GI Tract Part 2

Question 1

where are goblet cells located

Answer 1

interspersed among enterocytes

Question 2

what do goblet cells synthesize and what is it stored in

Answer 2

mucinogen stored in membrane bound granules

Question 3

what does mucinogen (mucus) do

Answer 3

lubricates and protects epithelium

Question 4

where are actively dividing stem cells located

Answer 4

at base of crypts

Question 5

where do actively dividing stem cells migrate as they mature

Answer 5

up villus, mature and are shed

Question 6

how often is the entire epithelial lining replaced

Answer 6

every 3-5 days

Question 7

where are paneth cells found

Answer 7

at the base of crypts

Question 8

what do paneth cells contain and what do they produce

Answer 8

large eospinophilic granules that produce antibacterial proteins called defensins and enzymes including lysozyme

Question 9

what do A cells secrete

Answer 9

glucagon

Question 10

what do K cells secrete

Answer 10

GIP

Question 11

where is MALT located

Answer 11

lamina propria and submucosa of small intestine

Question 12

what are M cells

Answer 12

squamoid enterocytes modified for Ag sampling and uptake of macromolecules

Question 13

what are Peyer’s patches

Answer 13

dome shaped areas grossly visible on surface of mucosa and project into lumen

Question 14

what is the duodenum characterized by

Answer 14

Brunner’s glands in submucosa

Question 15

what do Brunner’s glands contain

Answer 15

large numbers of highly convoluted branches, tubuloalveolar submucosal glands

Question 16

what do brunner’s glands do

Answer 16

secrete mucus and zymogens

Question 17

what is the main function of the duodenum

Answer 17

neutralize gastric acid and pepsin

Question 18

what assists the duodenum in its function

Answer 18

pancreas and gallbladder

Question 19

what do the pancreatic duct and bile duct empty into

Answer 19

duodenum at major duodenal papulla

Question 20

what does chyme from the stomach stimulate the release of

Answer 20

secretin and CCK from APUD cells

Question 21

what do secretin and CCK promote

Answer 21

section of exocrine pancreas

Question 22

describe the ph of pancreatic secretions and why

Answer 22

highly alkaline due to bicarbonate

Question 23

what does CCK stimulate

Answer 23

contraction of bladder and release of bile acids

Question 24

what do bile acids do

Answer 24

act as emulsifying agents for digestion of lipids to form micelles

Question 25

what do pancreatic secretions contain

Answer 25

proteolytic enzymes trypsin and chymotrypsin for digestion of proteins, and amylase and lipase

Question 26

what are enzymes in pancreatic secretions secreted as

Answer 26

inactive precursors (zymogens) such as trypsinogen and chymotrypsinogen

Question 27

why are enzymes secreted as inactive precursors

Answer 27

to prevent autolysis

Question 28

what is trypsin activated by

Answer 28

enterokinase

Question 29

what does trypsin activate

Answer 29

chymotrypsin

Question 30

what are the two steps in the digestion process

Answer 30

luminal digestion and membrane digestion

Question 31

what does luminal digestion involve

Answer 31

mixing of chyme with pancreatic enzymes that results in molecular breakdown

Question 32

what does membrane digestion involve

Answer 32

enzymes of glycocalyx on plasma membrane of enterocytes

Question 33

what do enterocytes synthesize

Answer 33

enzymes and carrier proteins for absorption of carbohydrates and amino acids

Question 34

what enzymes do enterocytes synthesize

Answer 34

peptidases, peptide hydrolases, disaccharidases,

Question 35

what are proteins initially denatured by and hydrolyzed by

Answer 35

denatured by HCl from parietal cells and hydrolyzed by pepsin into polypeptide fragments

Question 36

what continutes to breakdown proteins

Answer 36

pancreatic enzymes which results in small peptide fragments (AAs) that are absorbed by enterocytes via active transport by carrier proteins

Question 37

what are the types of carbohydrates

Answer 37

poly-, oligo-, and disaccharides

Question 38

what hydrolyzes starch to disaccharides

Answer 38

salivary and pancreatic amylase

Question 39

what are disaccharides further broken down into

Answer 39

monosaccharides

Question 40

what are examples of disaccharides? monosaccharides?

