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HUBS192 2024 > 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

How does saliva help in digestion?

A

Dissolves for allowing tasting

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16
Q

What dies lingual lipase break down?

A

Fats

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17
Q

What does alpha amylase break down?

A

Starch

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18
Q

What is saliva secretion regulated by?

A

Nervous system, autonomic nervous system

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19
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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20
Q

What does the parasympathetic nervous system do (saliva)?

A

Stimulates secretion of abundant quantities of fluid

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21
Q

What does the sympathetic nervous system do (saliva)?

A

Small volumes of viscous fluid

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22
Q

What amount of fluid does the stomach secrete per day?

A

2-3L

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23
Q

What is the rate of gastric secretion between meals?

A

slow (15-30ml/h)

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24
Q

What secretes gastric fluid between meals?

A

Goblet surface cells secrete mucus & bicarbonate

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25
Q

What is the rate of gastric secretion when eating?

A

Superimposed on basal rate

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26
Q

What secretes gastric fluid when eating?

A

Goblet surface cells secrete mucus & bicarbonate

Parietal cells secrete HCl acid and intrinsic factor

Chief cells secrete pepsinogen

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27
Q

What is the function of goblet cell secretion in the stomach?

A

Mucus for protection

Bicarbonate, dilution from stomach acid, sticks to mucus, forming a layer lining the surface of the stomach to protect epithelial cells.

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28
Q

What is the function of intrinsic factor in gastric secretions?

A

Absorption of vitamin B12 in the ilium (small intestine)

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29
Q

What is pepsinogen?

A

The inactive form of pepsin

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30
Q

How is pepsinogen converted to its active form?

A

By HCl in the stomach

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31
Q

What does pepsin start digestion of?

A

Proteins

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32
Q

What is the function of HCl acid in gastric secretions?

A

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

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33
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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34
Q

How is H+ secreted into the lumen?

A

By the H+/K+ ATPase

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35
Q

Where is H+/K+ ATPase found?

A

In the apical membrane of parietal cells

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36
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

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37
Q

What is the source of chloride?

A

Anion counter transporter

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38
Q

Where is the anion counter transporter?

A

On the basolateral membrane of parietal cells

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39
Q

What does the anion counter transporter do?

A

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

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40
Q

How is Cl- secreted?

A

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

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41
Q

What is regulation of gastric secretion coordinated with?

A

Eating and arrival of food

42
Q

What are the phases of gastric secretion?

A

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

43
Q

What is the cephalic phase for?

A

Preparation for arrival of food

44
Q

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

A

20%

45
Q

What are the stimuli for the cephalic phase?

A

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

46
Q

How is secretion regulated in the cephalic phase?

A

Parasympathetic nervous system acting via enteric nervous system

47
Q

What is stimulated in the cephalic phase?

A

Parietal cells,
chief cells,
goblet cells,
and G cells which secrete the hormone Gastrin

48
Q

What does gastrin do in the cephalic phase?

A

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

49
Q

What is the overall outcome of the Cephalic phase?

A

Increased secretion of mucus, HCO3-, HCl acid and pepsinogen in the stomach to prepare for food.

50
Q

What does the gastric phase ensure?

A

Sufficient secretion to handle ingested food

51
Q

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

A

70%

52
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)

53
Q

What are the stimuli sensed by in the gastric phase?

A

G cells, gastric mechano- and chemoreceptors

54
Q

What is the response coordinated by in the gastric phase?

A

Submucosal and myenteric plexus activated via the CNS and ENS

55
Q

What are the effectors in the gastric phase?

A

Parietal cells,
chief cells,
goblet cells,
and G cells which secrete the hormone Gastrin

56
Q

What is gastric motility stimulated by in the gastric phase?

A

Gastrin, leading to stronger retropulsion and waves of peristalsis

57
Q

What does the nervous system stimulate in the gastric phase?

A

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

58
Q

What does the intestinal phase control?

