What is the Difference Between Basal Lamina and Basement Membrane

The main difference between basal lamina and basement membrane is that basal lamina composes of lamina densa and lamina lucida, whereas basement membrane composes of lamina densa, lamina lucida, and lamina reticularis.

The basal lamina and basement membrane are two types of thin layers of the extracellular matrix (ECM). Epithelial cells secrete the extracellular matrix.

Key Areas Covered

1. What is Basal Lamina
– Definition, Structure, Function
2. What is Basement Membrane
– Definition, Structure, Function
3. Similarities Between Basal Lamina and Basement Membrane
– Outline of Common Features
4. Difference Between Basal Lamina and Basement Membrane
– Comparison of Key Differences

Key Terms

Basal Lamina, Basement Membrane

What is Basal Lamina

The basal lamina is a thin flexible layer of extracellular matrix secreted by epithelial cells. Apart from the epithelial tissue, basal lamina also occurs in the fat cells, Schwann cells, and skeletal muscle fibers. The main function of the basal lamina is to attach the epithelial cells to the extracellular matrix. In addition, it organizes proteins in the adjacent cell membranes. Also, it induces the differentiation and the metabolism of cells. On the other hand, the basal lamina serves as a route to cell migration. It has a function in cell polarity.

Figure 1: Basal Lamina

Furthermore, basal lamina is only visible under the electron microscope. It contains two layers: lamina lucida and lamina densa. Here, the lamina lucida is an electron-lucent layer occurring close to the basal surface of the cells. In comparison, lamina densa is an electron-dense layer. Also, the lamina lucida layer contains glycoprotein laminin, and the lamina densa layer contains type IV collagen.

What is Basement Membrane

The basement membrane is a thin, sheet-like extracellular structure forming an anatomical barrier where cells of the epithelium meet connective tissue. However, the basement membrane is visible under light microscopy. Under electron microscopy, the basement membrane contains three layers: lamina lucida, lamina densa, and lamina reticularis. The lamina reticularis layer is electron-lucent. On the other hand, examples of basement membranes include basilar membrane, Bruch’s membrane, Descemet’s membrane, and Glomerular basement membrane.

Figure 2: Basement Membrane

Moreover, the basilar membrane is the stiff structure within the cochlea of the inner year. It separates the two liquid-filled tubes running along the coil of the cochlea, the scala media, and the scala tympani. It also moves according to incoming sound waves. In comparison, Bruch’s membrane occurs as the innermost layer of the choroid of the eye. It provides structural support to the retinal pigment epithelium. In addition, Descemet’s membrane is an extracellular matrix occurring between the stroma and the endothelial layer of the cornea. It is secreted by the endothelial layer of the cornea. Apart from that, the glomerular membrane is a special case of the basement membrane, and it contains a fusion of podocytes and endothelial basal lamina. It serves as a permeability barrier to the production of urine.

Similarities Between Basal Lamina and Basement Membrane

• Basal lamina and basement membrane are two types of extracellular matrix secreted by epithelial cells.
• They act as a point of attachment by the epithelial cells.

Difference Between Basal Lamina and Basement Membrane

Definition

Basal lamina refers to a layer of extracellular matrix found on the basal surface of epithelial cells, and it is secreted by the epithelial cells, while basement membrane refers to a thin, dense layer of the extracellular matrix that lines most human tissues forming the supporting structure and scaffolding for epithelial tissue and separates different types of cells, such as nerve cells and muscle cells.

Visibility

The basal lamina is visible under an electron microscope, while the basement membrane is visible under light microscopy.

Layers

The basal lamina composes of lamina densa and lamina lucida, while the basement membrane composes of lamina densa, lamina lucida, and lamina reticularis.

Conclusion

In brief, the basal lamina and basement membrane are two types of thin layers of extracellular matrix allowing the attachment of epithelial cells. Also, they are secreted by epithelial cells. The basal lamina is a thin layer of extracellular matrix visible under the electron microscope. Also, it contains two layers: lamina densa and lamina lucida. In comparison, the basement membrane is a thin layer of extracellular matrix visible under light microscopy. In addition, it contains three layers: lamina densa, lamina lucida, and lamina reticularis. Therefore, the main difference between the basal lamina and basement membrane is the structure.

References:

1. Basal lamina. Basal Lamina – an overview | ScienceDirect Topics. (n.d.). 
2. Basement membrane: What is it, how it’s formed, and more – osmosis. (n.d.-a). 

Image Courtesy:

1. “Basal lamina” By Robert M. Hunt – Own work (Public Domain) via Commons Wikimedia
2. “Oral mucosa” By Wiki-minor – Own Work (CC-BY SA 3.0) via Commons Wikimedia