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PHYSL 214 > Gastrointestinal Physiology > Flashcards

Gastrointestinal Physiology Flashcards

1
Q

functions of the G.I tract

A

Motility
Digestion
Absorption
Secretion

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2
Q

Motility

A

refers to the movement of the GI tract and serves two purposes
1. moves contents from mouth to anus
2. mixes contents to facilitate digestion and absorption

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3
Q

Digestion

A

process of breaking down large particles of food and high-molecular weight substances into smaller molecules

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4
Q

Absorption

A

movement of the digestion of the product across the intestinal epithelium into the body

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5
Q

Secretion

A

Release of substances into the lumen of the GI which facilitates digestion, absorption and motility

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6
Q

What are the components of the digestive system

A

mouth, stomach, small intestine and large intestine
and the accessory organs : Salivary glands, Liver, Pancreas, Gallbladder

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7
Q

function of the epithelium of the intestinal wall

A

Barrier of cells that nutrients must traverse to be absorbed into the body

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8
Q

Function of the capillaries and lymphatics

A

aid in transport to and form the intestine, deliver O2 and other needed molecules

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9
Q

function the circular and longitudinal muscles

A

these layers of smooth muscle allow motile contractions of the intestine

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10
Q

function of the myenteric plexus

A

has a rich nerve supply that controls multiple aspects of motility and secretion, known as the brain of the gut

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11
Q

function of endocrine cells

A

secrete hormones into blood that regulate digestion and appetite

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12
Q

function of exocrine cells

A

secrete substances into lumen that aid digestion

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13
Q

function of mucous cells

A

Ducts from accessory organs

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14
Q

function of sphincters

A

ring of muscle creating a constriction point which regulates flow, flow is typically mouth to anus but there can be backflow an example being vomit

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15
Q

what are the type of sphincters and their location

A
  1. upper esophageal found between the pharynx and esophagus
    2.Lower esophageal found between the esophagus and stomach
  2. pyloric found between the stomach and small intestine
  3. ileocecal found between the small intestine and the large intestine
  4. internal anal
  5. external anal
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16
Q

mastication

A

chewing, break down of food by the teeth and facial muscles

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17
Q

preparation for swallowing

A

moistening of food bolus from saliva

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18
Q

onset of digestion

A

enzymatic breakdown of carbohydrates

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19
Q

what is the process of swallowing

A

oral phase: tongue pushes food bolus to the back of the mouth
pharyngeal phase: sift palate elevates to prevent food from entering the nasal passage
epiglottis covers the glottis preventing entry into the trachea the upper esophageal sphincter relaxes
esophageal phase: Food descends the esophagus

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20
Q

What is the function of the stomach

A

the stomach stores ingested material, continues digestion and regulates emptying into the small intestine

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21
Q

What is happening during Digestion

A

mechanical digestion occurs through the the folded surfaces such as rugae
chemical digestion: HCl provides the acidic environment of the stomach and helps with protein digestion. Pepsin enzyme that breaks down proteins

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22
Q

What does ingested food leave the stomach as

A

Chyme

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23
Q

The small intestine is spilt into three sections what are they?

A

Duodenum
Jejunum
Ileum

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24
Q

What is the primary site of digestion and absorption in the body

A

Small intestine

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25
Q

Digestion is aided by what?

A

aided by hydrolytic enzymes that break down dietary macromolecules

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26
Q

Why can the absorption of particles be so efficient

A

large surface area

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27
Q

What does an increase in surface area maximize?

A

maximize contact between intestinal contents and epithelium, facilitating digestion and absorption

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28
Q

What is the function of the large intestine?

A

store and concentrate undigested material prior to excretion

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29
Q

What are the parts of the Large intestine

A

Cecum
appendix
ascending colon
transverse colon
descending colon
sigmoid colon
rectum

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30
Q

what is the function of the appendx

A

it may act as a haven for gut bacteria

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31
Q

what is the function of the cecum

A

first part of the colon and in herbivores helps with cellulose digestion

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32
Q

What is the function of the ascending, transverse, descending and sigmoid colon

A

absorption of ions, water, bacterial metabolism

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33
Q

What is the general function of salivary glands, liver, gallbladder and pancreas

A

secrete substances into the GI tract that aid in digestion

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34
Q

what are the types of salivary glands

A

parotid salivary gland, sublingual, submandibular

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35
Q

What do the salivary glands secrete?

