4.1 Digestion

The digestive system is a complex network of organs working together to break down food and absorb nutrients. From ingestion to elimination, this process involves mechanical and chemical digestion, propulsion, and absorption. Understanding these stages is crucial for nurses to provide effective care.

Congenital anomalies can significantly impact the digestive system's function. These birth defects, ranging from cleft palate to Hirschsprung's disease, can cause feeding difficulties and malnutrition. Nurses must be aware of these conditions to provide appropriate care and support for affected patients.

Digestive System Overview

Stages of digestive process

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• Ingestion
  • Consuming food through the mouth (chewing, swallowing)
• Propulsion
  • Peristalsis involuntary muscle contractions move food through the digestive tract from esophagus to anus
• Mechanical digestion
  • Chewing (mastication) in the mouth breaks down food into smaller pieces increasing surface area for enzymes
  • Churning in the stomach further breaks down food into a semi-liquid mixture called chyme
• Chemical digestion
  • Enzymes break down macronutrients into absorbable forms
    • Carbohydrates broken down into monosaccharides (glucose, fructose, galactose)
    • Proteins broken down into amino acids (building blocks of proteins)
    • Fats broken down into fatty acids and monoglycerides (components of triglycerides)
• Absorption
  • Nutrients absorbed through the intestinal walls into the bloodstream via passive diffusion, facilitated diffusion, and active transport
• Elimination
  • Undigested materials (fiber, dead cells) removed from the body as feces through the anus via defecation

Major organs of digestion

• Mouth
  • Chewing (mechanical digestion) breaks food into smaller pieces
  • Salivary glands secrete saliva containing salivary amylase to initiate carbohydrate digestion (breaks starch into maltose)
• Esophagus
  • Muscular tube connects the mouth to the stomach
  • Lower esophageal sphincter prevents reflux of stomach contents back into esophagus (heartburn)
• Stomach
  • Muscular sac stores and churns food mixing it with digestive secretions
  • Secretes hydrochloric acid (HCl) and pepsinogen to initiate protein digestion (activates pepsin)
• Small intestine
  • Duodenum first segment receives chyme from the stomach and secretions from the pancreas and gallbladder
  • Jejunum and ileum segments major sites of nutrient absorption into bloodstream
  • Villi increase surface area for efficient nutrient absorption
• Pancreas
  • Secretes digestive enzymes (lipase, amylase, trypsin) into the duodenum to break down nutrients
  • Produces bicarbonate to neutralize stomach acid in duodenum
• Liver
  • Produces bile, which emulsifies fats (breaks into smaller droplets) and facilitates their digestion and absorption
• Gallbladder
  • Stores and concentrates bile produced by the liver
  • Releases bile into the duodenum when stimulated by fatty meals
• Large intestine (colon)
  • Absorbs water and electrolytes (sodium, potassium) from remaining digestive contents
  • Houses gut bacteria that ferment undigested materials (fiber) and produce vitamins (K, B12)
• Rectum
  • Stores feces prior to elimination during defecation
• Anus
  • Opening at the end of the digestive tract for feces elimination controlled by internal and external sphincters

Digestive System Function

• Motility: Coordinated muscle contractions that move food through the digestive tract
• Enzymes: Biological catalysts that break down complex nutrients into simpler forms for absorption
• Microbiome: Community of microorganisms in the digestive tract that aid in digestion and overall health

Congenital Anomalies

Congenital anomalies in digestion

• Cleft lip and palate
  • Openings in the upper lip and/or roof of the mouth fail to close during fetal development
  • Can cause difficulty with feeding and swallowing leading to aspiration (food entering lungs)
  • May lead to malnutrition if not properly managed with specialized feeding techniques (special bottles, palatal obturators)
• Esophageal atresia
  • Esophagus does not properly connect to the stomach during fetal development
  • Requires surgical correction to establish continuity and allow feeding
  • Feeding difficulties may persist post-surgery due to impaired esophageal motility
• Tracheoesophageal fistula
  • Abnormal connection between the trachea (windpipe) and esophagus
  • Can cause aspiration of food into the lungs leading to pneumonia
  • Requires surgical correction to separate the trachea and esophagus
• Pyloric stenosis
  • Narrowing of the pyloric sphincter between the stomach and duodenum due to thickening of the muscle
  • Causes forceful vomiting (projectile) and can lead to dehydration and malnutrition
  • Treated with surgical correction (pyloromyotomy) to relieve obstruction
• Hirschsprung's disease
  • Absence of nerve cells (ganglia) in the colon, causing difficulty with bowel movements (constipation, obstruction)
  • Can lead to bowel obstruction, perforation, and malnutrition if untreated
  • Treated with surgical removal of the affected portion of the colon (pull-through procedure)
• Anorectal malformations
  • Abnormalities of the anus and rectum (imperforate anus, cloaca) causing difficulty with bowel movements
  • Can cause obstruction, infection, and lead to malnutrition if not properly managed
  • Requires surgical correction and may necessitate specialized feeding techniques (ostomy, antegrade continence enema)