Sketches showing the anterior internal anatomy of an atlantic cod. The left image highlights the vasculature of the blood circulatory system (oxygenated in red, de-oxygenated in blue). Note the high levels of vasculature surrounding the gut (transportation of absorbed nutrients) and rete mirabile of the swim bladder (control volume of oxygen in swim bladder via root effect). The capillaries of the gills have been omitted in the left image but are present in the one on the right. The right hand image also illustrates well the alimentary canal complete with a blind ended pouch in the stomach, the mid-gut caece for enzyme production and absorptive intenstines. The latter image also shows the skeletal framework, kidneys (red below spine), gall bladder (green), swim bladder (white and frilly, below kidney), and the gonad (red, connected to vent).