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Related Concept Videos

Comparative Excretory Systems02:24

Comparative Excretory Systems

Animals have evolved different strategies for excretion, the removal of waste from the body. Most waste must be dissolved in water to be excreted, so an animal’s excretory strategy directly affects its water balance.
Physiology of the Gastrointestinal System I: Ingestion and Propulsion01:22

Physiology of the Gastrointestinal System I: Ingestion and Propulsion

The physiology of the gastrointestinal system begins with ingestion as food enters the mouth.
Physiology of the Gastrointestinal System II: Digestion and Absorption01:22

Physiology of the Gastrointestinal System II: Digestion and Absorption

The gastrointestinal (GI) tract, extending from the mouth to the anus, plays a pivotal role in the digestion and absorption of nutrients. This process involves both mechanical and chemical actions facilitated by various enzymes.
Digestion begins in the mouth, where food undergoes mechanical breakdown by chewing and combines with saliva. Salivary amylase, an enzyme in saliva, starts the breakdown of starches into maltose. The food then travels down the esophagus to the stomach.
In the stomach, a...
What is Monogastric Digestion?01:50

What is Monogastric Digestion?

The human body contains a monogastric digestive system. In a monogastric digestive system, the stomach only contains one chamber in which it digests food. Several other animal species also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter, however, focuses on the human digestive system.
Anatomy of the Gastrointestinal System01:26

Anatomy of the Gastrointestinal System

The human digestive system is an intricate and essential network for nutrient absorption and waste elimination. It encompasses the gastrointestinal (GI) tract and several accessory organs.
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Physiology of the Gastrointestinal System III: Elimination01:26

Physiology of the Gastrointestinal System III: Elimination

The gastrointestinal elimination process involves a complex interplay of neural and hormonal mechanisms that coordinate the final waste removal from the body. This intricate operation encompasses the absorption of water and electrolytes, vital for transforming the remaining indigestible food matter into feces. The large intestine is pivotal in water and electrolyte absorption, forming feces from unabsorbed minerals, undigested food, bacteria, bile pigments, and shed epithelial cells. Essential...

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Related Experiment Video

Updated: May 11, 2026

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease
06:04

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

Published on: February 9, 2016

Comparative digestive physiology.

William H Karasov1, Angela E Douglas

  • 1Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin, USA. wkarasov@wisc.edu

Comprehensive Physiology
|May 31, 2013
PubMed
Summary
This summary is machine-generated.

Gastrointestinal tract structure and function in animals adapt to diet, influencing digestive enzyme expression and gut microbiota. These adaptations, driven by genetics and environmental factors, optimize nutrient absorption and processing across species.

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Two-dimensional Porcine Intestinal Organoids Reflecting the Physiological Properties of Native Gut
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Two-dimensional Porcine Intestinal Organoids Reflecting the Physiological Properties of Native Gut

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Last Updated: May 11, 2026

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease
06:04

Ex Vivo Intestinal Sacs to Assess Mucosal Permeability in Models of Gastrointestinal Disease

Published on: February 9, 2016

Two-dimensional Porcine Intestinal Organoids Reflecting the Physiological Properties of Native Gut
09:13

Two-dimensional Porcine Intestinal Organoids Reflecting the Physiological Properties of Native Gut

Published on: January 31, 2025

Area of Science:

  • Comparative physiology
  • Animal biology
  • Nutritional science

Background:

  • Gastrointestinal (GI) tract morphology and function correlate with diet composition (carbohydrates, proteins, fats, refractory materials).
  • Digestive enzyme and nutrient transporter expression generally matches dietary substrate load, with limited excess capacity.
  • Species-specific variations in hydrolase activity are linked to gene copy number variations and single-nucleotide polymorphisms.

Purpose of the Study:

  • To explore the relationship between diet and the morphological and functional adaptations of gastrointestinal tracts in vertebrates and invertebrates.
  • To understand the mechanisms regulating digestive enzyme and nutrient transporter expression in response to dietary cues.
  • To investigate the role of gut microbiota and symbiotic fermentation in nutrient processing.

Main Methods:

  • Comparative analysis of gastrointestinal tract features across diverse animal species.
  • Examination of gene expression patterns for digestive enzymes and nutrient transporters.
  • 16S rRNA gene sequencing for gut microbiota analysis.
  • Investigation of phenotypic plasticity in digestive system size and digesta transit time.

Main Results:

  • GI tract features, including digestive enzyme expression and transporter function, are shaped by food chemistry.
  • Phenotypic changes in hydrolase and transporter expression are mediated by transcriptional and posttranscriptional regulation in response to diet.
  • Species exhibit flexible increases in digestive compartment size with higher food intake.
  • Gut microbiota taxon richness is significantly higher in vertebrates than invertebrates and is diet-influenced.
  • Nutrient transporters show orthology across phyla, with variations in ion coupling (e.g., K+ vs. Na+).
  • Natural toxins in food can impact digesta transit, enzymatic breakdown, microbial fermentation, and absorption.

Conclusions:

  • Animal GI tracts exhibit remarkable adaptations to dietary chemistry, involving genetic, molecular, and morphological adjustments.
  • Symbiotic microbial fermentation plays a crucial role in degrading recalcitrant materials, necessitating specialized GI structures.
  • Diet is a primary driver of gut microbiota composition and function, impacting overall nutrient assimilation.
  • Understanding these adaptations is key to comprehending animal physiology, evolution, and ecological interactions.