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Understanding the Avian Digestive System
Aug 27, 2024
Notes on Avian Gastrointestinal Tract
Overview of Avian Digestive System
Unique compared to mammals
Shorter intestinal tract
Structure and Function of Mouth
Beak:
Lightweight, used to swallow food whole
Tongue:
Collects, moves, swallows food
Covered with lateral barbs
Moves food to the back of the mouth
Salivary Glands:
Less developed but help lubricate food
Taste Buds:
Up to 300, located in the upper beak and anterior tongue
Laryngeal Mound:
Assists in moving food into the esophagus
Esophagus
Function:
Transports food from mouth to stomach
Thin-walled, expansive tube
Structure:
Four layers: mucosal, submucosal, muscular tunic, serosa
Sections:
Cervical (near beak)
Thoracic (near crop)
Glands:
More numerous in the thoracic esophagus
Movement:
Via myenteric plexus nerves, not muscle contractions
Crop
Structure:
Thin-walled pouch at base of thoracic esophagus
Function:
Holds food until released to the stomach
Storage Time:
Up to 12 hours
Note:
No digestion occurs here; softening of feed may happen
Condition:
Sour crop (fermentation and bacterial infection)
Proventriculus (True Stomach)
Function:
Actual digestion begins here
Structure:
Thick walls with five layers
Glandular tissue produces digestive secretions (HCl, pepsin, gastrin)
Processes:
Softens food, prepares it for the gizzard
Gizzard (Ventriculus)
Function:
Grinding of food
Structure:
Round organ with two lobes
Surface:
Lined with keratinized material (coilin) that withstands digestion
Muscle Action:
Requires grit and small rocks for effective grinding
Small Intestine
Length:
More than 4.5 feet
Sections:
Duodenum:
Pancreas lies here; digestive enzymes released
Jejunum and Ileum:
Majority of nutrient absorption occurs
Hormones:
Released to aid digestion (trypsin, chymotrypsin, amylase, lipase)
Nutrient Absorption:
Villi increase surface area for glucose, calcium, vitamin B12
Large Intestine
Length:
4 inches
Function:
Water reabsorption, storage of undigested waste
Structure:
Ends at cloaca; referred to as colon
Sica:
Blind pouches for water reabsorption and fermentation
Nutrient Production:
Bacteria produce fatty acids and B vitamins but minimal absorption occurs
Cloaca
Junction of digestive and urinary tracts
In hens, reproductive tract enters here
Waste mixed and excreted through the vent
Functionality:
Flexible to pass eggs from reproductive system
Conclusion
The avian digestive system is optimized for efficient processing of food, from swallowing to absorption and waste excretion.
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