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GI/ Resp. Physio > Week 1 Lecture/ Objectives > Flashcards

Week 1 Lecture/ Objectives Flashcards

1
Q

Name the 4 main functions of the GI system

A

digestion, absorption, excretion, immunity

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2
Q

Which immunoglobulin is produced in greatest quantity in the gut?

A

IgA

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3
Q

What are transit times for the stomach (50% and 100%), small investing (50%) and colon

A

stomach 50%: 2.5-3 hours, stomach 100% 4-5 hours, small intestine 50% 2.5-3 hours, colon 30-40 hours

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4
Q

Name 3 functional regions of the stomach

A

cardia (secrets mucus and bicarbonate) funds and body (secretion and reservoir) and the antrum (mixing/ grinding)

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5
Q

What are the elements of the duodenal cluster unit?

A

duodenum, pancreas and the liver

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6
Q

What are the two plexi that make up the enteric nervous system?

A

myenteric plexus and submucosal

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7
Q

Where are the myenteric and submucosal plexus found?

A

myenteric is located between the circular and longitudinal muscles, submucosal is between the submucosa and the muscularis externa

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8
Q

Name the tissue layers of the the digestive system (approx 3 main layers)

A

mucosa (epithelium, basement membrane, lamina propria with nerves and bv, muscular is mucosa), submucosa (including submucosal plexus) and muscularis propia (circular muscle, myenteric plexus and longitudinal) …. depending on the tissue could be surrounded by serosa or fiborsa

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9
Q

Name the two types of tissues you would find at the gastro-esophagela junction?

A

esophagus (squamous), stomach (columnar)

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10
Q

The small intestine has both villi and crypts but the colon has only _______

A

crypts

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11
Q

Which section of the small intestine is the primary site of absorption

A

the jejunum (SA about equal to a doubles tennis court

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12
Q

What part of the colon is termed the “forgotten organ”?

A

the abundant anaerobic bacterial ecosystem (40-50 species making up 60% of fecal mass)

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13
Q

During fasting what portion of the blood going to the liver is from the portal system?

A

⅔ is from the hepatic portal system and ⅓ is for hepatic perfusion from the hepatic artery (25-35% of the cardiac output)

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14
Q

What important pathways exists to make up the difference between the arterial and venous flow to the gut?

A

the lymph system (large), which is also very important for lipid assimilation

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15
Q

T/F the water inflow must equal the water outflow of the GI system

A

True- water balance between digestion and secretions must be equal to that volume that is absorbed

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16
Q

Name 4 modes of communication in the GI tract

A

endocrine (cell to blood), paracrine (cell to cell) neurocrine (axon to cell) immune/juxtacrine (cell to cell contact

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17
Q

What is the function of program circuits?

A

signal gut physiological status (can be sensory synapsing on smooth muscle within the gut)

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18
Q

What is the function of integration circuits?

A

relay PC circuit infer to and from the CNS to modify response or not

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19
Q

Relate the program circuits, integration circuits and the ENS

A

the ENS communicates between the PC and IC

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20
Q

Name the two components of extrinsic gut innervation.

A

parasympathetic (primary and via the vagus which sends preganglionic bodies to synapse on the myenteric plexus) sympathetic (secondary, mostly to shut down the gut circulation in an emergency via postganglionic adrenergic fibers from the pre vertebral ganglia)

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21
Q

Where is gastrin secreted?

A

G cells of mostly the antrum but also in the duo and jeju (stimulates gastric acid secretion)

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22
Q

Where is CCK secreted?

A

from I cells primarily in the duo and jeju but with reserve capacity in the ileum (stimulates gall bladder contraction and opening of sphincter of oddi)

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23
Q

Where is secretin secreted?

A

from S cells primarily in the duo and jeju but with reserve capacity in the ileum (stimulates bicarbonate secretion by pancreatic and biliary ducts)

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24
Q

Where is GIP secreted

A

from K cells in the duo and jeju (GIP stands for glucose-dependent insulinotropic peptide and it stimulates insulin secretion

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25
Q

Where is motilin secreted?

