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PHGY 210 > digestion - lecture 8 > Flashcards

digestion - lecture 8 Flashcards

1
Q

describe pancreatic lipases

A

Pancreatic procolipase – trypsin –> colipase

triglycerides – pancreatic lipase ph 8 –> fatty acids, di and monoglycerides
NEEDS colipase = cofactor, only happens when have it

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2
Q

describe liver

A

largest gland of body
right and left lobes
for storage, synthesis, detox, metabolism

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3
Q

what does liver secrete

A

bile from hepatic ducts
bile travels in common bile duct
bile released into si at same place as pancreatic juices

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4
Q

describe liver bile composition -comp stuff

A

0.5-1l/day
isotonic fluid - sodium, potassium, chloride, BICARB
ph 7.8-8.2 = helps neutralize acidic chyme

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5
Q

describe liver bile composition -solids stuff

A

~3% solids - NO digestive enzymes tho
bile acts - bile salts
bile pigments - hemoglobin breakdown products
cholesterol
phospholipids

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6
Q

describe bile secretion by liver

A

continuous
~0.5-1.0 l/day

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7
Q

describe entrance of bile into duo

A

intermittent = only when meal
volume of bile entering si is <500-700ml/day
moves into gallbladder

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8
Q

what is function of gallbladder

A

concentrates solids =
hepatic bile 3%
gall bladder bile 10-20% of bile
viscocity increases

reduces ph =
Hepatic bile 7.8-8.2
gall bladder bile 7.0-7.5 - less bicarb

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9
Q

what does gallbladder not do

A

DOES NOT synthesize bile salts = stores and concentrates THEMMM

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10
Q

What are the results of CHOLECYSTECTOMY

A

gall bladder removal
Usually bc gallstones
bile salts made from phospholipids precipitates and cholesterol = if not enough bile salts = gallstones and if block cystic duct = bad
but now if removed = still have liver bile only

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11
Q

what are bile salts

A

synthesized in liver from cholesterol

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12
Q

what do bile salts do

A

facilitates digestion, transport and absorption of FAT (including cholesterol) by forming water soluble complexes with fats = micelles
facilitates transport and absorption of fat soluble vitamins = a,d,e,k
reduces surface tension and stabilize emulsions = now can be acted upon by lipases

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13
Q

describe bile salts and micelle formation

A

ampthatic
micelle = inside non polar and outside polar
mixed micelle = a,d,e,k travel in micelle
Surrounded by bile acids
smaller if more bile salts
Circular smaller droplets = more lipases can act
help form stable emulsions = small emulsions = more sa for lipases to act

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14
Q

Describe bile salts - amounts in body

A

bile salt pool = 3.5g
daily synthesis= 0.5g
daily release into intestine = 15-20g
more bile salts reabs into portal blood and returned to liver via enterohepatic circ
entire bile salt pool recirculated several times a day between liver–>git–>liver

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15
Q

describe hepatic circulation

A

heart = via aorta to liver and via aorta to intestinal tract
liver secretions go to si
si to liver via hepatic portal vein
liver to heart = via hepatic vein to inferior vena cava

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16
Q

describe enterohepactic circulation

A

bile salts have diff roles in diff parts of body
absorb recycled and used
back to liver = portal venous return

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17
Q

name intraporal functions of bile salts - 2

A

regulate hepatic bile flow
regulate synthesis of new bile salts

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18
Q

Describe intraportal functions of bile salts - regulate hepatic flow

A

the more bile salt returned via portal blood = larger the vol of bile secreted
pos feedback

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19
Q

What will happen to bile secretion if we remove ileum

A

decrease since less reabs

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20
Q

Describe intraportal functions of bile salts - regulate synthesis of new bile salts

A

the more bile salt returned in portal blood = smaller the amount of new bile salt being synthesized = more comes back so make less
neg feedback

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21
Q

What will happen to bile salt synthesis if we remove ileum

A

liver produces more bile salts

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22
Q

name and describe intrahepatic functions of bile salts

A

keep cholesterol in solution = cholesterol is insoluble in water
if cholesterol precipitates = gives rise to gallstones
in bile solubility of cholesterol increases by 2x10^6

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23
Q

Describe intra intestinal functions of bile salts - 2

A

intestinal lumen contains v watery medium
act as detergents and help form stable emulsions
assist in transport of fat and fat soluble vitamins (a,d,e,k) from si lumen into intestinal cell

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24
Q

Describe intracolonic functions of bile salts - regulate hepatic flow

A

inhibit sodium transport and h20 absorp = do not want to absorb too much = constipation
excess bile salt in colon = diarrhea

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25
Q

summarize bile salt function

A

intraportal = regulate volume of bile secreted by liver and synthesis of new bile salts
intrahepatic = keep cholesterol in soln
intraintestinal = si - emulsify and transport fats
intracolonic = prevents too much water absorp

