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Flashcards in Physiology Deck (68):
1

what does the small intestine receive from the stomach?

chyme - via the pyloric sphincter

2

what does the small intestine receive from the pancreas?

pancreatic juice

3

what does the small intestine receive from the gallbladder?

bile

4

what does the small intestine secrete?

intestinal juices and moves remaining residue to the large intestine

5

name the adaptations of the small intestine which increases surface area

arranged in circular folds
contains villi
villi contain microvilli

6

Name the peptide hormones that the small intestine secretes (7)

gastrin
Cholecystokinin (CCK)
Secretin
Motilin
Glucagon like insulinotropic peptide (GIP)
Glucagon like peptide-1 (GLP 1)
Ghrelin

7

which cells are the peptide hormones secreted from in the small intestine?

endocrine cells within the mucosa into the blood

8

where does gastrin come from?

G cells of the gastric antrum and duoenum

9

where does CCK come from?

cells of the duodenum and jejunum

10

where does secretin come from?

s cells of the duodenum

11

where does motilin come form?

m cells of the duodenum and jejunum

12

where does GIP come from?

K cells of the duodenum and jejunum

13

Where does GLP-1 come from?

incretin from L cells of the gut

14

Where does ghrelin come from?

Gr cells of the gastric antrumm, small intestine and pancreas

15

which receptors do peptide hormones from the small intestine act on?

g-protein coupled receptors

16

what does incretin do?

acts on b-cells of the pancreas to stimulate the release of insulin

17

Control mechanisms of the succus entericus

arrival of chyme
gastrin
CCK
secretin
parasympathetic nerve activity - enhances activity
sympathetic nerve activity - decreases activity

18

what does secretion of the small intestine contain?

mucous and aqueous salt

19

steps of mixing of chyme

1. moved back and forth
2. contraction and relaxation initiate by pacemaker cells
3. segmentation of duodenum
4. segmentation in the ileum (empty) triggered by gastrin
5. overall net movement

20

what controls the segmentation of the small intestine during the mixing of chyme?

parasympathetic and sympathetic stimulation

21

what inhibits the migrating motor complex of peristalsis

feeding and vagal activity

22

what does peristalsis clear from the small intestine?

debris, mucus and endotheliac cells between meals

23

what are the components of the endocrine secretion of the pancreas?

insulin and glucagon onto the blood

24

what are the components of the exocrine secretion of the pancreas?

digestive enzymes and sodium bicarbonate

25

what do acinar cells secrete in the pancreas?

trypsinogen
chymotrypsinogen
procarboxypeptidase A and B
pancreatic amylase
pancreatic lipase

26

what does trypsinogen become in the duodenum?

trypsin (enterokinase is added)

27

what is autocatalysis

the process by which a substance catalyses its own production e.g. trypsin

28

what does chymotrypsinogen become in the duodenum?

chymotrypsin (trypsin is added)

29

what does procarboxypeptidase A and B become?

carboxypeptidase A and B (acted on by trypsin)

30

why do duct cells secrete alkaline fluid into the duodenum?

neutralises chyme to make optimum pH for pancreatic function and protects mucosa from acid erosion

31

What are the three phases of pancreatic secretion?

cephalic
gastric
intestinal

32

what mediates the cephalic stage of pancreatic secretion?

vagal stimulation of the acinar cells

33

what does the large intestine recieve from the ileum?

indigestible residue
unabsorbed biliary compounds
unabsorbed fluid

34

what is the function of the ilieocaecal sphincter?

1. maintains positive resting pressure
2. relaxes in response to distension of duodenum
3. contracts in response to ascending colon
4. prevents bacteria getting from the colon

35

What are the functions of the Large intestine?

1. absorbs water, Na and Cl
2. secrets K, bicarbonate and mucus
3. absorbs short chain fatty acids
4. storage for colonic content
5. elimination of faeces

36

what is haustration?

caused by contraction of the circular muscle which occurs in the proximal colon and mixes its content

37

what are peristaltic propulsive movements?

joint contraction of large sections of the circular muscle of the ascending and transverse colon

38

what are peristaltic propulsive movements triggered by?

after a meal via gastrocolic responses (gastrin and extrinsic nerve plexuses)

39

Where does most of the water in the body come from?

Secreted within the body itself

40

what is the absorption of water driven by?

The transport of Na from the lumen of the intestine to the blood stream

41

define diarrhoea in terms of fluid loss?

Loss of fluid and solutes from the GI tract in excess of 500ml per day

42

What are the 5 main ways that is Na reabsorbed?

1. Na+/glucose co-transport
2. Na+/amino acid co-transport
3. Na+/H+ exchange
4. Parallel Na+/H+ and Cl-/HCO3- exchange
5. Epithelial Na+ channels

43

where does Na+/glucose and Na+/amino acid co-transport take place?

small intestine

44

where does Na+/H+ exchange take place and what is it facilitated by?

duodenum and jejunum - facilitated by luminal HCO3-)

45

where does Parallel Na+/H+ and Cl-/HCO3- exchange take place?

ileum and colon

46

where are Epithelial Na+ channels and what facilitates reabsorption here?

colon - facilitated by aldosterone

47

Na+/H+ exchange in the jejunum occurs where?

both the apical and basolateral membranes

48

what is exchange of Na+/H+ stimulated by in the apical membrane of the jejunum?

the alkaline environment of the lumen due to the presence of bicarbonate from the pancreas

49

Does the lumen have a lower or higher concentration of protons compared to the cytoplasm?

Lower

50

what is the primary mechanism of absorption of Na in the interdigestive period?

Na+/H+ and CI-/HCO3- exchange

51

How is the absorption through Na+/H+ and CI-/HCO3- exchange described?

Electroneutral

52

what is Na+/H+ and CI-/HCO3- exchange regulated by?

intracellular cAMP, cGMP and Ca2+, all of which reduce NaCl absorption

53

What can a reduction in NaCl cause?

diarrhoea

54

what does Epithelial Na+ channels mediate?

electrogenic Na absorption in the distal colon

55

what increases Epithelial Na+ channels?

Aldosterone

56

What are the three actions of Aldosterone?

1. opens ENaC
2. inserts more ENaC into membrane from intracellular vesicle pool
3. increases synthesis of ENaC and Na+/K+-ATPase

57

what is the driving force of Cl absorption in the small intestine?

electrogenic transport of Na+ - Na+/glucose and Na+/amino acid

58

what is the driving force of Cl absorption in the late intestine?

electrogenic movement of Na+ through ENaC

59

What are the two other ways Cl is absorbed?

Cl--HCO3- exchange
Na+-H+ and Cl--HCO3- exchange

60

where does Na+-H+ and Cl--HCO3- exchange take place?

ileum and proximal colon

61

where does Cl--HCO3- exchange take place?

ileum and proximal and distal colon

62

What are the benefits of colonic flora?

increase intestinal immunity
promote motility
synthesise vitamin K2 and free fatty acids
activate certain drufs

63

How is intestinal immunity increased by colonic flora?

by competition with pathogenic microbes

64

where do gases released from the anus arise from?

swallowed air
bacteria in the colon attacking carbohydrate
gas which is not absorbed in the large intestine

65

Define constipation?

Presence of hard dried faeces within the colon from a delay in deification and enhanced absorption of water

66

what is constipation caused by?

ignoring the urge to defecate
decreased colonic motility
obstruction of faecal movement
impairment of defecation reflex

67

What symptoms can constipation cause?

abdominal discomfort
headaches
loss of apetite
malaise

68

what can hardened faecal matter cause?

appendicitis