Podcast
Questions and Answers
Which organ is responsible for mechanical digestion through mastication?
Which organ is responsible for mechanical digestion through mastication?
Where does chemical digestion begin for the predominant dietary carbohydrate and to a small degree on lipids?
Where does chemical digestion begin for the predominant dietary carbohydrate and to a small degree on lipids?
Which organ does NOT belong to the primary digestive organs in the GI tract?
Which organ does NOT belong to the primary digestive organs in the GI tract?
Which of the following is considered an accessory digestive organ?
Which of the following is considered an accessory digestive organ?
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What is the role of the liver in the digestive system?
What is the role of the liver in the digestive system?
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What is the function of the salivary glands?
What is the function of the salivary glands?
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Where does absorption of nutrients mostly occur in the small intestine?
Where does absorption of nutrients mostly occur in the small intestine?
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What is the function of the pyloric sphincter in the stomach?
What is the function of the pyloric sphincter in the stomach?
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What protects intestinal cells from the harsh gut environment?
What protects intestinal cells from the harsh gut environment?
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What is the role of the lower esophageal sphincter (LES) during swallowing?
What is the role of the lower esophageal sphincter (LES) during swallowing?
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Study Notes
Gastrointestinal Tract Structure
- The GI tract is a long tube with an input (mouth) and output (anus) and specialized areas with direct input from associated organs (liver, pancreas, and gallbladder).
- Sphincters along the tract separate major sections, regulating the flow of food into the stomach and chyme out of the stomach and through the intestines.
Functional Anatomy of Digestive System
- The digestive system consists of the gastrointestinal tract (GI tract) and accessory organs that help in digestion and absorption.
- The GI tract is a tubular structure, approximately 30 feet long, extending from the mouth to the anus, with both ends open to the external environment.
Primary and Accessory Digestive Organs
- Primary digestive organs: mouth, pharynx, esophagus, stomach, small intestine, and large intestine, where actual digestion takes place.
- Accessory digestive organs: teeth, tongue, salivary glands, exocrine part of pancreas, liver, and gallbladder, which help primary digestive organs in digestion.
Mouth
- Mechanical digestion occurs through mastication (chewing), and chemical digestion begins on starch and lipids.
- Salivary glands secrete saliva, which buffers and digests food, and lubricates it for swallowing.
Esophagus
- The esophagus is a tube that passes through the chest and into the stomach, with relaxation of the upper esophageal sphincter allowing the bolus of food to enter.
- The lower esophageal sphincter (LES) relaxes to allow the bolus into the stomach.
Stomach
- The stomach is a pouch for food storage, secretion of digestive enzymes and hydrochloric acid (HCl), and mixing of food and digestive juices to make chyme.
- The pyloric sphincter regulates the entry of chyme into the small intestine.
Small Intestine
- The small intestine is composed of three sections: duodenum (∼1 foot long), jejunum (∼8 feet long), and ileum (∼10 feet long).
- Secretions from the liver, gallbladder, and pancreas enter the small intestine via the common bile duct and through the sphincter of Oddi.
- The small intestine has finger-like projections (villus brush border) that increase the surface area for absorption.
- There is only one layer of intestinal epithelial cells (enterocytes) between the lumen and the systemic blood supply.
- Enterocytes are vulnerable to the harsh environment of the gut lumen and need protection from intestinal buffers and mucus.
Digestion and Absorption in the Small Intestine
- The majority of digestion occurs in the jejunum by pancreatic enzymatic action.
- Absorption occurs along the small intestine, with most nutrients absorbed by the mid-jejunum.
- The terminal part of the ileum is the site of vitamin B12 absorption and recycling of bile.
Large Intestine
- The large intestine functions in dehydration of chyme to produce feces and storage.
- Chyme that remains in the tract leaves the small intestine through the ileocecal sphincter and moves into the large intestine.
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Description
Test your knowledge on the functional anatomy of the digestive system, including the specialized areas, organs, and sphincters along the gastrointestinal (GI) tract. Learn about the regulation of food flow from the mouth to the anus, and the role of associated organs like the liver, pancreas, and gallbladder.
