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eye

(Encyclopedia)CE5 Cross section of human eye eye, organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of ey...

peptide

(Encyclopedia)peptide, organic compound composed of amino acids linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) o...

acupuncture

(Encyclopedia)CE5 Acupuncture points for treating diseases of the large intestine. acupuncture ăkˈyo͝opŭngˌchər [key], technique of traditional Chinese medicine, in which a number of very fine metal needl...

impotence

(Encyclopedia)impotence imˈpətəns [key], inhibited sexual excitement in a man during sexual activity that, despite an unaffected desire for sex, results in inability to attain or maintain a penile erection. Know...

ectoderm

(Encyclopedia)ectoderm, layer of cells that covers the surface of an animal embryo after the process of gastrulation has occurred. This outer layer, together with the endoderm, or inner layer, is present in all ear...

chromosome

(Encyclopedia)chromosome krōˈməsōmˌ [key], structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome is usually res...

hoopoe

(Encyclopedia)hoopoe ho͞oˈpo͞o, –pō [key], common name for a shy, solitary, Old World woodland bird, Upupa epops. Its body color ranges from cinnamon to chestnut, with white-barred, black wings and tail, and ...

autoimmune disease

(Encyclopedia)autoimmune disease, any of a number of abnormal conditions caused when the body produces antibodies to its own substances. In rheumatoid arthritis, a group of antibody molecules called collectively RF...

seasonal affective disorder

(Encyclopedia)seasonal affective disorder (SAD), recurrent fall or winter depression characterized by excessive sleeping, social withdrawal, depression, overeating, and pronounced weight gain. SAD effects an estima...

radioactive isotope

(Encyclopedia)radioactive isotope or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reache...