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Your Digestive System
The remainder of the material consists of waste and undigested food and are mixed with the urine in the cloaca and eliminated from the body as faeces. In clinically healthy animals, absorption exceeds secretion, ie, there is net absorption. Bitter, greenish liquid produced in the liver and stored in the gall bladder that dissolves fats. Try feeding the chicken and rice dog food recipe , substitute sweet potato for the white rice. The small bowel has 3 main sections: There are medications that can treat yeast infections but they are temporary fixes. Stomach is a sac- like structure.

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Movie: Digestive System

A crop , or croup, is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion. In some birds it is an expanded, muscular pouch near the gullet or throat.

In adult doves and pigeons, the crop can produce crop milk to feed newly hatched birds. Certain insects may have a crop or enlarged esophagus. Herbivores have evolved cecums or an abomasum in the case of ruminants. Ruminants have a fore-stomach with four chambers. These are the rumen , reticulum , omasum , and abomasum.

In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud or bolus.

The cud is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fibre, especially cellulose and hemi-cellulose , is primarily broken down into the volatile fatty acids , acetic acid , propionic acid and butyric acid in these chambers the reticulo-rumen by microbes: In the omasum, water and many of the inorganic mineral elements are absorbed into the blood stream.

The abomasum is the fourth and final stomach compartment in ruminants. It is a close equivalent of a monogastric stomach e. It serves primarily as a site for acid hydrolysis of microbial and dietary protein, preparing these protein sources for further digestion and absorption in the small intestine. Digesta is finally moved into the small intestine, where the digestion and absorption of nutrients occurs.

Microbes produced in the reticulo-rumen are also digested in the small intestine. Regurgitation has been mentioned above under abomasum and crop, referring to crop milk, a secretion from the lining of the crop of pigeons and doves with which the parents feed their young by regurgitation. Many sharks have the ability to turn their stomachs inside out and evert it out of their mouths in order to get rid of unwanted contents perhaps developed as a way to reduce exposure to toxins.

Other animals, such as rabbits and rodents , practise coprophagia behaviours — eating specialised faeces in order to re-digest food, especially in the case of roughage. Capybara, rabbits, hamsters and other related species do not have a complex digestive system as do, for example, ruminants. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft faecal pellets of partially digested food are excreted and generally consumed immediately.

They also produce normal droppings, which are not eaten. Young elephants, pandas, koalas, and hippos eat the faeces of their mother, probably to obtain the bacteria required to properly digest vegetation. When they are born, their intestines do not contain these bacteria they are completely sterile. Without them, they would be unable to get any nutritional value from many plant components.

An earthworm 's digestive system consists of a mouth , pharynx , esophagus , crop , gizzard , and intestine. The mouth is surrounded by strong lips, which act like a hand to grab pieces of dead grass, leaves, and weeds, with bits of soil to help chew. The lips break the food down into smaller pieces. In the pharynx, the food is lubricated by mucus secretions for easier passage. The esophagus adds calcium carbonate to neutralize the acids formed by food matter decay.

Temporary storage occurs in the crop where food and calcium carbonate are mixed. The powerful muscles of the gizzard churn and mix the mass of food and dirt. When the churning is complete, the glands in the walls of the gizzard add enzymes to the thick paste, which helps chemically breakdown the organic matter.

By peristalsis , the mixture is sent to the intestine where friendly bacteria continue chemical breakdown. This releases carbohydrates, protein, fat, and various vitamins and minerals for absorption into the body. In most vertebrates , digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing.

Digestion is separated into four steps:. Underlying the process is muscle movement throughout the system through swallowing and peristalsis. Each step in digestion requires energy, and thus imposes an "overhead charge" on the energy made available from absorbed substances. Differences in that overhead cost are important influences on lifestyle, behavior, and even physical structures. Examples may be seen in humans, who differ considerably from other hominids lack of hair, smaller jaws and musculature, different dentition, length of intestines, cooking, etc.

The major part of digestion takes place in the small intestine. The large intestine primarily serves as a site for fermentation of indigestible matter by gut bacteria and for resorption of water from digests before excretion.

In mammals , preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach. Mechanical and chemical digestion begin in the mouth where food is chewed , and mixed with saliva to begin enzymatic processing of starches.

The stomach continues to break food down mechanically and chemically through churning and mixing with both acids and enzymes. Absorption occurs in the stomach and gastrointestinal tract , and the process finishes with defecation.

The human gastrointestinal tract is around 9 meters long. Food digestion physiology varies between individuals and upon other factors such as the characteristics of the food and size of the meal, and the process of digestion normally takes between 24 and 72 hours.

Digestion begins in the mouth with the secretion of saliva and its digestive enzymes. 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.

Gastric juice contains hydrochloric acid and pepsin which would damage the walls of the stomach and mucus is secreted for protection. In the stomach further release of enzymes break down the food further and this is combined with the churning action of the stomach. The partially digested food enters the duodenum as a thick semi-liquid chyme.

In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile , pancreatic juice and intestinal juice. The intestinal walls are lined with villi , and their epithelial cells is covered with numerous microvilli to improve the absorption of nutrients by increasing the surface area of the intestine. In the large intestine the passage of food is slower to enable fermentation by the gut flora to take place.

Here water is absorbed and waste material stored as feces to be removed by defecation via the anal canal and anus. Different phases of digestion take place including: The cephalic phase occurs at the sight, thought and smell of food, which stimulate the cerebral cortex. Taste and smell stimuli are sent to the hypothalamus and medulla oblongata. After this it is routed through the vagus nerve and release of acetylcholine.

