Digestive system lecture

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Oral cavity functions

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123 Terms

1

Oral cavity functions

  • mastication

  • deglutination

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2

Pharynx/esophagus functions

  • swallowing

  • transport

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3

stomach functions

  • mechanical digestion

  • intital digestion of proteins and lipids

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4

small intestine functions

chemical and mechanical digestion

absorption

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5

large intestine functions

  • compaction of feces

  • absorption

  • defecation

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6

What is ingestion?

taking food and drinks into oral cavity

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7

what is digestion?

  • breaking down foods into usable forms

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8

What is the difference between chemical and mechanical digestion?

  • chemical: use of enzymes to break down polymers into monomers for absorption

  • mechanical: alters consistency of food to ease transport

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9

What is the movement of materials into digestive tract epithelium → interstitial fluid→ blood/lymph?

absorption

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10

What is compaction?

absorbing all usable material and consolidating the ingestible and nonabsorbable materials as feces

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11

What is the function of protection of the digestive system( (epithelium and lymphoid tissue)

  • epithelia protect against abrasion, chemical damage, pathogens

  • lymphoid tissue protects against pathogens that enter interstitial fluid

  • stomach acid

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12

What structures are included in the digestive tract (alimentary canal)?

mouth, esophagus, stomach, small intestine, large intestine

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13

What are the accessory organs?

teeth, tongue, salivary glands, liver, gallbladder, pancreas

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14

What are the functions of the accessory organs?

many produce secretions that are released into the lumen of digestive tract through ducts

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15

What are the 4 digestive tract layers? list from innermost to outermost.

  • mucosa

  • submucosa

  • muscularis externa

  • serosa

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16

What is the function of mucosa?

  • absorb monosaccharides, amino acids, lipids

  • protect from abrasion

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17

What are the functions of submucosa?

  • contains blood vessels and lymphatic vessels

  • exocrine glands

  • MALT

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18

What are the functions of muscularis externa?

  • inner circular/outer longitudinal smooth muscle

  • stomach contains a third oblique layer

  • churns and propels waste

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19

What are the functions of serosa?

  • secrete serous fluid

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20

Which membrane maintains spatial relationships between organs?

  • mesentery

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21

What is the function of mesentery?

  • supply blood vessels, nerves, lymphatic vessels, lymph nodes

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22

What are the two posterior mesenteries?

mesocolon and mesentery proper

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23

What are the two anterior mesenteries?

lesser omentum and greater omentum

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24

What is peritonitis?

acute inflammation of the peritoneum caused my infection microbes, GI tract rupture, perforated ulcer, trauma, appendicitis

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25

which cranial nerve controls the tongue?

CN XII (hypoglossal)

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26

What is the function of the tongue?

  • mechanically break up food

  • manipulate food into a bolus

  • glands secrete saliva and ligual lipase

  • ducts of salivary glands open near lingual frenulum

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27

What are the functions of saliva?

  • mucus for lubrication

  • enzymes that initiate the digestion of carbs and lipids

  • IgA antibodies and lysozyme

  • solvent for dissolving food molecules

  • bicarbonate that neutralizes bacterial acids

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28

What is the function of the upper esophageal sphincter?

prevents air from entering esophagus when contracted

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29

How many layers of muscularis externa is in the stomach? what is the function of the extra layer?

  • 3

  • prevents over-stretching and helps churn food

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30

What is the function of the mucus neck cell?

  • secrete acidic fluid containing mucin

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31

What do parietal cells secrete?

  • Hydrochloric acid (HCl)

  • intrinsic factor (IF)

  • Ghrelin

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32

What is ghrelin?

appetite stimulating hormone

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33

What is the importance of IF and B12?

  • essential for Hb synthesis

  • both get taken up via receptor mediated endocytosis

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34

What do the chief cells secrete?

  • pepsinogen

  • gastric lipase

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35

What activates pepsinogen to pepsin?

