Food passes from the crop of the bird into what organ where digestion begins to cure as the muscular walls of this organ contract.
Gizzard?
Proventriculus?
Proventriculus
To determine which organ the food passes into from the crop and where digestion begins as the muscular walls contract, we can analyze the functions of the two mentioned organs: the gizzard and the proventriculus.
1. Gizzard:
- The gizzard is a muscular organ found in the digestive tract of birds, reptiles, and some fish.
- In birds, the gizzard acts as a grinding organ because birds lack teeth. It aids in breaking down food mechanically by using stones or small pebbles that the bird has ingested to grind and macerate the food.
- The gizzard's strong muscular walls help in thoroughly breaking down tough food materials, such as seeds and insect exoskeletons, before passing them to the next stage of digestion.
2. Proventriculus:
- The proventriculus is another organ found in the digestive system of birds, it is located between the crop and the gizzard.
- The proventriculus is considered the true stomach of the bird, where chemical digestion starts.
- It secretes gastric juices, including enzymes and acids, which begin the breakdown of proteins and other food components, initiating the chemical digestion process.
Considering the functions of the two organs, the correct choice would be the proventriculus. The food passes into the proventriculus from the crop, where digestion begins with the contraction of its muscular walls and the secretion of gastric juices and enzymes.