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HUBS 192 > Lecture 25 > Flashcards

Lecture 25 Flashcards

1
Q

What are the secretions of exocrine glands?

A

Mucus
Electrolyte solution
Digestive enzymes

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2
Q

Function of mucus?

A

} Protection and lubrication

} Aids mechanical digestion

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3
Q

Function of electrolyte solution

A

} Dilutes food & provides optimal pH

} Essential for chemical digestion of food

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4
Q

Function of digestive enzymes

A

} Essential for chemical digestion of food } Aids absorption

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5
Q

composition of saliva?

A

Mucus
Dilution solution NaHCO3NaCl
Digestive enzymes (lingual lipase and a-amylase)

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6
Q

Functions of salivary secretions?

A

Not essential.
Aids talking, chewing and swallowing.
Hygiene.
Digestion.

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7
Q

How are salivary secretions regulated?

A

Nervous (stimulated by food)

Autonomic Nervous system: parasympathetic (copious quantities) Sympathetic (small volumes)

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8
Q

Gastric secretions between meals?

A

Surface cells secreting mucous at a slow rate.

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9
Q

Gastric secretions when eating?

A

Superimposed on basal rate.
Mucous cells - mucus
Parietal cells - HCL and intrinsic factor
Chief cells -0 pepsinogen

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10
Q

What is the function of intrinsic factor?

A

Absorption of vitamin B12 in the SI

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11
Q

Function of pepsinogen?

A

Converted to active form pepsin.by acid then starts digestion of proteins1`

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12
Q

Functions of gastric acid?

A 
Dilutes food 
Denatures protein 
Activates pepsinogen 
Creates optimum pH for pepsin action 
Protection
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13
Q

Source of acid (H+)

A

} Formation of H2CO3 by carbonic anhydrase
} CO2 + H2OóH2CO3
} Dissociation of H2CO3 to give H+ and HCO3-
} H CO óHCO - + H+ 233

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14
Q

Secretion of acid (H+)

A

H+-K+ ATPase
} Apical membrane of parietal cells
} Pumps H+ ions into lumen in exchange of potassium ions (K+)
} K+ return to lumen through membrane channel

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15
Q

`Source of chloride (CL-) ?

A

} Anion counter transporter

} Serosal membrane of parietal cells } Ejects HCO3- into interstitial fluid } Imports Cl- ions into cell

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16
Q

Secretion of chloride

A

} Cl- diffuse across cell

} Enters lumen via Cl- channel in apical membrane

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17
Q

How is gastric secretion regulated?

A

Cephalic phase - head controls secretion
Gastric phase - stomach controls secretion
Intestinal phase - intestine controls secretion.

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18
Q

Function of the cephalic phase?

A

Preparing for the arrival of food

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19
Q

What stimulates the Cephalic phase?

A

Higher senses

Chewing action and taste.

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20
Q

What regulates the Cephalic phase?

A

Parasympathetic Nervous System:
} Via enteric nervous system
} Stimulates parietal cells, chief cells and goblet
cells
} Stimulate secretion of hormone gastrin
¨ Released into blood
¨ Stimulates parietal cells and chief cells

21
Q

Function of the Gastric phase?

A

Ensures sufficient secretion to handle ingested food.

22
Q

What stimulates the Gastric phase?

A

Stimuli in the stomach:
} Stretch/distension stomach wall
} Products of digestion stomach lumen
} Elevated pH

23
Q

How is the gastric phase regulated?

A 
nervous and Hormonal regulation:
} Local nervous reflex
- Enteric nervous system
} External nervous reflex
- Parasympathetic nervous system
} Stimulate
- Secretion- Motility
- Gastrin secretion
¨ Further stimulation of secretion and motility
24
Q

What is the function of the Intestinal phase?

A

Control delivery to Small intestine.

25
Q

What stimulates the intestinal phase?

A

} Distension of duodenum
} Arrival in duodenum of
} Acid chyme
} Lipids and carbohydrates

26
Q

What regulates the intestinal phase?

