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1

Give the 3 basic features of Chyme and related these features to the actions of the duodenum

Acidic:

Aciditicy corrected in duodenum via secretion of HCO3- from pancreas, liver and duodenal mucosa

Hypertonic:

Corrected via osmotic movement of water over duodenal wall

Partially digested:

Digestion completed with enzymes from pancreas and small intestal mucosa ans well as bile salts from the liver

2

What are the two major functions of the pancreas?

Exocrine function

Endocrine function

3

Outline the exocrine pancreas functions

Secretes:

Alkaline juice

Enzymes:

- Chymotrypsinogen

- Trypsinogen

- Elastase

- Carboxypeptidase

- Amylases

- Lipases

4

What structural features are responsible for the exocrine functions of the pancreas?

Exocrine tissue is glandular:

Glands secrete enzymes

Ducts secrete Alkaline juice

5

Describe how the pancreas produces enzymes

Enzymes synthesised by ribosomes of Acinar gland epithelium

- mostly as inactive precursors

Then packaged into condensing vacuoles by golgi

Then form zymogen granules

- Secretory granules that appear dense

Zymogens granules secreted via exocytosis

Enzymes activated in the intestine by enzymatic cleavage

6

What is a haematological sign of pancreatic damage?

Pancretic enzymes appearing in blood (Amylase commonly looked for)

7

outline the control of Acinar secretion in the exocrine pancreas

Stimulated by cholecystokinin (CCK) during the Intestinal phase of GI control

- CCK released from duodenal APUD cells

CCK release stimulated by:

- Hypertonicity

- Fats

Some receptors also stimulated by gastrin due to receptor homology

Vagus nerve also stimulates via Ach during the cephalic phase of control (Advance secretion in preparation of food)

 

8

OUtline the process of ductal secretion in the exocrine pancreas

Ductal cells secrete HCO3-:

Basolateral Na+/K+ ATPase creates Na+ gradient across apical membrane

Basolateral Na+/H+ exchanger exports H+ to react with HCO3- in the ECF

CO2 and H2O taken into the cell and react

H+ produced is recycled

HCO3- is exported to duct lumen

9

How is ductal secretion in the exocrine pancreas controlled?

Stimulated by Secretin:

Secreted from jejunal cells

In response to low pH within jejunum

Action facilitated by CCK

10

What are the functions of the liver?

Haematogenous functions:

Energy metabolism

Detoxification

Plasma protein synthesis

GI functions:

Secretion of Bile (0.25-1.0L.day-1)

- Contains bile acids and alkaline juice for digestion as well as excreting bile pigments

11

Label this image

What does this image show?

Top row:

Bile duct

Bile canal

Kupffer cell

Hepatic cells

Bottom row:

Branch of hepatic portal vein

Branch of hepatic artery

Blood flow into the liver

Hepatic sinusoids

Central canal (blood flow out of liver)

Image shows the components of a liver lobule (Functional unit)

12

What are the two components of Bile and where are they snythesised?

Bile acid dependent:

Secreted into canaliculi (which drain into branches of the bile duct) by hepatocytes

Contains Bile acids and pigments

Bile acid independent:

Secreted by duct cells

Alakaline juice like that of the pancreas

13

What are bile acids?

Give examples and describe function

Related to cholesterol:

E.g. Cholic acid, Chenodeoxycholic acid

Conjugated to amino acids

Travel in the bile as micelles containing bile acids, cholesterol and phopsholipids

Function:

Needed for digestion and absorption of fat

14

Outline the breakdown of globules of fat in the GI tract

Fats tend to form large globules as stomach acid breaks down natural emulsions

- Low surface area for enzymes

Bile acids emulsify the fat into smaller globules with increased surface area

Lipases have greater area to act and cleave fatty acids and glycerol

Colipase links bile acids and lipases to spread them over the surface of globules

15

What form do fatty acids take once lipase has separated them from glycerol?

Give a brief description of form and function

Forms micelles:

Polar groups of bile acids surround hydrophobic fats

4-6nm in diameter (20 lipid molecules)

Requires a certain conc of bile acids

Also sequesters cholesterol, ADEK vitamins and phospholipids

Function:

Carries the fatty acids throught he aqueous limunal contents to the unstirred layer next to epithelia

Fatty acids etc. are released and enter cells via diffusion

16

What happens to fatty acids once they enter the epithelial in the gut?

Resynthesised as lipids internally

Exported to lymphatics as chylomicrons

- Lipid coated with polar protein and phospholipids

17

Describe the enterohepatic circulation of Bile acids

Bile acids formed in liver and released into the bile duct

Released into lumen of the gut after fatty acids have been absorbed

Absorpted actively by terminal ileum

Return to hepatic portal blood to hepatic sinusoids

Hepatocytes actively take up and resecrete bile acids

Most bile acid recovered, some unconjugated by gut bacteria and lost

Hepatocytes synthesise more

18

How is the gall bladder involved in enterohepatic circulation of bile acids?

BAs returned to liver between meals

Secreted by canalicular cells well before needed next

Gallbladder used for storage

Gallbladder concentrates the BAs via uptake of water and salt across its epithelium

19

What is the problem with storing high concentration Bicle acid in the gallbladder?

High concentration increases risk of precipitation (stone formation)

20

Outline control of the enterohepatic circulation

CCK stimulates gall bladder muscle, ejecting bile acids along with enzymes from pancreas

 

21

What is the concequence of bile acids and pancreatic enzymes not being released in adequate amounts?

Steatorrhoea

- Pale, floating, foul smelling

22

What are bile pigments?

Give an example and how it's formed and excreted

Excretory products:

E.g. Bilirubin

-Breakdown of haemoglobin produces an unconjugated form

- Conjugated in liver

- Secreted into bile

- Excreted in faeces

- Accumulates in blood with liver dysfunction leading to jaundice

23

Describe where the liver lies in the body using anterior surface markings/areas

Occupies mainly the right upper quadrant

Lies deep to ribs 7-11 on the right side and crosses the midline towards the left nipple

Liver occupies most of the right hypochondrium, the upper epigastrum and extends into the left hypochondrium

24

Label the image

Top to bottom:

Full expiration

Neutral respiratory position

Occupied 4-8cm at the midline

Occupies 6-12cm at right midclavicular line

Inspiration

 

25

Describe the surfaces of the liver and their relation

Convex diaphragmatic surface

Flatter visceral (postero-inferior) surface

Separated anteriorly by the inferior border that follows the right costal margin, inferior to diaphragm

26

Label this diagram

From top left clockwise:

Right lobe

Coronary ligament

Left triangular ligament

Apex

Left lobe

Falciform ligament

Round ligament (ligamentum teres)

Inferior border

Gallbladder

27

Label this diagram

From top left clockwise:

Left triangular ligament

Lesser omentum

IVC

Right triangular ligament

Portal vein

Hepatic ducts

Cystic duct

Gallbladder

Inferior border

Ligamentum teres

Falciform ligament

 

 

 

28

What are the subphrenic reccesses?

What structure separates them?

Superior extentions of the peritoneal cavity (greater sac) between the liver (superior and anterior aspects and the diaphragm

Split into left and right recesses by the falciform ligament wich extends between the liver and the anterior abd. wall

29

What structure is found within the falciform ligament?

Ligamentum teres

Round ligament, the embryonic remnant of the umbilical vein

30

What are the subhepatic spaces?

Portions of the Supracolic compartment of the peritoneal cavity directly infeior to the liver