Small intestine

Definition

The small intestine is a long, coiled tube that connects the stomach to the large intestine and is crucial for digestion and nutrient absorption. It is where most of the digestion of food occurs, aided by enzymes and bile, allowing the body to absorb vitamins, minerals, and other nutrients effectively.

5 Must Know Facts For Your Next Test

1. The small intestine is approximately 20 feet long in adults and is divided into three sections: duodenum, jejunum, and ileum.
2. Digestive enzymes from the pancreas and bile from the liver enter the small intestine to aid in breaking down food particles.
3. Nutrient absorption occurs primarily in the jejunum and ileum, with over 90% of nutrients absorbed in this organ.
4. The small intestine's lining contains millions of villi and microvilli, which dramatically increase its surface area for efficient nutrient uptake.
5. The pH of the small intestine is slightly alkaline, usually around 7 to 8, which is optimal for enzyme activity during digestion.

Review Questions

• How does the structure of the small intestine facilitate its function in digestion and nutrient absorption?
  • The structure of the small intestine is specifically designed to maximize its efficiency in digestion and nutrient absorption. Its long length allows for more time for food to be broken down, while the presence of villi and microvilli increases the surface area significantly. This extensive surface area enables more nutrients to be absorbed as chyme moves through, ensuring that the body can take in vital vitamins and minerals effectively.
• Discuss the role of digestive enzymes and bile in the function of the small intestine.
  • Digestive enzymes and bile play critical roles in the small intestine's ability to process food. Enzymes from the pancreas help break down carbohydrates, proteins, and fats into smaller molecules that can be absorbed. Bile, produced by the liver and stored in the gallbladder, emulsifies fats, making them easier for enzymes to act on. This collaborative action ensures that food is properly digested and that nutrients can be efficiently absorbed through the intestinal walls.
• Evaluate how malfunctions in the small intestine can affect overall health and nutrition.
  • Malfunctions in the small intestine, such as celiac disease or Crohn's disease, can severely impact overall health by impairing nutrient absorption. When this part of the digestive system is compromised, it may lead to malnutrition, deficiencies in essential vitamins and minerals, and various gastrointestinal symptoms. As a result, individuals with these conditions often require dietary adjustments or supplements to manage their health effectively and ensure they receive adequate nutrition despite impaired absorption.

Related terms

duodenum: The first part of the small intestine, where the majority of chemical digestion takes place, receiving bile from the liver and pancreatic juices.

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

ileum: The final section of the small intestine that absorbs remaining nutrients and connects to the large intestine.