Small Intestine and Pancreas

Small IntestineSmall Intestine:-“small”= Small diameter (7m long)- Main site for digestion and absorption

Duodenum:

Small IntestineSmall Intestine:-“small”= Small diameter (7m long)- Main site for digestion and absorption

Duodenum: First 25-30cm of the smallIntestine. Where most of the digestion occurs.

Small Intestine & the Pancreas

Moving food from stomach to small intestine: Remember the food that comes from the stomach is mixed with hydrochloric acid and pepsin. = dangerous for small intestine

Solution: -Release bicarbonate ions to neutralize acids

Controlling Bicarbonate Release1) Stomach acid and food moves into the small

intestine 2) Prosecretin is converted to secretin by acid

Controlling Bicarbonate Release1) Stomach acid and food moves into the small

intestine 2) Prosecretin is converted to secretin by acid3) Secretin is absorbed into the bloodstream4) As blood moves to pancreas the sectretin in

the blood causes the pancreas to release bicarbonate into the small intestine

Controlling Bicarbonate Release1) Stomach acid and food moves into the small

intestine 2) Prosecretin is converted to secretin by acid3) Secretin is absorbed into the bloodstream4) As blood moves to pancreas the sectretin in the

blood causes the pancreas to release bicarbonate into the small intestine

5) Bicarbonate neutralizes the acid to protect the walls of the small intestine

pH changes from 2 96) The new basic pH causes pepsin to become

inactive so it won’t digest the intestinal wall

Pancreas and the breakdown of food

Food: 3 main groups-Protein-Carbohydrates-Lipids (fats)

Breakdown of Protein:

Remember at this point protein is only broken down into short chains

Enterokinase: An enzyme in the small intestine that activates trypsinogen converting it into tripsin

Trypsin:

Erepsins (peptidases):

Breakdown of Protein:

Remember at this point protein is only broken down into short chains

Enterokinase: An enzyme in the small intestine that activates trypsinogen converting it into tripsin

Trypsin: Breaks down the peptone chains into shorter peptone chains

Erepsins (peptidases):

Breakdown of Protein:

Remember at this point protein is only broken down into short chains

Enterokinase: An enzyme in the small intestine that activates trypsinogen converting it into tripsin

Trypsin: Breaks down the peptone chains into shorter peptone chains

Erepsins (peptidases): Break down the shorter peptone chains into individual amino acids

Breakdown of Sugar (Carbohydrates)

Amylase (also released by salivary glands): Released by the pancreas. Breaks down the smaller sugar chains into disaccharides (di = 2. Saccharide = sugar)

Disaccharase enzymes:

Breakdown of Sugar (Carbohydrates)

Amylase (also released by salivary glands): Released by the pancreas. Breaks down the smaller sugar chains into disaccharides (di = 2. Saccharide = sugar)

Disaccharase enzymes: Break down disaccharides into glucose and fructose

Eg. Maltase breaks down maltose into 2 glucose molecules

Breakdown of Lipids (Fats)

Lipase: Lipid digesting enzymes released by the pancreas.

Two types of Lipase-Pancreatic lipase:

-Cholesterol lipase:

Breakdown of Lipids (Fats)

Lipase: Lipid digesting enzymes released by the pancreas.

Two types of Lipase-Pancreatic lipase: breaks down triglycerides into

fatty acids and glycerol-Cholesterol lipase: breaks off one fatty acid and

converts it into cholesterol

Liver and Gall Bladder

Liver: Has three functions related to digestion

1) Create bile salts2) Storage of nutrients3) Breakdown of

toxins

Bile Salts

Location of Bile Salts: Formed in the liver and collected in the Gall bladder where the excess water is removed (becomes more concentrated). They enter the duodenum via the bile duct.

Controlling the release of Bile Salts

1) Fats present in the small intestine2) Fats cause the release of Cholecystokinin

(CCK) a hormone.

Controlling the release of Bile Salts

1) Fats present in the small intestine2) Fats cause the release of Cholecystokinin

(CCK) a hormone. 3) CCK moves into blood 4) Blood reaches gall bladder5) Here CCK triggers the release of bile salts

from the gall bladder to the small intestine

Controlling the release of Bile Salts

1) Fats present in the small intestine2) Fats cause the release of Cholecystokinin (CCK) a

hormone. 3) CCK moves into blood 4) Blood reaches gall bladder5) Here CCK triggers the release of bile salts from the gall

bladder to the small intestine6) Once in the small intestine the bile salts break down

the large fat droplets into smaller drops (just like dish soap) = emulsification

7) This leaves a larger surface for pancreatic lipase to get at the fat

Gallstones and jaundice

Liver as a Storage organ

Storage in Liver: Stores glycogen and vitamins (A, B12, D)

Breakdown of Toxins: Breaks down harmful substances into less harmful chemicals that can be dissolved into blood and excreted in urine. This process does damage liver tissue

Eg. alcohol

y

g

j

jk

Problems with Detoxification

Problem with detoxification: The liver cells that are damaged when they try to breakdown toxins are replaced by connective tissue and fat.

= Erode the liver you lose the cells that perform functions needed by the body

This leads to Cirrhosis

Diagnostic Questions

• Symptom: