CoMo Science

What is this? 033

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What kind of bird is this?

A pigeon

What organ systems are represented in this diagram?
  • nervous system
  • respiratory system
  • digestive system
  • cardiovascular system
  • skeletal system
  • urinary system
What does the buccal cavity correspond to in humans?

The mouth or oral cavity

Bucca means “cheek”. The word itself is rarely used in human anatomy, but its adjective “buccal” is common as in:

  • buccal mucosa – the inside lining of the cheek
  • buccal artery – the artery supplying the cheek
  • buccal nerve – the nerve supplying the cheek
What labeled organs are not found in humans?
  • beak
  • crop
  • gizzard
  • cloaca
What part of the small intestine is not labeled?

jejunum

The small intestine has three segments: duodenum, jejunum, and ileum.

What labeled organs are part of the digestive system but not part of the alimentary canal?
  • liver
  • bile duct
  • pancreas
What labeled organs are part of a pair with the other not shown?
  • kidney
  • ureter
  • lung
How is the digestive system and the urinary system connected in birds?

They both empty into the cloaca and exit through one whole, instead of having separate exits in humans. This is the reason that bird droppings are not solid.

What seems strange about the bile duct?

A single bile duct leaves the liver and then branches to connect to the intestines in two places. In humans, the bile duct enters the duodenum in one location.

I initially thought this was an error in the drawing. Anatomy has a long history of having drawings made by people copying other drawings without ever looking at the actual anatomy, and I certainly don’t trust this image off the internet.

Further investigation led me to a research article which detailed the anatomy of the biliary system in pigeons. It turns out that the pigeon does have two bile ducts entering the intestine in two locations, although they also exit the liver in two locations, so the drawing is still incorrect in showing the bile duct branching after exiting the liver.

Comparative anatomy of the hepatobiliary systems in quail and pigeon, with a perspective for the gallbladder-loss – PMC

What organs of the alimentary canal seem out of order?

The cecum and rectum

In humans, the cecum is the initial part of the large intestine and the rectum is the final part. This diagram has the label for the rectum before the cecum, with the cecum branching off the rectum.

In fact, the cecum in birds is duplicated, and does branch off the intestines, similar to the human appendix. However, it still seems that in this diagram the label for the rectum would be better placed after the cecum label.

Goals of this image:
  • Use your knowledge of human anatomy to interpret a diagram of bird anatomy.
    • Differences
      • biliary system
      • cecum
      • cloaca
    • Possible errors
      • cecum and rectum
      • biliary system
    • What is not shown
      • jejunum
      • bilateral organs
    • Analogs to human anatomy
      • buccal cavity
  • Introduce you to the unique differences of the avian digestive system.
  • Raise your awareness of the risks of errors in anatomic drawings

Variants of this drawing show up repeatedly on the internet, including this one which has multiple misspellings and doesn’t even show the bile duct or pancreas that the arrows are supposedly pointing to:

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