Small Intestine  Structure that extends from pyloric Sphincter to the beginnings of large intestine

Other Functions  Receives secretions from liver and pancreas  Moves Chyme around for better absorption

Parts of Small Intestine  Consists of 3 portions: Duodenum, Jejunum, ileum

Duodenum  ~ 25 cm long, first portion  It neutralizes stomach acids and breaks down carbohydrates and fats.

Jejunum  Main section, ~ 15 feet  Responsible for absorption of most nutrients, except water

Ileum  Last section, ~ 6 feet  Responsible for absorbing water and vitamins

Intestinal Villi  Found in small intestine  Consists of a layer of simple columnar epithelium  Contains Lacteal, which is a core of blood capillaries and nerve fibers that absorbs nutrients

Enzymes  Enzymes embedded in membrane of Villi, used to break down food molecules  Peptidas- splits proteins down to amino acids  Sucrase, maltase, lactace- splits double sugars (disaccharides) into simple sugars (monosacchardies)  Lipase- splits lipids into single carbs

Passive Transport  Absorption of certain nutrients into villi without energy. Slow process  Concentration is greater outside the villi

Active Transport  Much faster process, requires energy  With help of carrier proteins called ATPase, Amino acid, monosaccharides, and fatty acids get absorbed

Carbohydrates and Protein Absorption  Soluble in water  Gets broken down and absorbed directly into blood stream

Fat Absorption  Insoluble in water, cannot be absorbed directly  Carrier protein take them to Lacteal where it passes through lymphatic system

Nutritional Terms  Macronutrients Carbohydrates, Lipids and Proteins Many bonds, longer to break down, may build up

Nutritional Terms  Micronutrients Vitamins, minerals Smaller bonds, easier to absorb

Free Radicals  When body takes in oxygen to pair and break down food, 1% of cells will get damaged in the process, creating “Free Radicals”  Very unstable, will steal from other cells to replace molecules.  When stolen, Free Radicals change DNA of cells, creating room for disease  Smoking is a great source of Free Radicals, can lead to cancer

Antioxidants  Chemicals that block free radicals from damaging other cells  Donate extra electrons Example: Vitamin E, Flavonoids (Nuts, seeds, fish oil, green tea