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HUBS192 Melia > Lecture 25: SECRETION > Flashcards

Lecture 25: SECRETION Flashcards

1
Q

How many pairs of salivary glands are there?

A

3

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2
Q

How much fluid do the salivary glands produce?

A

1.5L per day

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3
Q

What amount of saliva do each of the salivary glands secrete?

A

Sublingual (5%), submandibular (70%) and parotid (25%)

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4
Q

What is basal saliva secretion?

A

0.3 ml/min

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5
Q

What is stimulated saliva secretion?

A

1.5 ml/min

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6
Q

What is the composition of saliva?

A

Mucus, a dilute solution of NaHCO3 and NaCl, digestive enzymes

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7
Q

What is the purpose of mucus in saliva?

A

Lubrication

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8
Q

What is the purpose of a dilute solution of NaHCO3 and NaCl in saliva?

A

To dilute food and provide an optimal pH for digestive enzymes

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9
Q

What are the digestive enzymes in saliva?

A

Lingual lipase and alpha amylase (denatured in the stomach)

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10
Q

Is saliva essential?

A

No

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11
Q

What does saliva aid in?

A

Talking, chewing and swallowing

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12
Q

How does saliva aid in chewing and swallowing?

A

Dissolves and lubricates food

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13
Q

What is saliva also involved in?

A

Hygiene and digestion

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14
Q

How does saliva help in hygiene?

A

Irrigation (removal of old food)

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15
Q

What is xerostomia?

A

Dry mouth from limited or absent saliva

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16
Q

How does saliva help in digestion?

A

Dissolves for allowing tasting

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17
Q

What dies lingual lipase break down?

A

Fats

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18
Q

What does alpha amylase break down?

A

Starch

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19
Q

What is saliva secretion regulated by?

A

Nervous system, autonomic nervous system

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20
Q

What is the nervous system activated by (saliva)?

A

Thought, smell, sight of food and the presence of food in the mouth

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21
Q

What does the parasympathetic nervous system do (saliva)?

A

Stimulates secretion of abundant quantities of fluid

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22
Q

What does the sympathetic nervous system do (saliva)?

A

Small volumes of viscous fluid

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23
Q

How much gastric secretion occurs in a day?

A

2-3L

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24
Q

What is the rate of gastric secretion between meals?

A

slow (15-30ml/h)

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25
Q

What secretes gastric fluid between meals?

A

Surface cells secrete mucus

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26
Q

What is the rate of gastric secretion when eating?

A

Superimposed on basal rate

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27
Q

What secretes gastric fluid when eating?

A

Mucous cells - mucus, parietal cells -150 ml/h HCl acid pH=0 and intrinsic factor, chief cells - pepsinogen

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28
Q

What is the function of mucus in gastric secretions?

A

Protection from abrasion and acid

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29
Q

What is the function of intrinsic factor in gastric secretions?

A

Absorption of vitamin B12 in the small intestine

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30
Q

What is pepsinogen?

A

The inactive form of pepsin

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31
Q

What type of enzyme is pepsin?

A

Gastric proteolytic

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32
Q

How is pepsinogen converted to its active form?

A

By acid

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33
Q

What does pepsin start digestion of?

A

Proteins

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34
Q

What is the function of gastric acid in gastric secretions?

A

Dilutes food, denatures protein, activates pepsinogen to pepsin, creates optimum pH for pepsin and protection

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35
Q

What is the source of acid (H+)?

A

Formation of H2CO3 (carbonic acid) by carbonic anhydrase (CO2 +H2O <>H2CO3) then dissociation of H2CO3 (H2CO3 <>H+ +HCO3-)

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36
Q

How is H+ secreted into the lumen?

A

By the H+K+ ATPase

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37
Q

Where is H+K+ ATPase found?

A

On the apical membrane of parietal cells

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38
Q

What does H+K+ ATPase do?

A

Pumps H+ ions into the lumen in exchange for K+ ions ( to keep balance) and K+ then returns to the lumen through a membrane channel

39
Q

What is the source of chloride?

A

Anion counter transporter

40
Q

Where is the anion counter transporter?

A

On the serosal membrane of parietal cells

41
Q

What does the anion counter transporter do?

A

Ejects HCO3- into interstitial fluid and imports Cl- ions into the cell

42
Q

How is Cl- secreted?

A

It diffuses across the cell and enters the lumen via the Cl- channel in apical membrane

43
Q

What is regulation of gastric secretion coordinated with?

A

Eating and arrival of food

44
Q

What are the phases of gastric secretion?

A

Cephalic - head/brain controls secretion
Gastric - stomach controls secretion
Intestinal - intestine controls secretion

45
Q

What is the cephalic phase for?

A

Preparation for arrival of food

46
Q

How much secretion associated with meals is in the cephalic phase?

47
Q

What are the stimuli for the cephalic phase?

A

Higher centres (brain), thought, smell and sight of food, chewing action, taste

48
Q

How is secretion regulated in the cephalic phase?

A

Parasympathetic nervous system acting via enteric nervous system

49
Q

What is stimulated in the cephalic phase?

A

Parietal cells, chief cells and goblet cells to secrete acid, pepsinogen and mucus and well as secretion of hormone gastrin

50
Q

What does gastrin do in the cephalic phase?

