Step One of the Digestive System
The process of digestion starts as soon as we put food in our mouths. This is called ingestion (Beckett & Gallagher, 2001). Lips form entrance to the mouth. Inside the mouth, the lips are coated by mucous membrane, like the entire oral cavity. Cheeks form the sides of the mouth. The roof of the of the mouth is made up of soft and hard palates and they are made of bone, blood vessels, muscle fibers, and nerves. On the floor of oral cavity is the tongue. It is made up of muscle fiber so it can move in various directions. The surface of the tongue is rough and is called papillae. Some of these papillae have taste buds. They allow a person to experience flavors of food like sweet, salty, sour, or bitter. They are also sensitive to heat, cold, and pressure. The tongue helps to mix saliva with food in the process of chewing (Walker & Wood, 2003). Teeth are specialized to break down food while chewing. Chewing and eating are voluntary acts and this process is mechanical (Morrison 2001). Once the chewing is done, the chemical process of digestion starts. The saliva in the mouth has enzymes that help to break down the food in the mouth. The enzymes in saliva are amylase enzymes which attack starch molecules. When the food is soft enough, the tongue helps to mold it into a round lump called bolus (Ballard, 1997). The bolus is pushed back to the back of the mouth by the tongue. The pressure of the bolus helps the soft palate to turn upward. This keeps the food out of the nasal cavity. The epiglottis blocks the entrance to the windpipe to keep food out. When we swallow, the bolus is pushed into the next part of the digestive system, the esophagus (Ballard, 1997). Because these are voluntary actions, we can control the beginning actions of swallowing but when food touches the back of the mouth, the action becomes automatic. These are reflex actions.
The process of digestion starts as soon as we put food in our mouths. This is called ingestion (Beckett & Gallagher, 2001). Lips form entrance to the mouth. Inside the mouth, the lips are coated by mucous membrane, like the entire oral cavity. Cheeks form the sides of the mouth. The roof of the of the mouth is made up of soft and hard palates and they are made of bone, blood vessels, muscle fibers, and nerves. On the floor of oral cavity is the tongue. It is made up of muscle fiber so it can move in various directions. The surface of the tongue is rough and is called papillae. Some of these papillae have taste buds. They allow a person to experience flavors of food like sweet, salty, sour, or bitter. They are also sensitive to heat, cold, and pressure. The tongue helps to mix saliva with food in the process of chewing (Walker & Wood, 2003). Teeth are specialized to break down food while chewing. Chewing and eating are voluntary acts and this process is mechanical (Morrison 2001). Once the chewing is done, the chemical process of digestion starts. The saliva in the mouth has enzymes that help to break down the food in the mouth. The enzymes in saliva are amylase enzymes which attack starch molecules. When the food is soft enough, the tongue helps to mold it into a round lump called bolus (Ballard, 1997). The bolus is pushed back to the back of the mouth by the tongue. The pressure of the bolus helps the soft palate to turn upward. This keeps the food out of the nasal cavity. The epiglottis blocks the entrance to the windpipe to keep food out. When we swallow, the bolus is pushed into the next part of the digestive system, the esophagus (Ballard, 1997). Because these are voluntary actions, we can control the beginning actions of swallowing but when food touches the back of the mouth, the action becomes automatic. These are reflex actions.