Anatomy and Physiology: Digestive System

Anatomy and Physiology of the Digestive System

• The gastrointestinal tract includes the mouth, most of the pharynx, esophagus, stomach, small intestine, and large intestine.
• Accessory digestive organs consist of the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
• The peritoneal cavity holds the entire GI tract.

Functions of the Digestive System

• Ingestion involves taking food into the mouth.
• Secretion refers to the release of water, acid, buffers, and enzymes into the lumen of the GI tract.
• Mixing and propulsion involves churning and moving food through the GI tract.
• Digestion includes mechanical and chemical breakdown of food.
• Absorption refers to the passage of digested products from the GI tract into the blood and lymph.
• Defecation concerns the elimination of feces from the GI tract.

Parts of the Gastro-Intestinal System

Mouth

• Digestion starts here.
• Mechanical digestion happens through mastication (chewing).
• Chemical Digestion happens due to salivary amylase (ptyalin), breaking down starches to maltose-glucose.
• Deglutition (swallowing) happens once food breaks down and mixes with saliva, forming a food bolus.

Esophagus

• It serves as a passage for food bolus from mouth to stomach by peristalsis.
• The distal end is guarded by the lower esophageal sphincter (LES), preventing gastric reflux.

Stomach

• Located in the left upper quadrant of the abdomen with a capacity of 1,500ml.

• The regions include cardiac, fundus, body, and antrum or pyloric region, featuring lesser and greater curvatures.

• Mechanical digestion involves the physical breakdown of foods.

• Secretion sees gastric juice production, which includes Hydrochloric acid and pepsinogen (becomes pepsin), aiding in protein digestion.

• Chemical Digestion concerns protein and fats

• Protection is also a function of here.

• Absorption includes lipid-soluble substances like alcohol and aspirin.

• The stomach controls the passage of chyme to the duodenum.

Small Intestine

• It's about 6 meters long, from the pyloric sphincter to the ileocecal valve.

• It divides into the duodenum, jejunum, and ileum; most digestion completes in the duodenum, and most absorption occurs in the small intestine.

• Mucus secretion is a key function.

• Secretion of enzymes also essential.

• Secretion of hormones is important .

• Chemical Digestion occurs involving carbohydrates, fats, polypeptides, and nucleic acid.

• Absorption of amino acids, glucose, fructose, fats, water, minerals, and vitamins takes place.

• Motor Activities are also key here.

Large Intestine

• Extends approximately 1.5 meters from the ileocecal valve to the anus.

• It divides into the cecum, colon, rectum, and anus.

• The vermiform appendix is attached to the cecum.

• The colon divides into ascending, transverse, descending, and sigmoid sections.

• The final segment is the rectum and anus.

• Motor activity occurs in the large intestine.

• Secretion is part of its function.

• Absorption of water is a vital role.

• Vitamin Synthesis happens. -Feces formation is a key function.

• Defecation occurs.

Accessory Digestive Organs

Salivary Glands

• The parotid gland is located in the parotid fossa, with the facial nerve, external carotid artery, and retro mandibular vein running through it; it opens near the upper second molar tooth and is completely serous.
• The submandibular gland sits posteriorly in the submandibular triangle, supplied by the facial artery and vein.
• Its ducts cross the lingual nerves and open on the tongue frenulum; it's mostly serous but partially mucus.
• The sublingual gland, the smallest, sits beneath the oral mucosa in the floor of the mouth.
• It has many small openings and is almost completely mucus-secreting.

Teeth

• Used for mechanical breakdown
• Incisors are used for cutting.
• Canines are used for stabbing and holding.
• Molars have large surface area for grinding.
• Primary or deciduous teeth, total 20.
• Secondary or permanent teeth, total 32.

Pancreas

• A soft, tadpole-shaped gland that stretches along the abdomen, encircled by the C-shape duodenum.
• It features both endocrine and exocrine functions.
• Exocrine function: acinar cells cluster like raspberries around tiny ducts, responsible for secreting digestive enzymes.
• Endocrine function: pancreatic islets are responsible for glucose metabolism.

