Digestion notes
DIGESTIVE SYSTEM
Digestion:
- The breakdown of food into small soluble molecules
- occurs physically, chemically.
Absorption:
- the taking into the body of the specific compounds.
Elimination:
- The expulsion of materials not absorbed (taken into) the body.
- Excretion
I1. LOCATIONS OF PARTS.
Digestion:
- The breakdown of food into small soluble molecules
- occurs physically, chemically.
Absorption:
- the taking into the body of the specific compounds.
Elimination:
- The expulsion of materials not absorbed (taken into) the body.
- Excretion
I1. LOCATIONS OF PARTS.
Function for each
- oral cavity (mouth) - physical digestion
-#8 pharynx - common passage for digestion and respiration systems
- tongue, teeth - physical digestion and formation of a bolus (food ball)
- salivary glands - lubricate bolus, begin starch chemical digestion (salivary amylse)
-#9 epiglotis - direct food ball into esophagus and not in trachea
-#7 esophagus - tube through which food passes into stomach
-#6 stomach - physical digestion (churns) and chemical digestion (protein)
-#10 cardiac sphincter - muscular ring acts as valve to contain food in stomach (top)
-#3 duodenum - 1st 15 cm of small intestine. Bile and pancreatic ducts enter here
-#11 pyloric sphincter - muscular ring acts as valve to contain food in stomach
-#14 small intestine - chemical digestion of all foods, absorbtion of monamers
-#2 liver - produces bile (also helps maintain constant blood glucose)
-#13 gall bladder - stores bile which emulsifies fats
-#5 pancreas - neutralizes pH (NaHCO3), secretes several enzymes
-#4 large intestine (colon) - absorbtion of H2O, cultures E. coli
-#12 appendix - immune system
- rectum - last 20 cm of large intestine
- anus - undigested material passes out here
I2. DIGESTIVE ENZYMES
- These enzymes break down food into small molecules which are then absorbed.
Salivary Amylase:
Source: Salivary glands
pH: Neutral
Food digested: Starch
Product: Maltose (a disaccharide)
Pepsin:
Source: Stomach
pH: Acidic (pH 3.5)
Food Digested: Protein
Product: Peptides (short amino acid chains)
Note: Secreted as Pepsinogen , an inactive form. A low pH converts pepsinogen into the active pepsin
Pancreatic Amylase:
Source: Pancreas
pH: Basic (pH 7.5)
Food Digested: Starch
Product: Maltose
Trypsin:
Source: Pancreas
pH: Basic (pH 7.5)
Food Digested: Protein
Product: Peptides (short amino acid chains)
Lipase:
Source: Pancreas
pH: Basic (pH 7.5)
Food Digested: Fat
Product: Glycerol, Fatty Acids
Peptidases: (many different ones)
Source: Small intestine
pH: Basic (pH 7.5)
Food Digested: Peptides
Product: Amino Acids
Maltase:
Source: Small intestine
pH: Basic (pH 7.5)
Food Digested: Maltose
Product: Glucose
Nuclease:
Source: Small intestine and Pancreas
pH: Basic (ph 7.5)
Food Digested: Nucleic Acid (DNA & RNA)
Product: Nucleotides (A,C,G,T & U)
I3. SWALLOWING AND PERISTALSIS
- Swallowing involves the formation of a bolus (food ball) which is fromed by the mouth, teeth, tongue, and saliva from the salivary glands. When swallowing the esophagus moves the bolus into the stomach by peristalsis.
- peristalsis is a rythmic cotraction of the esophagus and intestine
- muscle contractions (smooth muscle) run along the tube and push food material in one direction
- oral cavity (mouth) - physical digestion
-#8 pharynx - common passage for digestion and respiration systems
- tongue, teeth - physical digestion and formation of a bolus (food ball)
- salivary glands - lubricate bolus, begin starch chemical digestion (salivary amylse)
-#9 epiglotis - direct food ball into esophagus and not in trachea
-#7 esophagus - tube through which food passes into stomach
-#6 stomach - physical digestion (churns) and chemical digestion (protein)
-#10 cardiac sphincter - muscular ring acts as valve to contain food in stomach (top)
-#3 duodenum - 1st 15 cm of small intestine. Bile and pancreatic ducts enter here
-#11 pyloric sphincter - muscular ring acts as valve to contain food in stomach
-#14 small intestine - chemical digestion of all foods, absorbtion of monamers
-#2 liver - produces bile (also helps maintain constant blood glucose)
-#13 gall bladder - stores bile which emulsifies fats
-#5 pancreas - neutralizes pH (NaHCO3), secretes several enzymes
-#4 large intestine (colon) - absorbtion of H2O, cultures E. coli
-#12 appendix - immune system
- rectum - last 20 cm of large intestine
- anus - undigested material passes out here
I2. DIGESTIVE ENZYMES
- These enzymes break down food into small molecules which are then absorbed.
