Imaylee Bio6 Unit 4: Digestive

Front 1

mechanoreceptors

Back 1

respond to stretch or pressure in the digestive tract

Front 2

osmoreceptors

Back 2

respond to changes in osmolarity in the digestive tract

Front 3

chemoreceptors

Back 3

respond to pH, substrates, and end products of digestion in the digestive tract

Front 4

long reflexes

Back 4

extrinsic control that involves integration from the medulla and output sent via autonomic nerves to GI tract to alter muscle and gland activity, level of hormone secretions, modify intrinsic activity, and coordinate different parts of the GI tract (ex. chewing food causes ↑ secretions in stomach)

Front 5

short reflexes

Back 5

intrinsic control that involves the enteric nervous system which are the myenteric and submucosal plexus with the digestive tract wall, and coordinates local activity; can work independently of the CNS or be influenced by extrinsic nerves because it is linked to long autonomic reflex arcs

Front 6

GI peptides

Back 6

can act as digestion hormones and paracrine signals, are released into the blood or ECF by cells of the digestive tract, can act on digestive organs and accessory organs to excite or inhibit motility or secretions, and can also act on the brain to trigger hunger or satiety

Front 7

amylase

Back 7

salivary enzyme secreted in the mouth that begins the chemical digestion of breaking down carbohydrates (polysaccharides→maltose)

Front 8

saliva

Back 8

secreted from serous and mucous cells in the glands of the mouth that consists of mostly water as well as amylase, mucus, lysozyme, and IgA

Front 9

mucus

Back 9

moistens food and holds bolus together

Front 10

lysozyme and IgA

Back 10

chemicals that provide antibacterial action in the mouth

Front 11

simple and acquired reflexes

Back 11

two reflexes that enhance salivary secretion

Front 12

simple reflex

Back 12

occur when ingested food stimulates chemoreceptors and pressoreceptors, the cortex trigger the salivary center in the medulla

Front 13

acquired reflex

Back 13

occur at the thought of food, the cortex triggers the salivary center in the medulla

Front 14

parasympathetic nervous system

Back 14

controls larger volume of saliva, more water, rich with amylase

Front 15

sympathetic nervous system

Back 15

controls smaller volume of saliva, more mucus, result in dry mouth

Front 16

deglutition

Back 16

another name for swallowing that involves the buccal and pharyngeal-esophageal phases that coordinate activity of the tongue, soft palate, pharynx, and esophagus

Front 17

buccal phase

Back 17

involve the bolus voluntarily being forced into the oropharynx

Front 18

pharyngeal-esophageal phase

Back 18

involve the involuntary controls from the medulla and lower pons

Front 19

paristalsis

Back 19

movement of food through the pharynx and the esophagus

Front 20

gastroesophageal sphincter

Back 20

where food enters the stomach from the esophagus

Front 21

intrinsic factor

Back 21

stomach secretes this which is required for absorption of vitamin B₁₂

Front 22

gastric filling

storage

mixing

emptying

Back 22

phases of gastric motility

Front 23

muscular antrum

Back 23

where gastric mixing occur

Front 24

mucous cells

Back 24

exocrine cells that produce mucus to protect stomach wall from harsh acids

Front 25

parietal cells

Back 25

exocrine cells that produce HCl and intrinsic factor

Front 26

Chief cells

Back 26

exocrine cells that produce pepsinogen

Front 27

pepsinogen

Back 27

an inactive form of the protein digesting enzyme pepsin

Front 28

HCl

Back 28

converts pepsinogen into pepsin

Front 29

pepsin

Back 29

enzyme released in the stomach that breaks down proteins into peptide fragments (proteins→peptides)

Front 30

G cells

Back 30

endocrine cells that produce gastrin

Front 31

gastrin

Back 31

hormone produced by G cells that stimulates parietal cells to produce HCl

Front 32

enterochromaffin (ECL) cells

Back 32

coffee stimulates gastrin secretion that stimulates this paracrine cell to secrete histamine; histamine stimulates parietal cells

Front 33

D cells

Back 33

low pH triggers this paracrine cell to secrete somatostatin that inhibits secretion of parietal, ECL, and G cells