A

unknown cells in the duo and jeju, (stimulates migrating motor complexes during fasting)

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26
Q

Name factors that would increase or decrease gastrin secretion.

A

increase: amino acids/protiens, stretch and neural stimulation; decrease: acid

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27
Q

Name factors that would increase or decrease CCK cells

A

increase: amino acids, fatty acids, peptide releasing factors and mural stimulation

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28
Q

Name factors that would increase or decrease secretin

A

increase: fatty acids or acid

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29
Q

Name factors that would increase or decrease GIP

A

fatty acids or glucose would increase GIP release

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30
Q

Name factors that would increase or decrease motilin

A

increase: neural stimulation decrease: amino acids, glucose or fatty acids

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31
Q

Name 6 functions of saliva.

A

lubrication by water and mucins (primary), solubilize food for taste, aids in speech, slightly alkaline, amylase begins starch digestion, and contains IgA in mucosal immunity

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32
Q

What is then maximum rate of secretion v. the daily rate of saliva secretion

A

max : 1 mL.min/g tissue or 1.5L/d which requires high blood flow

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33
Q

Name 4 phases of deglutition

A

oral predatory stage (voluntary); oral transport stage (voluntary, inspiration is inhibited, tongue pushes food bolus to back of mouth, soft palate rises); pharyngeal stage (involuntary, airway closure essential, epiglottis covers trachea); esophageal stage (involuntary)

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34
Q

Where is the swallowing center located?

A

medulla and pons

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35
Q

Describe the outflow nerves that regulate the different portions of the esophagus

A

somatic nerves regulated striated muscle and autonomic nerves regulate smooth muscle via enteric nervous system or directly

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36
Q

What controls esophageal muscles during vomitting?

A

muscles are passive during vomitting

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37
Q

What is a hiccup?

A

diaphragmatic flutter and closure of the glottis (closing sphincters and momentarily reducing intrathoracic pressure causes anything in the esophagus to drop towards gravity and air passing into the esophagus is the sound of hiccups

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38
Q

The opening of sphincter is regulated by a relaxation or contraction of the LES

A

a relaxation

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39
Q

Name the secretions of the cardia

A

mucous and bicarbonate

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40
Q

Name the source and function of HCl

A

parietal cells; hydrolysis and sterilization

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41
Q

Name the source and function intrinsic factor

A

parietal cell; B12 absorption

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42
Q

Name the source and function of pepsinogen

A

chief cells; protein digestion

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43
Q

Name the source and function of mucous, and bicarbonate

A

surface mucous cells; gastric protection

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44
Q

Name the source and function of gastrin

A

G cells; regulation of gastric secretion

45
Q

Describe the secretion and motility of the lower esophageal sphincter and cardia

A

secretes mucous and bicarbonate, prevents reflux and regulates eructation (belching)

46
Q

Describe the secretions and motility of the funds/body.

A

(intrinsic factor, H+, mucous, bicarbonate, pepsinogen and lipase); reservoir, applying tonic force while emptying

47
Q

Describe the secretion and motility of the antrum/pylorus?

A

secretes mucous, gastrin and bicarbonate; mixes grinding and regulating the emptying of the stomach

48
Q

Name the 3 layers of muscle in the stomach.

A

longitudinal, circular, and oblique muscles

49
Q

What types of cells would you find in a gastric pit (in the fundus and body of the stomach)?

A

mucus neck cells (stem cells), parietal cells, ECL cells and chief cells

50
Q

What do ECL cells secrete?

A

histamine acts via paracrine regulation; secretes into the lamina propria

51
Q

Describe the cellular difference(s) between a secreting and non-secreting parietal cell

A

increased mitochondria and opening of intracellular canaliculus (increases surface area) in secreting cell

52
Q

Gastrin is secreted into _____ as part of its endocrine function.

A

blood

53
Q

Pepsinogen and HCL are secreted into the stomach ______.

A

lumen

54
Q

What is the vago-vagal reflex

A

the action of vagal afferents to the CNS about gastric stretch that influences motility and reflexive stretching

55
Q

Gastrin can trigger the release of _____ into the stomach lumen.

