Why is the stomach the first site of chemical digestion in the frog?

The stomach is the first site of chemical digestion in frogs because it contains gastric juices that are rich in enzymes and acids, specifically pepsin and hydrochloric acid. These substances help break down proteins into smaller peptides, facilitating further digestion. Additionally, the stomach's muscular contractions mix the food with these digestive secretions, enhancing the breakdown of nutrients before they move to the intestines for further digestion and absorption.