A

It is released into the blood to stimulate parietal cells and chief cells

51
Q

What does the gastric phase ensure?

A

Sufficient secretion to handle ingested food

52
Q

How much secretion associated with meals is in the gastric phase?

53
Q

What are the stimuli in the stomach for the gastric phase?

A

Stretch/distension of stomach walls (receptors), products of digestion in the stomach lumen and elevated pH when food enters (because acidic mixing with ~neutral)

54
Q

What is the regulation of the gastric phase?

A

Nervous and hormonal

  • local nervous reflex (ENS)
  • External nervous reflex (Parasympathetic nervous system)
55
Q

What does the nervous system stimulate in the gastric phase?

A

Secretion, motility and gastrin secretion which further stimulates secretion and motility

56
Q

What does the intestinal phase control?

A

Deliver to the small intestine

57
Q

How much secretion associated with a meal is in the intestinal phase?

58
Q

What are the stimuli for the intestinal phase?

A

Distension of duodenum and arrival in the duodenum of acidic chyme, lipids and carbohydrates

59
Q

What is the regulation of the intestinal phase?

A

Nervous and hormonal
- hormones (GIP, CKK and secretin)
- nervous (eterogastriic reflex)
Both inhibit secretion and motility (in stomach)

60
Q

What type of organ is the pancreas?

A

Endocrine and exocrine

61
Q

How much pancreatic secretion is there in a day?

A

1-1.5L/day

62
Q

What are the components of pancreatic secretion?

A

Enzymes and alkaline fluid

63
Q

What are enzymes in pancreatic secretion secreted by?

A

Acinar cells

64
Q

What is the function of enzymes in the pancreatic secretion?

A

Chemical digestion of food

65
Q

What is alkaline fluid in pancreatic fluid secreted by?

A

Duct cells

66
Q

What is the function of alkaline fluid in the pancreatic secretion?

A

To neutralise acid and give optimum pH for enzymes

67
Q

What is the most important source of digestive enzymes?

68
Q

What is stimulating of secretion of pancreatic enzymes?

A

Hormone CCK

69
Q

What is CCK secretion stimulated by?

A

Arrival of lipids and carbohydrates in duodenum (stop secretion in stomach, start in pancreas)

70
Q

What is the function of pancreatic enzymes?

A

Luminal chemical digestion of food

71
Q

How are proteolytic enzymes secreted?

A

As inactive precursors and activated in the duodenum

72
Q

What are some proteolytic enzymes and their precursors?

A

Trypsin (trypsinogen), chymotrypsin (chymotrypsinogen and carboxypeptidase (procarboxypeptidase)

73
Q

What does activation of proteolytic enzymes in the small intestine involve?

A

Enterokinase/enteropeptidase converting trypsinogen to trypsin and then trypsin converts the other enzymes to their active form

74
Q

Where is enterokinase/enteropeptidase found?

A

Bound to the duodenal membrane

75
Q

What is secretion of alkaline fluid stimulated by?

A

Hormone secretin which is secreted when acidic chyme arrives in the duodenum

76
Q

What is the function of alkaline fluid?

A

To neutralise acidic chyme delivered from the stomach and create optimum pH (6.7-9.0) for pancreatic and intestinal digestive enzymes (increase pH)

77
Q

How much biliary secretion occurs?

A

0.5L per day

78
Q

What does biliary secretion consist of?

A

Products associated with digestion-bile salts and HCO3- rich fluid (ducts)
Excretory products - bile pigments (waste products) and cholesterol

79
Q

What is the function of biliary secretin?

A

Bile salts - fat digestion
HCO3- rich fluid - neutralises acid
Bile pigments - excretion

80
Q

When is bile secreted?

A

Constantly by the liver

81
Q

What is done will bile produced in the liver?

A

it is stored and concentrated in the gall bladder then delivered to the duodenum with arrival of food

82
Q

What is initial delivery of bile under control of?

A

Hormones (CCK)

83
Q

How is bile delivered?

A

By contraction of the gall bladder and relaxation of the hepatopancreatic ampulla

84
Q

What does secretion stimulate (biliary secretion)?

A

Mild stimulation of bile by the liver

85
Q

What does bile stimulate?

A

Its own secretion by the enterophepatic circulation

86
Q

Bile is ______ to produce?

A

metabolically expensive

87
Q

How much bile is reabsorbed into the ileum?

A

95% and 5% lost in faces

88
Q

Where is the bile reabsorbed in the ileum transported to?

A

The liver in enterohepatic circulation. It is reabsorbed and secreted (stimulation of bile secretion)

89
Q

How much small intestine secretion is there?

90
Q

What is in small intestine secretion?

A

Mucus, isosmotic fluid and digestive enzymes

91
Q

What is the function of mucus in small intestine secretion?

A

Lubrication to protect

92
Q

What is the function of isosmotic fluid in small intestine secretion?

A

Alkaline - mixture of NaCl and NaHCO3 which helps neutralise acid and dilutes food to aid in digestion

93
Q

What do digestive enzymes in small intestinal fluid do?

A

Shed cells

94
Q

What is in large intestine secretion?

A

Mucus for lubrication

HUBS192 Melia (38 decks)

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