Feature of epithelium of anal canal ?

Ans. is 'b' i.e., Upper pa contains anal columns of margagniThe interior of anal canal is divided by pectinate line and Hilton's white line into three pas.1) Upper pa (mucous pa)It is upper 15 mm pa of anal canal and extends upto pectinate line. It is lined by mucous membrane which is simple columnar. Mucosa shows 6-10 longitudinal folds called anal columns of Morgagni. Lower ends of these folds are united by sho transverse folds, anal valves. Line of attachment of anal valve is known as pectinate line or dentate line. Slight depression above each anal valve is known as anal sinus.2) Middle pa (transitional zone or pecten)This area is 15 mm in extent and intervenes between pectinate (dentate) line and Hilton's white line. It is lined by non-keratinized stratified squamous epithelium without sebaceous and sweat glands.3) Lower pa (cutoneous) paIt is about 8 mm in extent and is lined by true skin, i.e. stratified squamous keratimizing epithelium with sebaceous and sweat glands.