Digestive

Question 1

Digestion Time:

Answer 1

6-8 hours in stomach, SI

Large Intestine- ~ 40 hours (33 for men, children, 47 for women)

Question 2

Alimentary canal

Answer 2

§ Continuous hollow tube

Mouth, pharynx, esophagus, stomach, SI, LI, anus

Question 3

Functions of the Salivary Glands:

Answer 3

• Lubrication/binding
• Solubilization of dry food
• Oral hygiene- flushes away debris
• Begins starch digestion via salivary amylases
• Alkaline buffering
• Evaporative cooling
        Important for dogs

Question 4

Mastication (Chewing):

Answer 4

• Teeth
• Hardest structures in the body
	○ 20 deciduous
	○ 32 secondary 
• Incisors
	§ Rip and cut
• Canines
	§ Tear and pierce
• Premolars
	§ Grind and shear
• Molars
        Grinds

Question 5

Deglutition (Swallowing):

Answer 5

• Oral, pharyngeal, esophageal
• Requires 25 pairs of muscles in the mouth, pharynx, larynx, upper esophagus
§ Mouth, pharynx and upper esophagus are innervated by somatic motor neurons
Middle and lower esophagus are innervated by autonomic neurons

Question 6

Peptic Ulcers:

Answer 6

• Erosions of the mucosa can lead to peptic ulcers (stomach digests itself)
• Result of infection of the GT tract in ~50% of adults worldwide
• Nobel prize win for recognizing that that peptic ulcers are due to common bacteria Hlicobacter pylori degrading the mucosal membrane, rather than due to spicy food
Treat with antibiotics

Question 7

Duodenum

Answer 7

§ First 25cm

Mucous secretion, receives pancreatic secretions and bile from the liver

Question 8

Jejunum

Answer 8

§ 1m in length

Numerous folds and villi

Question 9

Ileum

Answer 9

§ Last 2m
§ Fewer folds/villi than jejunum
§ Absorbs primarily bile salts, water, and electrolytes
§ Contains Peyer’s patches (aggregates of lymph nodes)
Empties into the large intestine via the ilieocecal valce

Question 10

Goblet cells

Answer 10

Secrete mucus in SI

Question 11

Intestial crypts

Answer 11

Crypts of Lieberkuhn

Replace columnar epithelial cells (constant turnover)

Question 12

Paneth cells

Answer 12

Base of crypts

Secrtee antibacterial molecules to protect intestine from inflammation (lysozymes, antimicrobial peptides)

Question 13

Sucrase

Answer 13

Sucrose-> glucose + fructose

Question 14

Maltase

Answer 14

Maltose -> glucose

Question 15

Lactase

Answer 15

Lactose-> glucose, galactose

Question 16

Aminopeptidase

Answer 16

Cleaves polypeptides

Question 17

Enterokinase

Answer 17

Activates trypsin and indirectly other pancreatic enzymes

Question 18

Alkaline Phosphatase

Answer 18

Removes phosphate groups from organic molecules

Question 19

Pancreas

Answer 19

Exocrine and endocrine function
Pancreatic islet (of Langerhands)- endocrine- synthesize hormones- insulin, glucagon, somatostatin
Pancreatic acini- exocrin function- synthesizes digestive enzymes (trypsinogen, amylase, lipase)

Question 20

Absorption of cholesterol

Answer 20

Can be absorbed across intestinal mucosa as is (no digestion needed)

Question 21

Alpha-Dextrinase

Answer 21

Small glucose polymers-> glucose

Question 22

Brush Border Enzymes

Answer 22

Dextrinase
Glucoamylase
Lactase
Maltase
Sucrase

Question 23

Digestion of CHO in Mouth, Stomach

Answer 23

Salivary amylase
Stomach pH
Pancreatic amylase

Question 24

Digestion of CHO in SI

Answer 24

Pancreatic amylase (more potent than salivary amylase)

Question 25

Final Breakdown of CHo

Answer 25

Monosaccharides, water solluble 80% glucose 10% galactose 10% fructose

Question 26

Hepatic portal system

Answer 26

Blood leaving the villi of the small intestine drain into blood vessels that lead directly to the liver - the hepatic portal system Blood leaving the villi is rich in nutrients; if this nutrient load were allowed to enter the general circulation, blood viscosity would be increased with possible adverse effects on blood pressure As the blood passes through the blood vessels of the liver, much of the nutrient load is removed in the first pass effect

Question 27

Glycemic Index

Answer 27

High= Raises blood sugar quickly Low= Blood sugars handles better i..e pretzels= high, rice= low High GI foods leads to an increase in fat even when healthy Diabetic peoples should avoid high GI foods

Question 28

Type I Diabetes

Answer 28

Immune system destroys beta cells. Loses the ability to produce insulin

Question 29

Type II Diabetes

Answer 29

Doesn't produce enough insulin to meet needs. Amount becomes less and less.  Cells build resistance (even if insulin is around, glucose not uptaken into cells), more insulin needed

Question 30

Cholesterol Rich Foods

Answer 30

Shrimp, egg yolks, butter, oils, cream, meat

Question 31

Cholesterol

Answer 31

Most produced by liver (85%) | 15% comes from diet

Question 32

Lipid Digestion

Answer 32

Lingual lipase in saliva | Bile acids emulsify, pancreatic enzymes (lipases)- only occurs in SI

Question 33

Lymphatic System

Answer 33

TAGs resynthesized in enterocyte, leave cell via exocytosis (chylomicrons) and enter lacteals of the intestinal villi (lymphatic system) until they reach thoracic duct and move to the blood stream

Question 34

ApoE

Answer 34

In the blood, the chylomicrons add ApoE protein, which helps it ot bind to capillaries in the target muscles and adipose tissue Digested in target tissues by lipoprotein lipase, releasing the fatty acd Used by skeletal muscle for energy Used by adipose tissue for synthesis of stored fat

Question 35

Protein Digestion

Answer 35

Proteases cleave to peptides | Peptidases cleave to AA

Question 36

Pepsin

Answer 36

Digests protein in stomach Functons at pH of 2-3 Inhibited pH>5 (doesn't work in SI), doesn't last long in stomach One of the only enzymes capable to digest collagen (main component of connective tissue in meat)- breakdown of collagen is the first step of digestion of meat

Question 37

Protein Digestion in SI

Answer 37

Pancreatic secretions contain a number of proteolytic enzymes that act in the duodenum and upper jejunum Partial breakdown products generated from the stomach stimulate the release of pancreatic proteolytic enzymes Trypsin Chymotrypsin Carboxypeptidase Proelastase

Question 38

Protein Digestion in SI Villi

Answer 38

Enterocytes contain other peptidases that are specific for linkages between AA Endopeptidases (like trypsin) cleave internal bonds Exopeptidases cleave ends Digest remaining Di- and Tri-peptides into single AA >99% of final protein product are single amino acids that pass into the blood stream

Question 39

Absorption of Protein

Answer 39

Carrie mediated transport into enterocyte Peptides digested by crush border peptidases Transport proteins carry amino acids out of absorptive cells to capillaries of villi