Anatomy of the Small Intestine

Small Intestine

Structure

• Long, thin, and winding tube, approximately 6.9 meters (23 feet) long
• Divided into three regions:
  1. Duodenum (25 cm / 10 in long)
  2. Jejunum (2.5 meters / 8.2 feet long)
  3. Ileum (3.5 meters / 11.5 feet long)
• Inner wall lined with finger-like projections called villi, increasing surface area
• Microvilli on the surface of epithelial cells further increase surface area

Function

• Primary site for nutrient absorption
• Breakdown and absorption of carbohydrates, proteins, and fats
• Houses a large population of immune cells, aiding in immune function
• Produces digestive enzymes and absorbs vitamins and minerals

Absorption

• Nutrients absorbed into bloodstream through the walls of the intestine
• Carbohydrates, proteins, and fats broken down into simpler molecules
• Absorbed nutrients transported to the liver for processing and distribution
• Vitamin and mineral absorption also occurs in the small intestine

Digestion

• Pancreatic juices and bile from the liver and gallbladder mix with food in the small intestine
• Pancreatic enzymes break down carbohydrates, proteins, and fats
• Bile emulsifies fats, increasing surface area for enzyme activity
• Digestion occurs in the duodenum, with the majority of nutrient absorption occurring in the jejunum

Anatomy

• Located below the stomach, in the abdominal cavity
• Connected to the stomach by the pyloric sphincter
• Ileocecal valve separates the small intestine from the large intestine
• Rich blood supply from the superior and inferior mesenteric arteries

Small Intestine Structure

• The small intestine is a long, thin, and winding tube, approximately 6.9 meters (23 feet) long
• It is divided into three regions: duodenum, jejunum, and ileum
• The duodenum is 25 cm (10 in) long, the jejunum is 2.5 meters (8.2 feet) long, and the ileum is 3.5 meters (11.5 feet) long
• The inner wall of the small intestine is lined with finger-like projections called villi, increasing the surface area
• Microvilli on the surface of epithelial cells further increase the surface area

Small Intestine Function

• The small intestine is the primary site for nutrient absorption
• It breaks down and absorbs carbohydrates, proteins, and fats
• The small intestine houses a large population of immune cells, aiding in immune function
• It produces digestive enzymes and absorbs vitamins and minerals

Absorption and Digestion

• Nutrients are absorbed into the bloodstream through the walls of the intestine
• Carbohydrates, proteins, and fats are broken down into simpler molecules
• Absorbed nutrients are transported to the liver for processing and distribution
• Vitamin and mineral absorption also occurs in the small intestine
• Pancreatic juices and bile from the liver and gallbladder mix with food in the small intestine
• Pancreatic enzymes break down carbohydrates, proteins, and fats
• Bile emulsifies fats, increasing surface area for enzyme activity

Anatomy

• The small intestine is located below the stomach, in the abdominal cavity
• It is connected to the stomach by the pyloric sphincter
• The ileocecal valve separates the small intestine from the large intestine
• The small intestine has a rich blood supply from the superior and inferior mesenteric arteries

Learn about the structure and function of the small intestine, including its length, regions, and role in nutrient absorption.