CorpusHuman Anatomy
Cells & TissuesMembrane

Basement membrane

Membrana basalis

Also known as: basal lamina, reticular lamina, lamina densa, lamina lucida, glomerular basement membrane

A thin, sheet-like layer of specialised extracellular matrix — basal lamina plus reticular lamina — that underlies all epithelia and surrounds muscle cells, adipocytes and Schwann cells.

Blood Vessel Wall Intestinal Villus and Absorption

Overview

Basal lamina thickness≈40–120 nm
Main componentsType IV collagen, laminin, nidogen, perlecan
Glomerular basement membrane≈300–350 nm

In light microscopy the basement membrane is a thin PAS-positive layer between an epithelium and the connective tissue. Electron microscopy resolves two components. The basal lamina (≈40–120 nm), made by the epithelial cells, has an electron-lucent lamina lucida next to the cells and an electron-dense lamina densa; it consists of a network of type IV collagen and laminin polymers linked by nidogen (entactin) and the heparan sulfate proteoglycan perlecan. The reticular lamina, made by connective-tissue fibroblasts, contains type III (reticular) and type I collagen fibres; it is attached to the basal lamina by anchoring fibrils of type VII collagen and by fibrillin microfibrils.

Epithelial cells attach to laminin through integrins (including those of hemidesmosomes). Similar basal laminae (external laminae) surround muscle fibres, adipocytes and Schwann cells. In the kidney the glomerular basement membrane (≈300–350 nm), formed by fusion of the endothelial and podocyte basal laminae, is a major part of the filtration barrier; its heparan sulfate gives it a negative charge that repels anionic proteins such as albumin.

Parts & subdivisions

  1. Basal lamina — lamina lucida
    Electron-lucent layer with laminin and integrin anchoring.
  2. Basal lamina — lamina densa
    Type IV collagen network, perlecan, nidogen.
  3. Reticular lamina
    Type III collagen fibres from fibroblasts; anchoring fibrils (type VII).

Function

  • Anchors epithelium to underlying connective tissue.
  • Selective filtration barrier (glomerulus).
  • Scaffold guiding epithelial regeneration and cell migration.
  • Barrier to invasion by cancer cells.
  • Influences cell polarity, proliferation and differentiation (signalling via integrins).

Clinical significance

Goodpasture (anti-GBM) disease

Autoantibodies against the NC1 domain of the α3 chain of type IV collagen attack glomerular and alveolar basement membranes → rapidly progressive glomerulonephritis and pulmonary haemorrhage; linear IgG on immunofluorescence.

Alport syndrome

Mutations in type IV collagen chains (COL4A5, X-linked, in ≈80 %) → split, laminated GBM ("basket-weave"), haematuria progressing to renal failure, sensorineural deafness and anterior lenticonus.

Carcinoma in situ versus invasive

Malignant cells confined above an intact basement membrane are in situ; penetration of the basement membrane by matrix metalloproteinases defines invasion and the potential for metastasis. Diabetes thickens basement membranes of capillaries and glomeruli.

Test yourself

Which collagen type is the principal structural collagen of the basal lamina, targeted in Goodpasture syndrome?
  1. Type I
  2. Type II
  3. Type III
  4. Type IV

Answer: Type IV

Type IV collagen forms a non-fibrillar network in the basal lamina. Goodpasture syndrome targets the α3 chain in glomerular and alveolar basement membranes; Alport syndrome is caused by mutations in type IV collagen genes (usually COL4A5).

More cells & tissues questions

Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.