AV

digestion 2025-03-29T15:05:13.291Z

Valsalva Maneuver and Gastrointestinal Considerations

  • Valsalva Maneuver: Not applicable due to constantly open state.<br>- Important for patients to pay attention to constipation as they cannot use the Valsalva maneuver effectively, increasing the risk of difficulty in passing dry feces.

Physiology of Digestion and Absorption

  • Basic Principle: Nutrients like carbohydrates, proteins, and nucleic acids must be broken down into their fundamental components to be absorbed (monosaccharides, amino acids, nucleotides).

  • Absorption Process:

    • Active Transport: Requires energy at the apical surface of enterocytes (cells lining small intestine).

    • Facilitated Diffusion: Nutrients exit through the basal surface into capillaries.

  • Carbohydrates:

    • Only three monosaccharides are absorbable: glucose, fructose, and galactose.

    • Breakdown begins in the mouth (salivary amylase), continues with pancreatic amylase in the duodenum, and final enzymes at the brush border.

    • Lactose intolerance example: Lacking lactase results in undigested lactose drawing water into the intestine, causing discomfort.

Protein Digestion

  • Initial Breakdown: Begins in the stomach (hydrochloric acid denatures proteins), followed by enzymes like pepsin (activated from pepsinogen).

  • Further Breakdown: Small intestine’s alkaline environment inactivates pepsin; further digestion depends on pancreatic enzymes.

  • Transport: Amino acids are transported via active transport across the apical membrane and exit through facilitated diffusion at the basal side.

Lipid Digestion and Absorption

  • Complex Nature: Lipids (fats) are nonpolar; thus, they cannot use the same absorption methods as carbohydrates and proteins.

  • Emulsification: Bile salts act as detergents to mix fat with water, enabling pancreatic lipases to access and break down fats.

  • Digestion Process:

    • Triglycerides broken down into monoglycerides and free fatty acids.

    • Lipids form micelles (with bile salts) for absorption through the brush border of the enterocyte.

    • Inside cells, lipids are reassembled into triglycerides, forming chylomicrons, which enter lymphatic vessels (lacteals) instead of blood capillaries.

  • Circulatory Entry: Chylomicrons eventually enter the bloodstream after passing through lymphatic vessels and nodes.

  • Final Breakdown: Chylomicrons must be re-broken down into free fatty acids and glycerol for cellular use.

Nucleic Acid Digestion

  • Process: Breakdown of RNA and DNA into nucleotides, pentose sugars, and phosphate groups.

  • Enzymes cleave nucleic acids, allowing individual components to be absorbed into the bloodstream.