A gland that secretes digestive enzymes into the duodenum via a duct, and synthesizes and secretes the hormones insulin, glucagon, and somatostatin. It is located between the stomach and the duodenum.

The subdivision of the autonomic nervous system involved in restor-nervous systeming homeostasis; it is antagonistic to the sympathetic nervous system.

Two pairs of glands located on the thyroid that secrete hormones that regulate calcium and phosphorous metabolism.

A form of reproduction in which an unfertilized egg develops into a new individual, occurring commonly among insects and certain other arthropods.

Immunity acquired by the transfer of antibodies from another individual, as through injection or placental transfer to a fetus.

Transport along a gradient without the use of metabolic energy.

A flat triangular bone located in the combined tendon of the extensors of the leg and covering the front surface of the knee joint. Also called kneecap.

An agent that causes disease, especially a living microorganism such as a bacterium, virus, or fungus.

The proteolytic enzyme of gastric juice which catalyzes the hydrolysis of native or denatured proteins to form a mixture of polypeptides; it is formed from pepsinogen in the presence of acid or, autocatalytically, in the presence of pepsin.

The chemical bond formed between the carboxyl groups and amino groups of neighboring amino acids, constituting the primary linkage of all protein structures.

The part of the vertebrate nervous system constituting the nerves outside the central nervous system and including the cranial nerves, the spinal nerves, and the sympathetic and parasympathetic nervous systems.

The wormlike movement by which the alimentary canal or other tubular organs having both longitudinal and circular muscle fibers propel their contents, consisting of a wave of contraction passing along the tube for variable distances.