hyaloplasm

Hyaloplasm is a historical term in cell biology used to describe the clear, non-granular portion of the cytoplasm. It is considered the ground substance or matrix of the cytoplasm, surrounding organelles and inclusions and contrasting with granuloplasm, which contains granules and dense organelles. In older literature, hyaloplasm and granuloplasm were used to differentiate less dense, translucent regions from more granular, organelle-rich regions within the cytoplasm.

Composition and properties of hyaloplasm align closely with what modern cell biology would call the cytosol. This substance is primarily water with dissolved ions, small molecules, and soluble enzymes. It provides a medium in which many metabolic reactions occur and through which molecules diffuse between organelles. The hyaloplatic region can vary in viscosity and is often described as the more fluid, glassy part of the cytoplasm that surrounds cytoskeletal elements and organelles.

Function and context within the cell: Hyaloplasm facilitates diffusion and transport of nutrients, metabolites, and signaling molecules. It hosts various soluble enzymes and is the site of numerous cytosolic processes, while the more densely organized organelles reside within or are suspended in this matrix.

Historical note: The term hyaloplasm is largely historical and is used less frequently in contemporary texts. Modern terminology typically uses cytosol or cytoplasm to refer to the fluid, non-organelle component of the cell, with cytoplasm plus organelles describing the entire intracellular content. Hyaloplasm, when encountered, often reflects older histological descriptions of cell structure.