Acidity in the stomach is not buffered by food at this point and thus acts to inhibit parietal secretes acid and G cell secretes gastrin activity via D cell secretion of somatostatin. The gastric phase takes 3 to 4 hours. It is stimulated by distension of the stomach, presence of food in stomach and decrease in pH. Distention activates long and myenteric reflexes. This activates the release of acetylcholine , which stimulates the release of more gastric juices.

As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach. Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin , which in turn stimulates parietal cells to secrete gastric acid.

Gastric acid is about 0. The salivary glands run the whole length of the hard palate, the groups of glands merging to form one mass of glandular tissue under the epithelium. Lymphoid tissue is found in most glands. The pharynx is continuous with, and follows, the mouth.

The combined cavity of the mouth and the pharynx is often referred to as the oropharynx. The common opening for the two eustachian tubes is located in the middle of its dorsal wall roof. The tongue is long and pointed and conforms to the shape of the beak in which it operates.

The epithelium of the tongue is thick and horny, especially towards the tip. A transverse row of simple, large and horny papillae with their tips directed towards the rear of the mouth cavity are located on the posterior end. The hyoid bone provides the framework to support the tongue. The entoglossal bone extends longitudinally in the median plane. Small patches of lymphatic tissue are located throughout the corium. Mucous glands are located in the tongue with short ducts directed towards the rear.

Some believe that there are taste buds located on the tongue, but this belief is not universally held. In any case, the sense of taste appears to be very weak if at all present. The oesophagus is wide and is capable of being significantly stretched.

It connects the mouth region to the crop in close association with the trachea. The crop is a large dilation of the oesophagus located just prior to where the oesophagus enters the thoracic cavity. The crop provides the capacity to hold food for some time before further digestion commences. Inside the thoracic cavity, the oesophagus enters or becomes the proventriculus which is a very glandular part of the digestive tract often called the glandular stomach.

The wall of the oesophagus is composed of four layers of tissue, the innermost being mucous membrane. The mucous membrane is an important barrier to the entry of microbes and the mucous it produces is a lubricant that aids the passage of the food along the alimentary canal. The structure below the crop is similar to that above except there is less lymphoid tissue below the crop.

The crop structure is similar to that of the oesophagus except there are no glands present in fowls. Ducks and geese have glands in the crop mucous membranes. The glandular stomach, or proventriculus, is relatively small and tubular. The wall is very thick and is composed of five layers:. The glands form the greater part of the thickness of the organ. Simple single glands group to form lobules each of which converges into a common cavity near the surface.

The cavities converge to form a common duct that leads to the surface through the apex of a small papilla see figure below. These glands produce a number of juices or enzymes that are used in the digestion or breaking down of food into its constituent nutrients. The mucous membrane is raised into folds and between these folds are numerous simple tubular glands that produce hydrochloric acid as well as lymphoid tissue.

The muscular stomach or gizzard is located immediately after the proventriculus, partly between the lobes and partly behind the left lobe of the liver. It has a flattened, rounded shape somewhat like a convex lens, with one side slightly larger than the other. Each surface is covered by a glistening layer of tendinous tissue which is thicker at the centre and becoming thinner towards the edges. Under this outer layer there are located very powerful masses of red muscle.

The inner surface is lined with a creamy-coloured, thick, horny tissue raised in ridges. The gizzard almost always contains quantities of hard objects such as gravel or other grit that aids in the disintegration of food, which is the primary function of the gizzard. The entrance from the proventriculus and the exit to the duodenum are close together and dorsal in location.

The gizzard consists of a number of layers of tissues, some of which contain straight tubular glands. The innermost layer is a strong, flexible skin that is able to withstand the potentially damaging effects of the muscular action grinding the food often in the presence of stones or other insoluble material. The glands of the gizzard produce a liquid which is a keratinised material that passes to the surface of the horny lining where it hardens to replace tissue worn away by the grinding action of the organ.

The small intestine begins at the exit from the gizzard and ends at the junction of the small intestine, caeca and colon. It is relatively long and has a constant diameter. Of the three parts of the mammalian small intestine, the duodenum, jejunum and ileum, only the duodenum can be easily distinguished in the fowl. There is no clear demarcation between the jejunum and ileum and the small intestine appears as one long tube. Much of the digestion of the food and all of the absorption of the nutrients takes place in the small intestine and hence its structure is quite important.

The structure is as follows:. When a piece of the small intestine is immersed in water it takes on a very velvety appearance because of the presence of villi — long flattened, fingerlike projections that extend into the lumen inside of the intestine like flexible fingers. The villi are very actively involved in the absorption process. A single layer of columnar epithelium together with goblet cells covers the lining.

The goblet cells secrete mucous. A lacteal lymph vessels , capillaries, bundles of plain muscle fibres, nerves and other tissues and cells occupy the core of the villus. The villi have the function of providing a vastly increased surface area for the more efficient absorption of the nutrients. The digestive system includes the following: All these organs need proper nutrients to function properly.

Too little healthy foods and too much unhealthy foods can interfere with normal processes of your digestive system. Cells organize and form tissues, which organize and form organs. All cells need adequate nutrients to do work. Without proper nutrients, the cells can die or fail to function properly. Your body also needs antioxidants — substances commonly found in fruits and vegetables — to neutralize free radicals, or highly reactive molecules, that can harm your cells.

When free radicals attack the cells and impair them, they lose their ability to produce functioning enzymes -- specialized proteins needed in every facet of biological activity, including digestion and metabolic processes. Fiber saves time and discomfort. Without adequate dietary fiber, you increase your risk of constipation.

You may experience straining, lack of bowel movement and difficulty eliminating hard, dry stools. You may also feel bloated.

What Is the Main Function of the Digestive System?