Apart from the number of teeth – 30 permanent teeth in cats compared with 42 in dogs – and a few dozen centimetres longer in dogs, the anatomy of the digestive tract shows few differences between these two species.
The digestive system of our four-legged companions begins with the mouth – for the cat and the dog. The oral cavity consists of, among other things, the tongue, gums, teeth and salivary glands. It is followed by the pharynx, which allows swallowing. The stomach is followed by a long tube called the oesophagus. The food bolus – the food crushed in the oral cavity and mixed with saliva and gastric juices – is then evacuated from this pouch by passing through a valve called the pylorus. It then joins the first part of the small intestine: the duodenum. The second and third parts of this long tube (more than a metre long in cats!) are called the jejunum and the ileum. The small intestine is extended by the large intestine, also called the colon. This organ consists first of the cecum, then is divided into three parts: the ascending, transverse and descending colon, and ends with the rectum. The last part of the digestive tract is called the anus. Around this orifice are the anal glands.
There are also so-called accessory organs, such as the liver, gallbladder and pancreas. The spleen, although located in the abdominal cavity, has no function in the digestive processes.
When food is eaten, it is first crushed – very roughly – in the oral cavity by the tongue and teeth. The saliva of our four-legged friends, unlike ours, does not contribute to the pre-digestion of food, but only serves to lubricate it.
After being swallowed in the pharynx and passing through the oesophagus, the food remains in the stomach for a few hours, where it is mixed with gastric juices, the enzymes that allow it to be digested. The particularly acidic pH of the stomach also plays a role in this process.
After the gastric contents have passed through the pouch, which is made up of different layers of muscle, they are gradually discharged into the small intestine. All along this tube, the digestive contents are mixed with intestinal juice, digested into nutrients and absorbed through the wall, and then enter the circulation. It is into the first portion of this long tube, the duodenum, that bile and pancreatic juice are discharged. The former is produced by the liver, then stored in the gallbladder, before being discharged into the small intestine via the bile duct. Bile allows the breakdown of fats. Pancreatic juice is produced by the exocrine portion of the pancreas. It regulates the pH of the intestinal contents and digests proteins, sugars and fats.
The large intestine, or colon, completes the digestion process and collects the breakdown products and water to form faeces. It is populated by an abundant flora, also called microbiota.
Certain organs attached to the digestive tract, such as the liver and the pancreas, have a role to play in the digestion of food and the assimilation of nutrients, but not only! The liver, in addition to secreting bile, has functions :
The endocrine pancreas produces two hormones: insulin and glucagon, which are essential for regulating blood sugar levels.
The spleen, although considered an accessory organ, is not involved in digestion. It has a role as a blood reservoir and in immunity, and is involved in the renewal of blood cells.
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