Generally, sphincter are circular or ring - shaped muscles, surrounding the natural opening in the body. They control the movement of substances by opening and closing through expansion and contraction.
There are many sphincter in the body, examples are
* Cardiac sphincter...found at the upper area or portion of the stomach.
* Pupilary sphincter..found in the iris of the eye.
* Glisson's sphincter...controlling the secretion of the gall bladder,pancrease and the liver.
Hormone Signaling. The glands of the endocrine system secrete hormones directly into the extracellular environment. The hormones then diffuse to the bloodstream via capillaries and are transported to the target cells through the circulatory system.
