Digestion and Absorption

Digestion and Absorption

* Introduction
Digestion is defined as the breakdown of nutrients We consume: Proteins Carbohydrates Fats These are broken down into their simplest forms

* Mouth

Mechanical digestion: the act of chewingCarbohydrate digestion begins hereSaliva moistens food and contains the enzyme Salivary Amylase – breaks down complex carbs into simple sugarsChemical Digestion: enzymes breaking down carbohydratesBall of moistened, partially digested food, known as the “BOLUS”, moves into the esophagus

Digestion and Absorption

Carbohydrates, proteins and lipids are digested and absorbed in the small intestine Absorption The surface area for absorption in the small intestine is greatly increased by the presence of the brush border Pathways of Absorption - cellular - paracellular

Structure of intestinal wall

Longitudinal folds (finger-like villi) - longest in duodenum & shortest in ileum - increases surface area 600 fold The significance of villi & microvilli - increase the surface area - maximizing the exposure of nutrients to digestive enzymes