HCl

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36

Pepsin

initiates chemical digestion of protein

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37

what do enteroendocrine cells secrete

  • localized paracrines

  • gastrin from G cells

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38

What is the function of gastrin?

  • stimulates parietal and chief cell secretion

  • increases stomach motility, relaxes pyloric sphincter, constricts cardiac sphincter

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39

Regenerative cells

  • stem cells that replace lost pit and gland cells

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40

G cells

secrete gastrin

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41

Parietal cells generate __ from __ , then pump into lumen while exchanging __.

  • H+

  • carbonic acid

  • K+

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42

what is bicarbonate exchanged for in gastric hydrochoric acid?

  • plasma chloride ions

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43

CO2 is converted to carbonic acid, carbonic acid dissociates into _____ ,__ , , then , _ moves in and __moves out.

  • K+, H+, HCO3-

  • chloride moves in

  • bicarbonate moves out

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44

What pump facilitates the gastric hydrochloric acid formula

protein H+ K+ ATPase pump

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45

What is the function of gastric hydrochloric acid

  • kills microbes, denatures food enzymes, breaks down plant cell walls, meat CTs

  • activates pepsinogen and lingual lipase

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46

Where does the initial digestion of lipids take place, and by what?

in the mouth/stomach by lingual lipase and gastric lipase

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47

How is pepsin autocatalytic?

catalyzes own reaction by splitting amino acids to activate pepsinogen, that activates more pepsin

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48

why is there little absorption in the stomach?

  • thick mucus

  • lack of transport proteins

  • tight junctions

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49

Mucus cells contain ___________ which converts ethanol to acetaldehyde

alcohol dehydrogenase

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50

Function of duodenum

  • recieves chyme from stomach and secretions from accessory organs

  • neutralizes stomach acid

  • inactivates pepsin

  • emulsifies lipids

  • site of pancreatic enzyme function

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51

Jejunum function

  • majority of chemical digestion and absorption occur here

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52

Ileum function

  • lymphoid nodules protect against bacteria

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53

Small intestine villi

  • absorb nutrients and deliver to liver

  • each contains a lacteal

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54

What is a lacteal?

  • lymphatic capillary that absorbs lipids

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55

small intestine microvilli

  • form brush border enzymes (BBEs)

  • increase surface area for absorption

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56

BBE functions

  • carry out final stage of digestion

  • peptidases and enteropeptidase

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57

Small intestine - intestinal crypts

  • what does upper portion contain?

  • what does lower portion contain?

  • what cell secretes lysozyme?

  • upper: enterocytes, goblet cells

  • lower: stem cells

  • paneth cells

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58

What is the function of the duodenal glands?

  • produce mucus to protect epithelium

  • contains bicarbonate ions

  • increases pH

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59

__ of foodstuffs are used to make __ for biosynthesis

  • monomers

  • ATP

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60

What is a hydrolysis reaction?

use water to break polymers into monomers

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61

What initiates digestion of carbohydrates?

  • salivary amylase

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62

What initiates digestion of lipids?

  • lingual and gastric lipase

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63

what initiates digestion of proteins?

  • pepsin

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64

Maltase, sucrase, lactase:

  • source?

  • target?

  • products?

  • brush border of small intestine

  • maltose, sucrose, lactose

  • monosaccharides

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65

pancreatic amylase:

  • source

  • target

  • products

  • pancreas

  • starch

  • oligosacchardies, trisaccharides, maltose

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66

salivary amylase

  • source

  • target

  • products

  • salivary glands

  • starch

  • oligosaccharides, trisaccharides, maltose

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67

What bond does pepsin break?

tyrosine and phenylalanine bond

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68

Pepsinogen (pepsin) --- stomach

  • source

  • target

  • products

  • chief cells of gastric glands

  • proteins and polypeptides

  • smaller polypeptides

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69

pepsinogen (pepsin) remarks (3)?

