Small intestine

Definition

The small intestine is a long, coiled tube in the digestive system where most of the digestion and absorption of nutrients occurs. It connects the stomach to the large intestine and plays a crucial role in processing food by breaking it down with enzymes and absorbing essential nutrients into the bloodstream.

5 Must Know Facts For Your Next Test

1. The small intestine is approximately 20 feet long in adults, making it the longest part of the digestive tract.
2. It is divided into three main sections: the duodenum, jejunum, and ileum, each having distinct functions in digestion and absorption.
3. Nutrient absorption primarily occurs in the jejunum and ileum, where digested food is taken up into the bloodstream via villi and microvilli.
4. The small intestine also has a significant role in immune function, as it contains gut-associated lymphoid tissue (GALT) that helps protect against pathogens.
5. The pH level in the small intestine is slightly alkaline, which helps optimize enzyme activity for digesting carbohydrates, proteins, and fats.

Review Questions

• How does the structure of the small intestine facilitate its function in nutrient absorption?
  • The small intestine's structure significantly aids its function in nutrient absorption through features like villi and microvilli, which increase the surface area available for absorption. This extensive surface area allows for more efficient uptake of nutrients from digested food. Additionally, the coiled nature of the small intestine provides ample space for enzymes to act on chyme, ensuring that nutrients are broken down and absorbed effectively as they pass through.
• Analyze the differences between the three sections of the small intestine regarding their roles in digestion.
  • The small intestine consists of three sections: duodenum, jejunum, and ileum, each with specific roles. The duodenum is primarily involved in chemical digestion, receiving bile and pancreatic juices to break down food. The jejunum is where most nutrient absorption occurs, equipped with numerous villi to maximize this process. Finally, the ileum absorbs remaining nutrients and bile salts before they are recycled back to the liver. Each section contributes uniquely to overall digestive efficiency.
• Evaluate how dysfunctions in the small intestine can impact overall health and nutrition.
  • Dysfunctions in the small intestine, such as celiac disease or Crohn's disease, can severely impact overall health by hindering nutrient absorption. When nutrients cannot be adequately absorbed, it leads to deficiencies that can cause various health issues, including weakened immune function, fatigue, and growth problems in children. Moreover, chronic inflammation or damage to the intestinal lining can disrupt gut health and lead to complications such as malnutrition or increased susceptibility to infections, demonstrating how critical proper small intestine function is for maintaining health.

Related terms

Duodenum: The first section of the small intestine, where the majority of chemical digestion occurs, receiving bile from the liver and pancreatic juice from the pancreas.

Villi: Tiny, finger-like projections lining the walls of the small intestine that increase surface area for maximum nutrient absorption.

Chyme: The semi-liquid mass of partially digested food that passes from the stomach into the small intestine for further digestion and absorption.