Front 34

neural and hormonal mechanisms

Back 34

they regulate the release of gastric juices

Front 35

cephalic phase

Back 35

this reflex phase occur prior to food entry

Front 36

gastric phase

Back 36

this phase occur once food enters the stomach

Front 37

intestinal phase

Back 37

this phase occur as partially digested food enters the duodenum

Front 38

ACh

Back 38

hormone that stimulates parietal, G cells, and ECL cells

Front 39

excitatory events of cephalic phase

Back 39

events include:

sight or thought of food

stimulation of taste, smell, chewing

vagal stimulation releases ACh

Front 40

inhibitory events of cephalic phase

Back 40

events include:

loss of appetite or depression

decrease in stimulation of the parasympathetic division

Front 41

excitatory events of gastric phase

Back 41

events include:

stomach distention activates stretch receptors by neural activation

peptides, caffeine, and alkaline pH activate chemoreceptors

Front 42

inhibitory events of gastric phase

Back 42

events include:

acidic pH lower than 2 triggers somatostatin release

Front 43

intestinal phase

Back 43

phase in the regulation of gastric secretion that is mostly inhibitory

Front 44

inhibitory events of intestinal phase

Back 44

events include:

distention of duodenum, presence of fatty, acidic, or hypertonic chyme in the duodenum

Front 45

local reflexes

vagal nuclei

Back 45

inhibitory factors that closes the pyloric sphincter

Front 46

hormones cholecystokinin (CCK) and secretin

neural enterogastric reflex

Back 46

these factors regulate gastric emptying

Front 47

neural enterogastric reflex

Back 47

occurs when the duodenum fills, stretch receptors are stimulated and the pyloric sphincter closes

Front 48

cholecystokinin (CCK)

Back 48

fatty chyme entering the duodenum causes the duodenal wall enteroendocrine cells to release this hormone into the bloodstream and stimulate:

1. gallbladder to contract

2. hepatopancreatic sphincter to relax/release bile

3. pancreas to secrete digestive enzymes

Front 49

secretin

Back 49

acidic chyme entering the duodenum causes the duodenal wall enteroendocrine cells to release this hormone into the bloodstream and stimulate:

1. liver to produce bile more rapidly

2. pancreas to secrete bicarbonate-rich juices

Front 50

vagal stimulation

Back 50

1. together with secretin, causes weak contractions of the gallbladder to regulate bile release

2. causes release of pancreatic juice

Front 51

bile salt

Back 51

this is reabsorbed back into the blood in the ileum and returned by the hepatic portal system; about 5% escapes in feces

Front 52

gastric inhibitory peptides (GIP)

Back 52

hormone that inhibits gastric acid secretion, and promotes pancreas to release insulin

Front 53

gastric and duodenal factors

Back 53

factors that control the rate of gastric emptying

Front 54

amount of chyme

fluidity of chyme

extrinsic control of vagus nerve

gastrin

Back 54

gastric factors that increase gastric emptying

Front 55

fatty chyme: slower to digest/absorb

acidic chyme: need to be neutralized

hypertonicity: need time to absorb nutrients

distention: needs to cope w/ volume before receiving more

Back 55

duodenal factors that decreases gastric emptying

Front 56

duodenum

Back 56

region of the small intestines that function as chemical digestion and absorption

Front 57

jejunum
ileum

Back 57

region of the small intestine that function to absorb nutrients

Front 58

bile and digestive enzymes

Back 58

substances that are released into the duodenum to be mixed with the chyme

Front 59

produce bile to aid in digesting fats

store excess nutrients for later use

detoxify drugs and metabolites

produce plasma proteins

Back 59

functions of the liver

Front 60

hepatocytes

Back 60

cells in the liver that produce and secrete bile into ducts that empty into the common hepatic duct

Front 61

hepatopancreatic sphincter (sphincter of Oddi)

Back 61

this muscle at the base of the common bile duct prevents bile from entering the duodenum between meals

Front 62

gallbladder

Back 62

where bile backs up and is stored in concentrated form

Front 63

bile salts

cholesterol

lecithin

bilirubin

Back 63

composition of bile, an alkaline solution

Front 64

emulsify fats to increase surface area for lipase action

Back 64

function of bile

Front 65

acini cells

Back 65

cells of the pancreas that secrete digestive enzymes

Front 66

duct cells

Back 66

cells of the pancreas that secrete NaHCO₃⁻

Front 67

sodium bicarbonate (NaHCO₃⁻)

Back 67

aqueous solution that neutralizes acidic chyme

Front 68

proteolytic enzymes

Back 68

enzymes of the pancreas that are released in an inactive form and are activated in the duodenum, that function to break different peptide bonds into short peptides and amino acids

Front 69

trypsinogen

chymotrypsinogen

procarboxypeptidase

Back 69

types of inactive proteolytic enzymes

Front 70

enterokinase

Back 70

membrane-bound enzyme that activates trypsinogen into trypsin

Front 71

trypsin

Back 71

active proteolytic enzyme that activates chymotrypsinogen and procarboxypeptidase into chymotrypsin and carboxypeptidase, respectively.

