Lamellar bodies

Lamellar bodies are small organelles found in type II pneumocytes in the lungs and in keratinocytes in the skin. They are responsible for the storage and secretion of surfactant, a substance that reduces surface tension in the lungs and prevents the alveoli from collapsing. In the skin, lamellar bodies contribute to the formation of the epidermal barrier, which protects the body from dehydration and external threats.

Structure and Function

Lamellar bodies are named for their unique structure, which consists of concentric layers of lipid bilayers. These layers are composed primarily of phospholipids, the most abundant of which is dipalmitoylphosphatidylcholine (DPPC). DPPC is the main component of lung surfactant and is crucial for its function.

In the lungs, lamellar bodies are secreted by type II pneumocytes into the alveolar space, where they unfold into a monolayer that covers the alveolar surface. This surfactant layer reduces surface tension and prevents the alveoli from collapsing during exhalation.

In the skin, lamellar bodies are secreted by keratinocytes into the stratum corneum, the outermost layer of the skin. Here, they contribute to the formation of the epidermal barrier by releasing lipids and proteins that seal the spaces between corneocytes, the dead skin cells that make up the stratum corneum.

Clinical Significance

Abnormalities in lamellar body function can lead to several diseases. In the lungs, insufficient surfactant production or secretion can result in respiratory distress syndrome (RDS), a condition that causes severe breathing difficulties. In the skin, defects in lamellar body function can lead to ichthyosis, a group of skin disorders characterized by dry, scaly skin.

Lamellar body count (LBC) is a test used to assess fetal lung maturity. A high LBC indicates that the fetal lungs are producing sufficient surfactant and are likely mature enough for the baby to breathe independently after birth.

See Also

• Type II pneumocyte
• Keratinocyte
• Surfactant
• Respiratory distress syndrome
• Ichthyosis

References

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