A 
Nervous and hormonal regulation
} Hormones
- GIP, CCK, Secretin
} Nerves
- Enterogastric reflex
} Both inhibit secretion and motility
27
Q

Pancreatic secretion?

A

Endocrine and exocrine organ

28
Q

What are the components of pancreatic secretion?

A 
Enzymes
¨ Acinar cells
¨ Chemical digestion of food
Alkaline fluid
¨ Duct cells
¨ Neutralise acid
¨ Optimum pH for enzymes
29
Q

Why are pancreatic enzymes important?

A

Most important source of digestive enzymes - work on all classes of food

30
Q

Pancreatic enzymes?

A

} Lipolytic – lipase, phospholipase
} Amylytic – pancreatic amylase
} Proteolytic – Trypsin, chymotrypsin, carboxypeptidase
} Nucleolytic – ribonuclease, deoxyribonuclease

31
Q

What cells secrete pancreatic enzymes?

A

Acinar cells

32
Q

What stimulates the release of pancreatic enzymes by acinar cells?

A

cholecystokinin (CCK)

33
Q

What stimulates CCKL secretion)?

A

Arrival of lipids and carbohydrates in duodenum?\

34
Q

What is the function of pancreatic enzymes?

A

Luminal chemical digestion of food

35
Q

What are proteolytic enzymes?

A

Enzymes that are secreted as inactive

precursors & activated in duodenum

36
Q

proteolytic enzymes?

A

} Trypsin – trypsinogen
} Chymotrypsin – chymotrypsinogen
} Carboxypeptidase – procarboxypeptidase

37
Q

What does activation of proteolytic enzymes involve?

A 
} In small intestine activation involves
} Enterokinase (=enteropeptidase)
} Bound to duodenal membrane
} Converts trypsinogen to trypsin
} Trypsin converts other enzymes to active
form
38
Q

Describe the secretion of Alkaline (HCO3 rich) fluid?

A

Produced by duct cells in the pancreas, stimulated by hormone secretin which is stimulated by the arrival of acid chyme in the duodenum./

39
Q

Function of alkaline fluid?

A 
} Neutralises acid chyme delivered from
stomach
} Creates optimum pH (6.7-9.0)for
pancreatic and intestinal digestive
enzyme
40
Q

Volume of Biliary secretion?

A

0.5L per day consisting of products associated with digestion such as bile salts and HCO3 rich fluid As well has excretory products such as waste products, bile pigments and cholesterol.

41
Q

Functions of Biliary secretions?

A

Bile Salts for fat digestion.
HCO3 rich fluid to neutralise fluid.
Bile Pigments for excretion.

42
Q

How are biliary secretions regulated?

A

} Initial delivery of bile under hormonal control
} Hormone CCK (cholecystokinin)
} Produced in response to products of digestion in duodenum
} Contraction of gallbladder
} Relaxation of hepatopancreatic ampulla
} Hormone secretin
} Mild stimulation of bile by liver

43
Q

Where is Bile secreted?

A

Secreted constantly by liver but stored and concentrated in gallbladder. The delivered to duodenum with the arrival of food.

44
Q

What stimulates bile secretions?

A

Bile stimulates it’s own secretion - } Enterohepatic circulation

45
Q

What is } Enterohepatic circulation?

A 
Bile metabolically expensive to produce
95% reabsorbed in ileum
Transported back to liver in
enterohepatic circulation
Reabsorbed and secreted
Stimulation of bile secretion
46
Q

What is secreted by the small intestine?

A 
1.5L per day:
Mucus 
Isosmotic fluid (Alkaline - mixture of NaCl and
NaHCO3) 
Digestive enzymes
47
Q

zFunction of Isosmotic fluid secretions in the small intestine?

A

Neutralise food and dilute food to aid digestion.

48
Q

Function of digestive enzymes in the small intestine.

A

Shed cells.

HUBS 192 (37 decks)

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