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Pharmacy Y3- Inflammatory diseases > Week 4- Overview of gastrointestinal tract + Upper GI physiology > Flashcards

Week 4- Overview of gastrointestinal tract + Upper GI physiology Flashcards

1
Q

what organs are included in the gastrointestinal tract?

A
  • mouth
  • oesophagus
  • stomach
  • small intestine
  • large intestine
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2
Q

what glands are included in the gastrointestinal tract?

A
  • salivary glands in the mouth
  • pancreas
  • liver
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3
Q

what is the lumen of the gut?

A

the part of the gut where the food goes down

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4
Q

the lumen is said to be …. to the body?why

A

external

as the conditions for digestion is tolerated in the gut but not the body

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5
Q

what are the conditions for digestion in the gut? why cant they occur in the body?

A
  • pH of the stomach as low as 2.0 compared to body 6.8-8
  • pancreas has digestive enzymes that could destroy out tissue
  • microorganism in lower intestine
  • food are foreign particles need to broken down so body doesn’t attack them
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6
Q

what are the basic processes in the digestive system?

A
  • motility
  • secretion
  • digestion
  • absorption
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7
Q

what are the two types of motility in the digestive system and what are the actions causing them?

A

voluntary- skeletal muscles due to chewing, swallowing and defaecation
involuntary- smooth muscle contraction that mix and move forward content in the gut

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8
Q

what is the main type of secretion in the DS?

A

-digestive juices secreted by exocrine glands into lumen of the gut

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9
Q

what is part of the digestive juices?

A

-contains water, electrolytes, and specifc prodcuts for digestion or absorption e.g. mucus, enzyme bile salts

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10
Q

what need to happen for secretion to occur?

A

secretion cells need to extract large volumes of water and raw material which uses a lot of energy AT for raw material and secretion is reabsorbed into blood

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11
Q

what secretes gastrointestinal hormones?

A

endocrine glands

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12
Q

what do gastrointestinal hormones regulate?

A

motility and exocrine glands secretion

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13
Q

what is digestion?

A

biochemical breakdown of complex proteins,

carbohydrates and fats by enzymes

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14
Q

what is maltose hydrolysed by and to make what?

A

broken down by maltase to make glucose

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15
Q

where does protein digestion start?

A

in the stomach

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16
Q

what is pepsinogen?

A

it is in gastric juice and is converted to pepsin at low pH

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17
Q

What is pepsin?

A

it breaks down proteins into peptides

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18
Q

what is trypsinogen?

A

in pancreatic juice and is converted to trypsin at basic pH

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19
Q

what is trypsin?

A

breaks down proteins to peptides

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20
Q

what is peptidase?

A

found in the epithelial cell that lines the small intestine breaks down peptides into amino acids that can be absorbed into the blood capillary

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21
Q

what form is a dietary fat in?

A

triglyceride

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22
Q

what do fats start to break down?

A

in the duodenum

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23
Q

what 2 things make lipids breakdown into smaller molecules?

A

bile salts from the liver emulsifies large globules of fat making them smaller and lipase from the pancreas digests triglycerides to monoglycerides and fatty acids

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24
Q

how are lipoproteins also know as chylomicrons made?

A

the monoglycerides and fatty acids diffuse into the epithelial cells where they combine with proteins

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25
Q

what are the 3 types of polysaccharides?

A

starch
glycogen
cellulose

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26
Q

what is starch broken down by?

A

salivary amylase and then pancreatic amylase to

maltose

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27
Q

what is glycogen broken down into?

A

glucose

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28
Q

Is cellulose and other indigestible CHO broken down by gut enzymes?

A

no

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29
Q

what are the 3 main enzymes to break down disaccharides?

A

maltase
sucrase
lactase

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30
Q

what does maltase break down?

A

maltose to glucose

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31
Q

what does sucrase break down?

A

sucrose to glucose and fructose

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32
Q

what does lactase break down?

A

lactose into glucose and galactose

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33
Q

how does glucose get into the blood?

A

it is actively transported into the epithelial cells of villi and then onto the blood

34
Q

what is the mucosa?

A

it lines the lumen and the surface is highly folded for larger surface area for absorption

35
Q

what are the different layer of the digestive tract wall?

A

mucosa
submucosa
Muscularis externa
Serosa

36
Q

what helps regulate the digestive functions?

A
  • Autonomic smooth muscle function
  • Intrinsic nerve plexuses
  • Extrinsic nerves
  • Gastrointestinal hormones
37
Q

how does the autnomic smooth muscle help regulate digestive function?

