Digestion & Digestion & AbsorptionAbsorption

To the small intestines….and beyond….

So far…mechanical and chemical digestion in the mouth and stomach leave us with a “liquidy” substance called CHYME.

This continues to the small intestine to be further digested and absorbed…..

• Important digestive and absorptive functions– Secretions and buffers provided by pancreas,

liver, gall bladder– Most chemical digestion takes place here– 7m in length, 2.5cm in diameter

• Three subdivisions:– Duodenum (most digestion occurs here)– Jejunum – Ileum

Small intestine

Regions of the Small Intestine

In the small intestine digestion continues….

1.Carbohydrates are completely broken down into simple sugars by enzymes that are specific to the carb. Maltase to break down maltose, lactase to break down lactose…

Chemistry of Digestion: Carbohydrates

2.Lipids (fats) are emulsified by bile salts, then, broken down by special enzymes into molecules of fatty acids and glycerol or phospholipids

3. Proteins are broken down into smaller proteins and into individual amino acids.

Nutrient absorption:

• Most nutrient absorption occurs in the small intestine

• The walls have long finger like tubes called villi which increase surface area for absorption

The Intestinal Wall

Organs that add digestive juices:

Through the common bile duct• Pancreas• Liver/

gall bladder

Pancreas:

• Secretes bicarbonate to neutralize stomach acid

• Secretes insulin to keep blood glucose levels in equilibrium (homeostasis)

• Secretes enzymes that break down proteins

Liver/ Gall Bladder

• Liver produces bile that speeds up fat digestion.

• When the stomach is empty, the bile is stored in the gall bladder.

• Bile breaks down large globules of fats.

Main Functions of the liver:

1. Synthesis: produce bile salts2. Storage: glucose to glycogen 3. Detoxification: convert harmful

compounds (i.e. alcohol) to less harmful substances to be excreted

Functions of the large intestine

1. Reabsorb water and compact material into feces

2. Absorb vitamins produced by bacteria

3. Store fecal matter prior to defecation

The Whole Thing…

Excretion:

• What goes in must come out…