The lid like cartilaginous structure overhanging the entrance to the larynx, guarding it during swallowing.

See adrenalin.

The cellular covering of internal and external body surfaces, including the lining of vessels and small cavities. It consists of cells joined by small amounts of cementing substances and is classified according to the number of layers and the shape of the cells.

Red blood cell; corpuscle; one of the formed elements in peripheral blood. Normally, in humans, the mature form is a non-nucleated, yellowish, biconcave disk, containing hemoglobin and transporting oxygen.

The musculomembranous passage extending from the pharynx to the stomach.

A generic term for estrus-producing compounds; the female sex hormones, including estradiol, estriol, and estrone. In humans, the estrogens are formed in the ovary, adrenal cortex, testis, and fetoplacental unit, and are responsible for female secondary sex characteristic development, and, during the menstrual cycle, act on the female genitalia to produce an environment suitable for fertilization, implantation, and nutrition of the early embryo. Uses for estrogens include oral contraceptives, hormone replacement therapy, advanced prostate or postmenopausal breast carcinoma treatment, and osteoporosis prophylaxis.

The recurrent set of physiological and behavioral changes that take place from one period of estrus to another.

An organism whose cells have a true nucleus bounded by a nuclear membrane within which lie the chromosomes; eukaryotic cells also contain many membrane-bound organelles in which cellular functions are performed. The cells of higher plants and animals, fungi, protozoa, and most algae are eukaryotic.

A developmental process in which an organ or organism becomes more and more complex by differentiation of its parts; a continuous and progressive change according to certain laws and by means of resident forces.

The act or process of discharging waste matter from the blood, tissues, or organs.

A gland, such as a sebaceous gland or sweat gland, that releases its secretions to the body\'s cavities, organs, or surface through a duct.

A muscle that extends a joint.