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Semester 3 > GI Session 6 > Flashcards

GI Session 6 Flashcards

1
Q

What surrounds the major duodenal papilla?

A

Sphincter of Oddi

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2
Q

How is the pancreas divided into exocrine and endocrine portions?

A

Exocrine ~90%

Endocrine ~2%

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3
Q

What does the exocrine portion of the pancreas secrete?

A

Acinus secretes enzymes

Duct secretes aqueous solution

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4
Q

What does the endocrine pancreas secrete?

A

Insulin

Glucagon

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5
Q

How is the pancreas innervated?

A

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

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6
Q

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

A

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

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7
Q

Which enzymes are secreted in their active form?

A

Amylases

Lipases

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8
Q

What is a zymogen granule?

A

A membrane bound inactive precursor of an enzyme

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9
Q

How are zymogen granules formed?

A

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

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10
Q

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

A

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

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11
Q

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

A

Cl-HCO3- exchanger

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12
Q

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

A

More is secreted

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13
Q

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

A

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

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14
Q

What is the function of the liver?

A

Energy metabolism
Detoxification
Plasma protein production
Bile secretion

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15
Q

What are the components of bile?

A 
Mainly water
Bile salts
FA
Cholesterol
Proteins
Pigments
Alkaline juice
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16
Q

How much bile is secreted by the liver?

A

250 ml to 1 l per day

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17
Q

What forms 80% of liver mass?

A

Hepatocytes

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18
Q

How can hepatocytes be identified on histology?

A

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

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19
Q

What is the function of RER?

A

Protein production

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20
Q

What is the function of SER?

A

Fat processing and detoxification

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21
Q

What is the structural unit of the liver?

A

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

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22
Q

What is the surgical importance of the liver lobules?

A

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

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23
Q

What is the functional unit of the liver?

A

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

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24
Q

What is zone 1 of an acinus at risk of?

A

Toxins

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25
Q

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

A

Further away from arterial supply but closer to central vein

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26
Q

Describe how blood flows into the liver.

A

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

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27
Q

What are kupffer cells?

A

Stellate macrophages

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28
Q

Why are Kupffer cells present in the hepatic sinusoids?

A

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

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29
Q

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

A

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

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30
Q

How does bile flow in the liver?

A

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

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31
Q

What secretes bile acid dependent bile into the canaliculi?

A

Hepatocytes

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32
Q

What is the contents of bile acid dependent bile?

A

Bile acids

Pigments

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33
Q

What secretes bile acid independent bile?

A

Duct cells

34
Q

What is bile acid independent bile similar to?

A

Alkaline solution secreted by pancreatic duct cells

35
Q

What stimulates secretion of bile acid independent bile?

A

Secretin

36
Q

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

A

Cholic acid

Chenodeoxycholic acid

37
Q

Apart from the liver where else are bile acids formed?

A

Gut

38
Q

How do bile acids become bile salts?

A

Conjugation with glycine and taurine

39
Q

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

A

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
Q

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

A

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

41
Q

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

A

Emulsify to increase SA available for lipases to act

42
Q

What do bile salts from with products of lipid digestion?

A

Micelles containing cholesterol, mono glycerine sand free FA from lipid

43
Q

How do emulsified lipids enter enterocytes?

A

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

44
Q

What halogens to the reformed lipids once in the enterocytes?

A

Packaged as aporoteins–> chylomicrons

45
Q

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

A

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

46
Q

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

A

Too large

47
Q

What are lacteals?

A

Lymph capillaries

48
Q

How are bile salts recycled?

A

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

49
Q

What is the purpose of recycling bile salts?

A

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

50
Q

What is the function of the gallbladder?

A

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

51
Q

What stimulates bile release from the gallbladder?

A

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

52
Q

How does the gallbladder concentrate bile it stores?

A

Removes water/ions

53
Q

What causes faeces to be brown?

A

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

54
Q

What leads to steatorrhoea?

A

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

55
Q

Where does the SMA arise?

A

L1 vertebral level immediately inferior to coeliac trunk

56
Q

What does the right colic artery supply?

A

Ascending colon

57
Q

What does the middle colic artery supply?

A

Transverse colon

58
Q

What lies anterior to the SMA?

A

Pylorus
Splenic vein
Neck of pancreas

59
Q

What lies posterior to the SMA?

A

L renal vein
Uncinate process of pancreas
Inferior duodenum

60
Q

Describe the arrangement of jejunal and ileal arteries.

A

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

61
Q

How do jejunal and ileal arteries compare?

A 
Jejunal = fewer arterial arcades but longer vasa recta
Ileal = more arterial arcades but shorter vasa recta
62
Q

Describe the path of the inferior pancreaticoduodenal artery.

A

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
Q

What does the ileocolic artery supply?

A

Ascending colon
Appendix
Caecum
Ileum

64
Q

What is ligated in appendicectomy?

A

Appendicular artery from ileocolic artery

65
Q

How is the ileocolic artery positioned?

A

Passes inferiorly and R

66
Q

Where does the IMA arise?

A

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

67
Q

Is the IMA peritoneal, retroperitoneal or secondary retroperitoneal?

A

Retroperitoneal

68
Q

What does the sigmoid artery supply?

A

Descending colon and sigmoid colon via 2-4 branches

69
Q

What is the uppermost branch of the sigmoid arteries called?

A

Superior sigmoidal artery

70
Q

How are the sigmoid arteries positioned?

A

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

71
Q

What is the left colic artery?

A

1st branch of IMA

72
Q

What does the left colic artery supply?

A

Distal 1/3 of transverse colon

Descending colon

73
Q

How is the left colic artery positioned?

A

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
Q

What can the IMA cause in the developing kidney?

A

Horseshoe kidney

75
Q

Why does chyme become hypertonic in the stomach?

A

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

76
Q

What is the superior rectal artery?

A

Most inferior branch of IMA supplying the rectum

77
Q

Describe the passage of the superior rectal artery.

A

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
Q

What is the marginal artery of Drummond?

A

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

79
Q

What forms the marginal artery?

A 
Ileocolic
Right colic
Middle colic
Left colic
Sigmoid branches
80
Q

What is the arc of Riolan?

A

Anastomosis of middle colic and left coli arteries

81
Q

Describe the clinical relevance of the splenic flexure blood supply.

A

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
Q

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

A

SMA+IMA

Semester 3 (50 decks)

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