  • activated by HCl

  • autocatalytic

  • breaks bonds between tyrosine and phenylalanine

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70

enteropeptidase --- sm intestine

  • source

  • target

  • products

  • brush border and lumen of sm intestine

  • trypsinogen

  • trypsin

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71

trypsinogen --- sm intestine

  • source

  • target

  • products

  • pancreatic juice

  • proteins and polypeptides

  • smaller polypeptides

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72

chymotrypsinogen (chymotrypsin)

procarboxypeptidase (carboxypeptidase) --- sm intestine

  • source

  • target

  • products

  • activated by?

  • pancreatic juice

  • proteins and polypeptides

  • smaller polypeptides

  • activated by trypsin

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73

proelastase (elastase) --- sm intestine

  • source

  • target

  • products

  • activated by

  • pancreatic juice

  • elastin

  • smaller polypeptides

  • trypsin

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74

dipeptidases and peptidases --- sm intestine

  • source

  • target

  • products

  • brush border of small intestine

  • dipeptides and tripeptides

  • amino acids

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75

Which two factors break lipid globules into smaller globules?

  • stomach churning and segmentation

  • called emulsification

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76

and ___ from bile coat surface of small globules

  • lecithin

  • bile acids

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77

what is the purpose of coating the small globules?

  • prevent them from coming back together

  • increase SA for lipase enzymes

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78

Lipase breaks ____ into ____ and a ____

  • triglycerides

  • 2 FFAs

  • monoglyceride

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79

lingual lipase

  • source

  • target

  • products

  • glands of tongue

  • triglycerides

  • FFAs and monoglycerides

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80

gastric lipase

  • source

  • target

  • products

  • chief cells of gastric glands

  • triglycerides

  • FFAs and monoglycerides

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81

pancreatic lipase

  • source

  • target

  • products

  • pancreatic juice

  • triglycerides

  • FFAs and monoglycerides

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82

What 2 nucleases are contained in pancreatic juice?

  • deoxyribonuclease

  • ribonuclease

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83

what is the function of deoxyribonuclease and ribonuclease?

  • break polymers into nucleotides

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84

Brush border contains nucleosidases and phosphatases that result in which 3 things?

  • sugar (deoxyribose or ribose)

  • phosphate ions

  • nitrogenous base

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85

Carb absorption sm intestine

glucose and galactose move into columnar cell using which transporter?

Sodium-glucose transporter

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86

carb absorption sm intestine

What does fructose get converted to?

glucose via facilitated diffusion

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87

carb absorption sm intestine

which 3 monosaccharides enter ECF via facilitated diffusion?

  • glucose

  • fructose

  • galactose

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88

Carb absorption sm intestine

What is solvent drag?

When theres a high concentraion of solute in lumen, it pulls it to an area of low pressure (IF), to make solute concentration in IF higher

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89

protein absorption sm intestine

amino acids move with which transport molecule?

Na+

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90

protein absorption sm intestine

Dipeptides and tripeptides move into cells using which cotransport molecule?

H+

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91

Lipid absorption sm intestine

What 4 things get taken up by micelles?

  • FFAs

  • monoglycerides

  • cholesterol

  • fat-soluble vitamins

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92

What is a micelle?

  • sphere of bile components

  • travel to surface of epithelial cells and FFAs diffuse across apical cell membrane

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93

lipid absorption sm intestine

Inside the cell, FFAs get converted to ______ in the ___.

Then vescicles of ___ travel to the ___.

  • triglycerides

  • smooth ER

  • triglycerides

  • golgi apparatus

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94

lipid absorption sm intestine

What is a chylomicron?

  • triglyceride (and some cholesterol) coated with proteins and phospholipids

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95

what happens when chylomicrons leave the cell?

they get taken up by lacteals

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96

Functions of large intestine?

  • dehydrates food through absorption of water and ions

  • vitamin synthesis and absorption

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97

What do laneth cells in the large intestine produce?

lysozyme

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98

What is osmosis (water absorption) facilitated by?

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99

Pancreas exocrine functions

  • acinar cells secrete pancreatic juice into duodenum

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100

pancreas endocrine functions

islets produce and secrete insulin and glucagon

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