Salivary Amylase:
Source: Salivary glands
pH: Neutral
Food digested: Starch
Product: Maltose (a disaccharide)
Pepsin:
Source: Stomach
pH: Acidic (pH 3.5)
Food Digested: Protein
Product: Peptides (short amino acid chains)
Note: Secreted as Pepsinogen , an inactive form. A low pH converts pepsinogen into the active pepsin
Pancreatic Amylase:
Source: Pancreas
pH: Basic (pH 7.5)
Food Digested: Starch
Product: Maltose
Trypsin:
Source: Pancreas
pH: Basic (pH 7.5)
Food Digested: Protein
Product: Peptides (short amino acid chains)
Lipase:
Source: Pancreas
pH: Basic (pH 7.5)
Food Digested: Fat
Product: Glycerol, Fatty Acids
Peptidases: (many different ones)
Source: Small intestine
pH: Basic (pH 7.5)
Food Digested: Peptides
Product: Amino Acids
Maltase:
Source: Small intestine
pH: Basic (pH 7.5)
Food Digested: Maltose
Product: Glucose
Nuclease:
Source: Small intestine and Pancreas
pH: Basic (ph 7.5)
Food Digested: Nucleic Acid (DNA & RNA)
Product: Nucleotides (A,C,G,T & U)
I3. SWALLOWING AND PERISTALSIS
- Swallowing involves the formation of a bolus (food ball) which is fromed by the mouth, teeth, tongue, and saliva from the salivary glands. When swallowing the esophagus moves the bolus into the stomach by peristalsis.
- peristalsis is a rythmic cotraction of the esophagus and intestine
- muscle contractions (smooth muscle) run along the tube and push food material in one direction
Peristalsis
I4. GASTRIC, PANCREATIC, AND INTESTINAL JUICES
Salivary Glands:
- Saliva: H2O, mucus
- lubrication of food
- formation of a bolus (food ball)
- (salivary amalyse -- starch digestion)
Stomach: - Gastric juice
- water (for hydrolysis)
- Pepsinogen (inactive form of the enzyme Pepsin)
- HCl (Hydrochloric acid)
- lowers pH
- to activate Pepsin which digests large proteins to small amino acid chains (peptides)
- food becomes semi liquid mass called acid chyme
Pancreas: - Pancreatic juice
- Sodium Bicarbonate: (Baking Soda)
- very important in neutralizing stomach acid to give a slightly basic pH in intestine. (pH 3.5 in stomach to pH 7.5 in intestine)
- Enzymes:
- Pancreatic Amylase
- Trypsin
- Lipase
- Nuclease (digests DNA & RNA to nucleotides)
Small intestine (including duodenum)
Accessory glands (food does not directly pass through them)
- bile is secreted from the gallbladder into the duodenum
- pancreatic juice enters into the duodenum
Enzymes
- Maltase
- Peptidases
- Nucleases
I5. INSULIN (and Glucagon)
The hormone Insulin is produced by cells in the Pancreas called islets of Langerhans. Insulin acts upon the cell membranes of most cells andopens the protein gates in the membranes, allowing glucose to enter the cells from the blood. This has the affect of lowering blood sugar. Insulin also stimulates the liver and muscles to convert glucose to glycogen, as well as promoting the formation of fats and proteins.
A second hormone produced by the same cells called Glucagon does just the opposite of glucose, so will increase blood glucose levels.
I6. BILE
The liver is connected to the intestines (villi) by the Hepatic portal vein which carries blood rich in foods to the liver. The liver acts as the gatekeeper to the blood by keeping levels of various foods in the blood (Hepatic vein) constant.
An important digestive function of the Liver
- secretes bile , which is stored in the gall bladder- green fluid
- breakdown fluid of hemoglobin
- emulsifies fats
- breaks fat drops into tiny droplets which are homogeneous .
- stay in suspension.
- increases surface are of the fat droplets for Lipase to work on.
