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化生(metaplasia)

已有 425 次阅读 2015-12-27 18:05

化生(metaplasia) 是指一种已分化组织转变为另一种分化组织的过程。并非由已分化的细胞直接转变为另一种细胞,而是由具有分裂能力的未分化细胞向另一方向分化而成,一般只能转变为性质相似的细胞。机体的一种组织由于细胞生活环境改变或理化因素刺激,在形态和机能上变为另一种组织的过程,是机体的一种适应现象。如支气管黏膜的柱状上皮组织长期受刺激变为鳞状上皮组织。本词条内还有佛教用语的解释。

常见的化生有上皮化生、骨与软骨化生、浆膜化生、脂肪化生和骨髓化生。化生是局部组织在病理情况下的一种适应性表现,在一定程度上对人体可能是有益的。鳞状上皮的化生能增强粘膜的抵抗力,使粘膜在不利的情况下仍能生存。但支气管柱状上皮发生鳞状上皮化生时,丧失了纤毛,削弱了呼吸道的防御功能使易受感染。有时化生的细胞可以发生恶性肿瘤。如化生的鳞状上皮,有时未能分化成熟,产生不典型增生,可进而发生恶变,发生浸润成为鳞状细胞癌。胃粘膜的肠上皮化生与胃癌的发生可能有密切关系。

1.上皮组织化生
(1)鳞状上皮化生(squamous metaplasia) 气管和支气管粘膜的纤毛柱状上皮,在长期吸烟者或慢性炎症损害时,可转化为鳞状上皮。若其持续存在,则有可能成为支气管鳞状细胞癌的基础。鳞状上皮化生可增强局部的抵抗力,但同时也失去了原有上皮的功能。
(2)肠上皮化生(intestinal metaplasia) 这种化生常见于胃体和/或胃窦部。肠上皮化生常见于慢性萎缩性胃炎、胃溃疡及胃粘膜糜烂后粘膜再生时。
2.间叶组织化生
结缔组织化生也比较多见。多半由纤维结缔组织化生为骨、软骨或脂肪组织。如骨化性肌炎(myositis ossificans)时,由于外伤引起肢体近段皮下及肌肉内纤维组织增生,并发生骨化生。这是由于新生的结缔组织细胞转化为骨母细胞的结果。老年人的喉及支气管软骨可化生为骨。

http://baike.baidu.com/link?url=rxNgrfeLTt2fFwr433AoCFVoxbMTj29lZHGhpfdHKISBoZTBOBI-CRPj5Q5uLLitqGYgwGe74zch81foHz8D6K

一种已分化组织转变为另一种分化组织的过程为化生(metaplasia)。并非由已分化的细胞直接转变为另一种细胞,而是由具有分裂能力的未分化细胞向另一方向分化而成,一般只能转变为性质相似的细胞。机体的一种组织由于细胞生活环境改变或理化因素刺激,在形态和机能上变为另一种组织的过程,是机体的一种适应现象。如支气管黏膜的柱状上皮组织长期受刺激变为鳞状上皮组织。  

相关

化生(metaplasia),一种分化成熟的组织转变成另一种成熟组织可逆转的适应现象。常见的化生有上皮化生、骨与软骨化生、浆膜化生、脂肪化生和骨髓化生。化生是局部组织在病理情况下的一种适应性表现,在一定程度上对人体可能是有益的。鳞状上皮的化生能增强粘膜的抵抗力,使粘膜在不利的情况下仍能生存。但支气管柱状上皮发生鳞状上皮化生时,丧失了纤毛,削弱了呼吸道的防御功能使易受感染。有时化生的细胞可以发生恶性肿瘤。如化生的鳞状上皮,有时未能分化成熟,产生不典型增生,可进而发生恶变,发生浸润成为鳞状细胞癌。胃粘膜的肠上皮化生与胃癌的发生可能有密切关系。

2、佛教认为世间所有生灵都可以归到湿生、卵生、胎生、化生,出自《金刚般若波罗蜜经》(佛告须菩提:“诸菩萨摩诃萨应如是降伏其心:所有一切众生之类——若卵生、若胎生、若湿生、若化生,若有色、若无色,若有想、若无想、若非有想非无想,我皆令入无余涅盘而灭度之。)  

上皮组织化生

(1)鳞状上皮化生(squamous metaplasia) 气管和支气管粘膜的纤毛柱状上皮,在长期吸烟者或慢性炎症损害时,可转化为鳞状上皮。若其持续存在,则有可能成为支气管鳞状细胞癌的基础。鳞状上皮化生可增强局部的抵抗力,但同时也失去了原有上皮的功能。

