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RAD414 pt 2 > gastrointestinal tract > Flashcards

gastrointestinal tract Flashcards

1
Q

what are the 8 parts of the gastrointestinal tract/system

A

oral cavity
oesophagus
small intestine
liver
pancreas
gall bladder
large intestine

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2
Q

what is the total length of the GIT

A

6m

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3
Q

due to what can increase the SA of the intestinal lumen to almost 200 square meters

A

villi

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4
Q

what are the 5 things that make up the structure of the oesophagus

A
  1. stratified squamous epithelium
  2. muscular mucosa
    (1 and 2 together are simply considered as mucosa)
  3. submucosa
  4. circular muscle
  5. longitudinal muscle
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5
Q

what are the 3 pairs of salivary glands and where in the mouth are they found

A
  1. sublingual (under the tongue)
  2. parotid (overlying the cheek)
  3. submandibular gland (close to jawline)
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6
Q

why is saliva able to dissolve soluble food components

A

it is made of mostly water

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7
Q

what found in saliva can aid in digesting starch

A

amylase

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8
Q

how is the chewed food/bolus of food carried down into the stomach?

A

carried by the peristalsis (involuntary muscle movement) to stomach via cardiac sphincter (upper portion of stomach/lower oesophageal)

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9
Q

what prevents food from falling into the lungs

A

epiglottis covers the trachea

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10
Q

why is the oesophagus lined by squamous epithelium

A

to protect it from food which is abrasive

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11
Q

what makes the oesophagus squamous lining resilient

A

larger surface area attachment and long periphery attaching it to its neighbours

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12
Q

what role does the submucosa play when the squamous cells aren’t working well

A
  • they are relatively loose with many elastic fibres so can swell (due to pressure) during passage of food
  • they also contain small seromucous glands which aid lubrication
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13
Q

why is the oesophagus muscle layer thick

A

it undergoes waves of muscular contractions (peristalsis) to move food towards the stomach

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14
Q

what are the 3 sections of the stomach?

A
  1. fundus (dome shaped section at top of stomach)
  2. body ( main section that stored food till passing to small intestine)
  3. pylorus ( part of stomach that connects to small intestine/duodenum)
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15
Q

protein and fat are not acted on enzymatically

A
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16
Q

what 2 food groups are acted on in the stomach

A

lipids and protein

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17
Q

why is there mucosa in the folds/rugae of the stomach

A

to give stomach extra capacity when food distends it

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18
Q

where can the gastric glands of the stomach be found and what do they do?

A

found in the epithelium (simple columnar) of stomach which extends to open into stomach lumen via gastric pits

they secrete gastric juice (HCL, pepsinogen etc)

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19
Q

describe the 5 structural components of stomach

A
  1. mucosa
  2. submucosa
  3. (inner) oblique
  4. (inner) circular muscle
  5. (outer) longitudinal muscle
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20
Q

why does the stomach need an extra oblique layer compared to the oesophagus>

A

it provides strong musculature enabling the stomach to effectively churn food

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21
Q

what are the 4 structural components of the small intestine/ ileum

A
  1. villi
  2. submucosa
  3. circular muscle
  4. longitudinal muscle
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22
Q

what 3 additional structural components can be found within the small intestine

A
  1. goblet cells
  2. brunners glands
  3. crypt/ intestinal glands
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23
Q

what 3 things in the epithelium of the villi allow the digestion of lipids

A

pancreatic fluid
bile
enzymes

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24
Q

what specifically does pancreatic fluid contain to allow the breakdown of lipids and what does it breakdown into

A

lipase
breakdown into monoglycerides

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25
Q

how does bile acid aid in digestion of lipids

A

it acts as a detergent (emulsifies) lipid droplets down to 1micrometer diameter

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26
Q

once the monoglycerides pass through the epithelial cell of villi, what do they resynthesises into and using what

A

smooth endoplasmic reticulum resynthesises it into triglycerides

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27
Q

after triglycerides are resynthesises in the villi, what happens

A
  • Golgi surrounds it with protein coat forming chylomicron
  • chylomicrons discharged via exocytosis into lymph vessels, lacteals draining the villi
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28
Q

what proportion of ingested fats fail to breakdown and get digested hence released in feaces

A

1/3

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29
Q

what is a zymogen

A

proteins that contain an inactive enzyme

30
Q

explain how proteins are further broken down in the duodenum

A
  • further digested by 4 zymogens (produced by pancreas)
  • zymogens are activated in duodenum to form various endopeptidase
  • different endopeptidases cut at different places on peptide chain as they target different sequences
31
Q

what are the 4 different endopeptidases used to digest proteins

A
  • trypsin
  • chymotrypsin
  • elastase
  • carboxypeptidase
32
Q

what also the short peptide chains to further digest into amino acids

A

exopeptidase

33
Q

where are exopeptidase found

A

in the membrane of the ileum epithelial cells

34
Q

explain how 3 types of exopeptidase form amino acids

A
  • carboxypeptidase work on c-terminal end
  • aminopeptidases work on N-terminal end
  • dipeptidases cut dipeptides in half
35
Q

what transport mode is amino acids absorbed by

A

active transport via co-transport with sodium ions

36
Q

describe how further digestion of disaccharides occur in iileum

A
  • in general, dissachridases convert disaccharides into their monosaccharide units
  • maltase hydrolyses maltose into glucose
  • lactase hydrolyses lactose into glucose and galactose
  • sucrase hydrolyses sucrose into glucose and fructose
37
Q

how do each monosaccharide get absorbed

A
  • fructose simply diffuses into villi
  • glucose and galactose absorbed via active transport with co-trasport of sodium
38
Q

symbiotic (friendly) bacteria in ileum occur but less numerous than in colon

A
39
Q

what is the function of villi

A

maximise surface area for absorption of nutrients (mainly occurring in small intestine)

