Lamella (cell biology)

Lamella (cell biology) refers to a thin layer, membrane, or plate of tissue, especially in bone or cell biology. In the context of cell biology, lamellae are most commonly associated with the flattened membranous structures within chloroplasts and mitochondria, and also refer to certain structures in bone and the thin layers involved in the process of cell migration.

Structure and Function

In chloroplasts, the lamellae are known as thylakoid membranes, which are the sites of the light-dependent reactions of photosynthesis. These membranes contain photosynthetic pigments that capture light energy. The thylakoid membranes are arranged in stacks known as grana, where the light reactions of photosynthesis take place. The area surrounding the grana is called the stroma lamellae, which connects the grana to each other.

In mitochondria, the lamellae are referred to as cristae. These are the folds of the inner mitochondrial membrane. The cristae increase the surface area of the inner membrane, where the electron transport chain components are located, thus enhancing the mitochondrion's ability to produce ATP.

In the context of bone, lamellae refer to the thin layers of bone matrix in compact bone. These layers are organized around the central (Haversian) canals, forming the osteons or Haversian systems, which are the structural units of compact bone. The lamellae in bone contain collagen fibers, which provide strength and flexibility to the bone.

During cell migration, such as in wound healing or cancer metastasis, cells extend a type of lamella known as a lamellipodium. This is a broad, sheet-like extension of the plasma membrane that helps the cell to move over substrates.

Clinical Significance

The integrity and function of lamellae are crucial for the proper functioning of the cells and tissues they are part of. Disruptions in the structure of lamellae can lead to various diseases. For example, mutations affecting the structure of bone lamellae can lead to bone fragility and diseases such as osteogenesis imperfecta. Similarly, disruptions in the thylakoid membranes can affect the efficiency of photosynthesis, impacting plant health and productivity.

See Also

• Cell membrane
• Photosynthesis
• Bone remodeling
• Cell migration