GI S6 (Done)

Question 1

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

Answer 1

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

Question 2

What are the two major functions of the pancreas?

Answer 2

Exocrine function

Endocrine function

Question 3

Outline the exocrine pancreas functions

Answer 3

Secretes:

Alkaline juice

Enzymes:

• • Chymotrypsinogen*
• • Trypsinogen*
• • Elastase*
• • Carboxypeptidase*
• • Amylases*
• • Lipases*

Question 4

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

Answer 4

Exocrine tissue is glandular:

Glands secrete enzymes

Ducts secrete Alkaline juice

Question 5

Describe how the pancreas produces enzymes

Answer 5

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

Question 6

What is a haematological sign of pancreatic damage?

Answer 6

Pancretic enzymes appearing in blood (Amylase commonly looked for)

Question 7

outline the control of Acinar secretion in the exocrine pancreas

Answer 7

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)

Question 8

OUtline the process of ductal secretion in the exocrine pancreas

Answer 8

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

Question 9

How is ductal secretion in the exocrine pancreas controlled?

Answer 9

Stimulated by Secretin:

Secreted from jejunal cells

In response to low pH within jejunum

Action facilitated by CCK

Question 10

What are the functions of the liver?

Answer 10

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

Question 11

Label this image

What does this image show?

Answer 11

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)

Question 12

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

Answer 12

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

Question 13

What are bile acids?

Give examples and describe function

Answer 13

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

Question 14

Outline the breakdown of globules of fat in the GI tract

Answer 14

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

Question 15

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

Give a brief description of form and function

Answer 15

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

Question 16

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

Answer 16

Resynthesised as lipids internally

Exported to lymphatics as chylomicrons

- Lipid coated with polar protein and phospholipids

Question 17

Describe the enterohepatic circulation of Bile acids

Answer 17

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*

Question 18

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

Answer 18

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

Question 19

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

Answer 19

High concentration increases risk of precipitation (stone formation)

Question 20

Outline control of the enterohepatic circulation

Answer 20

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

Question 21

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

Answer 21

Steatorrhoea

- Pale, floating, foul smelling

Question 22

What are bile pigments?

Give an example and how it’s formed and excreted

Answer 22

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*

Question 23

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

Answer 23

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

Question 24

Label the image

Answer 24

Top to bottom:

Full expiration

Neutral respiratory position

Occupied 4-8cm at the midline

Occupies 6-12cm at right midclavicular line

Inspiration

Question 25

Describe the surfaces of the liver and their relation

Answer 25

Convex diaphragmatic surface Flatter visceral (postero-inferior) surface Separated anteriorly by the inferior border that follows the right costal margin, inferior to diaphragm

Question 26

Label this diagram

Answer 26

**From top left clockwise:** Right lobe Coronary ligament Left triangular ligament Apex Left lobe Falciform ligament Round ligament (ligamentum teres) Inferior border Gallbladder

Question 27

Label this diagram

Answer 27

**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

Question 28

What are the subphrenic reccesses? What structure separates them?

Answer 28

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

Question 29

What structure is found within the falciform ligament?

Answer 29

Ligamentum teres Round ligament, the embryonic remnant of the umbilical vein

Question 30

What are the subhepatic spaces?

Answer 30

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

Question 31

Describe the distribution of visceral peritoneal covering of the liver

Answer 31

**Diaphragmatic surface:** Covered with visceral peritoneum except at the bare area of the liver Bare area marked out by the coronary ligament (reflection of peritoneum from the liver to diaphragm) **Visceral surface:** Covered with peritoneum except at the fossa for the gallbladder and the Porta Hepatis (a transverse fissue where hepatic artery and lymphatics + the portal vein travel)

Question 32

What are the left and right triangular ligaments?

Answer 32

Where the reflections of the peritoneum from diaphragm to liver (Coronary ligaments) converge after surrounding the triangular bare area **LTL:** Found near the apex **RTL:** Where the coronary ligaments converge on the superior/diaphragmatic surface of the right lobe

Question 33

Label the diagram

Answer 33

**Top centre clockwise:** Bare area IVC Left triangular ligament Coronary ligament Left lobe Falciform ligament Coronary ligament Right lobe Hepatic veins Right triangular ligament Ligament of IVC

Question 34

What are the lobes of the liver and how are they divided?

Answer 34

**2 Anatomical lobes:** Divided on diaphragmatic surface by the falciform ligament **2 Accessory lobes:** Dived on the visceral surface by the right and left saggital fissures and the Porta Hepatis

Question 35

Label this diagram

Answer 35

**Top right anticlockwise:** Right sagittal fissure Caudate lobe Left lobe Left sagittal lobe Porta Hepatis Quadrate lobe Right lobe

Question 36

Label this diagram

Answer 36

**Left column:** Common hepatic duct Portal triad (Hepatic artery, hepatic portal vein, Bile duct) Galbladder **Right column:** Lesser Omentum (Hepatogastric ligament, Hepatoduodenal ligament) Common hepatic artery

