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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 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 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.

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.  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 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 chemical degradation and absorption of chyme. 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 small intestine produces enzymes for digestion of protein, carbohydrate and fat and absorbs the products of their digestion. Enzymes are produced by glands in the intestinal wall and the pancreas. The gall bladder produces bile which emulsifies fats for digestion. Absorption is facilitated by ridges in the small intestine and by the presence of villi and microvilli.