Volcanoes produce a wide variety of natural hazards that can kill people and destroy property. This simplified sketch shows a volcano typical of those found in the Western United States and Alaska, but many of these hazards also pose risks at other volcanoes, such as those in Hawaii. Some hazards, such as lahars and landslides, can occur even when a volcano is not erupting.
A sphincter is a ring of muscle which holds any kind of biological opening closed. Sphincters are an important part of almost any system in a body. They help to both regulate the exit, entrance and circulation of fluids, gasses, and solids.
Best Answer: First one is the Upper Oesophageal Sphincter, which allows entry of a food bolus into the oesophagus. Then the Lower Oesophageal Sphincter (also known as cardia, or cardiac sphincter), found at the entrance to the stomach. This stops reflux of food back up the oesophagus. Next is the pyloric sphincter, which allows stomach contents into the duodenum (small intestine) for further digestion. Then the ilio-caecal valve, which isn't a sphincter, but mediates movement of small intestine contents into the large intestine (caecum). There are two sphincters around the anus, the external sphincter and the internal sphincter.