L6: Avian Digestive Phyisology

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Last updated 8:45 PM on 10/13/26
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18 Terms

1
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Avian carnivores

  • Eat animal material

  • Birds of prey’ or ‘raptors’

  • Eat live prey or carrion

  • May be considered obligate scavengers (rare among vertebrates)


<ul><li><p>Eat animal material</p></li><li><p>Birds of prey’ or ‘raptors’</p></li><li><p>Eat live prey or carrion</p></li><li><p>May be considered obligate scavengers (rare among vertebrates) </p></li></ul><p></p>
2
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Avian herbivores

  • Eat plant material

  • Very rare for birds: Most are ‘opportunistic omnivores’ and supplement herbivorous diet with insects

  • Except... the hoatzin (aka stinkbird); Primarily folivore (leaves), some fruits, and flowers


<ul><li><p>Eat plant material</p></li><li><p>Very rare for birds: Most are ‘opportunistic omnivores’ and supplement herbivorous diet with insects</p></li><li><p>Except... the hoatzin (aka stinkbird); Primarily folivore (leaves), some fruits, and flowers </p></li></ul><p></p>
3
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Avian digestive anatomy components

  1. Headgut

  2. Foregut

  3. Midgut

  4. Hindgut


<ol><li><p>Headgut</p></li><li><p>Foregut</p></li><li><p>Midgut</p></li><li><p>Hindgut</p></li></ol><p></p>
4
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Avian digestive physiology: Headgut

a) Oral cavity:

Beak/bill

  • prehension of food (grasp, tear, crush food items)

  • Specialized based on diet consumed; e.g. flamingos have a sieve-like bill (filter feeding)

Salivary glands

  • most birds only have mucus secreting glands

  • some species secrete an adhesive compound

  • e.g. woodpeckers (capture prey)

  • e.g. swifts (nest building)


b) Pharynx (throat)

<p>a) Oral cavity:</p><p><strong>Beak/bill</strong></p><ul><li><p>prehension of food (grasp, tear, crush food items)</p></li><li><p>Specialized based on diet consumed; e.g. flamingos have a sieve-like bill (filter feeding)</p></li></ul><p><strong>Salivary glands</strong></p><ul><li><p>most birds only have mucus secreting glands</p></li><li><p>some species secrete an adhesive compound</p></li><li><p>e.g. woodpeckers (capture prey)</p></li><li><p>e.g. swifts (nest building)</p></li></ul><p></p><p>b) Pharynx (throat)</p>
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Avian digestive physiology: Foregut composition

a) Esophagus

b) Crop

c) Proventriculus

d) Ventriculus

6
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Avian digestive physiology: Esophagus purpose

  • Transfer food from pharynx to crop

  • allows for controlled regurgitation (some species)

  • e.g. regurgitate crop contents to feed young

  • e.g. regurgitate undigestible food


<ul><li><p>Transfer food from pharynx to crop</p></li><li><p>allows for controlled regurgitation (some species)</p></li><li><p>e.g. regurgitate crop contents to feed young</p></li><li><p>e.g. regurgitate undigestible food</p></li></ul><p></p>
7
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Avian digestive physiology: Crop purpose

  • major site of food storage for most bird species

  • site of microbial fermentation for the hoatzin


<ul><li><p>major site of food storage for most bird species</p></li><li><p>site of microbial fermentation for the hoatzin</p></li></ul><p></p>
8
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Avian digestive physiology: Proventriculus purpose

  • ‘true stomach’

  • secretes pepsinogen + HCL - pepsin

  • secretes mucus


<ul><li><p>‘true stomach’</p></li><li><p>secretes pepsinogen + HCL - pepsin</p></li><li><p>secretes mucus</p></li></ul><p></p>
9
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Avian digestive physiology: Ventriculus (aka gizzard) purpose

  • major site for trituration of food (turns it into small particles)

  • thick muscular walls with koilin membrane

  • gizzard stones (‘grit’); small ingested rocks used to help break down food

  • filter indigestible parts of food (mainly carnivores)

  • forms pellets to be egested


<ul><li><p>major site for trituration of food (turns it into small particles)</p></li><li><p>thick muscular walls with<strong> koilin membrane</strong></p></li><li><p>gizzard stones (‘grit’); small ingested rocks used to help break down food</p></li><li><p>filter indigestible parts of food (mainly carnivores)</p></li><li><p>forms pellets to be egested</p></li></ul><p></p>
10
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Avian digestive physiology: Midgut components

Small intestine

  1. duodenum

  2. jejunum

  3. ileum


<p>Small intestine</p><ol><li><p>duodenum</p></li><li><p>jejunum</p></li><li><p>ileum</p></li></ol><p></p>
11
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Avian digestive physiology: Duodenum purpose

  • Primary site of enzymatic digestion

  • Pancreatic/hepatic secretions

  • Alkaline/mucus secretions (pH balance)


<ul><li><p>Primary site of enzymatic digestion</p></li><li><p>Pancreatic/hepatic secretions</p></li><li><p>Alkaline/mucus secretions (pH balance)</p></li></ul><p></p>
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Avian digestive physiology: Jejunum purpose

  • Primary site of nutrient absorption

  • Villi and microvilli present (increase absorption)


<ul><li><p>Primary site of nutrient absorption</p></li><li><p>Villi and microvilli present (increase absorption)</p></li></ul><p></p>
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Avian digestive physiology: Ileum purpose

  • Vit B 12 and bile acid absorption


<ul><li><p>Vit B 12 and bile acid absorption</p></li></ul><p></p>
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Avian digestive physiology: Hindgut composition

  1. Cecum

  2. (Colon)

  3. Rectum

  4. Cloaca


<ol><li><p> Cecum</p></li><li><p> (Colon)</p></li><li><p> Rectum</p></li><li><p>Cloaca</p></li></ol><p></p>
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Avian digestive physiology: Cecum purpose and who has it

Site of microbial fermentation (VFA, Vit B, Vit K)

  • Paired (most birds) ‘ceca’


Exceptions:

  • Single (heron)

  • Functionless (most carnivores)

  • Absent (swifts, hummingbirds, woodpeckers, budgies; primarily because of their highly specialized, low-fiber diets and structural evolutionary adaptations for efficient flight


<p>Site of microbial fermentation (VFA, Vit B, Vit K)</p><ul><li><p>Paired (most birds) ‘ceca’</p></li></ul><p></p><p>Exceptions:</p><ul><li><p>Single (heron)</p></li><li><p>Functionless (most carnivores)</p></li><li><p>Absent (swifts, hummingbirds, woodpeckers, budgies; primarily because of their highly specialized, low-fiber diets and structural evolutionary adaptations for efficient flight</p></li></ul><p></p>
16
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Avian digestive physiology: Who has a colon

  • only the horned screamer and ostrich have a colon


<ul><li><p>only the horned screamer and ostrich have a colon</p></li></ul><p></p>
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Avian digestive physiology: Rectum purpose

  • short, straight remainder of the hindgut

  • water and mineral absorption → similar function to colon in mammals


<ul><li><p>short, straight remainder of the hindgut</p></li><li><p>water and mineral absorption → similar function to colon in mammals</p></li></ul><p></p>
18
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Avian digestive physiology: Cloaca purpose

  • combined outlet for fecal/urinary excretion


<ul><li><p>combined outlet for fecal/urinary excretion</p></li></ul><p></p>