Overview
The digestive system (gastrointestinal system) breaks down food, absorbs nutrients and water, and eliminates undigested waste.
It provides the body with nutrients needed for energy, growth, tissue repair, and normal cellular function.
The digestive system consists of two major groups:
- Alimentary Canal (Gastrointestinal Tract): Continuous tube through which food passes, from the mouth to the anus.
- Accessory Digestive Organs: Structures that assist digestion, including the salivary glands, liver, gallbladder, and pancreas.
Major Structures
Alimentary Canal
- Mouth (Oral Cavity): Begins digestion through chewing and mixing food with saliva.
- Teeth: Mechanically break food into smaller pieces.
- Tongue: Moves food during chewing and forms a bolus for swallowing.
- Salivary Glands: Produce saliva containing digestive enzymes, including salivary amylase.
- Pharynx (Throat): Passageway for swallowed food and liquids toward the esophagus.
- Esophagus: Muscular tube transporting food from the pharynx to the stomach through peristalsis.
- Stomach: Muscular organ that stores, mixes, and partially digests food using gastric acid and enzymes, producing chyme.
- Small Intestine: Primary site of chemical digestion and nutrient absorption.
- Duodenum: First segment; receives chyme, bile, and pancreatic digestive secretions.
- Jejunum: Middle segment; major site of nutrient absorption.
- Ileum: Final segment; absorbs remaining nutrients, including vitamin B12 and bile salts.
- Large Intestine (Colon): Absorbs water and electrolytes and forms feces.
- Cecum: First portion of the large intestine.
- Ascending Colon: Travels upward along the right side of the abdomen.
- Transverse Colon: Crosses the upper abdomen.
- Descending Colon: Travels downward along the left side.
- Sigmoid Colon: S-shaped portion leading to the rectum.
- Rectum: Stores feces before elimination.
- Anus: Opening through which feces leave the body, controlled by anal sphincters.
Accessory Digestive Organs
- Liver: Large organ in the upper right abdomen.
- Produces bile to assist fat digestion.
- Processes absorbed nutrients.
- Stores glycogen, vitamins, and minerals.
- Metabolizes medications and toxins.
- Produces important blood proteins.
- Gallbladder: Stores and concentrates bile produced by the liver, releasing it into the small intestine during digestion.
- Pancreas: Organ behind the stomach with digestive and endocrine functions.
- Exocrine Function: Produces digestive enzymes and bicarbonate delivered into the duodenum.
- Endocrine Function: Produces insulin and glucagon to regulate blood glucose.
Intestinal Lining
- Villi: Fingerlike projections in the small intestine that increase surface area for nutrient absorption.
- Microvilli: Microscopic projections on intestinal epithelial cells that further increase absorptive surface area.
- Intestinal Capillaries: Absorb many nutrients into the bloodstream.
- Lacteals: Specialized lymphatic vessels within villi that absorb dietary fats.
Important: Villi are characteristic of the small intestine, not the entire digestive tract.
Key Processes
Digestion
Digestion involves mechanically and chemically breaking food into smaller components that can be absorbed.
- Mastication: Chewing food to break it into smaller pieces.
- Salivation: Saliva moistens food and begins starch digestion.
- Swallowing (Deglutition): Coordinated movement of food from the mouth through the pharynx into the esophagus.
- Airway Protection: The epiglottis and other swallowing mechanisms help protect the airway.
- Peristalsis: Coordinated, wave-like smooth muscle contractions that move material through the digestive tract.
- Mechanical Digestion: Physical breakdown and mixing of food.
- Chemical Digestion: Enzymes and digestive secretions break nutrients into absorbable components.
Pathway of Food Through the Digestive Tract
- Mouth: Food is chewed, mixed with saliva, and formed into a bolus.
- Pharynx: Swallowing moves the bolus toward the esophagus.
- Esophagus: Peristalsis transports food into the stomach.
- Stomach: Gastric acid and enzymes begin significant protein digestion; muscular contractions produce chyme.
- Small Intestine: Bile and pancreatic enzymes assist digestion; most nutrients are absorbed.
- Large Intestine: Water and electrolytes are absorbed, and feces are formed.
- Rectum: Stores feces before defecation.
- Anus: Feces are eliminated during a bowel movement.
Nutrient Absorption
- Carbohydrates: Broken down into simple sugars, such as glucose.
- Proteins: Broken down into amino acids and small peptides.
- Fats: Bile helps emulsify fats, allowing digestive enzymes to break them down for absorption.
- Vitamins and Minerals: Absorbed primarily in the small intestine, with specific absorption sites depending on the nutrient.
- Water: Absorbed throughout the intestines, predominantly in the small intestine, with additional absorption in the colon.
Elimination
- Feces Formation: Undigested material, bacteria, water, and other substances form stool.
- Defecation: Coordinated contractions and relaxation of the rectum and anal sphincters allow stool to leave the body.
- Mucus Secretion: Helps lubricate intestinal contents and protect the intestinal lining.
Effects of Aging
- Changes in Oral Health: Tooth loss, reduced chewing efficiency, dry mouth, and dental problems may interfere with eating.
