Vertebrate Digestive System and Accessory Organs

Vocabulary flashcards covering the vertebrate digestive tract, its accessory organs, comparative anatomy, and factors influencing digestion efficiency and gut size.

Small Intestine

The organ starting posterior to the pylorus of the stomach where most chemical digestion occurs and which serves as the major site of nutrient absorption.

Villi

Digitations that, alongside spiraling and coiling, enlarge the internal surface area of the small intestine to increase absorption.

Large Intestine

The portion of the digestive tract starting posterior to the small intestine that compacts unabsorbed waste into feces and serves as the major site of water re-absorption.

Anus

The terminal opening of the digestive tract found in mammals and many fish that discharges feces.

Cloaca

The terminal opening found in sharks, amphibians, reptiles, and birds that discharges both urine and feces.

Cecum

A pouch in the wall of the digestive tract, located between the small and large intestine in birds and mammals, that typically contains bacteria aiding in digestion and is most developed in herbivores.

Pyloric Caeca

Multiple digestive pouches found in teleost fishes.

Human Appendix

A vestigial cecum structure in humans whose function is debated, with proposed roles including immune function, a reservoir of commensal bacteria, or no function.

Liver

The largest gland in the vertebrate body, located over the stomach, responsible for bile production, detoxification, blood circulation and filtration, blood glucose regulation, and the synthesis and storage of amino acids, proteins, vitamins, and fats.

Gallbladder

A blind sac that stores alkaline bile required for the breakdown of fats and neutralization of acid from the stomach.

Bile

An alkaline substance produced by the liver that neutralizes stomach acid and is necessary for fat breakdown, without which fat passes through unabsorbed.

Pancreas

An accessory organ that produces bicarbonate-rich juice to neutralize stomach acid along with enzymes that break down fats into glycerol and fatty acids, and carbohydrates into simple sugars.

Digestion Efficiency of Carnivorous Fish

The digestion efficiency range in carnivorous fish, which is $70-90\%$.

Digestion Efficiency of Herbivorous Fish

The digestion efficiency range in herbivorous fish, which is $40-50\%$.

Factors Influencing Digestive Tract Size

Body size, primary feeding mode (herbivore vs. carnivore), and the amount of indigestible material in the diet.