The Digestive System Parts and Functions
Mechanical Digestion A process of digestion in which food is cut, torn, mashed, and churned into smaller bits. This process starts in the mouth and ends in the stomach. This converts food into bolus, and then in chyme.
Chemical Digestion Process of digestion in which foods is broken down chemically using acids and enzymes secreted from various organs. This process starts in the mouth and ends in the small intestine.
The Basic Parts of The Digestive System
In the Mouth...
Teeth Teeth are used to bite and chew food, which is the first step in the digestion of food. This is called mechanical digestion. Each type of tooth has its own job.
Types of Teeth
Specialized Teeth Incisors - Are responsible for cutting up food into smaller pieces. Cuspids - Also known as canines, these teeth are used to tear food apart (like meat). Bicuspids - Also known as pre-molars, these teeth are for shredding food. Molars - Are for crushing, grinding and mashing food.
Number of Teeth in the Entire Mouth Incisors - 8 Cuspids - 4 Bicuspids - 8 Molars - 8-12* * The third set of molars are known as the wisdom teeth, some people never get these, while many others have them removed.
The Tongue Used in mechanical digestion. The tongue presses the food against the roof of the mouth so that it can be swallowed. It also moves the food around and mixes it with saliva to create bolus.
Salivary Glands These secrete enzyme filled saliva that mix with food and begin chemical digestion. Sublingual Submandibular Parotid
The Throat
The Throat Pharynx - The orifice through which food passes from the Mouth to the Esophagus. Uvula - Structure that hangs at the back of the throat. This covers the Nasal Passage during swallowing so that no food enters the nasal passageways. Epiglottis - A flap-like structure that covers the Trachea when swallowing, to prevent choking. Larynx - The Voice box. Is located in the top of the trachea, below the pharynx.
The Gastrointestinal Tract
Esophagus This is the passageway of bolus from the pharynx to the stomach. Moves bolus through using gravity and peristalsis (wave-like contractions of the esophagus wall). This also results in some mechanical digestion. No chemical digestion is
Stomach A sac-like organ that churns and mixes bolus with strong stomach acids, creating chyme. Chemical and mechanical digestion happen here. Food can stay for several hours in the stomach.
Small Intestine The breakdown of food is completed here. Enzymes from the liver and pancreas are secreted into the small intestine to complete digestion. Nutrients are absorbed into the bloodstream through the small intestine.
Large Intestine Food is compacted, dehydrated, and mixed with mucous and bacteria to form feces. 90% of water is absorbed into the body through the large intestine. Feces is also stored here until it can be pushed into the rectum where is is held until it is expelled from the body.
Rectum This is the final structure of the GI tract. Holds feces until it is expelled from the body in a process known as defecation. Peristalsis within the rectum moves the feces through the anus to the outside of the body.
Anus A sphincter - round muscular tissue. Relaxes and allows feces to exit the body
Accessory Organs These organs do not lie inside the GI Tract. They secrete enzymes that break down nutrients. These organs are connected to the GI Tract by ducts or tubes. Includes the pancreas, liver and gall bladder.
Pancreas Responsible for secreting enzymes into the small intestine. These enzymes are used to break down proteins.
Liver Secretes bile into the gallbladder until it is used to digest fat in the small intestine.