Islamic University of Gaza Islamic University of Gaza Faculty of NursingFaculty of Nursing

Chapter TwoChapter TwoDigestion, Absorption, and MetabolismDigestion, Absorption, and Metabolism

Nurs1206Nurs1206..

Ali H. Abu RyalaAli H. Abu Ryala

2010-20112010-2011

Digestion, Absorption, and Digestion, Absorption, and MetabolismMetabolism

DIGESTIONDIGESTION

The digestive system is The digestive system is responsible for processing responsible for processing food, and itself dependant food, and itself dependant

on our intake for its on our intake for its maintenance. maintenance.

Digestive SystemDigestive System

A series of organs that function to A series of organs that function to prepare ingested nutrients for prepare ingested nutrients for

digestion and absorption.digestion and absorption.

Segments of the Digestive SystemSegments of the Digestive System

Mouth, oropharynx, esophagus, Mouth, oropharynx, esophagus, stomach, small intestine, duodenum, stomach, small intestine, duodenum,

jejunum, ileum, large intestine, jejunum, ileum, large intestine, cecum, colon, ascending colon, cecum, colon, ascending colon,

transverse colon, descending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal.sigmoid colon, rectum, anal canal.

Accessory OrgansAccessory Organs

Salivary glands (parotid, Salivary glands (parotid, submandibular, sublingual), submandibular, sublingual),

tongue, teeth, liver, gallbladder, tongue, teeth, liver, gallbladder, pancreas, vermiform appendix.pancreas, vermiform appendix.

Gastrointestinal Tract GITGastrointestinal Tract GIT

The main organs of the digestive The main organs of the digestive system that form a tube that runs system that form a tube that runs

from mouth to the anusfrom mouth to the anus

Body food component Body food component travel together, through travel together, through

GIT into the cell.GIT into the cell.

Definition of DigestionDefinition of Digestion

The process through which foods The process through which foods are broken down into similar and are broken down into similar and similar units to prepare nutrients similar units to prepare nutrients

for absorption.for absorption.

Basic principles of digestionBasic principles of digestion• Digestion: prepares the food for the body use ,under Digestion: prepares the food for the body use ,under

effect of muscular and chemical reaction.effect of muscular and chemical reaction.• Muscular layer of the elementary system (serosa, Muscular layer of the elementary system (serosa,

submucosa, and mucosa), and fiber layer longitudinal or submucosa, and mucosa), and fiber layer longitudinal or circular layer, help in the movement of food and push it circular layer, help in the movement of food and push it forward ,this movement called peristalsis.forward ,this movement called peristalsis.

• Chyme: fluid secreted by GIT (gallbladder) to help in Chyme: fluid secreted by GIT (gallbladder) to help in digestion .digestion .

• The action of food is under control of nervous system at The action of food is under control of nervous system at GIT wall called intra-mural nervous plexus extend from GIT wall called intra-mural nervous plexus extend from esophagus to anus responsible for regulation of the rate esophagus to anus responsible for regulation of the rate and intensity of muscle contraction with coordination in and intensity of muscle contraction with coordination in various movement.various movement.

• Peristalsis: The rhythmic contractions of muscles Peristalsis: The rhythmic contractions of muscles causing wavelike motion that move food down causing wavelike motion that move food down the GI tract.the GI tract.

• Mucosa: The inside GI muscle tissue layer Mucosa: The inside GI muscle tissue layer composed of mucous membrane.composed of mucous membrane.

• Submucosa: A layer of connective muscle tissue Submucosa: A layer of connective muscle tissue under the mucosa.under the mucosa.

• Muscularis: A thick layer of muscle tissue Muscularis: A thick layer of muscle tissue surrounding the t submucosa.surrounding the t submucosa.

• Serosa: The outmost layer of the GI wall; made of Serosa: The outmost layer of the GI wall; made of serous membrane.serous membrane.

• Segmentation: The forward and the backward Segmentation: The forward and the backward muscular action that assists in controlling food muscular action that assists in controlling food mass movement through GI tract.mass movement through GI tract.

Types of GIT SecretionTypes of GIT Secretion• Enzymes: chemical action e.g. Enzymes: chemical action e.g.

lipase ,amylase .lipase ,amylase .• Hydrochloric acid & buffer ions : Hydrochloric acid & buffer ions :

necessary ph .necessary ph .• Mucous: protect the inside wall Mucous: protect the inside wall

tissue of GIT, lubricate &facilitate tissue of GIT, lubricate &facilitate food mass passage .food mass passage .

• Water & electrolyte.Water & electrolyte.

