The digestive system is the set of components that provide digestion. It includes the hollow organs (mouth, part of the pharynx, esophagus, stomach, small intestine, large intestine says the colon) and solid organ annexes to the digestive tract (salivary glands, liver the pancreas).

Mouth.
It opens anteriorly by the buccal cavity, bounded by two lips (upper and lower). Inside it is limited by the high roof of the mouth, below the floor of the mouth and laterally by the cheeks. It communicates posteriorly with the pharynx. It is fully lined with a mucous membrane and contains the tongue and teeth.

Language.
It is a fleshy body and mobile. It has a skeleton that is the hyoid bone and muscles that have a role in mastication. It has a role in swallowing and phonation. It is coated with a rough mucosa and it contains the sensory receptors of the gustatory apparatus. The lingual mucosa is characterized by the presence of papillae (goblet, filiform and fungiform). The tongue is innervated by the hypoglossal nerve, motor, and lingual sensory (trigeminal branch).:
The vascularity is ensured by the lingual artery, a branch of the external carotid artery. The blood off again by the lingual veins.

Teeth.
Each tooth has three parts.
- The root or which are located in the alveoli which are cavities in the upper and lower jaws.
- The crown is the part of the tooth visible emerging from the cell.
- The collar is between the root and crown.
The central part contains vessels and nerves.
The peripheral part is a hard part (ivory) which is covered by a protective part (the enamel).
The cementum is a bony part that covers the ivory at the root.
There are several kinds of teeth.
- 8 incisors, which have sharp cutting crowns.
- 4 canines for tearing.
- 8 premolars for crushing.
- 12 molars that have multiple roots for grinding.
There are two successive sets of teeth (milk teeth between 6 months and 7 years and the permanent dentition between 7 and 25 years).

The pharynx.
It is a meeting-place the airway and digestive tracts. It measures 15 cm and consists of three parts.
- A top which communicates with the nasal cavity.
- An intermediate part (mouth).
- The lower part corresponds to the larynx.
Muscles are of two types (elevators and constrictors) and are involved in swallowing.
Vessels.
- The external carotid arteries.
- The veins of the internal jugular vein.

The esophagus.
It is a tube that connects the pharynx above and below the stomach. It measures about 25 cm and a diameter of 2 to 3 cm. He describes four servings:
- A cervical portion of the neck and behind the trachea.
- Some chest in connection with the thoracic aorta, thoracic duct, heart, the vagus nerves and pulmonary pedicles.
- Some diaphragm.
- An abdominal part where it empties into the stomach through a hole called the cardia.
Vessels.
- The upper esophageal arteries.
- The branches of the thyroid arteries.
- The esophageal arteries middle and lower.
It is animated by peristaltic movements up and down.

The intra-abdominal organs
Distinguish 9 regions “virtual” in the abdomen.

  • The hypochondriac (right and left).
  • The epigastrium.
  • The sides (right and left).
  • The umbilical region.
  • The iliac fossa (right and left).
  • The hypogastric.

The peritoneum

  • The peritoneum is a serous membrane with two layers of enveloping the intestine:
  • The parietal layer lines the inner abdominal wall.
  • The visceral envelope digestive organs intra-peritoneal.
  • The peritoneum covers the entire height of the abdominal cavity.
  • Up until the diaphragm.
  • Down to the little pond.

A body is intra-peritoneal when free in the peritoneal cavity. All surfaces of the body are lined by the peritoneum and this organ is found attached to the abdominal wall by a mesentery (eg stomach).
Body is extra-peritoneal when located outside the peritoneum (the kidney).
The bodies partially extra-peritoneal are adherent to the peritoneal wall. The meso is gone and the peritoneum lining do only one side of the body (duodenum, pancreas, ascending and descending colon).

Stomach:
It is a pocket located between the esophagus and duodenum, J-shaped, with a capacity of 1 liter to 1.5 liter. The body of the stomach is called the fundus. It is an abdominal organ, under the diaphragm in the left upper quadrant and epigastrium. It measures 25 cm high and 10 to 12 cm wide. It has several parts:

  • The vertical segment.
  • The cardia (inlet).
  • The fundus (expanded portion).
  • The horizontal segment.
  • The cave.
  • The pylorus (outlet).
  • The greater curvature.
  • The small curvature.
  • The angle of His between the cardia and fundus.

Structure.
4 cell layers overlaid:
A mucous layer that lines the cavity of the stomach in full, interspersed with crypts, has gastric folds. Of these folds are the gastric glands:

  • The mucus cells (they secrete mucus).
  • Parietal cells (they secrete hydrochloric acid or called intrinsic factor).
  • G cells (they secrete the hormone gastrin).
  • The principal cells (they secrete pepsin).

Vasculature: It is highly vascularized by branches from the celiac trunk which arises from the aorta.
The innervation is provided by the vagus nerve or vagus X.

The small intestine.
Segment of the digestive tract that connects the stomach to the intestine, it measures approximately 7metres. It comprises two parts: the duodenum and the ileum-jugeno. The intestinal villi increasing the absorption surface.

  • The duodenum.
  • That portion of the digestive tract that immediately follows the stomach, which begins at the pylorus and extends to the duodeno-jejunal.
  • There are four sections which lead the ducts of the pancreas and biliary tract.
  • The large caruncle: an area where it empties the bile duct and pancreatic duct through a pocket called the ampulla of Vater in the duodenum.
  • The small caruncle which will confer an excretory duct of the pancreas, the duct of Santorini which empties into the duodenum. It contains glands of Brunner.
  • The Jejunoileal-ileum.

This is the part of the digestive tract that follows the duodenum, which begins at the corner Jejunoileal ulcer and ends at the ileocecal angle where he will confer the large intestine. It measures approximately 6 meters. He also villi, it is connected to the abdominal wall by the mesentery and has a particular fabric that will form the Peyer’s patches that have a role in the fight against bacteria. It contains a remnant embryonic diverticulum of the Meckel.

The colon
It measures 1.5 meters. It follows the small intestine and forms a frame (colon) and will end in the anus. There are several segments:
- The cecum: it is a pocket in the right iliac fossa. On the inside there is the ileocecal valve or ileocecal which drains the small intestine up to the cecum.
- The ascending colon (or right colon) that rises vertically to form the right angle of the colon and will continue through the transverse colon. The ascending colon is in contact with the underside of the liver.
- The transverse colon is up to the spleen. It is mobile and it is 40 to 80 cm.
- The descending colon (in the left side) and goes into the sigmoid colon, which will then form the rectum.

The rectum.
This is the final part of the digestive tract. There are two areas:
- An upper dilated that will form the rectum.
- A lower section which is narrow and runs through the perineum and open to the outside through the anus.
Vasculature.
- Differences areas.
- The superior mesenteric artery that supplies the cecum, ascending colon and right half of the transverse colon.
- The inferior mesenteric artery supplies the left side.
Innervation.: It is ensured by mesenteric nerve plexus, the pudendal nerve.

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