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Gastroenterology > Pancreas and Small Bowel > Flashcards

Pancreas and Small Bowel Flashcards

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1
Q

What part of the pancreas is sometimes absent as an adult

A

Accessory pancreatic duct and minor papilla

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2
Q

What is pancreas divisum

A

Where the ducts are separated

Higher occurance of pancreatitis

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3
Q

What are endocrine glands

A

Secretion into the blood stream to have an effect on distant target organ - ductless glands

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4
Q

What are exocrine glands

A

Secretion into a duct to have direct local effect

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5
Q

What are the main endocrine secretions of the pancreas

A

Insulin: anabolic hormone

Glucagon

Somatostatin - inhibitor

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6
Q

What is the percent of endocrine and exocrine glands of pancreas

A

Endocrine - 2%

Exocrine - 98%

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7
Q

What are the two pancreatic cells

A

Acini - grap like clusts of secretory units, secrete pro-enzymes into ducts

Islets - derived from branching duct system, lose contact with ducts and become islet, differentiate into alpha and beta cells into blood

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8
Q

Composition of islets

A

Alpha cells - 15-20% of islet tissue and secrete glucagon

Beta cells - 60-70 of islet tissue and secrete insulin

Gamma cells - 5-10% of islet tissue and secrete somatostatin

Acini

Islets are highly vascular

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9
Q

What is the composition of acini

A

Secretory acinar cells

Duct cells

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10
Q

What are the two components of pancreatic juice

A

Acinar cells - decrease volume, viscous, enzyme-rich

Duct and centroacinar cells - increase volume, watery, HCO3 rich

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11
Q

What is the fucture of bicarbonate secretion

A

Neutralises acid chyme - preevnts damage to duodenal mucosa, raises pH to optimum range for pancreatic enzymes to work

Washes low volume enzyme secretion out of pancreas

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12
Q

Why does HCO3 secretion stop when pH still acid

A

Bile also contains HCO3

Brunners glands secrete alkaline fluid

Duodenal ph<3 - not much more increase in HCO3 secretion

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13
Q

How does HCO3 secretion work

A
  1. Catalysed by carbonic anhydrase - separation of H and HCO3

Na moves down gradiant via paracellular tight junctions water follows

  1. Cl/HCO3 exchange at lumen (AE) , Na/H exchange at basolateral membrane into bloodstream (sodium-hydorgen exchanger (antiporter) typer 1 [NHE-1]

Exchange driven by electrochemical gradients

  1. Na gradient maintained by Na/K pump
  2. K returns to blood via K channel, Cl returns the blood via Cl channel (cystic fibrosis transmembrane conductance regulator (CFTR)
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14
Q

Composition of H and HCO3 in juice

A

Stomach

H+ - gastric juice

HCO3 - blood

Gastric venous blood is alkaline

Pancreas

HCO3 - juice

H+ - blood

Pancereatic venous blood is acidic

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15
Q

What are zymogens

A

Pro enzymes which enzymes for digestions are released and stored in

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16
Q

How are enzymes activated in the intestine

A

Pancreas contains a trypsin inhibitor to prevent trypsin activation

Enzymes only activated in duodenum

Blockage of MPD may lead to autodigestion

Activated in duodenum by enterokinase which converts trypsinogen to trypsin

Lipase secreted in active form but requires colipase and presence of bile salts

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17
Q

What are the side effects of Orlistat

A

Increase facal FAT

Pancreatic secretion decreases

Steatorrhoea - fatty stool

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18
Q

What are the phases of pancreatic juice secretion

A

Cepahlic phase - sight/smell/taste of food, enzyme rich component only, low volume

Gastric phase - stimulation of pancreatic secretion originating from food arriving in stomach

Intestinal phase - 70-80% of pancreatic secretion - hormonally mediate, both components of pancreatic juice stimulated - enzymes and HCO3 juice

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19
Q

How is the pancreatic juice enzyme secretion controlled by

A

Vagus nerve - cholinergic, vagal stimulation of enzyme secretion

Cholecystokinin (CKK) (Ca/PLC)

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20
Q

How is the pancreatic juice bicarbonate secretion controlled by

A

Duct and centroacinar cells

Secretin

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21
Q

What are the stimulaatory effect snad inhibitory effects of CCK from duodenal 1 cells

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A

Stimulatory - Fatty acids and amino acids in lumen

Inhibitory - trypsin

22
Q

What does secretin do

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A

Stimulate secretion of H20 and HCO3 from cells lining extralobular ducts

Secretion-stimulated secretion is richer in HCO3 in constrant to acinar secretion because of Cl/HCO3 exchange

