The small intestine is divided into duodenum, jejunum, and ileum, with the duodenum and jejunum being the major site of digestion and absorption. Chyme takes 2 to 4 hours to move through the 5 m of the small intestine. Segmentation, which mixes intestinal contents and enhances contact of the chyme with the intestinal microvilli, is [...]
The colon reabsorbs salts and water. About 1500 mL of fluid enters the colon each day, but only 50 to 100 mL of fluid is excreted in feces. Anatomically, the colon is divided into the cecum, ascending colon, transverse colon, and descending colon. Segmental contraction of the circular smooth muscle divides the colon into numerous [...]
The tonsils and mucosa associated lymphoid tissues are not structurally organs; however, they function as secondary lymphoid organs because they are sites of immune responses. Tonsils Tonsils (ton'-sils) are clusters of lymphoid tissue located just deep to the mucous membrane in the pharynx (fayr- inks), or throat, and oral cavity. Like all lymphoid tissue, they [...]
The alimentary canal is a muscular tube about 5 m (20 ft) in length that extends from the esophagus to the anus. Various portions of the alimentary canal are specialized to perform different digestive functions. The hollow space within the alimentary canal through which food passes is called the lumen. Structure of The Wall The [...]
The pharynx (fayr'-inks) is the passageway that connects the nasal and oral cavities with the larynx and esophagus. It is part of both the respiratory and the digestive systems. Its digestive function is the transport of food from the mouth to the esophagus during swallowing. The swallowing reflex is activated when food is pushed into [...]
The J-shaped stomach is a pouchlike portion of the alimentary canal. It lies just inferior to the diaphragm in the left upper quadrant of the abdominopelvic cavity. The basic functions of the stomach are temporary storage of food, mixing food with gastric juice, and starting the chemical digestion of proteins. Structure The stomach may be [...]
Nutrients are chemicals in foods that provide energy for powering life processes; chemicals aiding or enabling life processes; or materials to construct molecules for the normal development, growth, and maintenance of the body. There are six groups of nutrients: carbohydrates, lipids, proteins, vitamins, minerals, and water. All six groups provide raw materials for constructing new [...]
Inflammatory Disorders Appendicitis is an acute inflammation of the appendix. First symptoms include referred pain in the umbilical region and nausea. Later, pain is localized in the right lower quadrant of the abdominal wall. Surgical removal of the appendix is the standard treatment. Inflammatory bowel disease (IBD) is a group of chronic disorders that cause [...]
It can be helpful to think of the digestive system as a tube running through the body with an opening at each end, the mouth at the top and the anus at the bottom. The tube isn’t a neat, constant shape throughout its course. It swells into a muscular storage organ at the stomach where [...]
Mastication, or chewing, mixes food with salivary mucus. This action subdivides food and exposes ingested starch to salivary amylase to begin the digestive process. Mastication is not essential for normal GI function but facilitates the process. Swallowing propels food from the mouth into the esophagus. The initiation of swallowing is voluntary, but once started, the [...]