定义

基（底）膜（BM）是一种复合的细胞外结构，是在上皮和内皮之间形成的ECM薄层，是细胞外基质的特异区。

组成

• 基膜是由不同的蛋白纤维组成的网状结构
  • 主要包括：LN、IV型胶原、巢蛋白（Entactin）、肌腱蛋白、钙结合糖蛋白、硫酸肝素糖蛋白等。
  • 其中，层粘连蛋白LN是基膜的主要成分，也是基膜的组织者，IV型胶原是基膜的网状支架

• A current model of the molecular structure of a basal lamina. The basal lamina (A) is formed by specific interactions between the proteins type IV collagen, laminin, and entactin plus the proteoglycan perlecan (B). Arrows in (B) connect molecules that can bind directly to each other. (Based on P.D. Yurchenco and J.C. Schittny, FASEB J. 4:1577-1590.)

功能

1. 支持、分子渗透屏障（如：肾细胞基膜）
2. 调节分子、细胞运动
3. 影响细胞迁移（如：肿瘤细胞入侵）等

The connective tissue underlying an epithelial cell sheet.

• It consists largely of extracellular matrix that is secreted by the fibroblasts.

基膜是一种复合的细胞外结构，位于上皮细胞基底面与结缔组织的膜状结构。具有支持和连接作用，亦是物质通透的半透膜，便于上皮组织与结缔组织进行物质交换。

Scanning electron micrograph of fibroblasts in connective tissue.

The tissue is from the cornea（角膜） of a rat. The extracellular matrix surrounding the fibroblasts is composed largely of collagen fibrils. The glycoproteins, glycosaminoglycans（糖胺聚糖）, and proteoglycans（蛋白聚糖）, which normally form a hydrated gel filling the interstices of the fibrous network, have been removed by enzyme and acid treatment. (T. Nishida et al. Invest. Ophthalmol. Vis. Sci. 29:1887-1890)

Scanning electron micrograph of a basal lamina in the cornea of a chick embryo

Some of the epithelial cells (E) have been removed to expose the upper surface of the mat like basal lamina (BL). A network of collagen fibrils (C) in the underlying connective tissue interacts with the lower face of the lamina. (Courtesy of Robert Trelstad.)