GC: n
S: SDir – https://bit.ly/2HiPVdl (last access: 13 May 2019); MEDLP – https://bit.ly/2Vka9Zc (last access: 13 May 2019).
N: 1. 1748, Modern Latin (Frederick Ruysch), from Greek epi “upon” + thēlē “teat, nipple,” from suffixed form of PIE root *dhe(i)- “to suck.” Related: Epithelial.
2. Morphology and General Physiology – Epidermis and Dermis: epithelia.
Cellular tissue covering surfaces, forming glands, and lining most cavities of the body: it consists of one or more layers of cells with only little intercellular material.
3. Morphology and General Physiology: epithelium.
A primary animal tissue, distinguished by cells being close together with little intercellular substance; covers free surfaces and lines body cavities and ducts.
4. In animals, outgrowths or ingrowths from these surfaces form structures consisting largely or entirely of cells derived from the surface epithelium. In this way the central nervous system, the sensitive surfaces of special sense organs, glands, hair, nails, and other structures all originate. The epithelial cells possess typical microscopical characteristics: the cell outline is clearly marked, and the nucleus large and spherical or ellipsoidal. The cytoplasm of the cell is usually large in amount and often contains large numbers of granules.
5. Epithelium may be protective, absorptive, or secretory. It may produce special outgrowths (hairs, nails, horns on animals), and manufacture chemical material (e.g., keratin), in which case the whole cell becomes modified. In other instances it contains fat droplets, granules of various kinds, protein, mucin, watery granules, or glycogen. In a typical absorbing cell, granules of material are absorbed. A secreting cell forming specific substances stores them until they are utilized—e.g., fat, in sebaceous and mammary glands; enzymes in salivary and gastric glands; and various excretory substances in the renal epithelium of the kidney.
S: 1. OED – https://bit.ly/2E06qKr (last access: 13 May 2019). 2 & 3. TERMIUM PLUS – https://bit.ly/2WAJeto (last access: 13 May 2019). 4 & 5. EncBrit – https://bit.ly/30hnCVi (last access: 13 May 2019).
SYN:
S:
CR: epithelial cell, scutoid.
