The Digestive System: Anatomy and Structure

Digestive System Overview

• The digestive system consists of a continuous tract called the alimentary canal or gastrointestinal tract (GIT), which extends from the oral cavity to the anus.
• The GIT is accompanied by accessory organs, including the salivary glands, liver, gallbladder, and pancreas.

Upper GI Tract

• The upper GI tract consists of the oral cavity, oesophagus, and stomach.
• Digestion begins in the oral cavity, where food is broken apart by mastication (chewing).
• Food then moves to the pharynx and into the oesophagus, a collapsible tube that lubricates and moves food to the stomach by peristalsis (wave-like muscular contractions).
• The stomach is the next stop, where food is controlled by the cardiac sphincter, a ring-like muscle that regulates food flow from the oesophagus.
• After 3-4 hours in the stomach, food becomes a liquid called chyme.
• Chyme passes to the small intestines through the pyloric sphincter, a muscle at the distal end of the stomach.

Lower GI Tract

• The lower GI tract consists of the small intestines and large intestines.
• The small intestines are divided into three parts: the duodenum, jejunum, and ileum.
• The large intestine is divided into three parts: the cecum, colon, and rectum.
• The cecum has a blind tube attached to it called the appendix, which consists of lymphatic tissue.
• The colon is further subdivided into four parts: the ascending colon, transverse colon, descending colon, and sigmoid colon.