Extracellular molecules, such as nucleotides, lipids, short peptides or proteins, are released by cells and bind to receptors on the other cells, which are important mediators in cell-to-cell communications in multicellular organisms. In addition to single molecules, eukaryotic cells can also release membrane vesicles into extracellular environment, such as microvesicles, apoptotic blebs and exosomes.

1. Exosome Pathway
Extracellular molecules, such as nucleotides, lipids, short peptides or proteins, are
released by cells and bind to receptors on the other cells, which are important
mediators in cell-to-cell communications in multicellular organisms. In addition to
single molecules, eukaryotic cells can also release membrane vesicles into
extracellular environment, such as microvesicles, apoptotic blebs and exosomes.
Exosomes represent a specific subtype of secreted membrane vesicles, showing a
characteristic cup-shaped or well delimited round morphology when observed by
electron microscopy.
They are small membrane vesicles with a diameter of 30~100 nm. Derived from the
endosomal compartments called multivesicular bodies (MVBs), exosomes contain
diverse nucleic acids (mRNAs and miRNAs), lipids, peptides and proteins derived
from the parent cells. Therefore, exosomes are thought to play an important role in
intercellular communications, mediating numerous physiological processes (beyond
immunology to neurobiology, stem cell and tumor biology) of the recipient cells.
These features have prompted extensive research to exploit them as a source of
biomarkers for several pathologies, such as inflammatory diseases, autoimmune
disorders, neurodegenerative disorders and cancer.
Find more: https://www.creative-diagnostics.com/exosomes-pathway.htm