Liver-Bile Digestion, Diarrhea

Liver-Bile Digestion, Diarrhea

# Gastric Mucosal Barrier

The gastric mucosal barrier consists of protective layers:

• Surface epithelium: layer of mucus and bicarbonate.

• Epithelium: constantly regenerating due to prostaglandins and other factors.

• Sub-epithelium: blood vessels supplying oxygen.

# Factors that Damage Epithelial Cells

The main factors causing damage to gastric epithelial cells:

• Helicobacter Pylori: gram-negative bacteria, penetrates the mucus layer, produces toxins that damage the mucosa.

• Nonsteroidal anti-inflammatory drugs (NSAIDs): weakly acidic, easily penetrates the mucus layer, damages tissue and inhibits prostaglandin production.

• Other factors: alcohol, smoking, stress…

# Gastritis & Peptic Ulcer

• Gastritis: inflammation of the inner lining of the stomach.

• Peptic ulcer: a deep ulceration into the gastric mucosa.

# Harmful Effects of Helicobacter Pylori

Helicobacter Pylori damages the gastric mucosa by:

• Penetrating the mucus layer: directly reaching epithelial cells.

• Producing toxins:

• Urease: produces ammonia (NH3) which damages the mucosa and protects bacteria from stomach acid.

• Protease and phospholipase: break down glycoproteins in mucus, allowing bacteria to penetrate.

• Cytotoxin (Vac A, Cag A): causes inflammation, attracts white blood cells and releases chemicals that damage the mucosa, leading to ulcers.

# Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

NSAIDs damage the gastric mucosa by:

• Penetrating the mucus layer: due to their weak acidity.

• Damaging tissue: ionization at the high pH of the mucosa.

• Inhibiting prostaglandin production: prostaglandins play a protective role in the mucosa.

# Diarrhea

Diarrhea is a condition characterized by frequent bowel movements, loose stools, and increased stool volume. It can be caused by:

• Increased stool volume: due to increased undigested food.

• Increased water content: due to increased intestinal fluid secretion.

• Increased bowel frequency: due to increased intestinal motility.

# Classification of Diarrhea

• Acute diarrhea: lasts less than 2 weeks.

• Persistent diarrhea: lasts from 2 to 4 weeks.

• Chronic diarrhea: lasts over 4 weeks.

# Pseudo-diarrhea

Pseudo-diarrhea is a condition characterized by frequent bowel movements, small volume per bowel movement, accompanied by the urge to defecate. It can be caused by:

• Anal sphincter spasm: due to constipation, hemorrhoids…

• Nervous system damage: due to neurological diseases…

# Mechanisms of Diarrhea

There are four main mechanisms of diarrhea:

• Osmotic diarrhea: due to increased osmolality in the intestinal lumen, water moves from the blood into the intestinal lumen.

• Secretory diarrhea: due to increased intestinal fluid secretion, water moves from the blood into the intestinal lumen.

• Inflammatory diarrhea: due to inflammation of the intestinal mucosa, damage to epithelial cells, increased secretion, decreased absorption.

• Increased intestinal motility diarrhea: due to increased intestinal motility, the residence time of intestinal fluid in the intestine is short, reducing water absorption.

# Intestinal Mucosa

The intestinal mucosa is a semi-permeable membrane capable of absorbing and secreting fluids.

# Does the intestine usually absorb or secrete fluid?

The intestine usually absorbs water and nutrients. However, in some cases, the intestine can secrete fluid.

# Cases that stimulate intestinal fluid secretion

The intestine may secrete fluids when:

• Due to bacterial toxins: bacteria release toxins that stimulate intestinal mucosa to secrete fluid.

• Due to other factors: factors that irritate the intestine such as stress, allergies…

# Osmolality in the intestinal lumen

• Osmotic diarrhea: osmolality in the intestinal lumen is higher than osmolality in plasma.

• Secretory diarrhea: osmolality in the intestinal lumen is equal to osmolality in plasma.

# Water loss in diarrhea

• Osmotic diarrhea: hypertonic water loss (loss of more electrolytes).

• Secretory diarrhea: isotonic water loss (loss of less electrolytes).

# Consequences of diarrhea

• Osmotic diarrhea: hypertonic water loss, electrolyte imbalance.

• Secretory diarrhea: isotonic water loss.

# Mechanisms of secretory diarrhea

• Bacterial toxins:

• Cholera toxin: increases intracellular cyclic AMP.

• E. Coli: increases intracellular cyclic GMP.

• Chemical mediators:

• Serotonin, acetylcholine: increase fluid secretion, water enters the intestinal lumen.

# Agents causing inflammatory diarrhea

• Bacteria: Salmonella, Shigella…

• Parasites: Giardia, Cryptosporidium…

# Mechanisms of inflammatory diarrhea

• Bacteria, parasites invade the mucosa: destroy epithelial cells.

• Decreased absorption: due to damage to epithelial cells.

• Increased inflammatory fluid secretion: increases intestinal fluid permeability.

• Increased intestinal motility: due to inflammatory mediators such as PGE, histamine.

# Increased intestinal motility diarrhea

• Mechanism: increased intestinal motility, decreased residence time of intestinal fluid, decreased water absorption.

• Causes: due to gastrointestinal diseases, stress…

# Note

The information above is for reference only and should not replace the advice of a doctor. If you experience any digestive problems, consult a doctor for diagnosis and treatment.