chapter 26

Liver and Cirrhosis

  • Cirrhosis Overview: Chronic liver disease that can occur due to long-term injury, often resulting from chronic alcoholism.

    • Involves irreversible scarring of liver tissue.

    • Symptoms may include fatigue, easy bruising, swollen legs, and jaundice.

Gallbladder Anatomy and Function

  • Location and Structure: The gallbladder is located on the underside of the liver.

  • Function: Its primary role is to store bile, which is produced by the liver.

    • Gallbladder connects to the common bile duct, which facilitates bile flow.

Digestive Anatomy: Pancreas and Duodenum

  • Pancreas: Located near the duodenum and plays a crucial role in digestion by releasing digestive juices.

  • Ducts:

    • Major Pancreatic Duct: Main duct running through the pancreas; transports digestive enzymes.

    • Accessory Pancreatic Duct: Releases digestive juices earlier than the major duct at the minor duodenal papilla.

  • Duodenum: First part of the small intestine where the common bile duct and pancreatic juices enter to aid digestion.

Digestion Process

  • Pancreatic Secretions:

    • Composed of alkaline fluid, water, and various digestive enzymes (e.g., proteases).

    • Enzymes are released in inactive forms to prevent self-digestion in the pancreas.

Large Intestine Functions

  • Segments: Includes ascending, transverse, descending, and sigmoid colon.

  • Functions: Limited absorption of nutrients, primarily absorbs water and electrolytes, and stores feces.

  • Rectal Structure: Contains folds called rectal valves that aid in storing feces before defecation.

Peristalsis and Fecal Movement

  • Mass Movements: Strong contractions in the large intestine that propel fecal material towards the rectum, typically occurring post-meal.

  • Defecation Reflex: Triggered by fecal filling; involves coordination between internal and external sphincters and Valsalva maneuver.

Common GI Disorders

  • Fecal Transplant: A treatment for conditions like C. difficile; involves transferring fecal matter from a healthy donor to restore gut microbiota.

  • Diverticulosis vs. Diverticulitis:

    • Diverticulosis: Formation of small bulges in the intestinal lining due to low fiber intake.

    • Diverticulitis: Inflammation or infection of these bulges, which can lead to ruptures.

Carbohydrate Digestion

  • Types of Carbohydrates: Includes monosaccharides, disaccharides, and polysaccharides.

    • Monosaccharides: Simplest form (e.g., glucose).

    • Disaccharides: Composed of two simple sugars (e.g., sucrose, lactose).

    • Polysaccharides: Comprised of multiple monosaccharides (e.g., starch, cellulose).

  • Breakdown Process:

    • Salivary Amylase: Enzyme in saliva begins carbohydrate breakdown in the mouth.

    • Pancreatic Amylase: Continues carbohydrate digestion in the duodenum.

    • Brush Border Enzymes: Further break down carbohydrates at the intestinal lining to enable absorption.

Protein Digestion

  • Structure: Proteins made of amino acids linked by peptide bonds.

  • Digestion Process:

    • Begins in the stomach with pepsinogen, which activates to pepsin in the acidic environment.

    • Inactive enzymes from the pancreas (trypsinogen, chymotrypsinogen) are activated in the duodenum to further digest proteins.

Lipid Digestion

  • Types of Lipids: Includes triglycerides and cholesterol.

  • Digestion Process:

    • Lipases from saliva and gastric juices begin lipid breakdown.

    • In the small intestine, pancreatic lipase and bile salts emulsify fats for absorption.

Nucleic Acid Digestion

  • Protein Breakdown: Nucleases from the pancreas break down nucleic acids (DNA and RNA) into nucleotides for reuse in the body.

Micronutrient Absorption

  • Electrolytes: Absorbed primarily in the small intestine in an unregulated manner, with iron absorption being regulated according to body needs.

  • Vitamins: Vitamins are absorbed in the intestines, but mechanisms may vary based on the vitamin type.