matrix vesicle

Matrix vesicles are located within the extracellular space, or matrix.

Matrix vesicles bud from the plasma membrane at sites of interaction with the extracellular matrix.

Annexins are abundant in bone matrix vesicles, and are speculated to play a role in Ca entry into vesicles during hydroxyapatite formation.

Thus, matrix vesicles convey to the extracellular matrix calcium, phosphate, lipids and the annexins which act to nucleate mineral formation.

During normal calcification, a major influx of calcium and phosphate ions into the cells accompanies cellular apoptosis (genetically determined self-destruction) and matrix vesicle formation.

The subject area has not been thoroughly studied, however it has been speculated that annexins may be involved in closing the neck of the matrix vesicle as it is endocytosed.