Movie: Digestive System

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Digestive Diseases
Teeth chop food into small pieces, which are moistened by saliva before the tongue and other muscles push the food into the pharynx. For example, herbivores have a number of molars which are used to grind plant matter, which is difficult to digest. After the duodenum the small intestine forms a coil and is suspended from the dorsal wall of the abdominal wall by a thin membrane called the mesentery. The digestive tract begins at the lips and ends at the anus. It has a flattened, rounded shape somewhat like a convex lens, with one side slightly larger than the other. Food is formed into a bolus by the mechanical mastication and swallowed into the esophagus from where it enters the stomach through the action of peristalsis.

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Digestive system

On the inner surface of each cheek, opposite the second upper molar tooth, is a slight elevation that marks the opening of the parotid duct, leading from the parotid salivary gland , which is located in front of the ear. Just behind this gland are four to five mucus-secreting glands, the ducts of which open opposite the last molar tooth. The roof of the mouth is concave and is formed by the hard and soft palate. The hard palate is formed by the horizontal portions of the two palatine bones and the palatine portions of the maxillae, or upper jaws.

The hard palate is covered by a thick, somewhat pale mucous membrane that is continuous with that of the gums and is bound to the upper jaw and palate bones by firm fibrous tissue. The soft palate is continuous with the hard palate in front. Posteriorly it is continuous with the mucous membrane covering the floor of the nasal cavity.

The soft palate is composed of a strong, thin, fibrous sheet, the palatine aponeurosis, and the glossopalatine and pharyngopalatine muscles. A small projection called the uvula hangs free from the posterior of the soft palate.

The floor of the mouth can be seen only when the tongue is raised. In the midline is a prominent, elevated fold of mucous membrane frenulum linguae that binds each lip to the gums, and on each side of this is a slight fold called a sublingual papilla , from which the ducts of the submandibular salivary glands open. Running outward and backward from each sublingual papilla is a ridge the plica sublingualis that marks the upper edge of the sublingual under the tongue salivary gland and onto which most of the ducts of that gland open.

The gums consist of mucous membranes connected by thick fibrous tissue to the membrane surrounding the bones of the jaw. The gum membrane rises to form a collar around the base of the crown exposed portion of each tooth. Rich in blood vessels, the gum tissues receive branches from the alveolar arteries; these vessels, called alveolar because of their relationship to the alveoli dentales, or tooth sockets, also supply the teeth and the spongy bone of the upper and lower jaws, in which the teeth are lodged.

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Read More on This Topic. Page 1 of Next page The teeth. Learn More in these related Britannica articles: Right before hatch, the yolk sac is taken into the navel cavity of the embryo. The residual tiny sac is the Meckel's diverticulum. Location of the Meckel's diverticulum in the digestive tract of a chicken. The ceca plural form of cecum are two blind pouches located where the small and large intestines join.

Some of the water remaining in the digested material is reabsorbed here. Another important function of the ceca is the fermentation of any remaining coarse materials. During this fermentation, the ceca produce several fatty acids as well as the eight B vitamins thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid, and vitamin B Because the ceca are located so close to the end of the digestive tract, however, few of the produced nutrients are absorbed and available to the chicken.

Despite the name, the large intestine is actually shorter than the small intestine. The large intestine is where the last of the water reabsorption occurs. In the cloaca, the digestive wastes mix with wastes from the urinary system urates. Chickens usually void fecal material as digestive waste with uric acid crystals on the outer surface—that is, chickens do not urinate.

The color and texture of chicken fecal material can indicate the health status of the chicken's digestive tract: The reproductive tract also exits through this area. When a hen lays an egg, the vagina folds over to allow the egg to leave through the cloaca opening without coming into contact with feces or urine. These microflora aid in digestion.

When chicks hatch, their digestive tracts are virtually sterile. If raised by a mother hen, a chick obtains the beneficial microflora by consuming some of its mother's fecal material.

In artificial incubation and brooding, chicks do not have this option. Through the probiotics, the chicks receive the beneficial bacteria they need to fight off infection by pathogenic bacteria, such as salmonella. Intestinal disease in chickens normally occurs when the balance of normal microflora is upset—that is, the normal microflora are overrun by too many foreign organisms. The result is enteritis, or inflammation of the intestines. Enteritis produces symptoms that include diarrhea, increased thirst, dehydration, loss of appetite, weakness, and weight loss or slow growth.

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View publishing information about this page. Jacquie Jacob, University of Kentucky An understanding of the avian digestive system is essential for developing an effective and economical feeding program for your poultry flock and for recognizing when something is wrong and taking necessary actions to correct the problem. Parts of a Chicken Digestive Tract The chicken has a typical avian digestive system.

Digestive tract of a female chicken. It goes to the right ventricle to await disposal. It goes into the large intestine to await disposal. It goes into the small intestine to await disposal. Solid waste leaves the body through the rectum then the anus. Liquid waste leaves the body after passing through the Digestion takes place in a long tube-like canal called the alimentary canal, or the digestive tract. Food travels through these organs in the following order: The liver is located in the abdomen and performs many functions.

Which of the following is NOT a function of the liver? Healing itself when it is damaged.

Intestinal Microflora