A

water and mucus
amylase

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36
Q

what does the liver secrete?

A

Bile salts which facilitate fat digestion
Bicarbonate (neutralizes acidic chyme coming from the stomach)
organic waste products and trace metals (eliminated in feces)

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37
Q

Where is Bile stored?

A

Gallbladder

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38
Q

What is the Function of the Pancreas

A

exocrine pancreas is part of the digestive system: Acinar cells secrete into the small intestine via the pancreatic duct
Endocrine pancreas part of the endocrine system: islets of Langerhans secrete hormones into the blood stream

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39
Q

what do pancreatic secretions include?

A

Bicarbonate: acts to neutralize the acidity of Chyme
carbohydrate: pancreatic amalyse
protein: trypsin, chymotrypsin
Fat: Pancreatic lipase

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40
Q

what is peristalsis?

A

travelling wave of contraction that helps push contents of food along

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41
Q

What is Segmentation?

A

more of a mixing function alternating patterns of contraction, formation of individual pockets

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42
Q

what does stretch initiate?

A

initiates circular contraction behind the stimulant, and relaxation in front of it

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43
Q

What can reflex response be innervated by?

A

autonomic input

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44
Q

what is the general pattern of peristalsis?

A
  1. Local stretch responses cause release of serotonin
    • serotonin activates the myenteric plexus
  2. Neurons projecting “upstream” activated and release factors that cause smooth muscle contraction
  3. Neurons projecting “downstream” activated and release factors that cause smooth muscle relaxation
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45
Q

What is the General patterns of Segmentation?

A
  1. local contractions separate the intestine into pockets
  2. subsequent contraction divides pockets centrally
  3. rhythmic contractions continue to subdivide pockets mixing their contents
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46
Q

What is Basic electrical rhythm (BER)?

A

Rhythmic contractions of segmentation have their basis in underlaying oscillations in the membrane potential of smooth muscle cells

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47
Q

What are the interstitial cells of cajal

A

Rhythmic activity originates from pacemaker cells which establish the wavelength

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48
Q

How is BER modulated?

A

multiple factors help modulate intestinal motility
ACH increases activity, and simulates contraction
Epinephrine decreases activity and depresses contraction

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49
Q

What is the Migrating myoelectric Complex (MMC)?

A

after a meal has been absorbed, segmentation stops, and is replaced by a sweeping wave of contraction

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50
Q

What are the three phases associated with the MMC

A

phase 1: quiescent period, no activity
phase 2: irregular electrical and mechanical activity
phase 3: burst of regular electrical and mechanical activity

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51
Q

What does ingestion of a meal do?

A

inhibits the MMC

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52
Q

what is MMC activity controlled by?

A

Motilin

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53
Q

How does motilin affect the MMC?

A

increased plasma concentration of motilin triggers MMC
ingestion of a meal inhibits motilin secretion, plasma levels drop and MMCs stop

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54
Q

What is the purpose of mastication?

A

it is a voluntary movement that breaks up large food particles, and mixes the ingested food and aids in swallowing

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55
Q

What is the segment-specific motility in the stomach?

A
  1. activity of the lower esophageal sphincter
  2. gastric motility, gastric emptying
  3. Belching and vomiting
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56
Q

Describe the activity of the lower esophageal sphincter?

A

Tonically active, but relaxes on swallowing to allow entrance of food into the stomach

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57
Q

The lower esophageal sphincter contracts in response to _____ and Relaxes in response to _____

A

Ach,
NO and VIP

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58
Q

What are the three major components of the lower esophageal sphincter?

A
  1. internal sphincter- thickening of esophageal smooth muscle
  2. External sphincter- crural portion of the diaphragm surrounds the esophagus
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59
Q

What is repetitive relaxation?

A

Arrival of Food Bolus in the stomach

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60
Q

When the stomach relaxes the stomach allows ______ in ______ with a marginal increase in _____________

A

increase in volume with marginal increase in pressure

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61
Q

Overfilling of the stomach results in ______

A

belching or vomiting

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62
Q

What is Gastric peristalsis?

A

mixes the stomach and pushes Food through the Pyloric sphincter?

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63
Q

how does Gastric peristalsis happen?

A

peristaltic wave initiates at upper stomach and increases as the wave moves down the stomach mixing the contents

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64
Q

What is Pyloric Sensing?

