Exam 4 (Lecture 50) - Avian Digestion

Question 1

Describe the function of the avian oral cavity.

Answer 1

Prehension of food

Secretes saliva which wets feed to make it easier to swallow

Tongue aids in pushing food to the back of the oral cavity for swallowing

Question 2

Describe the function of the avian esophagus.

Answer 2

Large diameter

Swallowing = accomplished by esophageal peristalsis

Question 3

Describe the function of the avian crop.

Answer 3

Esophageal pouches (one or two in most species)

Food is diverted to the crop then later propelled into the stomach by waves of peristalsis in the crop

Question 4

Describe the function of the avian proventriculus (stomach).

Answer 4

Received food from the esophagus

Secretes:
- mucus
- HCl
- pepsinogen

Question 5

Describe the function of the avian ventriculus (gizzard).

Answer 5

Very muscular and contains small stones (in many birds) that facilitate grinding of foodstuffs

2 orifices:
- one receives ingesta from the proventriculus
- other empties into the duodenum

Question 6

Describe the function of the avian small intestine.

Answer 6

Absorption

Digestive enzymes in the duodenum = bile from the liver and enzymes from the pancreas

Question 7

Describe the function of the avian pancreas.

Answer 7

Resembles that of the mammal

Exocrine portion is tubuloacinar

Islets of Langerhans are abundant
- Columnar alpha cells characterize the alpha islet (glucagon)
- Polygonal beta cells are the principal cells of the beta islets (insulin)

Question 8

Describe the function of the avian liver.

Answer 8

Blood filter and secretion of bile, like in the mammal

Question 9

Describe the function of the avian ceca.

Answer 9

Paired ceca in birds (blind; elongated ceca)

Villi for absorption; become flattened toward the blind end

Important sites for fermentation and VFA generation in some species

Question 10

Describe the function of the avian large intestine.

Answer 10

Absorption of water and electrolytes

Question 11

Describe the function of the avian cloaca.

Answer 11

Common opening of the digestive, reproductive, and urinary tracts

Antiperistalsis assists in filling the ceca and flushing urine from the cloaca into the large intestine for water absorption.