chapter 37, part 1: disorders of gastrointestinal function

GI tract digests:

• food and absorbs nutrients

• motility, secretion, digestion, and absorption work together

• nutrients enter bloodstream or lymph after crossing intestinal wall

• large intestine prepares waste for elimination

upper part (part of GI tract)

• mouth, esophagus, and stomach

• an intake source and parts in which initial digestive processes take place

middle portion (part of GI tract)

• duodenum, jejunum, ileum

• most digestive and absorptive processes occur

lower segment (part of GI tract)

• cecum, colon, and rectum

• storage channel for elimination of waste

common symptoms of many GI disorders

• common symptoms: anorexia, nausea, and vomiting

• serve as protective mechanisms that help body detect and respond to disease

anorexia is loss or decrease of:

• appetite

• emotional stress, medications, and illnesses cna reduce appetite

• anorexia frequently precedes nausea and vomiting

• anoreaxia and anorexia nervosa and diff conditions

  • an is an eating disorder characterized by fear of gaining weight

nausea is the unpleasant, conscious sensation of:

• urge to vomit

• results from stimulation of medullary vomiting center in brain

• nausea often precedes vomiting

• common causes: motion sickness, dizziness, migraine headaches, gastroenteritis, food poisoning, severe pain

retching

• rhythmic, spasmodic contraction of diaphragm, chest, and abdominal muscles

• usually precedes or alternates w/ vomiting

vomiting (emesis)

• sudden, forceful expulsion of stomach contents through mouth

  • vomitus is expelled stomach contents

  • protective function removes harmful substances from stomach and upper small intestine

mechanism of vomiting

• vomiting center: located in medulla oblongata

• vomiting reflex involves:

  • deep inspiration

  • closure of airway (glottis)

  • relaxation of gastroesophageal

  • forceful contraction of diaphragm and abdominal muscles

  • expulsion of stomach contents through mouth

  • breathing temporarily stops

diarrhea

• excessive frequency of stools may be acute or chronic

• prolonged diarrhea may lead to dehydration, electrolyte imbalance, acidosis, malnutrition

large-volume (secretory or osmotic) diarrhea

• watery stool resulting from increased secretions into intestine from plasma

• often related to infection

• limited reabsorption due to reversal of normal carriers of sodium and/or glucose

small-volume diarrhea

• frequent passage of small amount of stool

• often due to inflammatory bowel disease

• stool may contain blood, mucus, pus

• may be accompanied by abdominal cramps

constipation

• less frequent bowel movements than normal

• result from decreased intestinal peristalsis, leading to prolonged transit time and increased reabsorption of water from stool

• periods of constipation may alter w/ period of diarrhea

common causes of constipation:

• weakness of smooth muscle due to age or illness

• inadequate dietary fiber

• inadequate fluid intake

• neurologic disorders

• drugs - opioids (slows down digestive tract) and iron supplements

• obstructions caused by tumors or strictures

blood in stool may occur with:

• diarrhea, constipation, tumors, or inflammatory conditions

  • hematochezia (frank blood): red blood - indicating bleeding from lower GI tract

    • usuaally from lesions in sigmoid colin and rectum

  • occult blood: small hidden amounts, detectable w/ stool test

    • may be caused by small bleeding ulcers

  • melena: dark colored tarry stool

    • may result from significant bleeding in upper digestive tract

fibromuscular tube that connects the lower part of: (esophagus structure and function)

• the pharynx to stomach

• length in adults: 8-10 inches

• anatoical relations: lies posteriorly to larynx and trachea as it descends through mediastinum btwn lungs

  • intersects diaphragm at lvl of t122 or t12 vertebra and passes through

• involuntary, “wave-like” muscle contractions properl its contents downwards - peristalsis

musculature and nerve supply (esophagus structure and function)

• upper 1/3rd - skeletal muscle fibers innervated by glossopharyngeal (CN IX) and vagus (CN X) nerves

• lower 2/3rds - smooth muscle fibers innervated by vagus (CN X) nerve

sphincters at either end of esophagus:

• upper esophageal - prevents reflux from esophagus into pharynx

• lower esophageal - prevents reflux from stomach to esophagus

• both sphincters remain closed except during swallowing

mastication (chewing)

• begins in digestive process

• saliva contains enzymes that break down complex molecules

deglutition (swallowing) phases

• buccal phase: food/drink is pushed upwards and backwards into pharynx by tongue

• pharyngeal phase: epiglottis closes the entrance to larynx, and upper esophageal sphincter relaxes to let food/drink into esophagus

• esophageal phase: food/drink moves downwards through esophagus into stomach

swallowing mechanism from deglutition

dysphagia

• difficulty in swallowing

• common causes:

  • xerostomia: due to reduced salivary secretions w/ age, dehydration, or poorly controlled diabetes

  • esophageal narrowing: due to scar tissue formation after chronic acid reflux or radiation therapy

  • brainstem injury: due to trauma, infections, or tumors

signs and symptoms of dysphagia

• difficulty swallowing foods or liquids

• choking or coughing during meals

• sensation of food sticking in throat or chest

• odynophagia — painful swallowing

achalasia

• disorder in which lower esophageal sphincter (LES) fails to relax

• caused by dmg to enteric nervous system and vagus nerve

when LES fails to relax:

• food cannot enter stomach causing enlargement of esophagus above LES

• food remains in esophagus for prolonged periods

retained food in esophagus cause:

• regurgitation

• aspiration into lungs and pneumonia

within achalasia, early diagnosis (endoscopy, barium studies) and appropriate:

treatment help to prevent complications

hiatal hernia

• condition in which part of stomach protrudes through esophageal hiatus of diaphragm into chest cavity

• occurs when opening in diaphragm becomes enlarged or weakened

types of hiatal hernia:

• sliding: most common, often associated w/ acid reflux

  • gastroesophageal junction and upper part of stomach slide above diaphragm

• paraesophageal: less common but carries higher risk of serious complications

  • part of stomach pushes through esophageal opening gastroesophageal junction remains in its normal position

GERD (gastroesophageal reflux disease)

• condition in which gastric contents reflux abnormally into esophagus, oral cavity

• one of the most common gastrointestinal disorders worldwide - !!

causes and mechanism of GERD:

• weak or incompetent LES allows gastric contents to reflux

• delayed gastric emptying increases gastric pressure and volume, promoting reflux

• refluxed gastric acid irritates the esophageal lining

• diagnostic criteria for GERD:

  • occurs more than twice per week or several weeks

specific symptoms of GERD:

• heartburn: burning sensation behind sternum

• regurgitation: backflow of gastric contents into mouth or throat

• symptoms commonly occur 30-60 mins after meals:

  • worsened by bending forward or lying down

  • relieved by sitting or standing upright

• additional symptoms: belching and chest pain: epigastric or retrosternal

complications of GERD:

• barrett esophagus: replacement of norm squamous epithelium w/ abnorm columnar epithelium

  • presence of tan tongues of epithelium interdigitating w/ more proximal squamous epithelium is typical of barrett esophagus