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Microheterogeneity

This general term refers to a polypeptide hormone that is secreted in different forms due to derivatisation ( e.g. addition of a sulphate ) of a single amino acid residue; thus the number of amino acids is the same in these different forms. For example, there are two groups of gastrins: one in which the tyrosine (in the 6th position from the carboxyl terminal) is sulphated and the other in which it is not . In other words, there are sulphated and non-sulphated gastrins. In the case of gastrins, the sulphated and the non-sulphated forms are in equal amounts and they are equally active.


GIT Secretitions

 

Gastrointestinal Secretion

 

Saliva

Gastric secretion

Pancreatic secretion

Bile

Main characteristic

Hypotonic; high bicarbonate; high K+; alpha amylase, lingual lipase

HCl; pepsinogen; intrinsic factor

High bicartonate, isotonic, pancreatic lipase, pancreatic amylase, proteases

Bile, salts, bilirubin, phospholipids, cholesterol

Factors stimulating

Stimulated by parasympathetic and sympathetic; by food in stomach

HCl: stimulated by histamine, acetylcholine, gastrin: Pepsinogen: stimulated by parasympathetic

Bicarbonate: stimulated by CCK, secretion and parasympathetic; enzymes: stimulated by CCK, secretion parasympathetic

CCK: stimulates GB; parasympathetic: stimulates GB

Factors inhibiting

By sleep, dehydration, atropine

Inhibited by HCl

 

Inhibited by iteal resection

 

 

Volume (in L/day)

Osmolality

pH

Na+

K+

Cl-

HCO3

Plasma

3

300

7.4

150

5

110

24

Saliva

1.5

100

7.5

40

15-30

25

30

Gastric Juice

3

200

1

50

10

100

0

Pancreatic Juice

1.5

300

7.8

140

5

70

80

Bile

0.5

300

7.5

140

5-12

80

20

 

At the end of

Volume (L/day)

Na

K+

Cl-

HCO3

Duodenum

9.2

55

15

55

12

Jejunum

3.2

145

8

95

35

Ileum

1.2

135

7

55

75

Colon

0.2

35

85

10

25

                         





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