Liver and Gallbladder

In both humans and mice, the liver is a regulatory center for nutrient processing, protein production, energy homeostasis, and detoxification. Nutrients are collected from blood arriving from the gastrointestinal tract via the portal vein, and toxins from intestinal bacteria and other sources are cleared. The human liver occupies the right upper quadrant of the abdomen, whereas the mouse liver spans the entire subdiaphragmatic space. Lobe patterns are different between the two species, and the human liver is traversed and suspended by surface ligaments that are not apparent in the mouse. Although lobar patterns are species-specific, basic lobular subunits are highly conserved in structure and function. Nevertheless, adaptations to unique exposures and dietary habits can be reflected even at the histologic level. Mixed arterial and portal venous blood enters the lobule from portal "triads" (actually composed of four structures: arterioles, venules, bile ductules, and lymphatics). Nutrients and macromolecules are freely exchanged between hepatocytes and plasma across sinusoids lined by fenestrated endothelium, while resident cells including hepatic stellate cells, Kupffer cell macrophages, and T and natural killer (NK) cells maintain close immune surveillance. Physiologic function is similar in both species, although there are some key differences reflected at the morphologic level. © 2012