Digestive System: Review
Digestive System: Absorption and Elimination Review
The digestive system is responsible for breaking down food to provide nutrients and energy to other organ systems in the body. There are three main functions to the digestive system: chemical and mechanical digestion, absorption, and defecation.
- The organs of the digestive system can be divided into two groups: alimentary canal organs and accessory structures. The alimentary canal is a hollow, muscular tube that runs through the ventral body cavity from the mouth to the anus. The alimentary canal is lined with smooth muscles that contract and push food through the canal in involuntary waves called peristalsis.
- Chemical and mechanical digestion begins in the mouth. Mastication breaks food down into smaller pieces, whereas saliva breaks down complex carbohydrates. The food is swallowed with the assistance of the tongue and soft palate and moves into the pharynx. The food then moves through the esophagus to the stomach. Mechanical and chemical digestion continues in the stomach as gastric juices break down food further and mechanically mix the food creating chyme. The chyme is then released through the pyloric sphincter into the small intestine.
- The accessory organs aid in the breakdown of food. The liver produces bile that aids in the digestion of fat. It is either stored in the gallbladder or released directly to the small intestine. The pancreas secretes pancreatic juice into the small intestine that helps to break down carbohydrates, proteins, and lipids in the chyme.
- The small intestine is the site where almost all digestion and absorption of nutrients and minerals from food take place. The small intestine has three parts: duodenum, jejunum, and ileum. The main function of the large intestine is to absorb water from the remaining indigestible food matter and then to pass the useless waste material from the body. The large intestine can also be divided into several sections: cecum, colon, rectum, and anal canal. After the excess water is absorbed, the remaining solid waste called feces is expelled through the anus during defecation.
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