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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
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

Semester 3 (50 decks)

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