Are all human cells spherical?

So far as I know (and someone correct me otherwise), no. Cell shape depends on its function, so while lymphocytes for example are spherical, whereas epithelial cells tend to be flat. Cell shape is also dependent on the environment. read more

Red blood cells are round and biconcave. White blood cells are ameboid or irregular in shape. Nerve cells are branched and elongated. Squamous epithelium of the walls of blood vessels are flattened. Cuboidal epithelium consists of cube like cells. Columnar epithelium has task and slender cells. read more

Yes, most cells are "spherical", and pictures like that are just cross-sections. There are some cells which are very thin, like the inner layer of blood vessel walls, and the cells that line your oesophagus, but all cells are 3D bags of biological stuff. A cell membrane consists of two layers of phospholipids. read more

Spherical cell shape in FLC-4 cells enhanced liver-specific gene expression, including albumin, apo A-I, CYP3A7, at a similar level to that of human liver (Laurent et al., 2012). However, common hepatoma cell lines did not show higher liver-specific functions in three-dimensional culture (Laurent et al., 2012). read more