the infarct, it is called hemorrhagic infarction, also calledRed infarct，（red infarct）。
Conditions of hemorrhagic infarction: ① Severe congestion.asPulmonary congestion, YesPulmonary infarctionImportance of formationprecondition。Because in the case of pulmonary congestion,pulmonary veinandblood capillaryThe increase of internal pressure affectspulmonary arteryEstablish effective pulmonary artery andBronchial arteryCollateral circulation, causing hemorrhagic infarction of lung;oophoritic cystortumourIn the ovarypedicle TwistVenous refluxIf it is obstructed, the arterial blood supply will be gradually reduced or even stopped, causing ovarian cyst or tumor infarction. ②Organ tissue structure is loose.The tissues of intestine and lung are relatively loose, and the lung can be accommodated in the tissue gap at the beginning of infarctionHemorrhagic infarction。
Hemorrhagic infarction of lung
Common types:① Pulmonary hemorrhagic infarction: its focus is usually located in the lungInferior lobe, which is more likely to occur at the costophrenic margin.It is often multiple, and the lesions are of different sizes, conical and wedge-shaped, with the tip facingHilum of lungThe bottom is close to the lung membrane, and there is cellulose exudate on the lung membrane surface.The infarct focus is solid due toDiffuseThe bleeding is dark red, slightly protruding to the surface, and over time, due to the disintegration of red blood cellsgranulation tissue When it grows in, the infarct becomes gray white, and the surface of the lesion subsides locally.Microscopically, the infarct is shownCoagulative necrosis, visibleAlveoliOutline, alveolar cavity, small branch airway cavity andPulmonary interstitiumFull of red blood cells.The early red blood cell contour was still preserved, and later disintegrated.Congestion, edema and hemorrhage of the lung tissue at the border of the infarct and normal lung tissue.Clinically possibleChest pain、coughandhemoptysis、feverandwhite blood cellThe total number of symptoms increased. ②intestinesHemorrhagic infarction: More common inmesenteric arterial embolish andVenous thrombosis, or onintussusception、Volvulus、Incarcerated herniaHemorrhagic infarction caused by tumor compression.The intestinal infarct was segmental dark red.Intestinal parietal factorblood stasis, edema and bleeding were significantly thickenedIntestinal wall necrosis, crispy and easily broken, intestinesSerous membraneThe surface may be covered with cellulosic purulent exudate.Clinically, due to vascular obstruction, intestinal wall muscle hypoxia causes continuous convulsion, resulting in severeabdominal pain；becauseIntestinal peristalsisStrengthening can produceCounter peristalsisCause vomiting;Necrosis and involvement of intestinal wallMuscularisAnd nerves, which can causeParalytic ileus；Perforation andperitonitis, causing serious consequences.
The impact of infarction on the body depends on the organ, size and location of the infarct.Infarction of kidney and spleen generally has little impact, and kidney infarction usually presents low back pain andhematuria, no impactrenal function；Pulmonary infarction has chest pain and hemoptysis;Intestinal infarction often causes severe abdominal painBloody stoolAnd symptoms of peritonitis;miocardial infarctioninfluencecardiac function, which can lead toheart failureeven to the extent thatDie suddenly；Cerebral infarction occurs in corresponding partsdysfunctionThe patients with large infarct focus may die.Extremities, lungs and intestines infarction can be secondaryPutrid fungusCaused bygangrene。It can also cause pyogenic bacteria infectionabscess。
Outcomes of infarction
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When the infarct is formedinflammatory reaction ，VasodilationCongestion and addictionNeutrophilandmacrophageExudationgranulation tissue 24~48 hours after the occurrence of the infarction, granulation tissue has begun to grow from around the infarct into the focus. Small infarcts can be completely replaced by granulation tissue and become fibrous scars over time.When the large infarct focus can not be completely organized, it will be wrapped by granulation tissue and later transformed scar tissue, and calcification may occur inside the focus.Cerebral infarction can be liquefied into a capsule, surrounded by hyperplastic glial scar.