Gallbladder

• Stores bile until immediate digestion needed.
• It expands when filled with bile.
• Contraction of the muscularis layer ejects bile into the common bile duct.
• When the small intestine is empty, the Sphincter of Oddi is closed.

Liver Functions

• Carbohydrate metabolism
• Lipid metabolism
• Proteins metabolism
• Processing of drugs and hormones is key
• Bilirubin excretion is esssential.
• Bile salts synthesis is required.
• Storage of vitamins (A, B12, D, E, K) and minerals (iron, copper)
• Phagocytosis function
• Vitamin D activation also occurs.

Role and Composition of Bile

• Hepatocytes secrete 800–1000 mL (about 1 qt) of bile daily; it's a yellow, brownish, or olive-green liquid with a pH of 7.6-8.6.
• Bile consists mostly of water, bile salts, cholesterol, a phospholipid called lecithin, bile pigments, and several ions.
• Bilirubin is the principal bile pigment, released through the phagocytosis of aged red blood cells.
• Stercobilin, one of its breakdown products, gives feces their normal brown color.
• Bile salts play part in emulsification, breaking down large lipid globules into small lipid globules.
• Bile flows into the gallbladder for storage between meals because the sphincter of the hepatopancreatic ampulla (Sphincter of Oddi) closes off entry to the duodenum.

Assessment of Patient with Gastrointestinal Disease and Diagnostic Procedures

Health History and Clinical Manifestations

• Subjective Data

• General Data

  • Includes presence and usage/comfort with dental prosthesis.
  • Any difficulty eating or digesting food.
  • Nausea or vomiting.
  • Weight loss.

• Specific Data

  • Situations or events affecting symptoms.
  • Onset, possible cause, location, duration, and character of symptoms.
  • Relationship with specific foods, smoking, or alcohol.
  • How symptoms managed before seeking medical help.

• Normal Bowel Elimination Patterns

  • Frequency and character of stool.
  • Usage of laxatives and/or enemas.

• Recent changes in normal bowel patterns

  • Changes in stool character include constipation, diarrhea, or alternating between both.
  • Changes include stool color (melena, hematochezia).
  • Drugs and medications affect patient.
  • Relief measures are important .

• Indigestion

  • Can arise from nervous system control of stomach.
  • Can result of a GI tract disorder located elsewhere in the body.

• Intestinal Gas

  • Gas accumulation can result in belching or flatulence.

• Nausea and Vomiting

  • Vomiting, typically after nausea, relates to odors, activities, or food intake.
  • Bright red emesis indicates recent hemorrhage.
  • Coffee-ground emesis indicates blood retained in the stomach, changed by digestive action

• Bowel Habits and Stool Characteristics

  • Diarrhea results from contents moving too rapidly through the intestine and colon to allow GI secretion absorption
  • Constipation is commonly associated with anal discomfort or rectal bleeding.
  • Blood in the stool should be investigated, presenting in varied ways.
  • Blood in the lower GI tract, passing rapidly, appears bright or dark red.
  • Streaking of blood on the stool surface indicates lower rectal or anal bleeding.

• Abnormalities in stool

  • Bulky, greasy, foamy, foul-odor stools, being grey with a silvery sheen.
  • Light gray or clay-colored stools, from an absence of urobilin.
  • Stool containing mucus threads of pus.
  • Scybala, consisting of dry, rock-hard masses, often streaked with blood.
  • Loose, watery stools potentially streaked with blood.

Physical Assessment

• Patient supine, knees flexed for abdominal assessment.
• Inspection occurs first of skin changes, scars of contour, symmetry, and peristaltic waves.
• Auscultation follows in all four quadrants for bowel sounds noted at high-pitched or gurgling frequency.
• Important frequency terms include:
  • Normal (sounds every 5-20 seconds)
  • Hypoactive (one or two sounds in 2 minutes)
  • Hyperactive (5-6 sounds in about 30 seconds)
  • Absent (no sounds in 3 - 5 minutes)
• Tympani or dullness are noted during percussion.
• Light palpation identifies tender zones or swelling.
• Deep palpation identifies quadrants and masses.
• The final is inspection of the anal and perineal area, checking rash and fissures or fistula opening.

