Digestive & Gastrointestinal Function

Digestive & Gastrointestinal Function

Two Groups: Gastrointestinal Tract

• Organs include: Mouth, Pharynx, Esophagus, Small Intestine, and Large Intestine.

Two Groups: Accessory Digestive Organs

• Organs include: Teeth, Tongue, Salivary Gland, Liver, Gallbladder, and Pancreas.

Upper and Lower GIT

• Upper GIT extends from the mouth to the small intestine.
• Lower GIT extends from the large intestine to the anus.

Mesentery & Mesocolon

• Holds the organs in place.

Greater Omentum

• Protects the organs.

Falciform Ligament

• Reduces friction between abdominal organs.

Functions of Digestive System

• Ingestion is the intake of food.
• Secretion involves release of H2O, acid, buffers, & enzymes into the lumen.
• Mixing and propulsion: Churning & propulsion of food.
• Digestion is Mechanical & chemical breakdown of food.
• Absorption: Passage of digested products from GIT to the blood & lymph.
• Defecation: Elimination of feces.

Mouth

• Endodontics: concerned with diseases affecting the pulp, root, periodontal ligament, and alveolar bone.
• Orthodontics: concerned with abnormal alignment of teeth.
• Periodontics: concerned with treatment of abnormal conditions of tissues surrounding the teeth like gingivitis.
• Mechanical & Chemical Digestion: mastication/chewing.
• Salivary Amylase: breakdown of starch.
• Lingual Lipase: breaks dietary triglycerides into fatty acids & diglycerides.

Pharynx

• A funnel-shaped tube that extends from the internal nares to the esophagus posteriorly and to the larynx anteriorly.
• Composed of skeletal muscle lined by mucous membrane.
• Divided into three parts: nasopharynx, oropharynx, and laryngopharynx.

Esophagus

• A collapsible muscular tube, about 25 cm (10 in.) long, that lies posterior to the trachea.
• Begins at the inferior end of the laryngopharynx and passes through the mediastinum anterior to the vertebral column.
• It pierces the diaphragm through an opening called the Esophageal Hiatus and ends in the superior portion of the stomach.
• The mucosa comprises non-keratinized stratified squamous epithelium, lamina propria, and a muscularis mucosae.
• Upper Esophageal Sphincter (UES): skeletal muscle.
• Lower Esophageal Sphincter (LES): smooth muscle.

Stomach

• Deglutition: Swallowing occurs in three stages.
• Voluntary Stage: bolus is passed into the oropharynx.
• Pharyngeal Stage: involuntary passage of the bolus through the pharynx into the esophagus.
• Esophageal Stage: involuntary passage of the bolus through the esophagus into the stomach.
• Isotonic (Slow) movement allows for Optimal Digestion.
• Hypertonic (Fast) movement causes Diarrhea (more water).
• Hypotonic (Slower) movement causes Constipation.
• Functions of stomach: Mixes saliva, food, and gastric juice to form chyme.
• Functions of stomach: Reservoir for food before release into the small intestine.
• Functions of stomach: Secretes gastric juice, which contains HCl, pepsin, intrinsic factor, and gastric lipase.
• Functions of stomach: Secretes gastrin into blood.

Pancreas

• Releases hormones/enzymes to promote balance.
• Endocrine functions: releases insulin (increase blood glucose) & glucagon (decrease blood glucose).
• Exocrine functions: releases amylase, lipase, & tripase to emulsify proteins, carbs, & fats.

Liver

• Functions: Cascade tissue fluid/H2O to prevent leak.
• Functions: Increase capillary permeability w/o: increase capillary permeability, causing edema, congestion and ascites.
• Increase immune system response w/o: infection & fever.
• Clotting Factor Functions: Factors I, II, IV, VII, VIII, IV, V and Vitamin K is needed.
• Metabolize Sex Hormones Function: Promote balance in primary & secondary sex hormones. -Testosterone - male. -Estrogen/Progesterone – female w/o: M (E/P) – gynecomastia; F’s (T) – Adam's apple, hirsutism, deep voice, & mustache.
• Synthesis of Unconjugated-Conjugated Bilirubin.
• Storage of Vitamins & Minerals: -ADEK - fat soluble: -A - Retinol, -D - Ergocalciferol, -E - Tocopherol, -K - Menadione. -B & C - water soluble: -Activation of vitamin D - release in vitamin K. -Vitamin D promotes the production of Vitamin K-dependent proteins, which require vitamin K for carboxylation in order to function properly. -Vitamin B12 deficiency – anemia and megaloblastic
• Bile: Hepatocytes secrete 800 - 1000 mL (about 1 qt) of bile, a yellow, brownish, or olive- green liquid. -It has a pH of 7.6 - 8.6 and consists mostly of water, bile salts, cholesterol, a phospholipid called lecithin, bile pigments, and several ions.
• The principal bile pigment is bilirubin. The phagocytosis of aged red blood cells liberates iron, globin, and bilirubin.
• One of its breakdown products- stercobilin- gives feces their normal brown color.
• Bile salts play a role in emulsification, the breakdown of large lipid globules into a suspension of small lipid globules.
• Between meals, after most absorption has occurred. Bile flows into the gallbladder for storage because the sphincter of the hepatopancreatic ampulla (sphincter of ODDI) closes off the entrance to the duodenum.
• Unconjugated: indirect bile.
• Conjugated: direct bile.