A

HCl

56
Q

The rate of stomach emptying varies with what? (related to the types of food ingested)

A

varies with nutrient content and state ie. liquid or carbohydrate will lead to relatively fast emptying and solids and proteins alter the rate of stomach emptying

57
Q

What is the name and location of pacemaker cells in the stomach.

A

interstitial cells of cajal in the pacemaker region of the body of the stomach (CNS has imput on motility but ENS allows independent activity)

58
Q

What is the BER

A

basal electrical rhythm determines the maximal contraction rate

59
Q

What are the BER of the stomach, duodenum, distal ileum and the colon (cycles/min)

A

stomach 3 c/m; duodenum 12 c/m; distal ileum 8-10 c/m and colon 3 c/m

60
Q

Additional input from the ANS will modulate the magnitude/rate of the contractions?

A

magnitude

61
Q

Approximately how many parietal cells per gastric pit?

A

4-5

62
Q

What does ECL stand for?

A

enterochromaffin-like cell

63
Q

Where are you likely to find G cells in the stomach?

A

in the atrium of the stomach to help stimulate acid projection

64
Q

Why does a secreting parietal cell require excess mitochondria

A

it is energy intensive to export against the pH gradient of the stomach

65
Q

What are the 3 direct stimulus to parietal cell secretion?

A

acetylcholine from vagal efferents, histamine released by ECL cells and gastrin from G-cells (primary stimulus)… an indirect stimulus is gastrin releasing peptide released by enteric efferents

66
Q

What are the postpranial phases of gastric secretion?

A

cephalic (stomach readies to receive meal, increased vagal outflow Ach and GRP secretion) gastric (food received in stomach amplifies secretion) intestinal (luminal pH falls as food leaves stomach and somatostatin suppresses gastrin release)

67
Q

What reaction is required for the production of protons in the parietal cells

A

carbon dioxide and water are converted to H+ and bicarbonate by the carbonic anhydrase reaction

68
Q

Describe the action of the proton pump.

A

ATPase pumps a proton out in exchange for a potassium (potassium is restored by a potassium channel)

69
Q

What is the post prandial alkaline tide?

A

the exchange of bicarbonate out the basal side of the parietal cells in exchange for a chloride leads to a basic shift in the contents of the blood

70
Q

Describe the magnitude of the H+ gradient of the stomach

A

~3x10^6

71
Q

How do NSAIDs affect gastric acid

A

NSAIDs reduce prostaglandins which decrease the excretion of mucus

72
Q

How does somatostain affect gastric acid secretion?

A

somatostatin (secreted by D cells in the antrum, duodenum and pancreas) blocks the release of gastrin, ECL secretion of histamines, and decreases parietal secretions

73
Q

Where in parietal are proton pumps situated in the parietal cells?

A

proton pumps are situated on the canalicului

74
Q

How do you change the viscosity of gastric mucin?

A

pepsin will convert it from a high viscosity tetramer to a low viscosity monomer (spreads better over stomach surface)

75
Q

How do foods, especially proteins affect the pH of the stomach

A

foods especially proteins buffer gastric luminal contents (raise the pH)

76
Q

Describe the secretions of pancreatic glands in the acinus v. the duct.

A

exocrine cells secrete enzymes and duct cells secrete bicarbonate

77
Q

Which type of enzyme is the greatest percent of pancreatic secretions

A

proteases (80%) also secreted are amylase, lipase’s and nucleases (plus several regulatory enzymes)

78
Q

Where does the majority of pancreatic secretion, which phase?

A

the intestinal phase (60-70%)

79
Q

Pancreatic DUCTULAR and ACINAR secretion is division by which hormone?

A

secretin (ductular) and CCK, Ach and GRP (acinar)

80
Q

How does secretion change in the intestine between the cephalic and gastric phase?

A

during the cephalic and gastric phases the enzyme concentration is high and the volume of secretion is low (mostly acinar cell secretion/ CCK mediated)

81
Q

What its the master regulator of the duodenal cluster unit?

