Digestive System

1. Definition:

The digestive system is a system of organs responsible for digesting food, absorbing nutrients, and eliminating waste products. The digestive system includes:

• Digestive tract: A long tube from the mouth to the anus. It includes:

• Mouth and its associated structures: lips, teeth, tongue, salivary glands.

• Pharynx: Connects the mouth to the esophagus.

• Esophagus: Connects the pharynx to the stomach.

• Stomach: Organ that stores food and secretes digestive gastric juice.

• Small intestine: Site of nutrient digestion and absorption.

• Large intestine: Site of water absorption and waste elimination.

• Accessory digestive organs: Liver, Pancreas, Salivary glands.

2. General structure of the digestive tract:

From superficial to deep, the digestive tract is composed of the following layers:

• Serosa: The outermost layer, covering most of the digestive tract.

• Subserosa: A thin layer of connective tissue, connecting the serosa to the muscularis.

• Muscularis: Smooth muscle layer, consisting of two layers of muscle fibers:

• Longitudinal fibers: Shorten the digestive tract.

• Circular fibers: Narrow the lumen of the digestive tract.

• Submucosa: A layer of connective tissue, connecting the muscularis to the mucosa.

• Mucosa: The innermost layer, in contact with food, consists of epithelium, connective tissue, and a thin layer of smooth muscle.

The structure of these layers varies in different sections of the digestive tract, adapting to the functions of each section.

3. Accessory digestive organs:

• Liver:

• Location: Right hypochondrium, epigastrium, and a small part in the left hypochondrium.

• Shape: Brownish-red, the largest organ in the abdominal cavity.

• Components: Diaphragmatic surface, visceral surface, inferior margin (anterior).

• Pancreas:

• Location: Behind the stomach, crossing the level of L2 vertebrae.

• Length: 12 to 15 cm.

• External shape: Head of pancreas, body of pancreas, tail of pancreas.

• Salivary glands: Parotid, submandibular, sublingual.

4. Mouth and its associated structures:

• Oral cavity boundaries:

• Anterior: Lips and oral fissure.

• Posterior: Oropharynx.

• Superior: Palate (hard and soft).

• Inferior: Floor of the mouth.

• Lateral: Cheeks.

• Oral cavity divisions:

• Vestibule: Space between the teeth and the lips/cheeks.

• Oral cavity proper: Space inside the teeth.

• Teeth:

• Number:

• Permanent: 32 teeth.

• Deciduous: 20 teeth.

• External shape:

• Crown.

• Root.

• Neck.

• Tongue:

• Location: Floor of the mouth.

• Function: Chewing, swallowing, speech, and taste.

• Shape:

• Tip.

• Root.

• Body.

5. Pharynx:

• Parts:

• Nasal: Connects to the nasal cavity.

• Oral: Connects to the oral cavity.

• Laryngeal: Connects to the trachea.

6. Esophagus:

• Boundaries:

• Superior: Continuous with the pharynx.

• Inferior: Empties into the stomach.

• Length: 25 cm.

7. Stomach:

• Location:

• Under the left hemidiaphragm.

• Epigastrium, left hypochondrium.

• External shape:

• Cardiac region.

• Fundus.

• Body.

• Pyloric region.

• Pylorus.

• Greater/lesser curvature.

• Boundaries:

• Superior: Continuous with the esophagus.

• Inferior: Continuous with the duodenum.

8. Small intestine:

• Components:

• Duodenum.

• Jejunum and ileum.

• Duodenum:

• Boundaries: From the pyloric orifice to the duodenojejunal flexure.

• Length: 25 cm.

• Jejunum, Ileum:

• Location: Within the peritoneal cavity.

• Length: Approximately 6 meters.

• Boundaries:

• Superior: Duodenojejunal flexure.

• Inferior: Ileocecal junction.

• Shape: Coiled into loops of intestines.

9. Large intestine:

• Location:

• Arranged in a frame-like structure.

• Peripheral to the abdominal cavity.

• Length: Approximately 1.5 meters.

• External shape:

• Haustral folds.

• Teniae coli.

• Epiploic appendages.

• Components:

• Cecum and appendix.

• Colon:

• Ascending/transverse/descending/sigmoid (located at the end of the colon).

• Rectum.

• Anal canal.

10. Peritoneum:

• The largest serous membrane in the body.

• Location: Within the abdominal cavity.

• Structure: Parietal/visceral layers and peritoneal mesentery.

Note: This document is a summary of basic information about the digestive system. To understand more about the organs, structures, and functions of the digestive system, you should refer to specialized literature.