A

slow controlled release of food to the small intestine

59
Q

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

A

10%

60
Q

What are the stimuli for the intestinal phase?

A

Stretch of the duodenal wall, decreased pH, fatty acids and amino acids in the duodenum

61
Q

What are the stimuli sensed by in the intestinal phase?

A

Mechano and chemo receptors in the duodenum walls

Enteroendocrine cells

62
Q

What is the Response coordinated by in the intestinal phase?

A

EEC which release:
CCK - cholecystokinin
GIP - Gastrin inhibiting hormone
Secretin

These hormones cause inhibition of chief and parietal cells.

Sympathetic nervous system activates which inhibits the submucosal plexus

63
Q

What is the outcome of the intestinal phase?

A

Decreased secretion of HCL and pepsinogen.

SNS Inhibits myenteric plexus and G cells causing less motility (stomach contraction) and less gastrin secreted.

64
Q

What type of organ is the pancreas?

A

Endocrine and exocrine

65
Q

How much pancreatic secretion is there in a day?

A

1-1.5L/day

66
Q

What are the components of pancreatic secretion?

A

Enzymes and alkaline fluid

67
Q

What are enzymes in pancreatic secretion secreted by?

A

Acinar cells

68
Q

What is the function of enzymes in the pancreatic secretion?

A

Chemical digestion of food

69
Q

What is alkaline fluid in pancreatic fluid secreted by?

A

Duct cells

70
Q

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

A

To neutralise acid and give optimum pH for enzymes

71
Q

What is the most important source of digestive enzymes?

A

Pancreas

72
Q

What begins the activation process of pancreatic secretions?

A

Arrival of fatty acids and amino acids in duodenum

Detected by duodenal EEC which release CCK.

73
Q

What is stimulating of secretion of pancreatic enzymes?

A

Hormone CCK

74
Q

What are digestive enzymes are classifiedon?

A

what they break down

75
Q

What are the types of digestive enzymes?

A

Nucelolytic
Lipolytic - lipase
Amylytic - amylase
Proteolytic - trypsinogen, chymo- trypsinogen, procarboxypeptidase

76
Q

What is the function of pancreatic enzymes?

A

Luminal chemical digestion of food

77
Q

How are proteolytic enzymes secreted?

A

As inactive precursors and activated in the duodenum

78
Q

What are some proteolytic enzymes and their precursors?

A

Trypsin (trypsinogen),

chymotrypsin
(chymotrypsinogen),

carboxypeptidase (procarboxypeptidase)

79
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

80
Q

Where is enterokinase/enteropeptidase found?

A

Bound to the duodenal membrane

81
Q

What is secretion of alkaline fluid stimulated by?

A

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

82
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)

83
Q

How much biliary secretion occurs?

A

0.5L per day

84
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

85
Q

What is the function of biliary secretin?

A

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

86
Q

When is bile secreted?

A

Constantly by the liver

87
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

88
Q

What is initial delivery of bile under control of?

A

Hormones (CCK)

89
Q

How is bile delivered?

A

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

90
Q

What does secretion stimulate (biliary secretion)?

A

Mild stimulation of bile by the liver

91
Q

What does bile stimulate?

A

Its own secretion by the enterophepatic circulation

92
Q

Bile is ______ to produce?

A

metabolically expensive

93
Q

How much bile is reabsorbed into the ileum?

A

95% and 5% lost in faeces

94
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)

95
Q

How much small intestine secretion is there?

A

1.5L/day

96
Q

What is in small intestine secretion?

A

Mucus, isosmotic fluid and digestive enzymes

97
Q

What is the function of mucus in small intestine secretion?

A

Lubrication to protect

98
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

99
Q

What do digestive enzymes in small intestinal fluid do?

A

Shed cells

100
Q

What is in large intestine secretion?

A

Mucus for lubrication

HUBS192 2024 (38 decks)

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