Glands are structures in the body which secrete liquid or semi-liquid material.They all have similar structures, consisting of one or of a multiple collection of little sac-like arrangements of cells which produce the characteristic secretion of the particular type of gland.
The secretion is discharged through a duct or little tube. however, some glands have no such outlets as ducts and are therefore called ductless glands, discharging"hormones" directly into the blood stream.
The skin glands excrete sweat, the gastrointestinal glands secrete digestive juices, and so do the salivary glands in the mouth. The skin and mucous membranes lining the inside of all organs are closely studded with glands, lubricating and protecting these parts.
The pancreas and the liver are also glands. The liver is the largest glands in the body, it is also the largest of the internal organs