Small Intestine

• Where digestion takes place.
• Half acidic & half alkaline.
• Segmentations mix chyme with digestive juices and bring food into contact with the mucosa for absorption; peristalsis propels chyme through the small intestine.
• Completes the digestion of carbohydrates, proteins, and lipids; begins and completes the digestion of nucleic acids.
• Absorbs about 90% of nutrients and water that pass through the digestive system.
• Segmentation: mix chyme with the digestive juices and bring the particles of food into contact with the mucosa for absorption.
• Migrating Motility Complex (MMC): begins at the lower portion of the stomach and pushes chyme forward along a short stretch of small intestine before dying out.
• UGIT Problem: Melena (black tarry stool).
• LGIT Problem: Hematochezia (blood in stool).

Large Intestine

• It is where storage of waste products occurs/
• Ascending colon: where most fluid stays (liquid/watery stool).
• Transverse colon: solid & liquid (mushy stool).
• Descending colon: solid (buck stool).
• Haustral churning, peristalsis, and mass peristalsis drive the contents of the colon into the rectum.
• Bacteria in the large intestine convert protein to amino acids, breakdown amino acids, and produce some B vitamins and vitamin K.
• Absorbs some water, ions, and vitamins.
• Forms feces.
• Defecation: emptying rectum.
• Diarrhea: Increase in the frequency, volume, and fluid content of the feces caused by increased motility of and decreased absorption by the intestines.
• Constipation: Infrequent or difficult defecation caused by decreased motility of intestines.

Phases of Digestion

• Cephalic Phase: The smell, sight, thought, or initial taste of food activates neural centers in the cerebral cortex, hypothalamus, and brainstem.
• The BRAIN STEM then activates the facial (VII), glossopharyngeal (IX), and vagus (X) nerves. The facial and glossopharyngeal nerves stimulate the salivary glands to secrete saliva, while the vagus nerves stimulate the gastric glands secrete gastric juice.
• Gastric Phase: Takes place in the stomach. It generally takes about three to four hours. With the Presence of food, the pH level decreases, and this causes the enlargement of the stomach, which is called DISTENSION. There can be many other reasons for distention.
• Distension accelerates the secretion of various enzymes in the stomach - gastric juices and acetylcholine.
• Intestinal Phase: Begins once food enters the small intestine. Those occurring during the intestinal phase have inhibitory effects that slow the exit of chyme from the stomach.

Health History & Clinical Manifestations

• Subjective Data -General Data: Presence of dental prosthesis & comfort of usage, Difficulty eating or digesting food, Nausea or vomiting, Weight loss, Pain. -Specific Data: Situations or events that affect symptoms, Onset, possible cause, location, duration, and character of symptoms. -Normal Pattern of Bowel Elimination: Frequency, character of stool, & Use of laxatives, and enemas. -Recent Changes in Normal Patterns: Changes in character of stool (constipation, diarrhea, or alternating constipation and diarrhea). Changes in color of stool like Melena & Hematochezia Medications being taken Measures that are taken to relieve symptoms
• Indigestion: can result from disturbed nervous system control of the stomach or from a disorder in the Gl tract or elsewhere in the body.
• Intestinal gas: the accumulation of gas in the Gl tract may result in belching or flatulence.
• Nausea And Vomiting: Vomiting is usually preceded by nausea, which can be triggered by odors, activity, or food intake.
• When vomiting occurs, soon after hemorrhage, the emesis is bright red.
• Stool with mucus threads or pus that may be visible on gross inspection of the stool.
• Small, dry, rock-hard masses called SCYBALA; sometimes streaked with blood from rectal trauma as they pass through the rectum.

Disorders of the Upper GI

Gastroesophageal Reflux Disease (GERD)

• Backward flow (reflux) of stomach.
• Reflux esophagitis: acute symptoms of inflammation.

Gastritis

• Inflammation of the gastric mucosa, is classified as either acute or chronic. -Common causes include NSAIDs and H. pylori.
• Clinical Manifestations: -Epigastric discomfort -Feeling of fullness, early satiety Belching, Flatulence, Severe nausea and vomiting

Medical Terminology

• Odynophagia-Painful swallowing.
• Hematemesis - Vomiting of blood.
• Dysphagia - Difficulty in swallowing
• Barrett's Epithelium - Normal squamous cell epithelium changing to columnar epithelium and has the potential of becoming malignant
• Melena - Black tarry stool
• Dyspepsia- Indigestion

Important Medications

Histamine2 (H2) Receptor Antagonist Famotidine, Ranitidine, Cimetidine, Nizatidine:Decreases acid production/secretion of parietal cells Proton Pump Inhibitors (PPI's) Omeprazole, Lansoprazole, Rabeprazole, Pantoprazole, Esomeprazole:Increases Reduce acid secretion in stomach/ Promotes healing in gastric lining; MetaclopramideIncrease gastric emptying, anti-emetic Aluminum Hydroxide, Magnesium Hydroxide, Maalox, Mylanta:Neutralizes HCI & deactivating pepsin / Decreases the release of acid congestion Laxative: medication that promotes bowel movement

Important Points

• Laparoscopic Nissen Fundoplication - Gold Standard for Surgical Management
• Small, dry, rock-hard masses called SCYBALA comes from rectal trauma
• The principal bile pigment is bilirubin