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BIOM 3200 > Digestive > Flashcards

Flashcards in Digestive Deck (39):
1

Digestion Time:

6-8 hours in stomach, SI
Large Intestine- ~ 40 hours (33 for men, children, 47 for women)

2

Alimentary canal

§ Continuous hollow tube
Mouth, pharynx, esophagus, stomach, SI, LI, anus

3

Functions of the Salivary Glands:

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

4

Mastication (Chewing):

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

5

Deglutition (Swallowing):

• 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

6

Peptic Ulcers:

• 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

7

Duodenum

§ First 25cm
Mucous secretion, receives pancreatic secretions and bile from the liver

8

Jejunum

§ 1m in length
Numerous folds and villi

9

Ileum

§ 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

10

Goblet cells

Secrete mucus in SI

11

Intestial crypts

Crypts of Lieberkuhn
Replace columnar epithelial cells (constant turnover)

12

Paneth cells

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

13

Sucrase

Sucrose-> glucose + fructose

14

Maltase

Maltose -> glucose

15

Lactase

Lactose-> glucose, galactose

16

Aminopeptidase

Cleaves polypeptides

17

Enterokinase

Activates trypsin and indirectly other pancreatic enzymes

18

Alkaline Phosphatase

Removes phosphate groups from organic molecules

19

Pancreas

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

20

Absorption of cholesterol

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

21

Alpha-Dextrinase

Small glucose polymers-> glucose

22

Brush Border Enzymes

Dextrinase
Glucoamylase
Lactase
Maltase
Sucrase

23

Digestion of CHO in Mouth, Stomach

Salivary amylase
Stomach pH
Pancreatic amylase

24

Digestion of CHO in SI

Pancreatic amylase (more potent than salivary amylase)

25

Final Breakdown of CHo

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

26

Hepatic portal system

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

27

Glycemic Index

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

28

Type I Diabetes

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

29

Type II Diabetes

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

30

Cholesterol Rich Foods

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

31

Cholesterol

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

32

Lipid Digestion

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

33

Lymphatic System

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

34

ApoE

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

35

Protein Digestion

Proteases cleave to peptides
Peptidases cleave to AA

36

Pepsin

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

37

Protein Digestion in SI

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

38

Protein Digestion in SI Villi

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

39

Absorption of Protein

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