Expansion
Basal lamina of lamina lucida and lamina densa, plus a reticular lamina
Expansion
Layers
- Basal lamina: lamina lucida (electron lucent, containing laminin and integrins) and lamina densa (type IV collagen, heparan sulphate proteoglycan)
- Reticular lamina: type III collagen, produced by underlying connective tissue
Functions: structural support and anchorage, selective filtration, a scaffold for regeneration and repair, and a barrier to invasion.
Clinical significance
- Carcinoma in situ becomes invasive carcinoma precisely when the basement membrane is breached, which is why this single feature determines staging and prognosis
- Alport syndrome: type IV collagen defect, giving haematuria, progressive renal failure, sensorineural deafness and lens abnormalities
- Goodpasture disease: antibodies to type IV collagen, causing linear immunofluorescence, glomerulonephritis and pulmonary haemorrhage
- Bullous pemphigoid: hemidesmosome antibodies causing subepidermal blistering
- Diabetic microangiopathy: basement membrane thickening throughout the body
It also stains with PAS because of its glycoprotein content, which is why PAS is used to assess the glomerular basement membrane.