A

CCK, effects the gallbladder contraction, pancreas acinar secretion, reduces stomach emptying and relaxes the sphincter of oddi

82
Q

***How is CCK secretion by duodenal cells regulated?

A

secretion of the duodenal I cells is regulated by CCK-RP and monitor protein(from pancreatic acinar cells); intestinal contents will occupy the amount of trypsin the can act on CCK-RP and monitor peptide

83
Q

How is pancreatic juice concentration affected by flow

A

greater flow will increase the bicarbonate concentration, reduce the Cl-

84
Q

How is secretin secretion from duodenal S cells by luminal pH meters

A

increased pH (due to increased bicarbonate) leads to less secretin secretion

85
Q

What is the mechanism for bicarbonate excretion from pancreatic duct cells.

A

carbonic anhydrase converts water and carbon dioxide creates bicarbonate

86
Q

Name the contents of saliva

A

water, bicarbonate, mucins, amylase, lysosome, IgA (and epidermal and nerve growth factors)

87
Q

Describe the combination of mucus and serous secretion in the parotid, sublingual and submandibular

A

parotid (watery); sublingual (mucus) and submandibular (mixed)

88
Q

What are factors that are important in regulation of salivary secretion

A

smell and fast act via higercenters and parasympathetic innervation (no hormonal control)

89
Q

Why is bicarb and other electrolytes important in the composition of saliva

A

increased electrolytes draw more water into saliva (greater flow, greater Na+ concentration and less viscous saliva)

90
Q

What is special about intercalated ducts

A

water is not allowed to leave the duct for this very small part of duct

91
Q

Saliva is (hypotonic/hypertonic) to plasma

A

hypotonic

92
Q

What increases the secretion of salivary glands?

A

parasympathetic stimulation (primarily) increases blood flow via arteriolar dilation

93
Q

What type of change in luminal transport causes diarrhea?

A

normally Na+ transport into cells keeps liquid in stool low, but when Cl- is secreted into the bowel, water follows passively ** note normal nutrient absorption continues

94
Q

SGLT couples which to nutrient for what type of nutrient absorption?

A

Na+/ Glucose transporter uses the Na+ gradient in active transport to transport glucose into enterocytes (ATPase pumps Na out of the basal membrane creating “vacuum”)

95
Q

What is the basal transporter of glucose?

A

GLUT 2 (passive transport) glucose travels passed on the glucose gradient between enterocytes and the blood

96
Q

Cholera causes exaggerated epithelial____ secretion

A

Cl-

97
Q

Name the two types of starches

A

amylose (straight chain glucose polymers) and amylopectin (branched-chain glucose polymers

98
Q

What is the role of dietary fiber (2)?

A

adds bulk to stool; digestion by bacterial hydrolyses yields fatty acid and energy for colonocytes

99
Q

Breakdown of amylose by amylase yields what products?

A

maltose, maltotriose and glucose olgiomers

100
Q

Amylase cannot break what types of bonds?

A

terminal a1-4 or a1-6bonds

101
Q

Are products of intestinal amylase absorbable by enterocytes?

A

no, enterocytes can only transport monosaccharides

102
Q

Where are brush border hydrolyses found?

A

concentrated at vilus tips of small intestine, not found in crypts

103
Q

How is fructose transported across the luminal membrane?

A

GLUT 5 through facilitated diffusion (Na independent)

104
Q

How are galatose and glucose transported through luminal membrane?

A

active transport through SGLT-1 (sodium glucose coTransporter

105
Q

Why are there more amino acid transporter than monosacchride transporters

A

there are 20 different naturally occurring amino acids and only 3 nutritionally significant monosaccharides.

106
Q

Final digestion of proteins occurs where?

A

within the enterocyte cytosol

107
Q

What factors affect absorption in the GI tract?

A

substances physiochemical characteristics, particularly hydrophilic/phobic properties

108
Q

How do NSAIDs affect the stomach acidic environment?

A

NSAIDs reduce prostaglandins that further more reduce the secretion of mucous secretagogues

GI/ Resp. Physio (4 decks)

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