I7. THE 6 FUNCTIONS OF THE LIVER:
I9. SMALL INTESTINE
I4. GASTRIC, PANCREATIC, AND INTESTINAL JUICES
Salivary Glands:
- Saliva: H2O, mucus
- lubrication of food
- formation of a bolus (food ball)
- (salivary amalyse -- starch digestion)
Stomach: - Gastric juice
- water (for hydrolysis)
- Pepsinogen (inactive form of the enzyme Pepsin)
- HCl (Hydrochloric acid)
- lowers pH
- to activate Pepsin which digests large proteins to small amino acid chains (peptides)
- food becomes semi liquid mass called acid chyme
Pancreas: - Pancreatic juice
- Sodium Bicarbonate: (Baking Soda)
- very important in neutralizing stomach acid to give a slightly basic pH in intestine. (pH 3.5 in stomach to pH 7.5 in intestine)
- Enzymes:
- Pancreatic Amylase
- Trypsin
- Lipase
- Nuclease (digests DNA & RNA to nucleotides)
Small intestine (including duodenum)
Accessory glands (food does not directly pass through them)
- bile is secreted from the gallbladder into the duodenum
- pancreatic juice enters into the duodenum
Enzymes
- Maltase
- Peptidases
- Nucleases
I5. INSULIN (and Glucagon)
The hormone Insulin is produced by cells in the Pancreas called islets of Langerhans. Insulin acts upon the cell membranes of most cells andopens the protein gates in the membranes, allowing glucose to enter the cells from the blood. This has the affect of lowering blood sugar. Insulin also stimulates the liver and muscles to convert glucose to glycogen, as well as promoting the formation of fats and proteins.
A second hormone produced by the same cells called Glucagon does just the opposite of glucose, so will increase blood glucose levels.
I6. BILE
The liver is connected to the intestines (villi) by the Hepatic portal vein which carries blood rich in foods to the liver. The liver acts as the gatekeeper to the blood by keeping levels of various foods in the blood (Hepatic vein) constant.
An important digestive function of the Liver
- secretes bile , which is stored in the gall bladder- green fluid
- breakdown fluid of hemoglobin
- emulsifies fats
- breaks fat drops into tiny droplets which are homogeneous .
- stay in suspension.
- increases surface are of the fat droplets for Lipase to work on.
I7. THE 6 FUNCTIONS OF THE LIVER:
- It removes poisonous substances (detoxifies blood)
- Stores glucose in the form of Glycogen . Converts glycogen to glucose when blood sugar levels drop.
- Destroys old red blood cells
- (converts hemoglobin to bile)
- stores bile in gall bladder to be used for fat emulsification.
- Produces urea from breakdown product of amino acids
- urea: nitrogenous waste
- Makes blood proteins
- Converts amino acids to glucose if necessary
- "Gluconeogenesis"
I9. SMALL INTESTINE
- 6 meters in length
- First 15cm is called Duodenum
- Produces digestive enzymes
- lactase, peptidases, maltase, nucleases
- Most important function: Absorption
- Structure:
- walls highly convoluted
- to increase surface area
- covered with villi
- tiny fingerlike projections
- gives small intestine large surface area
- Villi:
- absorbtion takes place through the collumnar cells. This involves active transport and requires much energy.
- sugar and amino acids are absorbed by the capillaries
- glycerol and fatty acids absorbed by the lymph lacteals
I10. E. coli AND THE LARGE INTESTINE
- includes the colon and rectum
Colon
- reabsorbtion of water
- 4/5 of large intestine
- also has a large pop. of E. coli bacteria which digest some undigestable material and produce:
a) gas (farts)
b) amino acids
c) vitamins
d) growth factors (proteins that stimulate cell growth)
- First 15cm is called Duodenum
- Produces digestive enzymes
- lactase, peptidases, maltase, nucleases
- Most important function: Absorption
- Structure:
- walls highly convoluted
- to increase surface area
- covered with villi
- tiny fingerlike projections
- gives small intestine large surface area
- Villi:
- absorbtion takes place through the collumnar cells. This involves active transport and requires much energy.
- sugar and amino acids are absorbed by the capillaries
- glycerol and fatty acids absorbed by the lymph lacteals
I10. E. coli AND THE LARGE INTESTINE
- includes the colon and rectum
Colon
- reabsorbtion of water
- 4/5 of large intestine
- also has a large pop. of E. coli bacteria which digest some undigestable material and produce:
a) gas (farts)
b) amino acids
c) vitamins
d) growth factors (proteins that stimulate cell growth)