- Changes in Swallowing: Some age-related changes in swallowing physiology may reduce swallowing reserve, especially during illness.
- Changes in Gastrointestinal Motility: Motility patterns may change, but significant slowing and constipation are not inevitable consequences of aging.
- Increased Constipation Risk: Reduced mobility, inadequate fluid or fiber intake, and medication effects can make constipation more likely.
- Changes in Liver Physiology: Liver size and blood flow may decrease with age, potentially affecting the metabolism of certain medications.
- Changes in Appetite: Taste, smell, medications, illness, and social factors can influence food intake.
Clinical Implications
- Increased vulnerability to poor nutritional intake.
- Dental problems and swallowing difficulties may affect safe eating.
- Reduced mobility and certain medications can increase constipation risk.
- Dehydration may worsen constipation.
- Medication effects may be more pronounced because of changes in metabolism.
- Greater importance of observing food intake, swallowing, bowel patterns, and changes from baseline.
Important: Persistent constipation, unexplained weight loss, difficulty swallowing, gastrointestinal bleeding, and significantly impaired digestion are not normal consequences of aging and require evaluation.
See Effects of Aging - Systems & Clinical Implications.
Common Diseases & Disorders
| Condition | Description | Common Causes / Risk Factors | CNA Considerations |
|---|---|---|---|
| Constipation | Infrequent or difficult bowel movements, often involving hard stools | Low fiber or fluid intake, immobility, medications such as opioids, certain medical conditions | Observe bowel patterns; encourage permitted fluids, fiber, and mobility according to the care plan; report changes |
| Fecal Impaction | Large mass of hardened stool lodged in the rectum or colon that cannot be passed normally | Chronic constipation, immobility, dehydration, medications, neurological disease | Report abdominal discomfort, rectal pressure, inability to pass stool, or liquid stool leakage; do not attempt manual removal |
| Gastroesophageal Reflux Disease (GERD) | Repeated reflux of stomach contents into the esophagus, causing troublesome symptoms or complications | Weakness or inappropriate relaxation of the lower esophageal sphincter, obesity, hiatal hernia, certain foods or medications | Observe heartburn, regurgitation, coughing, and discomfort after eating; follow prescribed positioning and meal plans |
| Peptic Ulcer Disease | Open sores in the lining of the stomach or duodenum | Helicobacter pylori infection, NSAID use; smoking increases risk | Report abdominal pain, vomiting blood, or black, tarry stools; bleeding symptoms require urgent response |
| Hernia | Protrusion of tissue or an organ through a weakened area of the surrounding muscle or connective tissue | Age-related tissue weakness, previous surgery, increased abdominal pressure, heavy straining | Report new painful bulges, swelling, vomiting, or severe abdominal pain; follow mobility precautions |
| Gallstones / Gallbladder Disease | Gallstones can obstruct bile flow and cause pain or inflammation of the gallbladder | Female sex, age, obesity, pregnancy, rapid weight loss, family history | Observe and report right upper abdominal pain, nausea, vomiting, fever, or jaundice |
| Diverticulosis | Formation of small pouches (diverticula) in the wall of the colon | Increasing age, genetics, and factors associated with colonic pressure | Observe bowel changes and report abdominal symptoms |
| Diverticulitis | Inflammation of diverticula, sometimes involving infection or other complications | Diverticulosis, obesity, smoking, certain medications, age | Report abdominal pain, fever, nausea, or changes in bowel habits |
| Gastroenteritis | Inflammation of the stomach and intestines, often causing diarrhea, vomiting, and abdominal discomfort | Viral or bacterial infections, contaminated food or water | Observe fluid intake, vomiting, diarrhea, and dehydration signs; follow infection-control precautions |
| Dysphagia | Difficulty swallowing food, liquids, or saliva | Stroke, neurological disorders, muscle weakness, structural abnormalities | Follow prescribed food textures, liquid consistencies, positioning, and swallowing precautions; report coughing or choking during meals |
Important Distinctions
- Constipation vs. Fecal Impaction: Constipation involves difficult or infrequent bowel movements; impaction involves stool that has become lodged and cannot be passed normally.
- GERD vs. Peptic Ulcer Disease: GERD involves reflux into the esophagus; ulcers involve open sores in the stomach or duodenal lining.
- Diverticulosis vs. Diverticulitis: Diverticulosis means diverticula are present; diverticulitis means they have become inflamed.
- Gallstones vs. Cholecystitis: Gallstones are hardened deposits in the gallbladder or bile ducts; cholecystitis is inflammation of the gallbladder, often due to gallstone obstruction.
- Diarrhea vs. Overflow Diarrhea: Liquid stool may leak around a fecal impaction, so loose stool does not always mean constipation is absent.
Important: CNAs observe and report gastrointestinal abnormalities rather than independently diagnosing conditions, performing disimpaction, or administering bowel treatments without appropriate authorization.
When to Report
- New or persistent constipation or diarrhea.
- Significant changes in bowel movement frequency, appearance, or consistency.
- New abdominal pain, swelling, or distention.