A

Interstitial cells of Cajal –
– pacemaker cells that instigate cyclic slow-wave activity
– located between circular and longitudinal muscle, allow whole sheets of
smooth muscle cells to contract together when threshold reached
-threshold is reached when enough food is present

38
Q

what is the guts own nervous system called?

A

enteric nervous system

39
Q

what does the Intrinsic nerve plexuses

A

primarily coordinate local activities

40
Q

how does the sympathetic system affect digestion?

A

slows down digestion

41
Q

how does the sympathetic and parasympathetic nerves influence motility and secretion?

A 
by modifying activity of
intrinsic nerve plexuses
– altering secretion of GI hormones
– directly acting on smooth muscle and
glands
42
Q

what is the effect of the parasympathetic nervous system on the digestive system?

A

(vagus nerve)
Increases smooth muscle motility
Promote GI hormone and enzyme secretion

43
Q

what are the 3 main types of sensory receptors in the tract?

A

– Chemoreceptors
– Mechanoreceptors
– Osmoreceptors

44
Q

what is the effect of stimulation of the sensory receptors?

A

results in neural reflexes or secretion of
hormones which alter activity of effector cells (smooth
muscle cells, exocrine and endocrine gland cells)

45
Q

how do hormones enter the blood?

A 
Endocrine gland cells in
mucosa of specific
regions of tract release
hormones into blood
upon stimulation
46
Q

what is the tongue?

A

a skeletal muscle important for chewing swallowing and speech and theres approx 10,000 taste buds in the mouth and throat

47
Q

how many receptors are on each taste bud?

A

50 which are long spindly, modified epithelial cells

48
Q

what is salt stimulated by and signalled by?

A
  • chemical salts especially NaCl

- through Na+ channels

49
Q

what is sour stimulated by and signalled by?

A
  • Acids with a free H+ ion

- hydrogen potassium channels

50
Q

what is sweet stimulated by and signalled by?

A

-Configuration of glucose
-Activates GPCR, cAMP,
phosphorylation and
blockage of K+ channels

51
Q

what is bitter stimulated by and signalled by?

A
  • they are complex and detect chemically diverse substances

- 50-100 receptors each responding to different bitter flavours

52
Q

what is umani (savoury) stimulated by and signalled by?

A

-Amino acids, especially
glutamate and MSG
-Glutamate binds to GPCR

53
Q

where is saliva secreted from?

A

3 types of salivary glands

  • parotid gland under the ear
  • sublingual gland under the tongue
  • submandibular gland near the jaw
54
Q

how much saliva is secreted a day and what is its composition?

A

1/2L a day

water, electrolytes, and proteins (amylase, mucos, lysozyme)

55
Q

what is the functions of saliva?

A

• Digestion of carbohydrates by salivary amylase
• Swallowing facilitated by moistening food
• Lubrication provided by mucus
• Antibacterial action – Lysozyme destroys bacteria – Saliva rinses away material that could serve as food
source for bacteria
• Solvent for molecules that stimulate taste buds
• Aids speech by facilitating movements of lips and
tongue
• Helps keep mouth and teeth clean
• Rich in bicarbonate buffers

56
Q

how is the secretion of saliva controlled?

A
  • its a simple reflex pressure receptors and chemoreceptors in the mouth
  • sends signals to the salivary centre in the medulla in the brain
  • this them switches on the autonomic nerves to switch salivary glands on to secrete saliva
57
Q

where does swallowing occur?

A

in the pharynx

58
Q

what is the oesophagus?

A

straight muscular tube extending between pharynx and stomach

59
Q

what is the top and the bottom of the oesophagus caller?

A
  • Pharyngoesophageal sphincter

* Gastroesophageal sphincter

60
Q

what is the role of the Gastroesophageal sphincter?

A

-controls food going into the stomach and prevents acid reflux back into the oesophagus once it has been swallowed

61
Q

how is food moved down the oesophagus?

A
  • the swallowing centre in the brain controls the peristaltic wave that pushes food through the oesophaus
  • mucus that is produced here keeps the bolus moist to keep it moving
62
Q

what are the 3 main sections of the stomach?

A
  • fundus mainly air
  • body stores the food
  • antrum mixing and where the enzymatic breakdown occurs
63
Q

what is the 3 main functions of the stomach?

A
  • store food in the body
  • secrete acid and enzymes that begin protein digestion
  • mixing of the food
64
Q

what are the 4 aspects of gastric motility?

A
  • filling of the stomach whereby receptive relaxation occurs allowing extra volume of food without a rise in stomach pressure which is mediated by the vagus nerve
  • storage in the body of the stomach
  • mixing in the antrum of stomach
  • emptying is slow and controlled by many different factors
65
Q

what are 5 factors that affect gastric emptying?

