Islamic University of Gaza Faculty of Nursing Chapter Two Digestion, Absorption, and Metabolism Nurs1206. Ali H. Abu Ryala

Digestion, Absorption, and Metabolism

DIGESTION

The digestive system is responsible for processing food, and itself dependant on our intake for its maintenance.

Digestive System A series of organs that function to prepare ingested nutrients for digestion and absorption.

Segments of the Digestive System Mouth, oropharynx, esophagus, stomach, small intestine, duodenum, jejunum, ileum, large intestine, cecum, colon, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal.

Accessory Organs Salivary glands (parotid, submandibular, sublingual), tongue, teeth, liver, gallbladder, pancreas, vermiform appendix.

Gastrointestinal Tract GIT The main organs of the digestive system that form a tube that runs from mouth to the anus

Body food component travel together, through GIT into the cell.

Definition of Digestion The process through which foods are broken down into similar and similar units to prepare nutrients for absorption.

Basic principles of digestion Digestion: prepares the food for the body use,under effect of muscular and chemical reaction. Digestion: prepares the food for the body use,under effect of muscular and chemical reaction. Muscular layer of the elementary system (serosa, submucosa, and mucosa), and fiber layer longitudinal or circular layer, help in the movement of food and push it forward,this movement called peristalsis. Muscular layer of the elementary system (serosa, submucosa, and mucosa), and fiber layer longitudinal or circular layer, help in the movement of food and push it forward,this movement called peristalsis. Chyme: fluid secreted by GIT (gallbladder) to help in digestion. Chyme: fluid secreted by GIT (gallbladder) to help in digestion. The action of food is under control of nervous system at GIT wall called intra-mural nervous plexus extend from esophagus to anus responsible for regulation of the rate and intensity of muscle contraction with coordination in various movement. The action of food is under control of nervous system at GIT wall called intra-mural nervous plexus extend from esophagus to anus responsible for regulation of the rate and intensity of muscle contraction with coordination in various movement.

Peristalsis: The rhythmic contractions of muscles causing wavelike motion that move food down the GI tract. Peristalsis: The rhythmic contractions of muscles causing wavelike motion that move food down the GI tract. Mucosa: The inside GI muscle tissue layer composed of mucous membrane. Mucosa: The inside GI muscle tissue layer composed of mucous membrane. Submucosa: A layer of connective muscle tissue under the mucosa. Submucosa: A layer of connective muscle tissue under the mucosa. Muscularis: A thick layer of muscle tissue surrounding the t submucosa. Muscularis: A thick layer of muscle tissue surrounding the t submucosa. Serosa: The outmost layer of the GI wall; made of serous membrane. Serosa: The outmost layer of the GI wall; made of serous membrane. Segmentation: The forward and the backward muscular action that assists in controlling food mass movement through GI tract. Segmentation: The forward and the backward muscular action that assists in controlling food mass movement through GI tract.

Types of GIT Secretion Enzymes: chemical action e.g. lipase,amylase. Enzymes: chemical action e.g. lipase,amylase. Hydrochloric acid & buffer ions : necessary ph. Hydrochloric acid & buffer ions : necessary ph. Mucous: protect the inside wall tissue of GIT, lubricate &facilitate food mass passage. Mucous: protect the inside wall tissue of GIT, lubricate &facilitate food mass passage. Water & electrolyte. Water & electrolyte.

Chemical or Secretary Digestion Three pairs of salivary glands,parotid,sub-maxillary, sub- lingual,secrete salivary amylase this enzyme is specific for starch digestion.

