Exocytosis is a process by which cellular products are secreted into the extracellular environment. Proteins and other molecules produced within the cell that are destined for export (secretion) are packaged within vesicles by an organelle known as the Golgi complex. In the process of exocytosis, these secretory vesicles fuse with the plasma membrane and release their contents into the extracellular environment (see fig. 3.13). Nerve endings, for example, release their chemical neurotransmitters in this manner (see chapter 7).
When the vesicle containing the secretory products of the cell fuses with the plasma membrane during exocytosis, the total surface area of the cell membrane is increased. This process replaces material that was lost from the plasma membrane during endocytosis.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.