Secretory pathway

A secretory pathway is a term used to describe different methods that cells use to transport material from the Golgi apparatus to the outside. There are two different pathways: constitutive and regulated.

Constitutive

In constitutive secretion, proteins are packaged in vesicles in the Golgi apparatus and are secreted immediately via exocytosis, all around the cell. They secrete continuously and unlike the regulated pathway, no external signal is needed to stimulate the process. Cells that secrete constitutively have many Golgi apparatus scattered throughout the cytoplasm. Fibroblasts, osteoblasts and chondrocytes are some of the many cells that use this pathway.

Regulated

In regulated secretion, proteins are packaged as described in the constitutive pathway, but they are only secreted in response to a specific signal, such as neural or hormonal stimulation. Cells that use the regulated secretory pathway are usually apical or polarized. The Golgi apparatus are found in a supranuclear position (between the nucleus and the secretory surface). Example cells that use regulated pathway are: goblet cells (secrete mucus), beta cells of the pancreas (secrete insulin) and odontoblasts (secrete dentin).