Small intestine

Definition

The small intestine is a long, coiled tube in the gastrointestinal tract where most digestion and absorption of nutrients occurs. It connects the stomach to the large intestine and is divided into three sections: the duodenum, jejunum, and ileum. This structure plays a crucial role in breaking down food with the help of digestive enzymes and facilitating the absorption of nutrients into the bloodstream.

5 Must Know Facts For Your Next Test

1. The small intestine is about 20 feet long and has a highly folded surface to maximize nutrient absorption.
2. It has a rich blood supply, allowing for efficient transport of absorbed nutrients into the bloodstream.
3. The small intestine produces its own enzymes, like lactase and maltase, to help break down sugars.
4. Peristalsis, a wave-like muscle contraction, helps move food through the small intestine for proper digestion and absorption.
5. The ileum, the final section of the small intestine, is particularly important for absorbing vitamin B12 and bile salts.

Review Questions

• How does the structure of the small intestine facilitate its function in digestion and absorption?
  • The small intestine's structure is designed for maximum efficiency in digestion and absorption. It has a large surface area due to its length and folds, as well as tiny finger-like projections called villi. These features allow for greater contact with nutrients and enhance absorption into the bloodstream. Additionally, the presence of specialized cells produces digestive enzymes that further assist in breaking down food.
• What role do pancreatic enzymes play in the digestive processes that occur in the small intestine?
  • Pancreatic enzymes are crucial for digesting macronutrients in the small intestine. They are secreted into the duodenum and work to break down proteins into amino acids, fats into fatty acids and glycerol, and carbohydrates into simple sugars. This enzymatic action ensures that nutrients are adequately processed before they enter the bloodstream for absorption. Without these enzymes, nutrient digestion would be significantly impaired.
• Evaluate how diseases affecting the small intestine can impact nutrient absorption and overall health.
  • Diseases such as celiac disease or Crohn's disease can severely affect the function of the small intestine by damaging its lining or disrupting its ability to absorb nutrients. This impairment can lead to malabsorption, resulting in deficiencies of essential vitamins and minerals, which may manifest as anemia, fatigue, or other health issues. Additionally, chronic inflammation can alter gut flora balance, further compounding health problems. The interconnectedness of digestion and nutrient absorption highlights how critical a healthy small intestine is for overall well-being.

Related terms

Duodenum: The first section of the small intestine, where most chemical digestion occurs through enzymes from the pancreas and bile from the liver.

Villi: Small finger-like projections lining the inner surface of the small intestine that increase surface area for absorption of nutrients.

Pancreatic enzymes: Digestive enzymes produced by the pancreas that aid in breaking down proteins, fats, and carbohydrates in the small intestine.