GASTRO INTESTINAL SYSTEM

The Gastro intestinal tract of an adult is about 9m long and extends from the oral cavity to the mouth.

Regions of GI tract can be broadly classified into

1. Oral cavity

2. Pharynx

3. Oesophagus

4. Stomach

5. Small intestine and

6. Large intestine

Image source: Kent, M. V. , Ward. R., & Sidney, L.P. (2013), Schaum’s Outline of Human Anatomy and

Physiology. (4th ed.). Retrieved from http://accessengineeringlibrary.com.ezproxy.cdu.edu.au/browse/

schaums-outline-of-human-anatomy-and-physiology-fourth-edition

Accessory digestive organs include teeth, tongue, salivary glands, liver, gallbladder and pancreas

Area of the digestive tract extending from the pharynx upto stomach is called oesophagusResting length of adult oesophagus ranges from 18 to 26cm. At the T10 vertebral level, the oesophagus passes through the diaphragmatic hiatus and enters into the cardia of the stomach at an oblique angle.

Stomach

Cardia is the upper narrow region

immediately (1-2cm segment)below the gastro-oesophageal

sphincter. Fundus is the superior portion

of the stomach lying above and slightlyposterior to the rest of the stomach.

Body is the large central portion.

Pylorus is the funnel-shaped terminal

portion that contains pyloric sphincter.

Image source: Kent, M. V. , Ward. R., & Sidney, L.P. (2013), Schaum’s Outline of Human Anatomy and Physiology. (4th ed.). Retrieved from http://accessengineeringlibrary.com.ezproxy.cdu.edu.au/browse/schaums-outline-of-human-anatomy-and-physiology-fourth-edition

Stomach and duodenum have 4 tissue layers1. Mucosa – secretion and absorption2. Submucosa – absorption of nutrients

and fluids in to capillaries3. Muscularis propria – segmental

contractions and peristalsis4. Serosa – binding and protection

Gastric mucosa is divided into epithelium, lamina propria and muscularis mucosae.

When the stomach is empty the mucosa and submucosa contract into thick folds called rugae. As the stomach distends the rugae flattens.

Blood supply

Gastric and duodenal blood supply are derived from the celiac artery and superior mesenteric artery (SMA) .

Celiac artery and SMA are derived from the abdominal aorta.

Celiac artery branches to form splenic, left gastric and common hepatic arteries. Vessels that branches from these arteries form a dense anastomotic network that encircles the stomach. Because of these extensive network gastric ischaemia is uncommon.

Inferior pancreaticoduodenal branch of the SMA supplies distal stomach, pylorus and duodenum.

Stomach and duodenum are innervated by sympathetic and parasympathetic neurons of the autonomic nervous system

Reference list Kent, M. V. , Ward. R., & Sidney, L.P. (2013), Schaum’s Outline of Human Anatomy and Physiology.

(4th ed.)

Alpers, D. H., & Yamada, T. (2009). Textbook of Gastroenterology. Chichester, West Sussex: Wiley