Factors affect salivary secretion Sight. Sight. Smell. Smell. Taste. Taste. Touch. Touch. Thought of like and dislike of food. Thought of like and dislike of food. Normal range of daily saliva secretion between ML, pH Neutral

Mouth and Esophagus Preparation and Delivery Mastication: chewing break-down food into smaller particles by teeth & jaw muscle with tongue. Mastication: chewing break-down food into smaller particles by teeth & jaw muscle with tongue. Swallowing: Swallowing: Occur at mouth and pharynx. Occur at mouth and pharynx. Rapid less than one second. Rapid less than one second. Coordination &swallowing comes from (swallowing centre area) in the brain stem. Coordination &swallowing comes from (swallowing centre area) in the brain stem. Gravity and muscle at the base of the tongue,help in the movement of the food down to esophagus,in the up-right position. Gravity and muscle at the base of the tongue,help in the movement of the food down to esophagus,in the up-right position. In the stomach food enter by opening of the sphincter to prevent reflux,&occurrence of heart burn In the stomach food enter by opening of the sphincter to prevent reflux,&occurrence of heart burn

Stomach : Storage and Initial Digestive Process. As the food enter the stomach,the muscle of the stomach mix the food,storage,&control emptying. As the food enter the stomach,the muscle of the stomach mix the food,storage,&control emptying. When the food mixed with chyme, the pyloric sphincter constrict & relax for control of emptying at duodenum. When the food mixed with chyme, the pyloric sphincter constrict & relax for control of emptying at duodenum.

Types of Stomach Secretion Acid : hydrochloric acid (HCL). Acid : hydrochloric acid (HCL). Mucous : protect the wall of lining stomach & lubricant. Mucous : protect the wall of lining stomach & lubricant. Enzymes: pepsin,break down of protein (pepsinogen converted to pepsin under HCL secretion ),gastric lipase for fat, rennin in child-hood aid in co- agulation of milk,but absent in adult. Enzymes: pepsin,break down of protein (pepsinogen converted to pepsin under HCL secretion ),gastric lipase for fat, rennin in child-hood aid in co- agulation of milk,but absent in adult. Gastrin: hormone secreted by stomach that increases the release of gastric juices. Gastrin: hormone secreted by stomach that increases the release of gastric juices.

Control Process of Gastric Secretion Under Effect of Nervous stimulus in response to sense,ingested food and emotions, e.g. anger & hostility increase secretion, while fear and depression, decrease secretion. Nervous stimulus in response to sense,ingested food and emotions, e.g. anger & hostility increase secretion, while fear and depression, decrease secretion. Hormonal stimulus in response to entrance of food into stomach. Hormonal stimulus in response to entrance of food into stomach. e.g. gastric enterogastrone.

Small Intestine Major Digestion and Absorption Under control of nervous plexuses or hormonal stimulation,the wall stretch from pressure of food. Under control of nervous plexuses or hormonal stimulation,the wall stretch from pressure of food. Small intestine is chemical digestion by secrete large number of enzymes and assistance of pancreatic enzyme. Small intestine is chemical digestion by secrete large number of enzymes and assistance of pancreatic enzyme.

Types of Secretion Enzymes.Enzymes. Mucous from glands near the duodenum to protect the mucosa of intestine.Mucous from glands near the duodenum to protect the mucosa of intestine. Chlecystokinin (CCK) hormones secreted by the small intestine that initiates pancreatic exocrine secretion, acts against gastrin, and activates the gallbladder to release bill alkaline juice.Chlecystokinin (CCK) hormones secreted by the small intestine that initiates pancreatic exocrine secretion, acts against gastrin, and activates the gallbladder to release bill alkaline juice. Bile secreted from liver &store by gall bladder to dissolve fat.Bile secreted from liver &store by gall bladder to dissolve fat. Hormones: Substance that act as messengers between organs to cause the release of needed secretionsHormones: Substance that act as messengers between organs to cause the release of needed secretions Secretin: A hormone secreted by the small intestine that causes the pancreas to relase bicarbonate to the small intestineSecretin: A hormone secreted by the small intestine that causes the pancreas to relase bicarbonate to the small intestine Bile: A substance that emulsifies fats to aid the digestion of lipids; produced by the liver and stored in the gallbladderBile: A substance that emulsifies fats to aid the digestion of lipids; produced by the liver and stored in the gallbladder

ABSORPTION

Thank All Of You My Best Wishes