Secretion is the movement of material from one point to another chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, is the removal of certain substances or waste products. The classical mechanism of cell secretion is via secretory portals at the cell plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structure at the cell plasma membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.

Secretion in bacterial species means the transport or translocation of effector molecules for example: proteins, enzymes or toxins (such as cholera toxin in pathogenic bacteria for example Vibrio cholerae) from across the interior (cytoplasm or cytosol) of a bacterial cell to its exterior. Secretion is a very important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation and survival.

Secretion in eukaryotic cells

Mechanism

Eukaryotic cells, including human cells, have a highly evolved process of secretion. Proteins targeted for the outside are synthesized by ribosomes docked to the rough endoplasmic reticulum (ER). As they are synthesized, these proteins translocate into the ER lumen, where they are glycosylated and where molecular chaperones aid protein folding. Misfolded proteins are usually identified here and retrotranslocated by ER-associated degradation to the cytosol, where they are degraded by a proteasome. The vesicles containing the properly folded proteins then enter the Golgi apparatus.

The secrete or secret, a French term adopted into English usage, was a type of helmet designed to be concealed beneath a hat.

Usage

In the 17th century, cavalrymen, especially fashion-conscious members of the gentry or aristocracy, who wished to wear fashionable broad-brimmed felt hats, but also retain some level of protection for the head, would employ a hidden helmet called a secrete. This type of helmet could also be worn by civilians, including some of the judges at Charles I's trial, who believed that their safety was threatened. The existence of a large number of secrete helmets of a very similar type all stored together in the Tower of London suggests that they were occasionally issued to troops as a uniform piece of military equipment.

Appearance

The secrete was usually a small skull-cap of iron or steel pierced around its rim. The piercing allowed it to be sewn into the inside of a hat. The secrete was then undetectable to any observer, but offered considerably more protection from edged weapons than could a felt hat alone. Many different designs were used, some had solid domes, others were ring-shaped with a scalloped lower edge, presumably to save weight. A few exceptional examples had a folding cage of bars, which could be drawn down to afford protection to the face when in action. A further type of head protection which could be considered to fall under the same category, as it was intended to deceive the observer and mimic civilian headgear, was an entire broad-brimmed hat made of iron or steel. Such hat-helmets were either covered in cloth, or blackened and given a dulled finish so as to resemble felt. King Charles I of England is recorded as possessing such a helmet.