SMALL INTESTINE

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

MacronutrientsCarbohydrates, Lipids and ProteinsMany bonds, longer to break down, may

build up

Nutritional Terms

MicronutrientsVitamins, mineralsSmaller 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