A

a small amount if liquid chyme is forced through the pyloric sphincter

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65
Q

What type of meals delay gastric emptying?

A

meals rich in protein or fat

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66
Q

What extrinsic factors control gastric emptying?

A

stomach and intestinal contents
acidity
distension
hypertonicity

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67
Q

How does stomach and intestinal contents affect gastric emptying

A

high fat and high protein meals delay gastric emptying

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68
Q

How does acidity affect gastric emptying?

A

feedback loops exist between stomach and small intestine, exposure of the duodenum to acidity inhibits gastric emptying

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69
Q

How does distention affect gastric emptying?

A

distension increases peristaltic contractions, there fore after a large meal stomach contractions are greater

distension of the duodenum will inhibit gastric emptying

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70
Q

how does hypertonicity affect gastric emptying?

A

gastric emptying is fastest when the duodenal contents are isotonic, a hypertonic solution will inhibit gastric emptying

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71
Q

if the duodenum is too hypertonic what does it affect?

A

water absorption

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72
Q

What is aerophagia?

A

Air unavoidably swallowed during eating and drinking

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73
Q

When there is air in the stomach it _____ gastric volume initiating a _______ _____ that ______ the lower esophageal sphincter allowing ______ to escape

A

increases
reflex response
relaxes
gas

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74
Q

What is emesis?

A

emesis or vomiting is an involuntary forceful expulsion of stomach contents via the mouth

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75
Q

What triggers can cause vomiting?

A

digestive issues such as bowel obstruction or food allergy
Sensory issues like motion sickness, drug reaction
emetics medically administered to prevent poisonings
social cues

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76
Q

What are tonic contractions?

A

relatively prolonged contractions that can isolate segments of the intestine

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77
Q

what is the gastrolienal reflex?

A

opening of the ileocecal valve in response to food leaving the stomach

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78
Q

What happens during defecation

A

increases in rectal pressure caused by mass contraction initiates defecation reflux

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79
Q

How do we know we have to defecate?

A

urge to defecate can be delayed by voluntary contraction of the external anal sphincter

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80
Q

What happens can initiated via voluntary straining?

A

Contraction of Abdominal muscles and relaxation of puborectalis combines to lower the pelvic floor, open the anorectal angle and facilitates defecation

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81
Q

How does the body regulate GI processes?

A

Stimulus, receptor, effector (neural/ hormonal), response

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82
Q

What are the four general factors triggering GI response?

A
  1. volume of the luminal contents
  2. osmolarity
  3. acidity
  4. nutrient composition
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83
Q

When a stimuli of volume is received it is received on ______ receptor and acts on ____________

A

mechanoreceptor, Smooth muscle

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84
Q

When a stimuli of Osmolarity is received it is received on ______ receptor and acts on ____________

A

Osmoreceptor, exocrine glands

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85
Q

When a stimuli of acidity is received it is received on ______ receptor and acts on ____________

A

Chemoreceptors, exocrine glands

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86
Q

When a stimuli of nutrients is received it is received on ______ receptor and acts on ____________

A

Chemoreceptors, exocrine glands

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87
Q

What are the two types of neural reflex loops?

A
  1. short reflexes
  2. long reflexes
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88
Q

What is the short reflex loop?

A

stimulus—> receptor—> nerve plexus—-> smooth muscle or gland—–> response

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89
Q

What is a long reflex loop?

A

Stimulus—> sight, smell, taste of food–> central nervous system ( emotional states/hunger) —->efferent autonomic neurons —-> nerve plexus—> smooth muscle or gland—-> response

90
Q

What is hormonal regultion

A

stimulus—> hormone secretion

91
Q

What is Gastrin

A

A stomach created hormone which stimulus acid secretion and motility

92
Q

What is CCK? responses?

A

A small intestine created hormone which inhabits acid secretion and motility in the stomach
stimulates enzyme secretion in the pancreas
simulate contraction of the gallbladder

93
Q

What is secretin? Where is it produced? and what is its responses?

A

it is a hormone created in the small intestine, that releases when acid is present
in the stomach it inhibits acid secretion and motility
in the pancreas and liver it stimulates HCO3- secretion

94
Q

What is GIP? Where it is produced? and what are its responses

A

it is a hormone produced in the small intestine, it is triggered when glucose and fat is present.
in the pancreas it stimulates insulin secretion

95
Q

What are the three phases of gastrointestinal regulation?