Front 72

duodenum

Back 72

where proteolytic enzyme activation occurs

Front 73

amylase

Back 73

pancreatic enzyme that hydrolyzes polysaccharides into disaccharides

Front 74

nuclease

Back 74

pancreatic enzyme that hydrolyzes nucleic acids into nucleotides

Front 75

lipase

Back 75

pancreatic enzyme that hydrolyzes triglyceride (emulsified fat) into monoglyceride and fatty acid

Front 76

maltase

sucrase

lactase

aminopeptidase

Back 76

types of brush border enzymes

Front 77

plasma membrane of the small intestine's mucosal cells

Back 77

where brush border enzymes are found and involved in carrying out final chemical digestion

Front 78

vitamins, nutrients, and electrolytes

Back 78

complete absorption of these occur in the small intestines

Front 79

A, D, E, and K absorbed with lipids

Back 79

fat soluble vitamins

Front 80

C and B passively absorbed with water

Back 80

water soluble vitamins

Front 81

Vitamin B₁₂

Back 81

this vitamin is combined with intrinsic factors and absorbed by receptor-mediated endocytosis in the ileum

Front 82

Ca²⁺ and iron

Back 82

minerals that are absorbed on an as needed basis by active transport

Front 83

depends on blood Ca²⁺ level

regulated by vitamin D and PTH

Back 83

when and how Ca²⁺ absorption occur

Front 84

ferritin

Back 84

absorbed iron is stored in the epithelial cells as this until needed

Front 85

transferrin

Back 85

if blood iron levels are low then it is released into the blood and carried by this to the bone marrow to be used for RBC production

Front 86

Cl⁻, H₂O, glucose, and amino acids

Back 86

absorption of these electrolytes depends on active transport of Na⁺ into interstitial fluid

Front 87

anions passively follow electrical gradient established by Na⁺

Back 87

what movement of anions depends upon

Front 88

cotransporter

Back 88

Na⁺ re-entry through this can drive solutes against the concentration gradient

Front 89

facilitated diffusion via cotransport with Na⁺

Back 89

how sugars and amino acids are absorbed

Front 90

hepatic portal vein

Back 90

how sugars and amino acids are transported to the liver

Front 91

synthesizes into triglycerides in the SER

combines with protein in the golgi apparatus

released by exocytosis

enters lacteals

transported systemically via lymph

Back 91

occur when micelle (sphere of lipid) gets close to the absorptive surface and diffuses into the intestinal cells

Front 92

chylomicrons

Back 92

combination of triglyceride and protein

Front 93

segmentation

Back 93

most common motion of the small intestine that is initiated by intrinsic pacemaker cells and function to mix chyme with digestive juices and exposes it to the absorptive surface of the small intestines before contents are moved steadily toward the ileocecal valve

Front 94

distention

gastrin

extrinsic nerves (PNS)

Back 94

factors that enhances the intensity of segmentation contractions

Front 95

migrating motility complex

Back 95

after nutrients have been absorbed, a series of peristaltic waves called this begins with each wave starting distal to the previous and sweeps remnants of the previous meal, bacteria, mucosal cells, and debris into the large intestine

Front 96

motilin

Back 96

this hormone regulates motility in the small intestine during the postabsorptive state

Front 97

mucosa endocrine cell

Back 97

cell that releases motilin

Front 98

gastroileal reflex

Back 98

this reflex is triggered by food entering the stomach, gastrin, and increased motility of the small intestines, thereby allowing chyme to pass into the large intestine by relaxing the ileocecal sphincter

Front 99

absorb remaining water, electrolytes, vitamin K

excrete indigestible food from the body

Back 99

function of large intestines

Front 100

gastrocolic reflex

Back 100

this reflex is triggered by gastrin and extrinsic nerves when food enters the stomach, causing contraction of the ascending and transverse colon that results in mass movement of content forward into the rectum