Answer 40

disaccharides: sucrose, lactose, maltose, isomaltose monosaccharides: glucose, galactose and fructose

Question 41

what are monosaccharides and AAs absorbed by

Answer 41

enterocytes lining villi, transported across epithelium, enter capillaries within lamina propria -> portal vein to liver for storage

Question 42

what are lipids and what are they emulsified by

Answer 42

triglycerides from diet, emulsified by bile acids

Question 43

what are lipids further broken down into

Answer 43

monoglycerides and fatty acids by pancreatic lipase to form extracellular micelles

Question 44

what are micelles absorbed by

Answer 44

enterocytes then re-synthesized into triglycerides within enterocytes and coated with proteins and phospholipids to form intracellular chylomicrons

Question 45

where are chylomicrons transported

Answer 45

across enterocytes to lacteals

Question 46

what are lacteals

Answer 46

blind ended lymph vessels within lamina propria of villi

Question 47

where are chylomicrons eventually carried to

Answer 47

thoracic duct and general circulation

Question 48

what does the large intestine include

Answer 48

cecum, appendix, ascending, transverse, descending and sigmoid colon, and rectum

Question 49

what does the large intestine lack

Answer 49

villi and plicae circulares

Question 50

what is the appendix

Answer 50

small, blind ended sac distal to ileo cecal junction

Question 51

what does the appendix contain

Answer 51

large amounts of submucosal MALT

Question 52

what is the primary function of the colon

Answer 52

water and electrolyte resporption -also produces mucus for elimination of undigested food and waste

Question 53

what does the colon contain

Answer 53

large numbers of goblet cells in epithelium and colonic glands in submucosa

Question 54

what does the colon not have

Answer 54

brunner's glands, villi, plicae circulares

Question 55

what is the mucosal epithelium in the colon similar to

Answer 55

small intestine but paneth cells are generally absent in adults

Question 56

what does the MALT not form in large intestine

Answer 56

Peyers patches

Question 57

are lacteals present in the lamina propria of the colon

Answer 57

NO

Question 58

where does epithelial replacement occur in the colon

Answer 58

from stem cells at the base of glandular crypts

Question 59

what type of bacteria is common in the colon

Answer 59

commensal bacteria

Question 60

describe the outer longitudinal muscle layer in muscularis externa of the colon

Answer 60

reduced or incomplete- forms 3 longitudinal strips called taenia coli

Question 61

what are taenia coli responsible for

Answer 61

formation of haustra

Question 62

what are polyps

Answer 62

adenomas - any mass arising from the wall of the colon that protrudes into the lumen

Question 63

what is the most common sign of polyps

Answer 63

rectal bleeding

Question 64

what is colon cancer

Answer 64

adenocarcinoma

Question 65

what decreases colon cancer risk

Answer 65

increased fiber in diet which decreased transit time and increases GI motility

Question 66

describe the rectum

Answer 66

short dilated terminal portion of large intestine

Question 67

what does the rectum contain

Answer 67

transverse rectal folds and large numbers of mucus glands

Question 68

what is the transition of mucosa at anal canal

Answer 68

simple columnar epithelium to stratified squamous epithelium

Question 69

what does the anal canal contain

Answer 69

longitudinal folds called anal columns

Question 70

where are anal glands located

Answer 70

extend into submucosa and muscularis externa

Question 71

describe the type of glands anal glands are

Answer 71

branched, straight, tubular glands that secrete mucus

Question 72

what is the external anal sphincter made of? internal?

Answer 72

external: skeletal muscle internal: smooth muscle

Question 73

what are occasional enlargement and irritation of submucosal veins called

Answer 73

hemorrhoids

Question 74

what is the anus

Answer 74

external opening, exit of GI tract