A

Cephalic phase, Gastric phase, Intestinal phase

96
Q

What is the Cephalic phase?

A

sight, smell, taste

97
Q

What is the Gastric phase?

A

Distension, acidity, amino acids/peptides

98
Q

What is the intestinal phase?

A

Distention, acidity, osmolarity, digestive products

99
Q

Where do the majority of secretions into the gastrointestinal tract occur?

A

the accessory glands

100
Q

What are the salivary secretions? and their purpose

A

there are around 1500mL of secretions released, these include water, electrolytes, mucus (lubrication). enzymes and immune modulators

101
Q

how are salivary secretions regulated?

A

ANS regulated
Sympathetic N.S: thicker secretion, respiration role, regulated by norepinephrine
Parasympathetic N.S: watery secretion, Digestion role, regulated by Ach

102
Q

What are the Gastric secretions and their functions?

A

around 2000mL secreted
Mucus- lubricates/protect stomach lining
HCL: solubilizes some food, kills microbes, cleaves pepsinogen
Enzymes: pepsinogen–> pepsin, cleaves proteins
Hormones

103
Q

Where are the Gastric secretions secreted from?

A

mucus– surface mucous cells
HCl- parietal cells
Histamine- ECL cell
pepsinogen- Chief cells

104
Q

What are the pancreatic secretions and their function?

A

about 1500mL secretions
Bicarbonate - acts to neutralize the acidity of chyme
enzymes

105
Q

How is HCO3- regulated

A

neutralization of intestinal acid provides a negative feedback on secretin stopping its production or limiting it

106
Q

What are the secretions of the Gallbladder? and their function?

A

daily production aprrox 500mL
Water
Bile salts- solubilize water-insoluble fats
Bilirubin- hemoglobin breakdown, excreted
Fats- includes cholesterol and lecithin; aids digestion

107
Q

When does the gallbladder release bile?

A

Water and NaCl fare absorbed, making it more concentrated, and in response to CCK, the gallbladder contracts and the sphincter of Oddi relaxes, allowing bile to be secreted in the duodenum

108
Q

What are the intestinal secretions and their functions?

A

around 1500mL
water/electrolytes: maintains fluidity of intestinal contents
Mucus: lubrication and protection
enzymes: aid digestions

109
Q

Where are the secretions of the intestine occur?

A

intestinal crypt, when the epithelial cells secrete ions water follows by osmosis

110
Q

how can the osmolarity in the duodenum changes?

A

Chyme entering, high concentration of solutes = hypertonic environment
osmotic forces drive water from the plasma into the intestinal lumen

111
Q

What is digestion?

A

process of breaking down large particles of food and high-molecular weight substances into small molecules

112
Q

What are the three macronutrients?

A

Fats, Carbohydrates, Protein

113
Q

What is the role of carbohydrates?

A

major energy source, and essential for human tissues

114
Q

what are the types of dietary carbohydrates?

A

monosaccharides, Disaccharides, Polysaccharides

115
Q

What are types of monosaccharides

A

simple sugars such as glucose and fructose

116
Q

What are Disaccharides?

A

composed of two monosaccharides, sucrose, maltose, lactose

lactose==> glucose + galactose
maltose==> glucose+ glucose

117
Q

What are Polysaccharides?

A

polymers of sugar residues
starch, glycogen

118
Q

What is the role of fat?

A

Major source of energy, most abundant is triglyceride

119
Q

how is composition of fatty acids affect its physical properties

A

fatty acyl composition affects the physical properties
this creates saturated fatty acids, mono-unsaturated fatty acids (more fluidity)
poly-unsaturated fatty acids

120
Q

How can you tell the composition of triglycerides?

A

if it is solid it will be mainly saturated fat 85%, 6% monounsaturated
semi-solid: 56% monosaturated, 29% monounsaturated, 3% polyunsaturated
oil/liquid: 13% saturated, 26% monounsaturated, 59% polyunsaturated

121
Q

What is the function of proteins?

A

major source of building blocks for numerous biological functions ( new proteins, neurotransmitters)

122
Q

What is the primary structure of a protein?

A

a linear sequence of amino acids in a polypeptide chain

123
Q

what is the secondary structure of a protein?

