AP BIOLOGY

Detailed explanation-1: -The gizzard is why chickens do not need teeth. It is a muscular part of the stomach and uses grit (small, hard particles of pebbles or sand) to grind grains and fiber into smaller, more digestible, particles. From the gizzard, food passes into the small intestine, where nutrients are absorbed.

Detailed explanation-2: -Located between the saclike crop and the intestine, the gizzard has a thick muscular wall and may contain small stones, or gastroliths, that function in the mechanical breakdown of seeds and other foods. In this sense, the gizzard is comparable to the teeth of other animals.

Detailed explanation-3: -The chicken digestive tract is like other monogastric (single stomach) animals, such as the pig, horse, and dog, but also has its own unique differences. The most notable include the lack of teeth, crop, proventriculus, ventriculus (aka gizzard), ceca, and cloaca.

Detailed explanation-4: -Mechanical digestion is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with saliva.

Detailed explanation-5: -The gizzard is the mechanical stomach of a bird. It is located just after the true or glandular stomach in the gastrointestinal system. Since poultry have no teeth and swallow feed whole, this muscular organ, sometimes called hen’s teeth, mechanically grinds and mixes the bird’s feed.