- Nausea, vomiting, or inability to tolerate food or fluids.
- Difficulty chewing or swallowing.
- Coughing, choking, or a wet-sounding voice during meals.
- Blood in stool or unusually dark, tarry stools.
- Poor appetite, unexpected weight loss, or decreased fluid intake.
- New bowel incontinence or suspected fecal impaction.
- Signs of dehydration.
Emergency signs: Severe sudden abdominal pain, vomiting blood, substantial gastrointestinal bleeding, inability to breathe from choking, or signs of shock require immediate emergency response.
Study Notes
Clinical Connections
- Assisting with Feeding: Proper meal assistance supports nutrition and safe swallowing.
- Dysphagia & Aspiration Precautions: Swallowing problems can increase choking and aspiration risk.
- Elimination Care: Bowel patterns and continence are important aspects of resident care.
- Constipation: Mobility, fluids, diet, and medications influence bowel function.
- Dehydration: Vomiting, diarrhea, and poor fluid intake can disturb fluid balance.
- Hand Hygiene: Certain gastrointestinal infections can spread through contaminated hands and surfaces.
- Vital Signs: Changes in temperature, pulse, and blood pressure may accompany dehydration, bleeding, or infection.
- Patient Positions: Appropriate positioning supports comfort, feeding, and aspiration precautions.
Questions
- What distinguishes the alimentary canal from accessory digestive organs?
- What is the correct sequence food follows through the digestive tract?
- What is the difference between mechanical and chemical digestion?
- What is peristalsis?
- What are the three regions of the small intestine?
- Where does most nutrient absorption occur?
- How do villi and microvilli increase nutrient absorption?
- What are the functions of the liver, gallbladder, and pancreas?
- What is the difference between a bolus and chyme?
- What are the primary functions of the large intestine?
- How can aging affect digestion, appetite, and bowel function?
- What distinguishes constipation from fecal impaction?
- How do GERD and peptic ulcer disease differ?
- What is the difference between diverticulosis and diverticulitis?
- What digestive symptoms should a CNA report immediately?
Sources
- CNA Module 13 — Anatomy, Physiology & Aging
- NIDDK — Your Digestive System & How It Works
- NIDDK — Digestive Diseases
- MedlinePlus — Digestive Diseases
Flashcards
What is the primary function of the digestive system?01-foundations / anatomy-physiology / digestive
Answer
Break down food, absorb nutrients and water, and eliminate undigested waste.
What is the alimentary canal?01-foundations / anatomy-physiology / digestive
Answer
Continuous digestive tract extending from the mouth to the anus.
What are the main accessory digestive organs?01-foundations / anatomy-physiology / digestive
Answer
Salivary glands, liver, gallbladder, and pancreas.
What is mastication?01-foundations / anatomy-physiology / digestive
Answer
Chewing food into smaller pieces.
What is peristalsis?01-foundations / anatomy-physiology / digestive
Answer
Coordinated, wave-like muscle contractions that move material through the digestive tract.
What is the function of the epiglottis during swallowing?01-foundations / anatomy-physiology / digestive
Answer
Helps protect the airway as food passes toward the esophagus.
What is chyme?01-foundations / anatomy-physiology / digestive
Answer
Partially digested food mixed with gastric secretions.
What are the three parts of the small intestine?01-foundations / anatomy-physiology / digestive
Answer
Duodenum, jejunum, and ileum.
Where does most nutrient absorption occur?01-foundations / anatomy-physiology / digestive
Answer
Small intestine.
What is the purpose of intestinal villi and microvilli?01-foundations / anatomy-physiology / digestive
Answer
Increase surface area for nutrient absorption.
What is the main function of the large intestine?01-foundations / anatomy-physiology / digestive
Answer
Absorb water and electrolytes and form feces.
What are the four main sections of the colon?01-foundations / anatomy-physiology / digestive
Answer
Ascending, transverse, descending, and sigmoid colon.
Which organ produces bile?01-foundations / anatomy-physiology / digestive
Answer
Liver.
What is the function of the gallbladder?01-foundations / anatomy-physiology / digestive
Answer
Store and concentrate bile, releasing it during digestion.
What is the digestive function of the pancreas?01-foundations / anatomy-physiology / digestive
Answer
Produce digestive enzymes and bicarbonate for the small intestine.
How can aging contribute to constipation risk?02-mechanisms / anatomy-physiology / digestive
Answer
Reduced mobility, medication effects, and inadequate fluid or fiber intake.
What is fecal impaction?01-foundations / anatomy-physiology / digestive
Answer
A mass of hardened stool lodged in the rectum or colon.
What is GERD?01-foundations / anatomy-physiology / digestive
Answer
Reflux of stomach contents into the esophagus causing symptoms or complications.
What is the difference between diverticulosis and diverticulitis?02-mechanisms / anatomy-physiology / digestive
Answer
Diverticulosis is the presence of pouches; diverticulitis is inflammation of them.
What should a CNA do if a resident vomits blood or passes black, tarry stool?03-application / anatomy-physiology / digestive
Answer
Summon immediate nursing help and follow emergency-response procedures.