Placoid scales are found in sharks and rays, and can vary greatly in external appearance. Scales of a White Shark. Photographer: Sue Lindsay Â© Australian Museum. Unlike the scales of bony fishes, placoid scales do not increase in size as the fish grows, instead new scales are added between older scales.Placoid scales are often referred to as denticles.Each placoid scale consists of a flattened rectangular base plate which is embedded in the fish, and variously developed structures, such as spines, which project posteriorly on the surface.The spines give many species a rough texture.here are large differences in the development of these spines between different species. Placoid scales are composed of a vascular (supplied with blood) inner core of pulp, a middle layer of dentine and a hard enamel-like outer layer of vitrodentine.
Approach Considerations. The treatment of gallstones depends upon the stage of disease. Ideally, interventions in the lithogenic state could prevent gallstone formation, although, currently, this option is limited to a few special circumstances. Asymptomatic gallstones may be managed expectantly.
But if the pain is severe or if you have had gallbladder pain before, you may need to have your gallbladder removed. Depending on where a stone blocks the flow of bile, symptoms can include nausea, vomiting, fever, and severe abdominal pain that lasts longer than 6 hours.If you have these symptoms, you may need surgery to remove your gallbladder or the gallstone causing the blockage.In rare cases, gallstones can cause pancreatitis, an inflammation of the pancreas.Gallstones back up the flow of digestive enzymes made by the pancreas.allstones that cause symptoms. The most common problem caused by gallstones occurs when a gallstone periodically blocks the cystic duct, which drains the gallbladder. It often causes bouts of pain that come and go as the gallbladder contracts and expands.