Avian Intestines - Anatomy & Physiology

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Structure

• The inestines occupy the caudal part of the body

• Contacts the reproductive organs and gizzard

• The small intestine is long and relatively uniform in shape and size

• There is no demarcation between the jejunum and the ileum

• The duodenum passes caudally over the gizzard then loops back towards the stomach where it joins the jejunum
  • Arises from the right dorsal aspect of the The Gizzard - Anamtomy & Physiology
  • Loop lies ventral on the abdominal floor
  • The pancreas lies within the loops
  • 3 pancreatic ducts and one bile duct enter the caudal duodenum at a common papila

• Jejunum
  • Loose coils around the mesentery
  • Thin walls so content appears green
  • Suspended from the dorsal wall of the abdomen by the mesentery

• Ileum
  • Begins opposite the apices of the caeca or at the vitelline diverticula
  • Suspended from the dorsal wall of the abdomen by the mesentery

• A short colon
  • The colon lies ventral to the synasacrum and opens into the cloaca
  • Runs ventral to the vertebrae
  • Terminates in the coprodeum

• 2 caeca from the ileocaecal junction run with the ileum caudally
  • Blind sacs about 16-18cm long
  • Extend towards the liver then fold back on themselves
  • Mesentery runs between the caeca then on towards the ileum
  • Often contain dark coloured material
  • 3 parts of each caeca
  • Bacterial breakdown of cellulose occurs

• Bile ducts and 3 pancreatic ducts

Vitelline Diverticula

• Small outgrowth on the [Jejunum - Anatomy & Physiology|jejunum]]

• Former connection will yolk sac

• Also called Meckel's diverticulum

Function

• See small intestine

Vasculature

• See small intestine

Innervation

• See small intestine

Lymphatics

• Patches of lymphoid nodules are present

• Most abundant in the duodenum

Histology

• Caeca
  • Serous coat has nerve plexuses
  • Columnar epithelium and goblet cells
  • Smooth muscle in folds at base
  • Caecal sphincter at proximal part containing a lot of lymphoid tissue (caecal tonsil)
  • Middle section has thin walls and appears green
  • The bulbous blind ends have thicker walls

• See small intestine

Species Differences

• Duck and goose have several loops of 'U' shaped jejunum

• Pigeons have a circular mass of jejunum with inner and outer turns

• Long caeca in turkey and chicken

• Pigeons and song birds have short caeca

• Parrots do not have caeca