The gastric juices, which include enzymes in the stomach, act on the food particles and continue the process of digestion. Further breakdown of food takes place in the small intestine where enzymes produced by the liver, the small intestine, and the pancreas continue the process of digestion. The nutrients are absorbed into the blood stream across the epithelial cells lining the walls of the small intestines. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces; it is stored until it is excreted through the rectum.
Figure 2. However, in the rabbit the small intestine and cecum are enlarged to allow more time to digest plant material. The enlarged organ provides more surface area for absorption of nutrients.
Rabbits digest their food twice: the first time food passes through the digestive system, it collects in the cecum, and then it passes as soft feces called cecotrophes. The rabbit re-ingests these cecotrophes to further digest them. Birds face special challenges when it comes to obtaining nutrition from food. They do not have teeth and so their digestive system, shown in Figure 3, must be able to process un-masticated food. Birds have evolved a variety of beak types that reflect the vast variety in their diet, ranging from seeds and insects to fruits and nuts.
Because most birds fly, their metabolic rates are high in order to efficiently process food and keep their body weight low. The stomach of birds has two chambers: the proventriculus , where gastric juices are produced to digest the food before it enters the stomach, and the gizzard , where the food is stored, soaked, and mechanically ground. The undigested material forms food pellets that are sometimes regurgitated.
Most of the chemical digestion and absorption happens in the intestine and the waste is excreted through the cloaca. Figure 3. The avian esophagus has a pouch, called a crop, which stores food. In the avian digestive system, food passes from the crop to the first of two stomachs, called the proventriculus, which contains digestive juices that break down food.
From the proventriculus, the food enters the second stomach, called the gizzard, which grinds food. Some birds swallow stones or grit, which are stored in the gizzard, to aid the grinding process. Birds do not have separate openings to excrete urine and feces. Instead, uric acid from the kidneys is secreted into the large intestine and combined with waste from the digestive process. This waste is excreted through an opening called the cloaca.
Birds have a highly efficient, simplified digestive system. Recent fossil evidence has shown that the evolutionary divergence of birds from other land animals was characterized by streamlining and simplifying the digestive system. Unlike many other animals, birds do not have teeth to chew their food. In place of lips, they have sharp pointy beaks. The horny beak, lack of jaws, and the smaller tongue of the birds can be traced back to their dinosaur ancestors.
Mechanics of expiration. Related Books Free with a 30 day trial from Scribd. Related Audiobooks Free with a 30 day trial from Scribd. Views Total views. Actions Shares. No notes for slide. Difference between digestive tract and cavity 1. Total views 9, On Slideshare 0. From embeds 0. Number of embeds 5. Downloads 6. Shares 0. Comments 0. Likes 0. You just clipped your first slide! The gastrovascular cavity is a digestive tract found in two major primitive phyla in kingdom Animalia.
It is a primary organ involved in the digestion of food and circulation of nutrients throughout the body. Moreover, the gastrovascular cavity aids in the circulation of oxygen and wastes. The gastrovascular cavity has only one opening to the environment. This opening serves as both mouth and anus.
Food goes in, and waste goes out from the same opening, making it a two-way digestive tract. The gastrovascular cavity is an extensively branched canal system. Only two phyla of kingdom Animalia have a gastrovascular cavity. Those phyla are phylum Cnidaria and phylum Platyhelminthes.
The gastrovascular cavity in cnidarians is known as coelenteron. Figure Gastrovascular Cavity of the Flatworm Dugesia. The alimentary canal is an organ which extends from mouth to anus. It is the muscular tube by which food enters our body and moves out through the anus after digestion.
Therefore, there are two openings in the alimentary canal, making it a one-way digestive tract. Foods go in through the mouth, and wastes are excreted out from the anus.
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