Illustration of a liver cell, or hepatocyte. Cells in the liver are arranged in close contact with the blood to take on a blood detoxifying role. Here, the inner structure of one liver cell is shown. At top, the cell membrane is folded forming microvilli which increase the surface area in contact with blood. A central nucleus (brown) is surrounded by elongated tubules of endoplasmic reticulum (ER). The surface of ER is studded with ribosomes which synthesize blood proteins. The cytoplasm (orange) stores fat droplets (yellow); these active cells have many mitochondria (purple) for respiration. Bile capillaries or cholangioles (green) flush out blood toxins as bile.