Basement Membrane
Also written as BM.
Alveolar‑capillary membrane – thin type I pneumocytes, basement membrane, capillary endothelium: The primary site of gas exchange; inflammation or fibrosis thickens this barrier → ↓ diffusion capacity (low DLCO) and hypoxaemia on exertion.
What our notes say
- Alveolar‑capillary membrane – thin type I pneumocytes, basement membrane, capillary endothelium: The primary site of gas exchange; inflammation or fibrosis thickens this barrier → ↓ diffusion capacity (low DLCO) and hypoxaemia on exertion. (Interstitial Lung Diseases)
- Alveolar‑capillary membrane – thin type I pneumocytes, basement membrane, capillary endothelium: Site of gas exchange; fibrosis or inflammation (silicosis, asbestosis, HP) thickens this barrier → ↓ diffusion, hypoxaemia, exertional dyspnoea. (Occupational Lung Disease)
- The glomerular filtration barrier has three layers: fenestrated endothelium, glomerular basement membrane and the foot processes of podocytes with their filtration slits. (Paediatrics and Child Health end of semester examination (MBPE): 10 January 2023)
- Other causes (focal segmental glomerulosclerosis, membranous nephropathy) damage the basement membrane or podocytes directly. (Paediatrics and Child Health end of semester examination (MBPE): 10 January 2023)
- Urea 16 mmol/L, creatinine 140 µmol/L, eGFR 16, and anti-glomerular basement membrane (anti-GBM) antibodies. (Junior Clerkship in Internal Medicine (MBIM4100) main exam, Paper One: 31 Januar)
- Damage to podocytes or basement membrane produces haematuria and proteinuria, pointing to intrinsic glomerular disease. (Acute kidney injury)
Study material on Basement Membrane
- Harrisons Pulmonary and Critical Care Medicine
- Glomerular diseases
- FSGS & HIV Nephropathy: Causes, Symptoms, Diagnosis & Prognosis — Notes
- Histology Flashcards
- 3 - Summary and MCQs
- L20- Glomerular diseases
- Immunopathology complete MCQs
- Immunopathology
- Davidson's Essentials of Medicine - 2nd
- BABY NELSON PEADS
- Oncopathology Hallmarks of Cancer MCQs
- ONCOPATHOLOGY MCQs - HALLMARKS OF CANCER
Images
Practice questions on Basement Membrane
A 24-year-old male smoker presents with haemoptysis and progressive dyspnea. Urinalysis shows proteinuria and red cell casts. CXR reveals bilateral alveolar infiltrates. Anti-GBM antibodies are strongly positive. Renal biopsy shows linear IgG deposits along the glomerular basement membrane. Most likely diagnosis?
- Granulomatosis with polyangiitis
- Microscopic polyangiitis
- Systemic lupus erythematosus
- Goodpasture syndrome
Answer: D. The combination of pulmonary hemorrhage (haemoptysis, alveolar infiltrates on CXR), glomerulonephritis (proteinuria, red cell casts), positive anti-GBM antibodies, and linear IgG deposits on renal biopsy is pathognomonic for Goodpasture syndrome.
Cleavage of basement membrane collagen IV and laminin by MMPs serves what additional purpose beyond degradation?
- It generates novel binding sites that promote tumor cell migration
- It completely inactivates these proteins
- It produces potent angiogenesis inhibitors
- It activates p53-mediated apoptosis
Answer: A. ** Cleavage of collagen IV and laminin by MMP-2 or MMP-9 generates novel sites that bind to receptors on tumor cells and stimulate migration. The matrix is thus modified in ways that actively promote invasion and metastasis, not just passively allowing passage.
Normal epithelial cells undergo apoptosis when they lose attachment to basement membrane. Why are tumor cells resistant to this?
- They have inactivated death receptor pathways
- They are resistant to this form of cell death (anoikis)
- They produce excessive survival factors
- They have activated autophagy
Answer: B. ** Loss of adhesion in normal cells leads to induction of apoptosis (called anoikis), while tumor cells are resistant to this form of cell death. This resistance allows detached tumor cells to survive during invasion and metastasis, a critical capability for successful metastatic spread.
Which enzyme is responsible for cleaving type IV collagen in basement membranes and releasing VEGF from ECM-sequestered pools?
- MMP-2
- Cathepsin D
- MMP-9
- Urokinase plasminogen activator
Answer: C. ** MMP-9 is a gelatinase that cleaves type IV collagen of epithelial and vascular basement membranes and stimulates release of VEGF from ECM-sequestered pools.
What is the consequence of MMP-mediated cleavage of basement membrane proteins like collagen IV and laminin?
- Complete inhibition of tumor spread
- Generation of novel binding sites that stimulate tumor cell migration
- Restoration of normal tissue architecture
- Induction of tumor cell apoptosis
Answer: B. ** MMP-2 and MMP-9 cleavage of collagen IV and laminin generates novel sites that bind to receptors on tumor cells and stimulate migration.
What is the primary function of integrins on normal epithelial cells in relation to the basement membrane?
- Act as polarized receptors maintaining cells in resting, differentiated state
- Promote cell proliferation
- Stimulate angiogenesis
- Degrade the ECM
Answer: A. ** Normal epithelial cells have integrins at their basal surface for basement membrane components that help maintain cells in a resting, differentiated state.