Introduction
The crop is a food storage device present in avian species. It is usually used when the muscular stomach (gizzard) is full. The crop also softens food.
It is useful tool for avian veterinarians and owners of assessing when the bird last ate and it is especially important to ensure young chicks always have full crops. It is also a common site for impactions and surgical entry to remove foreign bodies.
Structure and Function
- Muscular chamber
- Fusiform enlargement of the oesophagus
- Thoracic inlet of ventral wall of oesophagus
- Bulges and lies against the breast muscles
Innervation
- Vagus nerve (CN X)
Species Differences
- Crop small in ducks and geese
- Crop much larger and muscular in seed eating birds
- Pigeons have epithelial cells in their crop sensitive to prolactin which slough when chicks (squabs) hatch producing crop milk
- Owls have no storage facility in their crops, so produce a pellet of indigestible material after every meal