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26
Q

describe purpose of phases of secretion

A

cephalic = psychic and gustatory, increase secretion from lover and pancrease to prepare for meal
gastric = not increase secretion at level of si
Intestinal = also increase secretion at si

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27
Q

describe regulation of pancreas secretion

A

contains cells that release =
larg vol of juice rich in bicarb
small vole of juice rich in - if have lots of acid in duo, decrease acidity of chyme enzymes - fatty meal and need lots of lipases

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28
Q

describe regulation of bile flow

A

choleretics = agents which cause liver to secrete larger amount of bile
cholagogues = agents which cause increase in gall bladder emptying

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29
Q

describe law of reciprocal activity

A

if gallbladder contarcted the spincter of oddi will be realxesd and vise versa
if have cck in system

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30
Q

describe summary of Summary of Regulation of Bile and Pancreatic Juice - vagus

A

cephalic - thinking of food
liver = +
gb contracts and sphincter relaxes = +++
pancreas (low vol/high enzyme/low ph )= +++
pancreas (high vol/low enzyme/high ph) = –

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31
Q

describe summary of Summary of Regulation of Bile and Pancreatic Juice - gastrin

A

gastric - food in stomach
liver = +
gb contracts and sphincter relaxes = +
pancreas (low vol/high enzyme/low ph) = +
pancreas (high vol/low enzyme/high ph) = +

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32
Q

describe summary of Summary of Regulation of Bile and Pancreatic Juice - cck

A

released from duo, when fat and protein rich meal
liver = –
gb contracts and sphincter relaxes = +++
pancreas (low vol/high enzyme/low ph) = +++
pancreas (high vol/low enzyme/high ph) = –

33
Q

describe summary of Summary of Regulation of Bile and Pancreatic Juice - secretin

A

lots of acidic conetnts in si
liver = + vol/hco3
gb contracts and sphincter relaxes = –
pancreas (low vol/high enzyme/low ph) = –
pancreas (high vol/low enzyme/high ph) = +++

34
Q

describe summary of Summary of Regulation of Bile and Pancreatic Juice - bile salts

A

liver = +++
gb contracts and sphincter relaxes = –
pancreas (low vol/high enzyme/low ph) = –
pancreas (high vol/low enzyme/high ph) = –

35
Q

what happens to polysaccharides as a result of salivary, gastric, pancreatic, and hepatic secretions

A

salivary and pancreatic amylase make polysacc to dissach must still go to monosacc tho

36
Q

what happens to proteins as a result of salivary, gastric, pancreatic, and hepatic secretions

A

pepsin, trypsin and chymotrypsin = convert proteins to small peptides
must still go to aas, di and tri peptides

37
Q

what happens to fats as a result of salivary, gastric, pancreatic, and hepatic secretions

A

fats —> mono, diglycerides and FAs
by lipase, colipase and bile salts

38
Q

describe final steps in digestion

A

Mediated by intestinal enzymes
produced by mucosa at site where absorption happens

39
Q

what does si secrete

A

intestinal juice = water mucus ions

40
Q

what does si receive

A

pancreatic juice enzymes to aid digestions

41
Q

what does si contain

A

brush border enzymes
attached to microvilli of si epi cells

42
Q

describe si mechanical digestion

A

involves segmentation at si = contact absorptive cells

43
Q

describe si chemical digestion

A

occurs as chyme mixes with pancreatic juice, intestinal juice and bile

44
Q

describe si absorption

A

of digested nutrients at level of si

45
Q

describe Increased Surface Area in the Stomach for Secretion

A

tubular glands - secretion
enterocytes = have microvilli, in villus region and also has crypt region = invaginations where fluid secretion happens, completes digestion and absorption - secretion, digestion and absorption

46
Q

describe crypt cells

A

lack digestive enzymes
Secrete a large vol - 3l/day of alkaline fluid known as succus entericus

47
Q

describe secretions in si

A

crypts –> succus entericus
vol = 3l.day
isotonic = na, k, cl, hco3-
ph ~7.5-9
VILLI do not secrete fluid

48
Q

what are villi cells

A

dont secrete fluid but complete digestion and absorb nutrients and fluids
enterocytes in villi make digestive enzymes which remain in brush border

49
Q

describe small intestine enzymes - vili

A

enterokinase - lumen epi cells
amylase, lipase, aminopeptidases, dipeptidases

50
Q

describe disaccharases - vili

A

brush border
sucrase, maltase, isomaltose, lactase

51
Q

what do villi cells do

A

RAPId turnover
cells mature as they migrate up to villus regions - divides and differentiates upwards
cells at tip apoptose and slough into lumen - die by enzymes

52
Q

describe absorption of digested nutrients in villus

A

fats absorbed via lacteals = chylomicrons - absorbed at lacteal
carbs and sugars absorbed via capillaru and go to liver via hepatic portal vein

