GC: n

S: SDir – https://bit.ly/2sJKnl2 (last access: 13 May 2019); MEDLP – https://bit.ly/2JhTmBG (last access: 13 May 2019).

N: 1. – epithelial (adj): From “epithelium” (1748, Modern Latin -Frederick Ruysch-, from Greek epi “upon” + thēlē “teat, nipple,” from suffixed form of PIE root *dhe(i)- “to suck.” Related: Epithelial) and “-al” (suffix forming adjectives from nouns or other adjectives, “of, like, related to, pertaining to,” Middle English -al, -el, from French or directly from Latin -alis).

– cell (n): early 12c., “small monastery, subordinate monastery” (from Medieval Latin in this sense), later “small room for a monk or a nun in a monastic establishment; a hermit’s dwelling” (c. 1300), from Latin cella “small room, store room, hut,” related to Latin celare “to hide, conceal,” from PIE root *kel- “to cover, conceal, save.”
From “monastic room” the sense was extended to “prison room” (1722). The word was used in 14c., figuratively, of brain “compartments” as the abode of some faculty; it was used in biology by 17c. of various cavities (wood structure, segments of fruit, bee combs), gradually focusing to the modern sense of “basic structure of all living organisms” (which OED dates to 1845).
Electric battery sense is from 1828, based on the “compartments” in very early types. Meaning “small group of people working within a larger organization” is from 1925. Cell-body is from 1851, cell-division from 1846, cell-membrane from 1837 (but cellular membrane is 1732), cell wall from 1842.

2. One of the closely packed cells forming the epithelium.

3. Epithelial cells are the safety shields of the body. Take another look at your hand. It is covered with epithelial cells that protect your body by being a barrier between your internal cells and the dirt and microbes in the environment. They also are able to stretch so you can move your fingers and arms into many positions. You can also thank your epithelial cells for making the sweat that cools you down when you’re exercising or when it’s hot outside.

4. Other epithelial cells help you experience your environment by having special sensors, called receptors, that collect signals. When you taste a favorite food or smell a flower, the receptors in these cells send the signal to your brain so you can enjoy every bite and sweet smell.

5. Once you swallow that bite of food, it travels down a path lined with epithelial cells. When it gets to your intestines, another set of epithelial cells absorbs and transports nutrients from the foods you eat and helps process it for energy your body can use. Converting food energy to energy your body can use is the work of molecules called enzymes. Once again, it is epithelial cells that make and secrete the enzymes in your stomach. Epithelial cells also secrete hormones into your blood vessels, mucous in your nose and the breast milk which mothers feed their young.

S: 1. Etymonline – https://bit.ly/2Jzr73g; https://bit.ly/2WEu06E; https://bit.ly/2Q4e237 (last access: 13 May 2019). 2. TFD – https://bit.ly/2JnRsSX (last access: 13 May 2019). 3 to 5. Askbio – https://bit.ly/1TIU1gQ (last access: 13 May 2019).

SYN:
S:

CR: epithelium, scutoid.