The Digestive System P2

The Abdominal Cavity

The stomach and intestines are enclosed in the space between the diaphragm and pelvis. The abdomen is lined with a membrane called the peritoneum. The mesentery, a fold of the peritoneum connects a portion of the intestines to the abdominal wall. The omentum, a double fold of the peritoneum attaches to the stomach, connecting it to the internal tissues of the abdomen.

This is a very important area to learn to feel, as many thoroughbred have particularly sensitive digestive systems and fluid builds up and can fill the tissues in this area. A key area to look at is between the tuber coxae and the last rib.

Small Intestines

Small intestines occupy a large portion of the abdomen and are made up of three parts, and juices from the pancreas and liver are secreted here to aid digestion.

  • Duodenum – which attaches to the stomach and receives the pancreatic and common bile ducts, which empties into it. Digestion and absorption take place here.
  • Jujumum – held in place by the mesentery, rapidly moves fluid contents into the ileum.
  • Ileum – is the longest section of the small intestines and where most food absorption takes place.

Large Intestines

The large intestines are made up of the cecum, small and large colon. Water absorption occurs in the large intestines as well as the presence of bacteria to break down the cellulose elements of the food.

  • Cecum – The contents left in the ileum are passed into the cecum. For herbivores, much of fermentation occurs at this point. For equines, this is more so than that of many single stomached herbivores, this is marked by the larger cecum and colon size. The role of the cecum is to break down fibrous materials.
  • Small Colon – is a relatively short, narrow tube attached to a long mesentery allows freedom within the abdominal cavity. It coils close to the jejunum, its freedom predisposes it to volvulus and torsions, which can lead to colic. It is the small colon that the undigested residue is formed into faecal balls by the segmented contractions of its walls and pushed towards the rectum by peristalsis (a muscular contraction). It is otherwise active in the final water and electrolyte absorption and some fermentation activity as well.
  • Rectum: The rectum dilates to store faeces until their expulsion. The anus is the end of the digestive tract where faeces is expelled.
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