epithelium
noun
ep·i·the·li·um ˌe-pə-ˈthē-lē-əm 
plural epithelia ˌe-pə-ˈthē-lē-ə
1
: a membranous cellular tissue that covers a free surface or lines a tube or cavity of an animal body and serves especially to enclose and protect the other parts of the body, to produce secretions and excretions, and to function in assimilation
2
: a usually thin layer of parenchyma that lines a cavity or tube of a plant
Example Sentences
Recent Examples on the Web The disease damages a layer of neurons called the retinal pigment epithelium, which is crucial to the survival of the photoreceptors. 
Ron Winslow, WSJ, 4 Sep. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 In ulcerative colitis, the barriers provided by mucus and the epithelium are dysfunctional. Jill Seladi-schulman, SELF, 15 Feb. 2022 The scientific name for this layer of cells is the epithelium. Jill Seladi-schulman, SELF, 15 Feb. 2022 See More
Ron Winslow, WSJ, 4 Sep. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 At the very top of the nasal cavity, up between the eyes, sits mucosal tissue known as the olfactory epithelium. Genevieve Fullan, Longreads, 12 Apr. 2022 In ulcerative colitis, the barriers provided by mucus and the epithelium are dysfunctional. Jill Seladi-schulman, SELF, 15 Feb. 2022 The scientific name for this layer of cells is the epithelium. Jill Seladi-schulman, SELF, 15 Feb. 2022 See More Word History
Etymology
New Latin, from epi- + Greek thēlē nipple — more at feminine
First Known Use
1748, in the meaning defined at sense 1
Medical Definition
epithelium
noun
ep·i·the·li·um ˌep-ə-ˈthē-lē-əm
plural epithelia -lē-ə
: a membranous cellular tissue that covers a free surface or lines a tube or cavity of an animal body and serves especially to enclose and protect the other parts of the body, to produce secretions and excretions, and to function in assimilation