A

-Amount of chyme (broken down food) stomach influences strength of
contraction
-fat in the duodenum= as fat slows down absorption because small intestine is the only place fat digests-lipase
-amount of acid in the duodenum as it shoudl be neutral in there or it will damage the duodenal mucosa
-Osmolarity of the duodenum =as osmolarity rises, gastric emptying inhibited
-Distension of the duodenum = large volume of chyme inhibits
gastric emptying

66
Q

what do the 5 factors that affect gastric emptying trigger to occur?

A

– Neural response through intrinsic nerve plexuses (short
reflex) and autonomic nerves (long reflex), collectively
called enterogastric reflex
– Hormonal response with release of hormones
(enterogastrones) from duodenal mucosa which inhibit
gastric emptying – Secretin (produced by S cells) – Cholecystokinin (CCK, produced by I cells)

67
Q

what are some additional factors that influence gastric motility?

A
  • emotions= sadness and fear tends to decrease motility snd anger and aggression tends to increase motility.
  • intense pain= tends to inhibit motility
68
Q

what is the 2 main distinct areas of gastric mucosa that secrete gastric juice?

A

– Oxyntic mucosa which lines body and fundus

– Pyloric gland area (PGA) which lines the antrum

69
Q

what are the 3 types of cells that are found in the gastric pits?

A

– Mucous cells
• Line gastric pits and entrance of glands
• Secrete thin, watery mucus protects from acid
– Chief cells
• Secrete enzyme precursor, pepsinogen
– Parietal (oxyntic) cells
• Secrete HCl and intrinsic factor

70
Q

what do enterochromaffin cells secrete?

A

hormones

71
Q

what is the function of HCL?

A

-aids breakdown of connective tissue and muscle fibers
-denatures protein by uncoiling
-activates pepsinogen by cleaving it to become pepsin and
provides acid medium for
optimal pepsin activity
-Along with salivary
lysozyme, kills most of the
microorganisms ingested
with food

72
Q

what is purpose of the gastric mucosal barrier?

A

Enables stomach to contain acid without

injuring itself and producing ulcers

73
Q

what are some components of gastric mucosal barrier that protect it from acid?

A
  • the membranes of the gastric mucosal cells are impermeable to H+ so that HCL from penetrate into the cells
  • cells are joined by tight junctions that prvent HCL penerating in
  • a mucosa coating over the gastric mucosa serves as a physical barrier to acid peneration
  • the HCO-3 rich mucus also serves as a chemical barrier that netrilises acid in the vicinity if the mucosa.even when luminal pH is 2, the mucus ph is 7
74
Q

what are the other components of the gastric juice?

A

-pepsinogen stored in the zymogen granules of the chief cells, HCl in stomach converts it to pepsin, which is autocatalytic, Acts optimally in acid, breaking specific peptide bonds
-mucus prtects mucosa against mechanical injury, protects stomach wall from digestion by pepsin, alkaline neutrilising HCL in vicinity of gastric lining
-Intrinsic factor secreted by parietal cells, Essential for vit B12 absorption, allows binding to receptor in terminal
ileum and absorption by receptor-mediated endocytosis

75
Q

what helps regulate gastric secretion?

A

hormones that are released by the gastric endocrine glands
– Gastrin, released by protein presence and Ach
from G cells, stimulates HCl and pepsinogen
– Somatostatin, released from D cells inhibits HCl,
pepsinogen and gastrin

76
Q

what are he 3 phases of gastric secretion?

A
  • Cephalic phase
  • Gastric phase
  • Intestinal phase
77
Q

what is the cephalic phase?

A

-– Increased secretion of HCl and pepsinogen that occurs in response
to stimuli acting in the head before food reaches stomach

78
Q

what is gastric phase?

A

– Begins when food actually reaches the stomach

– Presence of protein increases gastric secretions – Presence of caffeine or alcohol

79
Q

what is the intestinal phase?

A

– Inhibitory phase – acid, fat, hypertonicity, distension
– Helps shut off flow of gastric juices as chyme begins to empty into
small intestine

80
Q

what is digestion in the stomach?

A

– Carbohydrate digestion from salivary amylase continues in
body of stomach as little mixing here
– Protein digestion by pepsin begins in antrum as mixed with
digestive juices in this region

81
Q

what is absorption in the stomach?

A

– Alcohol – lipid-soluble, diffuses slowly through mucosa into
blood
– Aspirin and other weak acids – un-ionised, lipid-soluble so
absorbed quickly

Pharmacy Y3- Inflammatory diseases (32 decks)

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