1. simple squamous epithejjan Description: Single layer of flat cells with disc-shaped central nuclei Top view: Polygonal, central nuclei Side view: Squamous, central nuclei Function: Allows passage of material by diffusion filtration and reduces friction by providing a smooth surface &e secreting lubricating serous fluid1. simple squamous epithelia Description: Single layer of flat cells with disc- shaped central nuclei. Top view: Polygonal, central nuclei Side view: Squamous, central nuclei Function: Allows passage of material by diffusion & filtration and reduces friction by providing a smooth surface & secreting lubricating serous fluid