GI Session 6 Flashcards Preview

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Flashcards in GI Session 6 Deck (82):
1

What surrounds the major duodenal papilla?

Sphincter of Oddi

2

How is the pancreas divided into exocrine and endocrine portions?

Exocrine ~90%
Endocrine ~2%

3

What does the exocrine portion of the pancreas secrete?

Acinus secretes enzymes
Duct secretes aqueous solution

4

What does the endocrine pancreas secrete?

Insulin
Glucagon

5

How is the pancreas innervated?

ANS: sympathetic stimulation inhibits secretion, parasympathetic via vagus stimulates secretion

6

Describe the pathway that leads to enzyme secretion by the acinus.

Hypertonicity and fats detected in duodenum --> vagus nerve and CCK activates --> active and inactive enzymes produced

7

Which enzymes are secreted in their active form?

Amylases
Lipases

8

What is a zymogen granule?

A membrane bound inactive precursor of an enzyme

9

How are zymogen granules formed?

Cis-trans RER --> Golgi --> condensing vacuole --> zymogen granules

10

What is the alt heavy of aqueous solution secretion from the duct cells in the pancreas?

Hypertonic chyme in duodenum --> secretin activated --> production and secretion of HCO3- into duodenal lumen

11

What transporter is used to move HCO3- into the duodenal lumen?

Cl-HCO3- exchanger

12

At high flow rates in the duodenum how does HCO3- secretion change?

More is secreted

13

What occurs in the blood due to HCO3- production by the pancreas?

Opposite of alkaline tide as H+ produced move into pancreatic venous drainage causing a transient decrease in pH

14

What is the function of the liver?

Energy metabolism
Detoxification
Plasma protein production
Bile secretion

15

What are the components of bile?

Mainly water
Bile salts
FA
Cholesterol
Proteins
Pigments
Alkaline juice

16

How much bile is secreted by the liver?

250 ml to 1 l per day

17

What forms 80% of liver mass?

Hepatocytes

18

How can hepatocytes be identified on histology?

Lots of rough and smooth ER, glycogen and stacks of Golgi membranes

19

What is the function of RER?

Protein production

20

What is the function of SER?

Fat processing and detoxification

21

What is the structural unit of the liver?

Lobule formed by collections of hepatocytes divided by invaginations of the liver capsule

22

What is the surgical importance of the liver lobules?

Similar to bronchopulmonary segments so can be removed individually causing minimal damage to remaining tissue

23

What is the functional unit of the liver?

Acinus formed by distance between two central veins to form the long axis and distance between portal triads for the short axis

24

What is zone 1 of an acinus at risk of?

Toxins

25

Why is zone 3 of an acinus at higher risk of hypoxia than toxin damage in comparison to zone 1?

Further away from arterial supply but closer to central vein

26

Describe how blood flows into the liver.

Venous portal blood and arterial blood in hepatic arteries --> central vein --> healthcare veins --> IVC

27

What are kupffer cells?

Stellate macrophages

28

Why are Kupffer cells present in the hepatic sinusoids?

All blood from gut drains through liver so presents possible pathogen entry

29

Describe the path of blood from branches of the hepatic portal vein to the IVC in a hepatic sinusoid.

Branch --> central canals which merge to form --> hepatic veins --> IVC

30

How does bile flow in the liver?

Flows outwards from canaliculi --> bile ducts at periphery --> duodenum

31

What secretes bile acid dependent bile into the canaliculi?

Hepatocytes

32

What is the contents of bile acid dependent bile?

Bile acids
Pigments

33

What secretes bile acid independent bile?

Duct cells

34

What is bile acid independent bile similar to?

Alkaline solution secreted by pancreatic duct cells

35

What stimulates secretion of bile acid independent bile?

Secretin

36

What are the two primary bile acids produced by the liver?

Cholic acid
Chenodeoxycholic acid

37

Apart from the liver where else are bile acids formed?

Gut

38

How do bile acids become bile salts?

Conjugation with glycine and taurine

39

What is the purpose of conjugating bile acids to become bile salts?

Gives them and amphipathic structure so they can act at the oil/water interface for emulsification of dietary lipid
Makes the soluble at duodenal pH

40

Why aren't fats completely digested by enzyme action in the duodenum?

Tend to form large globules by the time they reach here so there is a small SA for enzymes to act on

41

What is the action of bile salts in large lipid globules?

Emulsify to increase SA available for lipases to act

42

What do bile salts from with products of lipid digestion?

Micelles containing cholesterol, mono glycerine sand free FA from lipid

43

How do emulsified lipids enter enterocytes?

