Digestion

=Digestion=

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Within the lumen of the gastrointestinal tract, large food molecules are hydrolyzed into their monomers. These monomers pass through the inner layer, or mucosa, of the small intestine to enter the blood or lymph in a process called absorption. Digestion and absorption are aided by specializations of the gastrointestinal tract.

Functions of the digestive system include:

1. Motility- movement of food through the digestive tract 2. Secrection- both exocrine and endocrine 3. Digestion- breakdown of food 4. Absorption- passage of digested end products into the blood and lymph 5. Storage and elimination- temporary storage and subsequent elimination of indigestible food 6. Immune barrier- columnar epithelium that lines the intestine

From mouth to stomach: [|Process of Digestion] http://www.youtube.com/watch?v=Q-n_Q0qKXzg&feature=related

Questions:


 * Stomach**- The J- shaped organ is the most distensible part of the GI tract. The esophagus connects to the stomach superiorly and empties into the duodenum of the small intestine. The functions of the stomach are to store food, to initiate the digestion of proteins, to kill bacteria with the strong acidity of gastric juice, and to move the food into the small intestine as a pasty material called chyme. Swallowed food is delivered from the esophagus to the cardiac region of the stomach. An imaginary horizontal line drawn through the cardiac region divides the cardiac region divides the stomach into an upper fundus and a lower body, which together compose about 2/3 of the stomach. The distal portion of the stomach is called the pyloric region. The pyloric region begins in a somewhat widened area, the antrum, and ends at the pyloric sphincter. Contraction of the stomach churn the chyme, mixing it more thoroughly with the gastric secretions. These contractions also push partially digested food from the antrum through the pyloric sphincter and into the first part of the small intestine.


 * Small Intestine**: The mucosa of the small intestine is folded into vili that project into the lumen. The cells that line the villi have foldings fo their plasma membrane called microvilli. These greatly increases the surface area for absorption and improves digestion. The small intestine (also known as the small bowel) is the longest portion of the digestive tract - it is more than 6 meters long and is located within the middle of the abdomen. It has three sections, the duodenum, jejunum and ileum.Much of the small intestine is coiled and suspended in a thin layer of fat - which gives the intestine a lot of flexibility and mobility. Digestion of fats, proteins and carbohydrates contained in the foods you consume, is completed within the small intestine. The resulting nutrients produced are absorbed through the lining of the small intestine and transferred to the bloodstream.


 * || Carbohydrates || Proteins || Lipids ||
 * Where it is digested || Mouth, and duodenum || Stomach and duodenum || duodenum ||
 * Enzymes || Salivary amylase, pancreatic amylase, brush border enzymes || Pepsin, trypsin, chymotrypsin, elastase, carboxypeptidase, aminopeptidase || Pancreatic lipase, colipase, phospholipase A ||
 * Absorbed || Secondary active transport (Na+) || Cotransport (Na+), secondary active transport (H+) || Pass through epithelial cells of small intestine, secreted into lacteal ||
 * How the body uses this || Used for energy || Use to make enzymes for function || Energy, stored energy ||

Personal Application: Diet is very important in everyone. Understanding what foods to eat and include in your diet will help you to increase energy, sleep better, avoid osteoporosis, and control diabetes. It is very important to have a knowledge of a proper diet to give to your patients.

References: Information obtained to this page was taking from our text: Human Physiology by Stuart Ira Fox.