Diagnostic Evaluation

• Common blood tests include:
  • Carcinoembryonic antigen (CEA)
  • Complete blood count (CBC)
  • Liver function tests
  • Serum cholesterol and triglycerides

Stool Tests

• Specimens require a basic exam for consistency and color.
• Basic examination tests for occult blood, urobilinogen, fat, nitrogen, parasites, pathogens, food reside, & substances.
• Hematest is the most widely used occult blood test.
• False-positive results may occur if rare meat, poultry, turnips, salmon, or horseradish are consumed within 7 days before testing.
• Medications that can cause gastric irritation such as aspirin, ibuprofen or corticosteroids may also cause false-positive results.

Breath Tests

• Hydrogen breath tests assess carbohydrate absorption.
• This test can aid in the diagnosis of intestinal bacterial overgrowth and short bowel syndrome.
• Urea breath tests detect Helicobacter pylori.
• This requires patients to take a capsule of carbon labeled urea and then provide a breath sample 10 to 20 minutes later.
• Patients are instructed to avoid antibiotics or loperamide for 1 month before the test, and sucralfate & omeprazole for 1 week.

Abdominal Ultrasonography

• Aids in the diagnosis through images of abdominal organs and structures produced on screen.

• Procedure is used to determine the size and configuration of abdominal structures.

• Endoscopic Ultrasonography (EUS) is a special endoscopic method, that aids in diagnosis by way of targeted area viewing.

• Nursing interventions before US

  • Patients need to fast for 8 – 12 hours to lower bowel gas.
  • If gallbladder studies occur, patients should consume very limited fat the previous evening.
  • If barium studies need to be performed make sure they are after Ultrasound or barium affects US.

Imaging Studies

• Includes x-ray and contrast studies
• Includes computed tomography (CT) scans
• Includes magnetic resonance imaging (MRI)
• Includes scintigraphy (radionuclide imaging)

Upper GI Tract Study

• X-rays delineate GI after contrast is entered.

• The test varies in the upper Gl study, by double-contrast and enteroclysis styles.

• In the double-contrast method, thick barium is administered over stomachs with tablets of dioxide given.

• Nursing interventions before procedure

  • Maintain patients on a low-residue diet a few days before the test.
  • Receive NPO by midnight before the test
  • Physicians may need to prescribe laxatives to clean out the tract.
  • No smoking.

• Nursing interventions after procedure

  • needed to maintain completely elimination of ingested bariums.
  • Fluid taken after the test increase stool evacuation alongside barium. - Check patients stool until it returns to its normal color. - Enemas of laxatives may be needed.

Lower GI Tract Study

• Barium enema happens when barium is rectally instilled to visualize the lower GI tract.

• Barium Enema helps identify polyps, tumors, any lesions of intestine while showing any anatomy & bowel malfunctions.

• Procedure is around 15 to 30 min over which x-rays are created.

• Nursing interventions:

  • Before procedure:
    • Patients need low reside diets 1 – 2 days before the test.
    • A clear diet and laxative must be ingested before the enema.
    • Nothing through the mouth is permitted after midnight.
    • Cleansing enemas until it shows pure next morning.
    • Ensure that Barium enemas occur pre any upper GI checks.

• Contraindications:

  • When patients possess a risk of colon and GI issues such as bleeding enemas can have prohibitive effect in patient healing.

• after the Procedure:

  • The administration of laxative and enemas are key to maintain bariums removal.
  • The increase of fluid intake aids barium elimination.
  • Patients can be checked for barium at given times.

Computed Tomography (CT)

• CT scans provide cross images of organs and structures in abdomen.
• Computer reconstruct multiple X-rays from many angles, shown as results of images on screen.
• Scanning shows various liver, kidney, and pelvic scans.
• Tool detects inflammations in colon with appendicitis, diverticulitis e.t.c

Magnetic Resonance Imaging (MRI)

• MRI supports US or tomography scans when gastroenterology is needed.

