Gastrointestinal Tract Structure Quiz

Layers of the GI Tract

• The mucosa layer is responsible for absorption and secretion in the GI tract.
• The submucosa layer provides a connective tissue layer that supports the mucosa layer.
• The muscularis layer enables the movement of substances lengthwise in the GI tract.
• The outermost layer of the GI tract is called the serosa.

Stomach Function

• The stomach is responsible for mechanical and chemical digestion of food.
• The stomach has a pH of 1.5-3.5, which is acidic.
• Chief cells in the stomach secrete pepsinogen, which is converted to pepsin in the presence of hydrochloric acid.
• Hydrochloric acid in the stomach denatures proteins and activates pepsinogen.
• Gastric mixing waves are initiated by the contraction of the stomach muscles.

Phases of Gastric Digestion

• The cephalic phase of gastric digestion involves the production of gastrin in response to the sight, smell, and taste of food.

Digestive System

• The digestive system begins at the oral cavity and ends at the anus.
• The major accessory organs of the digestive system are the liver, gallbladder, pancreas, and salivary glands.
• Digestion is the process in which food is broken down by both mechanical and chemical processes.

Functions of GI Tract Layers

• The epithelial cells lining the GI tract are responsible for absorption and secretion.
• The mucosa layer of the GI tract is composed of a mucous membrane and is responsible for absorption and secretion.
• Substances that are not digested or absorbed in the GI tract are eliminated from the body through the anus.

Bile and Pancreas

• The liver stores bile, which is released into the small intestine to facilitate fat digestion.
• Mechanical digestion mainly occurs in the mouth and stomach.
• Bile emulsifies fats, making them more accessible to enzymes.

Large Intestine

• The last portion of the colon is called the rectum.
• The overall function of the large intestine is to absorb water and electrolytes and store feces until elimination.

Enzymes and Hormones

• Enzymes are biological molecules that speed up chemical reactions in the body.
• Enzymes break down complex nutrients into simpler molecules that can be absorbed by the body.
• The three phases of digestion that occur in the stomach are the cephalic, gastric, and intestinal phases.
• The two hormones released in response to chyme containing glucose and fatty acids in the small intestine are secretin and cholecystokinin (CCK).
• Cholecystokinin (CCK) stimulates the release of bile and digestive enzymes from the pancreas and gallbladder.
• Secretin stimulates the release of bicarbonate-rich pancreatic juices to neutralize acidic chyme.

Salivary Glands and Tongue

• The submandibular glands produce saliva that moistens food and breaks down carbohydrates.
• Saliva does not aid in the absorption of nutrients.
• The uvula aids in swallowing by directing food into the esophagus.
• The lower esophageal sphincter marks the lower end of the esophagus and upper end of the stomach.
• The tongue mixes food with saliva and forms a bolus during digestion.