23
Q

What is the negative feedback loop of bicarbonate

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A

S cells increase scretin

Secretin increas HCO3

Cause pH to decrease

Which will increase production of S cells

24
Q

What is the coupled stimulation reactions of CCK

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A

CCK and secretin markedly increase HCO3

Vagus nerve has similar effect to CCK

25
When does pancreatic enzymes release peak
30 mins
26
What is the function of the small bowel
Absorb nutrients, salt and water
27
What are the dimension of small bowel
25cm -duodenum Jejunum -2.5m Ileum - 3.75m 3.5cm diameter
28
What is the function of mesentery
Suspends small and large bowel from posterior abdominal wall achoring them in place and allowing some movement Provides conduit for blood vessels, nerves and lymphatic vessels
29
Facts about villi
Only in small intestine Motile Rich blood and lymph supply 1 cell thick Dominated by enterocytes - columnar absorptive cells
30
What are the different cell types in small bowel
Enterocytes Scattered goblet cells Enteroendocrine cells Paneth cells Stem cells
31
Facts about enterocytes
Specialised for absorption and transport of substances Short lifespan of 1-6 days 500flod of surface area of small bowel to folds, villi and microvilli
32
Facts about microvilli
Make up the brush border Surface of microbilli covered with glcocalyx
33
What is the glycocalyx
Rich carbohydrate layer on apical membrane Serves as protection from digestional lumen yet allows for absorption Traps a layer of water and mucous known as unstirred laeyr Regulates rate of absoprtion from intestinal lumen
34
Facts about goblet cells
2nd most abbundatn epithelial cell Mucous - large glycoprotein that gacilities passage of amterial Increase abundance of goblet cells along entire length of bowel
35
Facts about enteroendocrine cells
Columnar epithelial cells Lower parts of crypts Hormone secreting - influences gut motility
36
Facts about paneth cells
Bases of crypts Large, acidophilic granules Antibacterial enzyme lyosozyme - protect stem cells Glycoproteins and zinc to aid number of enzymes Engulf bacteria and protozoa Regulating intestinal flora
37
Facts about stem cell sin GI tract
Undifferentiated cells Eptihelial stem are essnetial in GI tract to continually replenish surface epithelium Divide by mitosis Migrate to tip of villus Old cells digested and reabsorbed
38
Why do enterocytes have a rapid turnover
Enterocytes are first line defense agaisnt GI pathogens Effects of agents will be diminished Lesions will be short live If escaltor like transit diminised, severe intestinal dysfunction will occur - radiation
39
How is the duodenum distinguish
Presence of brunner's glands Submucosal coiled tubular mucous glands secreting alkalin fluid Open into base of crypts
40
Difference between jejunum and ileum
Jejunum - wider, redder, thicker, numerous plicae circulares Arterial arcades more sufficient in ileum
41
Functions of small bowel motility
Mix ingested food with digestive secretions and enzymes Facilitate contact between contents of intestine and intestinal mucosa Propel intestinal contents along alimentary tract
42
Types of motility in small bowel
Segmentation - mixes content, contraction of circular muscles, more frequent contractions in duodenum, net effect is movement to colon Peristalsis (propelling) - sequential contraction of adjacent rings, propels towards colon, travels only 10m Migrating Motor Complez - smooth muscle contractions sweeping through gut, begin in stomach to colon, next wave starts in duodenum, prevents migration of colonic bacteria into ileum
43
Digestion in the duodenum
Occurs in an alkaline enviornment Enter through main pancreatic duct and common bile duct Eptihelium also produces its own digestive enzymes
44
How does digestion of carbs work
Salivary alpha amylase which is destroyed in stomach Pancreatic alpha amylase - needs cl for optimum activity and slightly alkaline pH, actsm mainly in lumen, digestion of amylase products and simple carbs happen at the brush border
45
How are the carbs absorbed
Glucose adn galactose - secondary active transport - SGLT-1 on apical membrane Fructose - facilitated diffusion - GLUT-5 on apical membrane GLUT-2 facilitats exits at basolateral membrane
46
How are proteins digested
Protein digestion begins in lumen of stomach by pepsin Pancreatic proteases secreted as precursors - lumen of small bowel (trypsinogen) Trypsin activated by enterkinase Trypsin makes singel amino acids and oligopeptides
47
How do enterocytes absorb proteins
Via action fo H+/oligopeptide cotransporter PepT1 Small peptides are digested to AA by peptidases in cytoplasm
48
How is the digestion of lipids happening
Secretion of bile salts and pancreatic lipases Emulsification - increase surface area Enzymatic hydrolysis of ester linkages - colipase complexes with lipase, prevents bile salts displacing lipase from fat droplet Solubilisation of lipolytic products in bile salt micelles
49
How does the absorption of lipids happen
FA and MG leave micelles and enter enterocytes FA and MG resyntehsized in triglycerides by monoglyceride acylation (major) and phosphatidic acid pathway (minor) Chylomicrons - lipoprotein particles synthesised as an emulsion(80-90% TG) phospholipids, protein, in golgi Chylomicrons secreted across basment membrane by exocytosis Lymph transports them away from bwoel
50
What is the ileocaecal valve
Prevents balck flow of bacteria into ileum Relaxation and contraction controls passage of amteral into colon

Gastroenterology (9 decks)

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