Diffuse down concentration gradient and are re-esterified back into triglycerides, phospholipids and cholesterol

44

What halogens to the reformed lipids once in the enterocytes?

Packaged as aporoteins--> chylomicrons

45

Describe the passage of chylomicrons from enterocytes into the L subclavian vein.

Exocytosis from basolateral enterocyte membrane --> lacteals --> lymphatic system --> thoracic duct --> L subclavian vein

46

Why don't chylomicrons enter capillaries after exocytosis from enterocytes?

Too large

47

What are lacteals?

Lymph capillaries

48

How are bile salts recycled?

Remain in gut lumen until terminal ileum --> reabsorbed --> portal blood --> liver extracts

49

What is the purpose of recycling bile salts?

Reduces energy demand for constantly making new ones although this has to happen to some degrees as some are lost

50

What is the function of the gallbladder?

Store continuously produced bile until it is stimulated to release
Concentrate bile

51

What stimulates bile release from the gallbladder?

Detection of hypertonicity and lipid presence --> CKK release from duodenum --> sphincter of Oddi relaxes

52

How does the gallbladder concentrate bile it stores?

Removes water/ions

53

What causes faeces to be brown?

Hb broken down --> conjugated in liver to become soluble --> bile --> stercobilinogen --> brown faeces

54

What leads to steatorrhoea?

If bile salts or pancreatic lipases a not secreted in adequate amounts

55

Where does the SMA arise?

L1 vertebral level immediately inferior to coeliac trunk

56

What does the right colic artery supply?

Ascending colon

57

What does the middle colic artery supply?

Transverse colon

58

What lies anterior to the SMA?

Pylorus
Splenic vein
Neck of pancreas

59

What lies posterior to the SMA?

L renal vein
Uncinate process of pancreas
Inferior duodenum

60

Describe the arrangement of jejunal and ileal arteries.

Pass between layers of mesentery to freon anastomotic arches --> vasa recta

61

How do jejunal and ileal arteries compare?

Jejunal = fewer arterial arcades but longer vasa recta
Ileal = more arterial arcades but shorter vasa recta

62

Describe the path of the inferior pancreaticoduodenal artery.

1st branch of SMA --> anterior and posterior branches --> anastomose with branches of superior pancreaticoduodenal artery from coeliac trunk --> supply inferior head of pancreas, uncinate process and duodenum

63

What does the ileocolic artery supply?

Ascending colon
Appendix
Caecum
Ileum

64

What is ligated in appendicectomy?

Appendicular artery from ileocolic artery

65

How is the ileocolic artery positioned?

Passes inferiorly and R

66

Where does the IMA arise?

L3 vertebral level, near inferior border of duodenum 3-4 cm from the aortic bifurcation

67

Is the IMA peritoneal, retroperitoneal or secondary retroperitoneal?

Retroperitoneal

68

What does the sigmoid artery supply?

Descending colon and sigmoid colon via 2-4 branches

69

What is the uppermost branch of the sigmoid arteries called?

Superior sigmoidal artery

70

How are the sigmoid arteries positioned?

Run inferiorly, obliquely and L --> cross over psoas major, L ureter and L internal spermatic vessels

71

What is the left colic artery?

1st branch of IMA

72

What does the left colic artery supply?

Distal 1/3 of transverse colon
Descending colon

73

How is the left colic artery positioned?

Anterior to psoas major, L ureter and L internal soermatic vessels then:
Ascending branch crosses L kidney anteriorly and enters T colon mesentery moving superiorly
Descending branch moves inferiorly and anastomoses with superior sigmoid artery

74

What can the IMA cause in the developing kidney?

Horseshoe kidney

75

Why does chyme become hypertonic in the stomach?

Exponential increases in the number of molecule present combined with impermeability of stomach wall to water

76

What is the superior rectal artery?

Most inferior branch of IMA supplying the rectum

77

Describe the passage of the superior rectal artery.

Crosses pelvic brim crossing L iliac artery and vein --> at S3 forms 2 terminal branches either side of rectum --> within wall smaller branches eventually communicate with middle and inferior rectal arteries

78

What is the marginal artery of Drummond?

Continuous arterial circle along inner border of colon with vasa recta extending to the colon

79

What forms the marginal artery?

Ileocolic
Right colic
Middle colic
Left colic
Sigmoid branches

80

What is the arc of Riolan?

Anastomosis of middle colic and left coli arteries

81

Describe the clinical relevance of the splenic flexure blood supply.

Watershed area due to dual blood supply from most distal branches of two large arteries --> more resistant to ischaemia in occlusion of one artery but more sensitive to systemic hypoperfusion

82

The junction of which two arterial supplies is found at the splenic flexure?

SMA+IMA