Epithelia squamous

Squamous epithelium Flattened, interlocking, toughened epithelial cells. 

The corneal epithelium is a stratified squamous epithelium like the epidermis of the skin but is nonkeratinized like other mucosal epithelia such as the intestinal and airway epithelia. Although the corneal epithelium, five to seven cells thick, represents less than 10% of the entire corneal thickness, it provides as much as 99% resistance to the diffusion of small electrolytes such as Na+ and Cl [55-57],... 

The mouth is the region from the lips to the pharynx. The first step in the digestive process is chewing, or mastication, which is an initial mechanical breakdown of the food that facilitates its movement to the stomach. The mouth is lined with stratified squamous epithelium that provides extra protection from injury by coarse food materials. Three pairs of salivary glands secrete saliva into the oral cavity ... 

A similar process of differentiation has been demonstrated in the basal cell layer of the squamous epithelium of the skin which seems to contain the stem cells... 

The situation is, however, different in the alveolar region of the lung where the respiratory gas exchange takes place. Its thin squamous epithelium is covered by the so-called alveolar surface liquid (ASL). Its outermost surface is covered by a mixture of phospholipids and proteins with a low surface tension, also often referred to as lung surfactant. For this surfactant layer only, Scarpelli et al. [74] reported a thickness between 7 and 70 nm in the human lung. For the thickness of an additional water layer in between the apical surface of alveolar epithelial cells and the surfactant film no conclusive data are available. Hence, the total thickness of the complete ASL layer is actually unknown, but is certainly thinner than 1 gm. 

Nonneoplastic proliferative lesions of the forestomach were observed in high-dose Osborne-Mendel rats in the chronic gavage study of 1,2-dibromoethane conducted by the National Cancer Institute (NCI 1978). These consisted of acanthosis and hyperkeratosis of forestomach squamous epithelium. Similar lesions occurred in high-dose B6C3Fi mice. These dose levels are not plotted and recorded in Figure 2-2 and Table 2-2, respectively, since these doses also caused forestomach squamous cell tumors. 

We have recently shown, in Seg-1 cells derived from a patient with esophageal adenocarcinoma, that bile acids and low pH induce the dramatic formation of autophagic vacuoles (unpublished data). We also showed that persistent treatment of Het-IA cells (derived from normal human esophageal squamous epithelium) with a bile-acid cocktail and low pH resulted in the development of mutated clones that contain a partly duplicated chromosome 16 (unpublished data from a CGH microarray). In addition to other protective genes, this chromosome 16 duplication resulted in the duplication of the major ATPase necessary for the acidification of vesicles associated with the autophagic process. 

The stomach of rats and mice is anatomically different from the human stomach. A part of the stomach in rodents is devoid of glands this part is called the forestomach. The squamous epithelium in the non-glandular rodent forestomach resembles the epithehum covering the esophagus. Therefore, the human esophagus must be regarded as similar with respect to the epithelium of the non-glandular rodent forestomach. 

Morphological damage by aminoglycosides is not limited to hair cells, and the cochlear sensory epithelium may become completely replaced by a squamous epithelium after prolonged drug treatment. Changes also occur in the... 

All rats survived dermal doses of up to 60 mg/rat administered over 13 weeks. Mean body weights were up to 14% lower than controls, and redness, scabs, and ulceration occurred at the application site. In mice, applications of up to lOmg/mouse produced increased liver and kidney weights. Compound-related skin lesions included sebaceous gland hyperplasia and hyperplasia and hyperkeratosis of the stratified squamous epithelium at the site of application ovarian atrophy was also considered to be compound related. 

Slaughter DP, Southwick HW, Smejkal W. Field cancerization in oral stratified squamous epithelium clinical implications of multicentric origin. Cancer 1953 6 963. 

The skin consists of two main compartments, the epidermis, a stratified squamous epithelium, and the underlying dermis, a richly vascularized tissue embedded in a connective tissue matrix (Fig. 41.1). The epidermis consists of multiple layers of keratinocytes, which differentiate into the outermost layer, the stratum corneum. This layer contains the hydrophilic structural... 

The characteristics of the nasal lesions in mice following chronic inhalation of ethylene dibromide were investigated. Male and female B6C3F, mice were exposed to 10 or 40 ppm [77 or 308 mg/m- ] ethylene dibromide for 6 h per day on five days per week for 103 (10 ppm) or 90 (40 ppm) weeks. The incidence of hyperplastic lesions was related to the dose of ethylene dibromide and was equivalent in males and females. Lesions consisted of focal areas of cuboidal to columnar cells arranged in a glandular pattern with foci of hyperplastic squamous epithelium also seen occasionally. Lesions were usually located in the anterior (respiratory turbinates) of the nasal cavities. A broad spectrum of proliferative lesions was observed (Stinson et al., 1981). 

Morimoto, K., Tsuji, K., Osawa, R. Takahashi. A. (1990) DNA damage test in forestomach squamous epithelium of F344 rat following oral administration of ethyl acrylate. Eisei Shikenjo Hokoku, 108, 125-128 (in Japanese)... 

Stratification of the vaginal squamous epithelium in postmenopausal women... 

Navab A, Koss LG, LaDue JS. Estrogen-like activity of digitalis its effect on the squamous epithelium of the female genital tract. JAMA 1965 194(l) 30-2. 

Conventional light microscopy of multifocal lesions of VIN may not show VIN 3 and instead may show VIN 2, VIN 1, or even normal squamous epithelium (van Beurden et al., 1998). Interobserver variation in the interpretation of the grading of VIN is not uncommon. To determine correct treatment of the patient, it is necessary to know which lesions show VIN 3 and which do not. The standard treatment for VIN 3 is drastic surgical excision of all visible lesions. However, an alternate approach is taking multiple biopsies the removal of involved skin using cold knife surgery or laser vaporization without radical surgery (van Beurden et al., 1998). 

Squamous epithelium A layer of flattened epithelial cells. 

---