1. Today's objectives
Explain where different nutrients (proteins, carbohydrates, and lipids) are broken down in the digestive system
Connect the digestive system with the process of maintaining homeostasis.
Explain where the majority of digestion and all of absorption occurs in the human body

2. The Small Intestine
The small intestine is the major site for digestion and absorption of nutrients.
98% of digestion and 100% of absorption of nutrients occurs in the small intestines.
Small intestine is made up of 3 parts
Duodenum
Jejunum
Ileum

3. From Stomach to Duodenum
Chyme – Liquefied food
Acidic Chyme is pushed from the lower part of the stomach through the pyloric sphincter into the Duodenum (first part of small intestines).
The stomach empties over a 1 to 2 hour period.

6. Small Intestines (Doudenum)
Chyme is pushed out of the stomach into the small intestines. The acid chyme simulates the Liver and the Pancreas.
The pancreas secretes digestive enzymes and stomach acid-neutralizing sodium bicarbonate.(2 pH  8 pH)
Enzymes - Lipase, Amylase, Trypsin
The liver produces bile, which is stored in the gall bladder before entering the bile duct into the duodenum.
Bile emulsifies fats (breaks fats into little pieces)

8. Carbohydrate Digestion step by step
The chyme is pushed into your small intestines (duodenum) which triggers the release of Pancreatic juice from the pancreas
Amylase is one of the enzymes in the pancreatic juice which breaks down Polysaccharides into disaccharides
Finally the intestinal glands release intestinal juice which includes the enzyme maltase. (jejunum)
Maltase breaks down the disaccharides into monosaccharide which are absorbed by the blood stream.
Monosaccharides are absorbed into blood steam and carried to the cells (ileum)

10. Protein Digestion Step by Step
Proteins begin to be digested by Pepsin in the stomach while being liquefied by the acid HCL.
The chyme is pushed into your small intestines (duodenum) which triggers the release of Pancreatic juice from the pancreas
Trypsin is one of the enzymes in pancreatic juice which continues the breakdown of proteins into Peptide bonds
Finally the intestinal glands release intestinal juice which includes peptidase which breaks peptide bonds into amino acids. (jejunum)
Those amino acids are absorbed into the blood steam and carried to the cells (ileum)

11. Digestion of Lipids
The chyme is pushed into your small intestines (duodenum) which triggers the release of Pancreatic juice from the pancreas and bile from your gall bladder.
Bile emulsifies (chews) the lipids to incease surface area
Lipase that is found in pancreatic juice hydrolyses lipids into a glycerol and 3 fatty acids
The products are absorbed by the small intestines and carried to the cells for use. (jejunum and ileum)

13. Enzymes and were they are Used
Salivary amalyase (starch  sugar) MOUTH
Pepsin (proteins  Polypeptides) STOMACH
Bile (emulisification of lipids) DUODENUM
Pancreatic Juice DOUDENUM
Amylase (polysacchardies  disacchardies)
Trypsin (peptones and proteoses  peptides)
Lipase (lipids  gylcerol and fatty acids)
Intestinal Juice JUJUMIN and ILEUM
Peptidase (peptides  amino acids)
Maltase (Disaccharide  Monosacchardies)

14. Villi and MircoVilli
The small intestine is lined with vill and microvilli
The purpose of villi and microvilli are to increase surface area in the small intestines. Increase the speed at which nutrients are absorbed
The small intestines a 6 meter long tube has a surface area of 300 square meters or the surface area of a m long tube.
Each villus has a capillary network supplied by a small artery. Absorbed nutrients pass through the microvilli into the capillary (blood stream), usually by passive transport (diffusion).

17. The Large Intestine
The large intestine is made up by the cecum, appendix, colon, and rectum.
Digested food is pushed from the small intestines into the large intestine.
No digestion takes place in the large intestines
Material in the large intestine is mostly indigestible residue and liquid.
Water, and salts are absorbed, the remaining contents form feces (mostly cellulose, bacteria, bilirubin).
Bacteria in the large intestine, such as E. coli, produce vitamins (including vitamin K) that are absorbed.

18. There are 3 parts to the Colon
Ascending Colon
Transverse Colon
Descending Colon

19. The Liver and Gall Bladder
The Liver makes Bile and stores it in the gall bladder.
The Gall bladder sends bile to the small intestine when the acidic chyme from the stomach. Bile contains bile salts, which emulsify fats, making them susceptible to enzymatic breakdown.
The liver also stores excess glucose in the form of glycogen.

21. The Pancreas
When the acidic chyme is pushed out of the stomach into the small intestines. IT simulates the pancreas to send pancreatic juice, which neutralizes the chyme, begins digestions of Carbohydrates, Lipids and continues digestion of protein.
Pancreatic juice also contains Lipase which digested emulsified Lipids

23. Stomach HCl Hydrochloric acid does not directly function in digestion:
it kills microorganisms that cause food poisoning.
lowers the stomach pH to between 1.5 and 2.5
activates pepsinogen (to pepsin) Pepsin is an enzyme that starts protein digestion.
HCl inhibits further carbohydrate breakdown started by salivary amylase.
HCl aids in the liquefaction of masticated food
Epithelial cells secrete mucus that forms a protective barrier between the cells lining the inside of the stomach and the stomach acids.

24. Ulcers
Peptic ulcers result when the protective mucus fails and the HCl eats away at the lining of the stomach.
Bleeding ulcers result when tissue damage is so severe that bleeding occurs into the stomach.
Perforated ulcers are life-threatening situations where a hole has formed in the stomach wall.
At least 90% of all peptic ulcers are caused by Helicobacter pylori (bacteria). Other factors, including stress and ibuprofen, can also produce ulcers.