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[[Image:Alimentary Canine.jpg|thumb|right|300px|The Alimentary Tract (Canine) - Copyright Prof. Pat Mccarthy]]

[[Image:Alimentary Canine.jpg|thumb|right|300px|The Alimentary Tract (Canine) - Copyright Prof. Pat Mccarthy]]

==Introduction==

==Introduction==

The anatomy of the alimentary system begins rostrally with the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]], which is the first section of the alimentary tract that recieves food. It provides the digestive functions of prehension, [[Mastication|mastication]] and insalivation and also plays a role in the respiratory system through oral breathing when the nasopharynx is impaired. The oral cavity or mouth, includes accessory structures - [[Oral Cavity - Salivary Glands - Anatomy & Physiology|the salivary glands]], projecting structures - [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|the teeth]], and [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]] and the boundaries enclosing the oral cavity; the [[Lips - Anatomy & Physiology|lips]], [[Cheeks - Anatomy & Physiology|cheeks]], [[Soft Palate - Anatomy & Physiology|soft]] and [[Hard Palate - Anatomy & Physiology|hard palates]], and the [[Oral Cavity - Oropharynx - Anatomy & Physiology|oropharynx]]. In anatomical terms, the oropharynx is common to both the alimentary and the respiratory system, and the hard and soft palate forms the boundary between the oral and the nasal cavities in many species.

The anatomy of the alimentary system begins rostrally with the [[Oral Cavity Overview - Anatomy & Physiology|oral cavity]], which is the first section of the alimentary tract that recieves food. It provides the digestive functions of prehension, [[Mastication|mastication]] and insalivation and also plays a role in the respiratory system through oral breathing when the nasopharynx is impaired. The oral cavity or mouth, includes accessory structures - [[Oral Cavity - Salivary Glands - Anatomy & Physiology|the salivary glands]], projecting structures - [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|the teeth]] and [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]], and the boundaries enclosing the oral cavity; the [[Lips - Anatomy & Physiology|lips]], [[Cheeks - Anatomy & Physiology|cheeks]], [[Soft Palate - Anatomy & Physiology|soft]] and [[Hard Palate - Anatomy & Physiology|hard palates]], and the [[Oral Cavity - Oropharynx - Anatomy & Physiology|oropharynx]]. In anatomical terms, the oropharynx is common to both the alimentary and the respiratory system, and the hard and soft palate forms the boundary between the oral and nasal cavities in many species.

Food passes from the oral cavity into the [[oesophagus - Anatomy & Physiology|oesophagus]] and from here to the stomach. In evolutionary terms, various adaptations to the anatomy of the stomach reflect the digestive needs of the species, based on their natural diet. The [[Stomach and Abomasum - Anatomy & Physiology|ruminant stomach]] for example, is composed of 4 separate compartments; the rumen, the reticulum, the omasum and the abomasum. The first three compartments are adapted to digest complex carbohydrates with the aid of microorganisms which produce [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acids]] - the major energy source of ruminants. The last compartment, the abomasum resembles the simple [[Forestomach - Anatomy & Physiology|monogastric stomach]] of a carnivore in structure and function.  As a further adaptation, the [[Oesophageal groove|oesophageal groove]] is present in newborn ruminants; it is a channel which directs milk from the oesophagus into the rumen, omasum and then abomasum, bypassing the reticulum.  

Food passes from the oral cavity into the [[oesophagus - Anatomy & Physiology|oesophagus]] and from here to the stomach. In evolutionary terms, various adaptations to the anatomy of the stomach reflect the digestive needs of the species based on their natural diet. The [[Stomach and Abomasum - Anatomy & Physiology|ruminant stomach]] for example, is composed of 4 separate compartments; the rumen, the reticulum, the omasum and the abomasum. The first three compartments are adapted to digest complex carbohydrates with the aid of microorganisms which produce [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acids]] - the major energy source of ruminants. The last compartment, the abomasum resembles the simple [[Forestomach - Anatomy & Physiology|monogastric stomach]] of a carnivore in structure and function.  As a further adaptation, the [[Oesophageal groove|oesophageal groove]] is present in newborn ruminants; it is a channel which directs milk from the oesophagus into the rumen, omasum and then abomasum, bypassing the reticulum.  

The stomach passes into the [[Small Intestine - Anatomy & Physiology|small intestine]], which is subdivided into three sections; the [[Duodenum - Anatomy & Physiology|duodenum]], the [[Jejunum - Anatomy & Physiology|jejunum]] and the [[Ileum - Anatomy & Physiology|ileum]]. The small intestine recieves the ingested food from the stomach and is the main site of the chemical degradation and absorption of ingesta. Fats are exclusively broken down in this part of the alimentary tract. Carbohydrates and proteins that are not degraded in the small intestine are available for microbial fermentation in the large intestine. The wall of the small intestine produces enzymes for the digestion of protein, carbohydrate and fat. The [[Pancreas - Anatomy & Physiology|pancreas]] also produces digestive enzymes to aid this process. The [[Gall Bladder - Anatomy & Physiology|gall bladder]] stores bile which is produced in the [[Liver - Anatomy & Physiology|liver]] and emulsifies fats for digestion. Absorption in the small intestine is facilitated by ridges in the small intestine and by the presence of villi and microvilli.  

The stomach passes into the [[Small Intestine - Anatomy & Physiology|small intestine]], which is subdivided into three sections; the [[Duodenum - Anatomy & Physiology|duodenum]], the [[Jejunum - Anatomy & Physiology|jejunum]] and the [[Ileum - Anatomy & Physiology|ileum]]. The small intestine recieves the ingested food from the stomach and is the main site of the chemical degradation and absorption of ingesta. Fats are exclusively broken down in this part of the alimentary tract. Carbohydrates and proteins that are not degraded in the small intestine are available for microbial fermentation in the large intestine. The wall of the small intestine produces enzymes for the digestion of protein, carbohydrate and fat. The [[Pancreas - Anatomy & Physiology|pancreas]] also produces digestive enzymes to aid this process. The [[Gall Bladder - Anatomy & Physiology|gall bladder]] stores bile which is produced in the [[Liver - Anatomy & Physiology|liver]] and emulsifies fats for digestion. Absorption in the small intestine is facilitated by ridges in the small intestine and by the presence of villi and microvilli.  

The [[Large Intestine - Anatomy & Physiology|large intestine]] begins at the [[Caecum - Anatomy & Physiology|caecum]], and includes the [[Colon - Anatomy & Physiology|colon]], the [[Rectum - Anatomy & Physiology|rectum]] and the [[Anus - Anatomy & Physiology|anus]]. Water, electrolytes and nutrients are absorbed which concentrates the ingesta into faeces. There is no secretion of enzymes and any digestion that takes place is carried out by microbes. All species have a large microbial population living in the large intestine, which is of particular importance to the [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenters]] such as the horse. For this reason, hindgut fermenters have a more complex large intestine with highly specialised regions for fermentation. The colon absorbs the volatile fatty acid products of microbial fermentation.  

The [[Large Intestine - Anatomy & Physiology|large intestine]] begins at the [[Caecum - Anatomy & Physiology|caecum]], and includes the [[Colon - Anatomy & Physiology|colon]], the [[Rectum - Anatomy & Physiology|rectum]] and the [[Anus - Anatomy & Physiology|anus]]. Water, electrolytes and nutrients are absorbed which concentrates the ingesta into faeces. There is no secretion of enzymes and any digestion that takes place is carried out by microbes. All species have a large microbial population living in the large intestine, which is of particular importance to the [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenters]] such as the horse. For this reason, hindgut fermenters have a more complex large intestine with highly specialised regions for fermentation. The volatile fatty acid products of microbial fermentation are absorbed in the colon.  

The stomach, small intestines and large intestines are situatied within the abdominal or [[Peritoneal cavity - Anatomy & Physiology|peritoneal cavity]]. The peritoneum is the serous membrane that lines the abdominal cavity; it  produces fluid to lubricate abdominal viscera and enhances the immune response and walls off infection in the abdomen to prevent peritonitis.  

The stomach, small intestines and large intestines are situatied within the abdominal or [[Peritoneal cavity - Anatomy & Physiology|peritoneal cavity]]. The peritoneum is the serous membrane that lines the abdominal cavity; it  produces fluid to lubricate abdominal viscera and enhances the immune response and walls off infection in the abdomen to prevent peritonitis.