・「細胞の接着・生存・分化・移動を制御し、組織構築に重要な役割を果たしている」（大阪医科薬科大学）
以下は「ウィキペディア」から抜粋した解説になる。
・生体膜とは異なり脂質は含まれない。
・代表的な成分はⅣ型コラーゲン、ラミニン、ヘパラン硫酸プロテオグリカン、エンタクチンなどである。
（組織や場所によって成分が多様）
■ 写真やイラストを掲載しているサイト ■
・ イラストや写真を掲載しているサイト-Ⅰ
・ イラストや写真を掲載しているサイト-Ⅱ
・ イラストや写真を掲載しているサイト-Ⅲ
以下は「Wikipedia」の解説文となる。
The basement membrane, also known as base membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling.[1][2] The basement membrane sits between epithelial tissues including mesothelium and endothelium, and the underlying connective tissue.[3][4]
【Structure】
Normal
histology of the
breast, with basement membrane annotated near center-right.
As seen with the
electron microscope, the basement membrane is composed of two layers, the
basal lamina and the
reticular lamina.
[4] The underlying connective tissue attaches to the basal lamina with
collagen VII anchoring fibrils and
fibrillin microfibrils.
[5]
The basal lamina layer can further be subdivided into two layers based on their visual appearance in electron microscopy. The lighter-colored layer closer to the epithelium is called the
lamina lucida, while the denser-colored layer closer to the connective tissue is called the
lamina densa. The
electron-dense lamina densa layer is about 30–70
nanometers thick and consists of an underlying network of reticular
collagen IV fibrils which average 30 nanometers in diameter and 0.1–2
micrometers in thickness and are coated with the heparan sulfate-rich proteoglycan
perlecan.
[6] In addition to collagen, this supportive matrix contains intrinsic macromolecular components. The lamina lucida layer is made up of
laminin,
integrins,
entactins, and
dystroglycans. Integrins are a key component of
hemidesmosomes which serve to anchor the epithelium to the underlying basement membrane.
To represent the above in a visually organised manner, the basement membrane is organized as follows:
The primary function of the basement membrane is to anchor down the epithelium to its loose connective tissue (the dermis or lamina propria) underneath. This is achieved by cell-matrix adhesions through substrate adhesion molecules (SAMs).
The basement membrane acts as a mechanical barrier, preventing malignant cells from invading the deeper tissues.[7] Early stages of malignancy that are thus limited to the epithelial layer by the basement membrane are called carcinoma in situ.
The basement membrane is also essential for angiogenesis (development of new blood vessels). Basement membrane proteins have been found to accelerate differentiation of endothelial cells.[8]
The most notable examples of basement membranes is the glomerular basement membrane of the kidney, by the fusion of the basal lamina from the endothelium of glomerular capillaries and the podocyte basal lamina,[9] and between lung alveoli and pulmonary capillaries, by the fusion of the basal lamina of the lung alveoli and of the basal lamina of the lung capillaries, which is where oxygen and CO2 diffusion occurs (gas exchange).
As of 2017, other roles for basement membrane include blood filtration and muscle homeostasis.
[1] Fractones may be a type of basement membrane, serving as a
niche for
stem cells
【 語 句 】
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