Sweat glands are made up of a coiled acinar secretory structure in the dermis and a straight duct that connects this acinar structure to the epidermis's surface (Figure 4). The epithelial cells of the duct wall contain abundant mitochondria with well-developed cristae, indicating high metabolic activity. Near the opening of the duct into the skin's surface, there is an intraluminal granular material composed mainly of mucin and salts. This material may play a role in preventing bacteria from entering the duct. The excretory portion of the sweat gland is called the "acini" which release their contents by exocytosis into the lumen of the duct. Exocytosis is the fusion of small vesicles with the cell membrane, releasing their contents into the space between the cells. These contents include salt and water for secretion into the duct, proteins involved in inflammation, and hormones. The result is a reduction in cell volume and expansion of the intercellular space causing obstruction of the duct. This mechanism allows the body to remove toxic substances from the blood stream without having to use the filtration system of the kidney. The rate at which you can lose water through your skin depends on several factors such as your size, temperature, how much you sweat, etc.