What does SI mean? Definitions for SI Here are all the possible meanings and translations of the word SI.
The sebaceous glands are microscopic exocrine glands in the skin that secrete an oily or waxy matter, called sebum, to lubricate and waterproof the skin and hair of mammals.ebaceous glands secrete the oily, waxy substance called sebum (Latin: fat, tallow) that is made of triglycerides, wax esters, squalene, and metabolites of fat-producing cells. Sebum waterproofs and lubricates the skin and hair of mammals.
â¢ Sweat gland secretes sweat, which is watery in nature. Sebaceous glands secretes sebum, which is oily in nature. â¢ Sweat glands are important to control the temperature of the body and excrete waste products, whereas sebaceous glands are important to make the skin soft and moist.