A

structural motifs in the polypeptide chain, alpha-helices and beta pleated sheets

124
Q

What is the tertiary structure of a protein?

A

three dimensional structure formed by a polypeptide chain

125
Q

What is the quaternary structure of a protein?

A

complexes with multiple polypeptide chains, hemoglobin

126
Q

What is the supramolecular protein assemblies?

A

protein complexes, myofilaments, collagen fibers

127
Q

What are micronutrients?

A

trace amounts of minerals and vitamins to maintain good health

128
Q

What are the fat soluble vitamins?

A

A, E, D

129
Q

What are trace elements required for a diet?

A

iron, iodine, zinc

130
Q

How are carbohydrates broken down?

A

they are broken down from polysaccharides to monosaccharides, and are broken down via their enzymatic breakdown

131
Q

how are carbohydrates broken down in the mouth?

A

salivary amylase

132
Q

how are carbohydrates broken down the small intestine?

A

Pancreatic amylase
- soluble protein
cleaves polysaccharides into smaller fragments will cleave between the subunits
Brush border enzymes
- contain many enzymes that are specific to different disaccharides

133
Q

How to carbohydrates get absorbed?

A

they must cross the intestinal epithelium to be absorbed by the body

134
Q

how does fiber affect the GI tract?

A
  1. delayed gastric emptying and increased satiety
  2. impaired absorptions in the small intestine
  3. fiber fermentation in the large intestine
  4. fecel bulking
135
Q

how are fats digested?

A

they must be emulsified first and then acted on by lipase enzymes

136
Q

what does emulsification require?

A

mechanical digestion
emulsifying agents contained in bile: phospholipids and bile salts

137
Q

how can dietary fat be absorbed?

A

small fraction can be absorbed across the epithelial cell membrane
uptake of fatty across occurs by simple diffusion across a cell membrane (flip-flop)

138
Q

What is protein broken down into?

A

broken down into amino acids and absorbed

139
Q

how is protein digestion mediated?

A

by proteolytic enzymes which are secreted as their inactive forms

140
Q

how are protease enzymes classified as?

A

endopeptidases
exopeptidases

141
Q

What is the function of endopeptidases?

A

cleave proteins at interior peptide bonds
these can be trypsin, chymotrypsin, elastase

142
Q

what is the function of exopeptidases?

A

cleave proteins at their n and c termini and are called aminopeptidases and carboxypeptidases

143
Q

What happens when protein enters the stomach?

A

in the highly acidic environment denatures the protein
pepsin is secreted which cleaves large polypeptides

144
Q

How is protein digested in the small intestine?

A

pancreatic enzymes and intestinal brush border enzymes

145
Q

how are pancreatic enzymes activated?

A

through the activity of enterokinase and trypsin

146
Q

why is enterokinase important?

A

it cleaves trypsinogen to yield trypsin, which actives more trypsinogen in a feed forward loop, and then cleaves other pancreatic proenzymes into their active forms

147
Q

What does intestinal brush border enzymes contain?

A

aminopeptidases, carboxypeptidases and endopeptidases

148
Q

What do the enzymes in the intestinal brush border do?

A

generate individual amino acids, dipeptides and tripeptides

149
Q

How does protein absorption occur?

A

small peptides are taken up into epithelial cells by transport protein called PepT1
once in cell cleaved to amino acids and exit cell via facilitated diffusion

150
Q

majority of water-soluble vitamins are absorbed first into the ___________

A

small intestine

151
Q

How is Folate absorbed?

A

folate absorption is dependent on a proton coupled folate transporter

152
Q

How is B12 absorbed?

A

occurs in the ileum and requires binding to IF

153
Q

for Fat soluble vitamins esters must first be_________ in the gut

A

Hydrolyzed

154
Q

What is tight regulation of iron absorptions?

A

the amount taken up matches what is lost. so whole the average iron intake is 20mg only 5% is absorbed

155
Q

Iron is most commonly found in the form of what?

A

ferric iron

156
Q

What must happen to iron before it can be absorbed? How does this occur?

A

it must be changed to its ferrous form. a ferric reductase in the brush border epithelium reduces ferric iron to Ferrous iron

157
Q

What allows the uptake of ferrous iron?

A

DMT1

158
Q

Where is ferrous iron uptake into and what happens once inside?

A

they are taken into the enterocytes, and some of it is stored and bound to ferritin and the remainder is transported out of the cell and into circulation

159
Q

How is ferrous exported?