40
Q

what additional feature does the duodenum have compared with the proximal jejunum and ileum

A

burners glands

41
Q

what is the function of brunners glands and where is it found

A
  • lies in submucosa deep to the muscular mucosae
  • secrete alkaline mucus which neutralises the acidic chyme passing down from the stomach
42
Q

what are paneth cells + function

A
  • secretory cells in the crypt
  • can occur in duodenum and provide host defence against microbes
43
Q

what is the only difference between the jejunum and ileum

A

jejunum has no aggravated lymph nodes (Peyers patches)

44
Q

why are the villi in the ileum shorter than int he duodenum

A

most absorption happens here so faster

45
Q

what is the function of goblet cells in the mucosa

A

produce mucin for lubrication of intestinal contents and protection of epithelieum

46
Q

explain the role of the gallbladder and pancreas in digestion

A
  • chyme enters duodenum
  • hormones secretin and cholecystokinin stimulates pancreas and gall bladder to discharge pancreatic fluid and bile into duodenum
47
Q

what is the role of liver in digestion

A
  • detoxifies foreign compounds in foods and drugs
  • secretes bile
  • veins draining intestine lead to 2nd set of capillary beds in liver and here the liver removes many of the materials absorbed by intestine
48
Q

how do the liver and gall bladder work together in digestion

A
  • bile released by the liver accumulates in the gallbladder
49
Q

how does bile aid in digestion

A
  • contains salts derived from cholesterol
  • salts help emulsify fats
50
Q

what makes poo brown

A
  • breakdown of haemoglobin from old RBC makes bile pigments which form brown colour
51
Q

how does the liver aid in digesting non-nutritive molecules

A

liver screens blood reaching it in the hepatic portal system (removes and detoxifies) so blood composition when leaving liver is close to normal

52
Q

how does the liver deal with excess amino acids

A
  • removed and deaminated
  • amino group is converted to urea
  • residue enters pathway of cellular respiration and oxidised for energy
53
Q

glucose is removed from the blood in liver and converted into glycogen.

other monosaccharides are removed and converted into glucose

A
54
Q

how is pancreatic fluid moved into the duodenum?

A
  • pancreas consists of endocrine cells (islets of langerhand) and exocrine cells
  • their secretion drains into duodenum
55
Q

what 4 types of things is pancreatic fluid consisted of

A
  • sodium bicarbonate (neutralise acid)
  • pancreatic amylase
  • lipase
  • 4 zymogens
56
Q

why does pancreatic fluid consist of inactive enzymes (zymogens)

A

protease enzymes are dangerous so synthesised by RER as inactive forms

57
Q

how/what are the 4 different zymogens activated

A
  • trypsinogen activated to trypsin by enterokinase (secreted from duodenum epithelium)
  • trypsin activates chymotrysinogen to chymotrypsin
  • proelastase to elastase
  • procarbozypeptidase to carboxypeptidase
58
Q

what are the 2 main structures of large intestine

A
  • circular muscle
  • longitudinal muscle
59
Q

what 2 additional structures does the large intestine/colon have

A

goblet cells
lymphoid

60
Q

what does the residue from ileum consist of in the colon

A
  • mainly water
  • non digested materials
61
Q

what is there a large population of in the colon

A

bacteria (mainly harmless)

62
Q

what can the intestinal flora/bacteria do

A
  • capable of fermenting indigestible carbohydrates to short-chain fatty acids e.g acetate
  • acids formed can be energy source for host
  • they can also produce vitamin k, biotin, folic acid, thiamine, vitamin b12 (absorbed in colon)
63
Q

what 5 beneficial components can the bacteria in our colon produce

A
  • folic acid
  • vitamin b12
  • vitamin k
  • biotin
  • thiamine
64
Q

what causes diarrhoea

A

irritation of large intestine causing discharge of contents before water reabsorption

65
Q

what causes constipation

A

colon retains contents for too long, fecal matter dries out and compresses

66
Q

what is the main function of the colon

A

reabsorption of water

67
Q

what 2 types of cells does the mucose epithelium of the colon contain

A
  1. absorptive cells
  2. mucus-secreeting goblet cells
68
Q

absorptive cells decrease in number from proximal to distal while goblet cells increase in number

A
69
Q

what is particular about the structure of goblet cells in the colon

A

arranged in closely packed straight tubular glands/crypts which extend to muscular mucosa

70
Q

why does mucus because increasingly important as faeces pass along the colon

A

faeces become progressively dehydrated so mucus required to protect mucosa from trauma

71
Q

the anus has stratified squamous mucosa

A
72
Q

the appendix is located in which area of the GI tract

A

small intestine

RAD414 pt 2 (33 decks)

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