Epithelium

Membranous tissue covering internal organs and other internal surfaces and external surfaces of the body, including the lining of vessels and other small cavities that is of ectodermal and entoderm origin.  For the lining of the capillaries and air sacs, it is called squamous epithelium.  For the linings of the ducts in glands, the airways, and the mouth, it referred to as cuboidal epithelium, columnar epithelium, and stratified squamous epithelium, respectively. 

See Blastula, Bronchi, Cilia, Collagen, Ectoderm, Entoderm (or endoderm), Fallopian tubes, Histology, Olfaction, Proliferative cells, Squamous cells