Chemical or Secretary DigestionChemical or Secretary Digestion

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

Factors affect salivary secretionFactors 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 Normal range of daily saliva secretion between 800-1500ML, pH Neutral between 800-1500ML, pH Neutral

6.0 7.4 6.0 7.4

Mouth and Esophagus Mouth and Esophagus Preparation and DeliveryPreparation and Delivery

• Mastication: chewing break-down food into smaller Mastication: chewing break-down food into smaller particles by teeth & jaw muscle with tongue.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 Coordination &swallowing comes from (swallowing

centre area) in the brain stem.centre area) in the brain stem.• Gravity and muscle at the base of the tongue ,help in Gravity and muscle at the base of the tongue ,help in

the movement of the food down to esophagus ,in the the movement of the food down to esophagus ,in the up-right position .up-right position .

• In the stomach food enter by opening of the sphincter In the stomach food enter by opening of the sphincter to prevent reflux ,&occurrence of heart burn to prevent reflux ,&occurrence of heart burn

Stomach : Storage and Initial Stomach : Storage and Initial Digestive Process.Digestive Process.

• As the food enter the stomach ,the As the food enter the stomach ,the muscle of the stomach mix the muscle of the stomach mix the food ,storage ,&control emptying .food ,storage ,&control emptying .

• When the food mixed with chyme, When the food mixed with chyme, the pyloric sphincter constrict & the pyloric sphincter constrict & relax for control of emptying at relax for control of emptying at duodenum.duodenum.

Types of Stomach SecretionTypes of Stomach Secretion • Acid : hydrochloric acid (HCL).Acid : hydrochloric acid (HCL).• Mucous : protect the wall of lining stomach Mucous : protect the wall of lining stomach

& lubricant .& lubricant .• Enzymes: pepsin ,break down of protein Enzymes: pepsin ,break down of protein

(pepsinogen converted to pepsin under HCL (pepsinogen converted to pepsin under HCL secretion ),gastric lipase for fat , rennin in secretion ),gastric lipase for fat , rennin in child-hood aid in co- agulation of milk ,but child-hood aid in co- agulation of milk ,but absent in adult .absent in adult .

• Gastrin: hormone secreted by stomach that Gastrin: hormone secreted by stomach that increases the release of gastric juices.increases the release of gastric juices.

Control Process of Gastric Secretion Control Process of Gastric Secretion Under Effect ofUnder Effect of

• Nervous stimulus in response to Nervous stimulus in response to sense ,ingested food and emotions, sense ,ingested food and emotions, e.g. anger & hostility increase e.g. anger & hostility increase secretion, while fear and depression, secretion, while fear and depression, decrease secretion .decrease secretion .

• Hormonal stimulus in response to Hormonal stimulus in response to entrance of food into stomach.entrance of food into stomach.

e.g. gastric enterogastrone .e.g. gastric enterogastrone .

Small Intestine Small Intestine Major Digestion and AbsorptionMajor Digestion and Absorption

• Under control of nervous plexuses Under control of nervous plexuses or hormonal stimulation ,the wall or hormonal stimulation ,the wall stretch from pressure of food .stretch from pressure of food .

• Small intestine is chemical Small intestine is chemical digestion by secrete large number of digestion by secrete large number of enzymes and assistance of enzymes and assistance of pancreatic enzyme .pancreatic enzyme .

Types of SecretionTypes of Secretion • Enzymes .Enzymes .• Mucous from glands near the duodenum to protect the Mucous from glands near the duodenum to protect the

mucosa of intestine .mucosa of intestine .• Chlecystokinin (CCK) hormones secreted by the small Chlecystokinin (CCK) hormones secreted by the small

intestine that initiates pancreatic exocrine secretion, acts intestine that initiates pancreatic exocrine secretion, acts against gastrin, and activates the gallbladder to release bill against gastrin, and activates the gallbladder to release bill alkaline juice .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 Hormones: Substance that act as messengers between organs to cause the release of needed secretionsto cause the release of needed secretions

• Secretin: A hormone secreted by the small intestine that Secretin: A hormone secreted by the small intestine that causes the pancreas to relase bicarbonate to the small causes the pancreas to relase bicarbonate to the small intestine intestine

• Bile: A substance that emulsifies fats to aid the digestion of Bile: A substance that emulsifies fats to aid the digestion of lipids; produced by the liver and stored in the gallbladderlipids; produced by the liver and stored in the gallbladder

ABSORPTIONABSORPTION

Thank All Of YouThank All Of You

My Best Wishes My Best Wishes