Small intestine

Definition

The small intestine is a crucial part of the digestive system, primarily responsible for nutrient absorption and digestion. It follows the stomach and consists of three main sections: the duodenum, jejunum, and ileum, each playing distinct roles in processing food and absorbing nutrients into the bloodstream. Its extensive surface area, created by villi and microvilli, enhances its ability to efficiently absorb essential nutrients and minerals from the chyme.

5 Must Know Facts For Your Next Test

1. The small intestine is about 20 feet long in adults, making it the longest part of the gastrointestinal tract.
2. The primary function of the small intestine is to break down food using enzymes and to absorb nutrients into the bloodstream.
3. The surface area of the small intestine is increased significantly by folds, villi, and microvilli, which together maximize absorption efficiency.
4. The secretion of digestive enzymes from the pancreas and bile from the liver occurs primarily in the duodenum, aiding in fat and carbohydrate digestion.
5. Movement through the small intestine is facilitated by peristalsis, a series of wave-like muscle contractions that propel food along the digestive tract.

Review Questions

• How does the structure of the small intestine facilitate its function in digestion and absorption?
  • The structure of the small intestine is specifically designed to enhance its function in digestion and absorption. Its length of about 20 feet provides ample space for nutrient breakdown and absorption. Additionally, the inner walls are lined with folds, villi, and microvilli that drastically increase surface area. This design allows for a larger area for digestive enzymes to work on food particles, leading to efficient nutrient absorption into the bloodstream.
• Discuss the roles of bile and pancreatic enzymes in the small intestine's digestive process.
  • Bile and pancreatic enzymes play critical roles in digestion within the small intestine. Bile, produced by the liver and stored in the gallbladder, helps emulsify fats, breaking them into smaller droplets that are easier for enzymes to digest. Pancreatic enzymes are secreted into the duodenum and include amylase for carbohydrates, lipase for fats, and proteases for proteins. Together, these substances facilitate chemical digestion by breaking down complex food molecules into simpler forms that can be absorbed effectively by the intestinal lining.
• Evaluate how disorders affecting the small intestine can impact overall health and nutrient absorption.
  • Disorders affecting the small intestine, such as celiac disease or Crohn's disease, can significantly impact overall health and nutrient absorption. In celiac disease, for instance, ingestion of gluten leads to damage of the intestinal lining, resulting in malabsorption of vital nutrients like vitamins and minerals. This can lead to deficiencies that affect many bodily functions, such as weakened immunity or poor bone health. Similarly, Crohn's disease causes inflammation which can disrupt normal digestive processes and lead to further complications like weight loss or anemia. Overall, maintaining a healthy small intestine is essential for proper nutrition and overall well-being.

Related terms

duodenum:

The first segment of the small intestine where most chemical digestion occurs, particularly with the help of bile and pancreatic enzymes.

villi:

Tiny, finger-like projections lining the inner wall of the small intestine that increase its surface area for maximum nutrient absorption.

ileocecal valve:

A valve located at the junction of the small intestine and large intestine that regulates the flow of material between these two parts of the gastrointestinal tract.