Avian Digestion and Crop Physiology

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Questions and Answers

Which of the following is a primary function of the crop in avian digestion?

  • Nutrient absorption, particularly of fats and carbohydrates.
  • Secretion of digestive enzymes like pepsin and $HCl$.
  • Mechanical breakdown of food particles using muscular contractions.
  • Ingesta storage and early microbial digestion. (correct)

What controls the movement of food from the crop to the proventriculus in birds?

  • The amount of salivary amylase present in the crop.
  • The bird's circadian rhythm.
  • The fullness of the proventriculus and intestines (feedback long reflex). (correct)
  • The pH level of the ventriculus.

Which anatomical feature is typically absent in owls and insectivorous birds concerning the esophagus?

  • Glandular stomach.
  • Cloaca.
  • Ventriculus.
  • Crop. (correct)

What is the primary function of the ventriculus (gizzard) in avian digestion?

<p>Mechanical digestion through grinding, often with the aid of grit. (D)</p> Signup and view all the answers

What is a unique characteristic of the avian ileum?

<p>There is no distinct physical difference in muscle thickness from the jejunum. (A)</p> Signup and view all the answers

What is the cloaca's primary role in birds?

<p>Acting as a shared chamber for the urinary and digestive systems. (D)</p> Signup and view all the answers

Which bird species lacks a gallbladder?

<p>Pigeon. (D)</p> Signup and view all the answers

What substance is 'crop milk' primarily composed of, for birds that produce it?

<p>High fat content from apocrine secretion. (B)</p> Signup and view all the answers

Which of the following best describes the function of reverse peristalsis in the colon of birds?

<p>Moving urine and digesta from the colon and cloaca into the ceca for salt and water absorption and fermentation. (C)</p> Signup and view all the answers

What is the primary function of the gizzard's thick muscle contractions in avian digestion?

<p>Grinding food and moving it back into the proventriculus for further gastric digestion. (C)</p> Signup and view all the answers

How does reverse peristalsis in the duodenum contribute to the digestive process in birds?

<p>It refluxes duodenal content back into the gizzard for further gastric digestion. (C)</p> Signup and view all the answers

In predatory birds like owls and hawks, what physiological process is associated with the egestion of gastric pellets?

<p>The regular egestion of indigestible materials such as bone and hair. (A)</p> Signup and view all the answers

What occurs immediately before defecation in birds, with regards to colonic motility?

<p>The cessation of reverse peristalsis and contraction of the entire colon. (A)</p> Signup and view all the answers

Flashcards

Crop

An enlargement in the esophagus for storage of ingesta in birds.

Proventriculus

The glandular stomach in birds, located before the muscular stomach.

Ventriculus

Also known as the gizzard, it's the muscular stomach for grinding food.

Ceca

Paired pouches in most birds that aid in digestion and fermentation.

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Gallbladder in Birds

An organ that stores bile, present in most birds except pigeons.

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Digestion in Crop

In birds, initial digestion starts in the crop using microbial action.

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Gastroduodenal cycle

The process that controls the movement of food from the stomach to the intestine.

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Long Reflex in Digestion

A feedback mechanism that regulates movement from crop to proventriculus based on fullness.

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Gizzard Function

Gizzard muscles grind food and aid gastric digestion.

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Peristaltic Waves

Waves that move digesta from proventriculus to gizzard.

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Reverse Peristalsis

Reflux of digesta back to the gizzard for further digestion.

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Colonic Motility

Movement of digesta and urine toward the ceca for absorption.

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Cecum Functions

Absorbs salt and water, aids in fermentation.

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Study Notes

Avian Digestion

  • Birds lack teeth, but have a ventriculus (with grit)
  • Some birds have a crop (esophagus enlargement, absent in some)
  • A glandular stomach (proventriculus) is located near the muscular stomach (gizzard)
  • Duodenal loop and jejunum/ileum regions aren't distinctly different in muscles
  • Most birds have paired ceca
  • A short colon empties into the cloaca (urine and feces)
  • Most birds have gallbladders (exceptions include pigeons)

Crop Physiology

  • Crop is used for food storage (similar to a proximal stomach)
  • Food moves from the crop to the proventriculus
  • Movement is controlled by fullness signals in the proventriculus and intestines
  • Regurgitation is possible (like "crop milk") to feed young
  • High-fat content in regurgitated "milk" from some species

Gastroduodenal Cycle

  • Thin gizzard muscles contract in 2-3 peristaltic waves
  • Thick gizzard muscles contract, grind, and reflux food for further digestion
  • Some birds (hawks, owls) regularly regurgitate indigestible materials (like bone and hair) as pellets
  • Gastric pellets are formed and expelled, and regular peristaltic waves occur (back and forth) to digest food within the proventriculus
  • Reverse peristalsis occurs every 15 minutes
  • Duodenal content cycles back to the gizzard for further gastric digestion

Colonic Motility

  • Constant reverse peristalsis pushes contents towards the ceca and the cloaca.
  • Water and salt are absorbed alongside fermentation in the ceca
  • Reverse peristalsis stops in preparation for defecation and the whole colon contracts during defecation.

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Avian Digestion PDF

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