(2)肠上皮化生(intestinal metaplasia) 这种化生常见于胃体和/或胃窦部。肠上皮化生常见于慢性萎缩性胃炎胃溃疡及胃粘膜糜烂后粘膜再生时。  

间叶组织化生

结缔组织化生也比较多见。多半由纤维结缔组织化生为骨、软骨或脂肪组织。如骨化性肌炎(myositis ossificans)时,由于外伤引起肢体近段皮下及肌肉纤维组织增生,并发生骨化生。这是由于新生的结缔组织细胞转化为骨母细胞的结果。老年人的喉及支气管软骨可化生为骨。  


http://www.a-hospital.com/w/%E5%8C%96%E7%94%9F


Metaplasia
From Wikipedia, the free encyclopedia
This article needs additional citations for verificationPlease help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2014)
-plasia and -trophy
  • Anaplasia (structural differentiation loss within cell or group of cells)
  • Aplasia (organ or part of organ missing)
  • Hypoplasia (congenital below-average number of cells, especially when inadequate)
  • Hyperplasia (proliferation of cells)
  • Neoplasia (abnormal proliferation)
  • Dysplasia (change in cell or tissuephenotype)
  • Metaplasia (conversion in cell type)
  • Prosoplasia (development of new cell function)
  • Desmoplasia (connective tissue growth)
  • Atrophy (reduced functionality of an organ, with decrease in the number or volume of cells)
  • Hypertrophy (increase in the volume of cells)
  • Dystrophy (any degenerative disorder occur due to improper or faulty nutrition)
Metaplasia
Pancreatic acinar metaplasia - high mag.jpg
Micrograph of a gastro-esophageal junction with pancreatic acinar metaplasia. The esophageal mucosa (stratified squamous epithelium) is seen on the right. The gastric mucosa (simple columnar epithelium) is seen on the left. The metaplastic epithelium is at the junction (center of image) and has an intensely eosinophilic (bright pink) cytoplasm. H&E stain.
Classification and external resources
MeSHD008679

Metaplasia (Greek: "change in form") is the reversible replacement of one differentiated cell type with another mature differentiated cell type. The change from one type of cell to another may generally be a part of normal maturation process or caused by some sort of abnormal stimulus. In simplistic terms, it is as if the original cells are not robust enough to withstand the new environment, and so they change into another type more suited to the new environment. If the stimulus that caused metaplasia is removed or ceases, tissues return to their normal pattern of differentiation. Metaplasia is not synonymous with dysplasia and is not directly considered carcinogenic.[1] It is also contrasted with heteroplasia, which is the abnormal growth of cytologicand histologic elements without a stimulus.

Causes[edit]

When cells are faced with physiological or pathological stresses, they respond by adapting in any of several ways, one of which is metaplasia. It is a benign (i.e. non-cancerous) change that occurs as a response to change of milieu (physiological metaplasia) or chronic physical or chemical irritation (pathological metaplasia). One example of pathological irritation is cigarette smoke that causes the mucus-secreting ciliated pseudostratified columnar respiratory epithelial cells that line the airways to be replaced by stratified squamous epithelium, or a stone in the bile duct that causes the replacement of the secretory columnar epithelium with stratified squamous epithelium (Squamous metaplasia). Metaplasia is an adaptation that replaces one type of epithelium with another that is more likely to be able to withstand the stresses it is faced with. It is also accompanied by a loss of endothelial function, and in some instances considered undesirable; this undesirability is underscored by the propensity for metaplastic regions to eventually turn cancerous if the irritant is not eliminated.

The cell of origin for many types of metaplasias are controversial or unknown. For example, there is evidence supporting several different hypotheses of origin in Barrett's esophagus. They include direct transdifferentiation of squamous cells to columnar cells, the stem cell changing from esophageal type to intestinal type, migration of gastric cardiac cells, and a population of resident embryonic cells which are present through adulthood.

Significance in disease[edit]

Normal physiological metaplasia - such as that of the endocervix is highly desirable.

The medical significance of metaplasia is that in some sites where pathological irritation is present cells may progress from metaplasia, to develop dysplasia, and then malignant neoplasia(cancer). Thus, at sites where abnormal metaplasia is detected, efforts are made to remove the causative irritant, thereby decreasing the risk of progression to malignancy. The metaplastic area must be carefully monitored to ensure that dysplastic change does not begin to occur. A progression to significant dysplasia indicates that the area could need removal to prevent the development of cancer.

Examples[edit]
A micrograph of Barrett's esophagus.

Barrett's esophagus is an abnormal change in the cells of the lower esophagus, thought to be caused by damage from chronic stomach acid exposure.

The following table lists some common tissues susceptible to metaplasia, and the stimuli that can cause the change:

TissueNormalMetaplasiaStimulus
AirwaysPseudostratified columnar epitheliumSquamous epitheliumCigarette smoke
Urinary bladderTransitional epitheliumSquamous epitheliumBladder stone
EsophagusSquamous epitheliumColumnar epitheliumGastro-esophageal reflux (Barrett's Esophagus)
CervixGlandular epitheliumSquamous epitheliumLow pH of vagina
See also[edit]Notes[edit]
  • The AMA Home Medical Encyclopedia, Random House, p.683
  • Robbins and Cotran - Pathologic Basis of Disease, 7th Edition, Saunders, p. 10
References[edit]
  1. Jump up^ Abrams, Gerald. "Neoplasia I". Retrieved 23 January 2012.
https://en.wikipedia.org/wiki/Metaplasia




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