53
Q

name added enzymes by si = for digestion

A

disaccharases = disacc to monosacc
peptidases = small peptides to aas di and tripeptides

54
Q

where is digestion and absorption of nutrients completed

A

in small INTESTINEEE

55
Q

describe colonic secretions

A

small vol
alkaline [bicarb] = 100-150meq/l and [potassium] = 100-150meq/l
lots of mucin for lube
no digestive enzymes or absorption
Bacterial activity = health of body and git, keep bacteria at level of colon

56
Q

describe regulation of intestinal secretions

A

Local enteric reflexes
Vago-vagal reflexes
Hormonal factors

57
Q

describe input vs output - daily (feces)

A

in = 2000ml h2o, solids 500g
out = 100ml h2o, solids 50g =
(30% bacteria, 30% undigested fiber, 10-20% lipids, 10-20% inorganic matter)

58
Q

describe daily ml of secretion

A

Salivary glands = 1500ml
stomach = 2500ml
bile = 500ml
pancreas = 1500ml
intestine = 1000ml

2l ingested + 7l secreted = ~9l must be reasb

59
Q

what else is reabs into git - besides water

A

Very large quantities of ions are also reabsorbed from lumen of the GIT

60
Q

describe Proteins Released into the GIT via Secretions

A

50g enzymes
30g as cells
80g protein - broken down into aas = aa pool need to return aas for homeostasis

61
Q

WHAT is being absorbed?

A

Most of absorption is REABSORPTION

62
Q

WHERE is it being absorbed?

A

sites of exchange characterized by = v large sa of si and intimate contact with bvs

63
Q

describe structure of si

A

circular folds, villi, microvilli, relative sa = 600
area in excess of need
only gi organ essential to life = colon cannot take over nutrient absorption

64
Q

describe villus

A

postprandial flow to intestine = 1-2l/min
efficient absorption = each villus has capillary loop and lacteal, large sa close to blood and lymph flow
Lymph flow = 1-2l/min

65
Q

name and describe major areas of absorption

A

duo = most of iron, calcium, cho and protein lipids sodium and water, least bile salts
jejunum = less than duo but still cho and proteins lipids na and h2o, little bile salts
Ileum = less than both above but still cho, proteins lipids na and h20, also only place to have vit b12 and most of bile salts

66
Q

HOW does absorption take place?

A

Simple Diffusion
Facilitated Diffusion Active Transport
Pinocytosis
osmosis - water always follows osmotic gradient generated by movement of ions and nutrients

67
Q

What Limits Absorption?

A

requirements for absorption =
Adequate Digestion – Enzymes (activated), optimal pH and ionic composition
Adequate Sites for Absorption
Adequate Transit Time for Absorption
Adequate Co-factors, Transporters

68
Q

describe absorption - by which parts

A

si = 7l and colon = 2l

69
Q

describe absorption of water

A

can absorb more than we usually take in
mac capacity of si = 15l/day
max capacity of li = 4-5l/day

70
Q

describe carb digestion and absorption

A

lactose - if no lactase = lactose intolerance – broken down to galactose and glucose
starch = need salivary amylase, and pancreatic amylase and many si enzymes in brush border - critical for them to move into cells – broken down to glucose
sucrose – broken down to fructose and glucose

71
Q

describe protein digestion and absorption

A

need pepsin, pancreatic proteases - broken down to aas
either peptidases break in to small peptides or free aas go through carrier mediated transport to aas into cel

72
Q

describe fat digestion and absorption

A

triglycerides converted. by lipase, colipase, bile salts to monoglycerides and free fatty acids

monoglycerides either become free fatty acids or glycerol and go directly to capillary
if free fatty acids = makes micelle, help of conjugated bile salts, liver and ileum
micelle into enterocyte = triglycerides resynthesized and mixes with protein, cholesterol and phospholipids to make chylomicrons and go to lacteals

73
Q

describe efficiency of git

A

carbs = 99%
fats = 95%
Proteins = 92%

74
Q

why is git highly efficient

A

effective coordination of activities - neural, hormonal, motor, secretory, enzymatic - within an organ and between organs

75
Q

in response to a meal…

A

wave of secretory activity preceding, accompanying and trailing behind meal
wave of motor activity which receives, accommodates and conveys the meal

76
Q

describe git transit times

A

related to functional activities of each organs = times tailored to what needs to be done in terms of processing

mouth = <1sec
eso = seconds
stomach = mins-hours
si = several hours
li = hours -days

77
Q

name all protective mechanisms

A

Mucin
Inactive Proteases, Trypsin Inhibitor
Gastric Mucosal Barrier
Sphincters prevent reflux
Negative Feedback Inhibition of Gastrin
Neutralization of duodenal contents
MyogenicMotorComplex= “HOUSEKEEPiING”
* Etc.,Etc.

78
Q

what does liver produce

A

bile salts

PHGY 210 (36 decks)

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