A

exported via the basolateral transporter ferroprotein1

160
Q

What do secretions from the liver facilitate?

A

digestion and absorption

161
Q

Where do the absorptive segments of the GI tract drain

A

the hepatic portal vein

162
Q

Where does the liver receive blood from and where does it drain its blood?

A

it receives blood frim the aorta and through venous drainage via the vena cava

163
Q

What is the hepatic portal vein?

A

gives blood to liver, from the stomach and intestines

164
Q

Why does the liver receive blood via the hepatic portal system?

A

substances absorbed in the intestine must pass through the liver and be processed before entering the general circulation system

165
Q

What does the portal triad contain?

A

portal vein, hepatic artery and Bile duct

166
Q

What is the function of the hepatic artery?

A

arterial blood flows from the hepatic artery to the central vein oxygenating hepatocytes

167
Q

What is the function of the portal vein?

A

Blood from the portal vein percolates between the hepatocytes, emptying into the central vein

168
Q

What is the function of the bile duct in regards to the hepatic lobes?

A

bile produced by the hepatocytes drains into the bile duct

169
Q

Blood travelling through the __________________ can flow through gaps in the ______________________ entering the space of _________ to come into direct contact with ______________

A

hepatic sinusoids, endothelial cell layer, Disse, Hepatocytes

170
Q

Why is lobule (liver) organization important?

A

it creates a graded microenvironment that leads to zonation of the hepatic metabolism

171
Q

On the P-C axis the cells closet to the central vein control what?

A

glycolysis, bile acid production, glutamine synthesis, xenobiotic metabolism

172
Q

On the P-C axis the cells closet to the portal tract do what?

A

gluconeogenesis, beta-oxidation, cholesterol biosynthesis, Ureagenesis and protein secretion

173
Q

On the P-C axis the cells in between the central vein and portal tract do what?

A

Iron homeostasis, Modulation of insulin growth factors

174
Q

What does drug overdose cause?

A

toxic metabolite accumulation and damage in the pericentral zone

175
Q

What does cholangitis damage?

A

the periportal zone

176
Q

What is the livers role in carbohydrate metabolism?

A

it uptakes and stores glucose through glycogenesis and stores it as glycogen
it can release glucose when blood sugar drops through Glycogenolysis
and it can synthesize glucose through gluconeogenesis

177
Q

What is the Livers role in lipid metabolism?

A
  1. it can store fatty acids as triglycerides
  2. it can cleave fatty acids through beta-oxidation( energy production)
  3. De novo lipogenesis to create more fatty acids when glucose is high
  4. lipoprotein secretion
178
Q

What is non-alcoholic fatty livre disease?

A

secondary to obesity, where the liver becomes fatty

179
Q

Where is vitamin A stored?

A

in liver specifically in the hepatic stellate cells

180
Q

Hepatocytes express detoxifying enzymes what are they and what do they do?

A

they express CYPs which mainly detoxify xenobiotics and toxins primarily through oxidation

181
Q

What is the most common reaction catalyzed by CYPs?

A

mono-oxygenase reaction

182
Q

How is alcohol metabolized?

A

Ethanol —CYP2E1—-> Acetaldehyde

183
Q

When you have to take a medication such as acetaminophen what normally happens? and what happens when you mix it with alcohol?

A

normally it will go through Glucoronidation leading to stable metabolite excretion
how ever when mixed with alcohol CYP2E1 reacts causes a toxic metabolite

184
Q

Why must ammonia be tightly regulated and detoxified by the liver?

A

it is membrane permeable and is toxic to the central nervous system

185
Q

how is ammonia metabolized?

A

within a hepatocyte mitochondria ammonia is metabolized to urea

186
Q

Why can the liver regenerate its self?

A

because its role is to detoxify the liver can become damaged and therefore regenerate its self

187
Q

What is Fatty liver disease?

A

it is the first stage of liver disease and its deposits of fat can lead to liver enlargement
this is seen throughfibrous portal expansion

188
Q

What is liver Fibrosis?

A

scar tissue formation, intralobular degeneration

189
Q

What is Cirrhosis?

A

Growth of connective tissue destroys liver cells.

190
Q

What are the roles of bile?

A

central role is in digestion and absorption but also facilitates the excretion of lipid soluble waste products into the feces

191
Q

Where is bile secreted from?