• MRIs implement magnetic field & radio waves, and are minimally invasive.

• It aids tissue evaluation as well as abnormal issues such as sources of bleeding.

• Contraindications:

  • Are present when patients are at consistent electrical problems. Also any internal metal issues can cause hazards too.

Scintigraphy:

• Depends on isotopes that reveal structures, tumor mass like abscesses.
• Tag red cells to show concentrations.
• Blood samples are mixed with other substances, reinjected back to test bodily reaction.

Gastrointestinal Motility Studies

• Radionuclide tests are implemented to assess gastric emptying & colonic transit time
• Markers are placed across components of test liquid which must mark the presence of radionuclide as time passes.
• X Rays are done at 24 hr intervals up to 4-5 days.

Endoscopic Procedures

• Can involve esophagogastroduodenoscopy
• Can involve Anoscopy or Proctoscopy
• All are connected to evaluation, and include small-bowel and ostomy use cases.

Upper Fibroscopy/Esophagogastroduodenoscopy

• Tests help visualize the lower and upper mucosa through endoscope.

• Help evaluate issues that stem for infective process.

• Aid mobility, collect specimens etc.

• Patients should take nothing 6–12 hrs pre- endoscope

• Help patients spray medication, administered pre-scope

• Saliva drainage occurs with L side placement

• NPO up until gag reflex is returned.

• Test and evaluation check signs and symptoms.

Anoscopy, Proctoscopy, And Sigmoidoscopy

• Test to see lower portions of colon for any processes.

• Anoscopes assess rectum areas while knee placement on the patient.

• The preparation involves enemas.

• After patient monitoring is vital.

Fiberoptic Colonoscopy

• Can be used for cancer check & evaluation purposes

• Used for blockage and can provide areas for polyp removal

• Patient needs to draw up to chest.

• Colon function testing:

1. Fluid intake checks
2. Clear & clear tests
3. Bowel & Electrolyte checks

Gastrointestinal Motility Testing

• Measure pressure coordination.
• Perform an electrophysiology to check disturbances.

Analysis & Stimulation

• Help stomach mucosa from presence of retention
• Keep patients NPO for 8 – 12 hours before procedures.
• The process may have patients feel flushed.

Laparoscopy

• Visual for growths and issues within patient

Enema

• For diagnostic work and or meds (clears wastes)

Nutrition

• Aid clients that cannot do standards foods.

Common GIT Symptoms and Management

Constipation

• abnormality
  • Laxatives are prescribed
  • Increase H20

Diarrhea

• abnormality
• Intake of Fluid increase

Dumping syndrome

• abnormality
• CHO are diluted in the small intestine

Pernicious anemia

• Abnormality
• Injections of Vitamin B are needed

Conditions of the Upper GI System

Hiatal Hernia

• (abdominal organ) moves in to diaphragm ✓ Test the barium swallow - small feed frequent. Do not lay -elevate head on 8 inch block.

Esophageal varices

• Emergent condition (dilation & tortuosity) ✓ esophagoscopy performed. -strict vitals signs, Monitor blood.

Reflux GERD

• Sphincter or motility disorder -Test pH and avoid the stimulus ✓eat low high in fib, avoid drink, weight loss.

Gastritis

• may test the gastrointestinal mucosa infection ✓ Test the barium -monitor complications and give bland foods

Peptic ulcers

-ulcer with disease ✓ Test acidity

• bed rest & bland diet "" meds Bleeding interventions

Conditions of the Lower Tract

Crohn’s Disease

• Inflammatory disease ✓ Abdominal Pain ✓ Fever ✓Diarrhea

Ulcerative Colitis

• Inflammation on GI

Condition of the GIT Accessory Organs

Liver

• cirrhosis damage to cells.

Gallbladder

• cholecystitis causes inflammation bile ✓Test ultra sound → check w blood

Pancreas

• pancreatitis can damage the pancreas.