Endocrine glands release hormones (chemical messengers) into the bloodstream to be transported to various organs and tissues throughout the body. For instance, the pancreas secretes insulin, which allows the body to regulate levels of sugar in the blood. The thyroid gets instructions from the pituitary to secrete hormones which determine the pace of chemical activity in the body (the more hormone in the bloodstream, the faster the chemical activity; the less hormone, the slower the activity).

Striae in the popliteal fossa: Striae or stretch marks result from stretching of the skin, or other influences such as Cushing's syndrome. Most pregnant women experience striae at some point during their pregnancy. This picture shows striae in the popliteal fossa (the area on the back side of the leg at the knee joint). When the striae first appear they have a violaceous (red-purple) color, but over time they take-on a dull white appearance.

Stretch marks (striae) result from rapid stretching of the skin which may occur with obesity, pubertal growth spurts, pregnancy, or from other influences such as Cushing syndrome.