A

the hepatocyte into the bile canaliculi which drains into the bile duct

192
Q

What is enterohepatic circulation?

A

liver secretes about 500mL of bile a day much of which is reabsorbed into the intestine and then excreted again

193
Q

why does bile have yellow-green colouration?

A

due to the presence of bilirubin and biliverdin

194
Q

What are bilirubin and biliverdin products of?

A

products of hemoglobin catabolism, which are continually produced in the liver and spleen when old/damaged red blood cells are broken down

195
Q

when circulating bilirubin is bound to albumin it can be taken up by the _______ and metabolized into ________ ______

A

hepatocytes, bilirubin glucuronide

196
Q

What is Bilirubin glucuronide?

A

it is a highly water soluble molecule which can be transported into the bile canaliculi for secretion

197
Q

What is jaundice?

A

caused when bilirubin accumulates in the blood

198
Q

What are the origins of jaundice?

A

pre-haptic origin (increased RBC breakdown), hepatic origin (liver disease) or post-hepatic (obstruction of bile seertion)

199
Q

What can hyperbilirubinemia lead to?

A

leads to bilirubin accumulation in the CNS causing brain damage

200
Q

what is neonatal jaundice caused by?

A

associated with the breakdown of fetal hemoglobin and delayed maturation of metabolic pathways in the liver
treated via phototherapy

201
Q

Why does the stomach not digest itself?

A

in the gastric lumen you have pepsinogen and pepsin which interact with the mucous bicarbonate barrier which neutralizes the acidity of the stomach.

202
Q

How is the stomach protected?

A

stomach lining is protected from proteolytic enzymes and acidic contents by alkaline mucus, tight junctions and turnover of damaged cells

203
Q

What happens when the the mucosal barrier breaksdown?

A

can lead to erosin of gastric epithelium and ulcer formation

204
Q

What is the main cause of stomach ulcers?

A

the bacterium Helicobacter pylori

205
Q

How can stomach ulcers be identified?

A

medical history and physical
laboratory test for H.Pylori
endoscopy
barium meal

206
Q

What is the treatment for stomach ulcers?

A

antibiotics
neutralization of stomach acids
Inhibition of stomach acid
- Histamine blockers-block specific histamine receptor
-proton pump inhibiotrs

207
Q

What are the two types of gall stones?

A

cholesterol
calcium bilirubinate

208
Q

How do cholesterol stones develop?

A

cholesterol stones develop when concentration of cholesterol in the bile increases to the point where it precipitates out of solution

209
Q

How can Biliary cholesterol increase?

A

can result from increased hepatic secretion of cholesterol or too much ion and water absorption

210
Q

Small Gallstones that form in the gallbladder can what?

A

be easily passed into the intestine and excreted

211
Q

Larger gallstones can cause what?

A

larger stones may be trapped leaving the gallbladder, causing pain however digestion is largely unaffected

212
Q

When larger stones get trapped in the bile duct what can happen?

A

may cause consequences with fat digestion/absorption, causing diarrhea. this can also cause backflow, and decrease bilirubin excretion and cause obstructive jaundice

213
Q

When larger gallstones get trapped in ampulla of vater what can happen?

A

this will block bile and pancreatic secretions, and may cause problems with nutrient digestion/absorption and cause nutritional deficiency

214
Q

How can gallstones be diagnosed?

A

Medical history
ultrasound
Ct scan

215
Q

How can gallstones be treated?

A

medication such as ursodiol
surgical removal of the gallbladder

216
Q

What is colitis?

A

inflammation of the inner lining of the colon

217
Q

What are the symptoms of colitis?

A

abdominal pain, cramping
diarrhea

218
Q

What can cause colitis?

A

infection
IBS
ischemia

219
Q

Clostridium difficle is a bacteria which can cause colitis which type can it cause?

A

health associated infective diarrhea also known as community acquired colitis

220
Q

what can be some symptoms associated with a c.diff infection?

A

self -limiting diarrhea–> fulminant colitis–> pseudomembranous colitis —-> toxic megacolon –> bowel perforation and sepsis—> multiple organ dysfunction syndrome

221
Q

How can C.diff be treated?

A

1.antibiotic therapy
pro: effectively targets C.diff
Con: antibiotic resistance
2. Fecal microbiota transplant

222
Q
A

PHYSL 214 (2 decks)

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