Question 37

Where is the gallbladder found? Describe the gallbladder

Answer 37

**Where:** Found in the fossa for gallbadder on the visceral surfece of the liver, it is enclosed in the fibrous capsule of the liver **Gallbladder:** Has three parts: * - Neck* * - Body* * - Fundus* Neck of the gallbladder joins the cystic duct

Question 38

Describe the biliary tree

Answer 38

**From hepatocytes:** Hepatocytes secrete bile into canaliculi which merge to form interlobular biliary ducts These in turn merge to form the Collecting bile ducts Collecting ducts merge on each side to form the right and left hepatic ducts R+L Hepatic ducts merge to form the common hepatic duct shortly after leaving the Porta Hepatis CHD joined on the right by the cystic duct to form the Bile ducts Bile duct conveys bile to the duodenum, draining into it via the ampulla of vater Shortly before this the pancreatic duct joints the bile duct

Question 39

Label the diagram

Answer 39

**Top down, left to right:** Right Hepatic duct Left Hepatic duct Common hepatic bile duct Cystic duct Common bile duct Pancreatic duct Ampulla of Vater Duodenum

Question 40

Describe the differences in symptoms experienced from gall stones based on where they lodge

Answer 40

**Gall bladder:** Asymptomatic **Cystic duct:** Acute cholecystitis **Common bile duct:** Biliary obstruction **Terminal duct (Post pancreatic duct joining):** Pancreatitis

Question 41

Describe the arterial supply of the Gallbladder

Answer 41

Coeliac trunk --\> Common hepatic --\> Right hepatic --\> Cystic Cystic artery usually arises in the triangle between the common hepatic duct, cystic duct and the visceral surface of the liver (The cystohepatic triangle)

Question 42

Label the Diagram

Answer 42

**From top centre clockwise:** Gallbladder Right hepatic artery Left hepatic duct Common hepatic duct Bile duct Cystic duct Cystic artery

Question 43

Describe the anatomical position of the pancreas

Answer 43

Retroperitoneal Transversely crosses the bodies of L1 and L2 (transpyloric plane) on the posterior abd. wall Lies posterior to the stomach Lies between the duodenum on the right and spleen on the left The transverse mesocolon attaches to the anterior margin

Question 44

Label the diagram

Answer 44

**Left to right:** Head Neck Body Tail

Question 45

Describe the head of the pancreas and its surrounding structures

Answer 45

Expanded section of the gland, embranced by the curve of the duodenum Found to the right of the SMA (unlike the rest of the pancreas) and just inferior to the transpyloric plane (L1-L2)

Question 46

Describe the neck of the pancreas

Answer 46

Short Overlies the Mesenteric vessels Anterior surface is covered by peritoneum and lies adjacent to the pylorus of the stomach SMV joins the splencic vein posterior to the neck forming the portal vein

Question 47

Describe the body of the pancreas and its surrounding structures

Answer 47

Continues from the neck, lies left of the SMV/A Passess over the aorta and the L2 vertebrae, continues above the transpyloric plane posterior to the omental bursa Anterior surface is covered in peritoneum, posteior is devoid of peritoneum (retroperitoneal organ remember) Body is in contact with the Aorta, left kidney and suprarenal gland and renal vessels posteriorly

Question 48

Describe the tail of the pancreas and its surrounding structures

Answer 48

Lies anterior to the left kidney Closely related tot he splenic hilum and the left colic flexure Tail is relatively mobile and passes between the layers of the splenorectal ligament with the splenic vessels

Question 49

What is the main pancreatic duct?

Answer 49

Begins at the tail and runs through the gland to the head where it turns inferiorly and joins the common bile duct

Question 50

Describe the blood supply of the pancreas

Answer 50

**Neck, Body, Tail:** Supplied by **Greater Pancreatic Artery**, a branch of the **Splenic** **Head:** Supplied by branches of the **Gastroduodenal artery** and **SMA** that anastomose/form arches * Common hepatic --\> Gastroduodenal --\> Anterior/Posterior Superior Pancreaticoduodenal arteries* * SMA --\> Inferior Superior Pancreaticoduodenal --\> Anterior/Posterior Superior Pancreaticoduodenal Arteries*

Question 51

Describe the venous drainage of the pancreas

Answer 51

**Neck, Body, Tail:** **Pancreatic veins** drain into the **Splenic vein** **Head:** **Inferior Pancreaticoduodenal vein **and **Superior Pancreaticoduodenal veins** drain into the **SMV**

Question 52

Describe the spleen and it's location

Answer 52

**Spleen:** Ovoid, purplish, pulpy mass about the size and shape of a fist Delicate **Location:** In the Upper left quadrant (Left hypochondrium to be more precise) Entirely covered by a layer of visceral peritoneum except at the hilum where the splenic artery and vein enter and exit

Question 53

Describe the relations of the spleen:

Answer 53

**Anteriorly:** Stomach *Attached via gastrosplenic ligament* **Posteriorly:** Left part of diphragm, separating it from thoracic structures and the abd. wall **Inferiorly:** Left colic flexure **Medially:** Left kidney *- Attached via the splenorenal ligament*

Question 54

Describe Arterial supply of the Spleen

Answer 54

Supplied by the splenic artery, the largest branch of the coeliac artery Follows a tortuous course posterior to the omental bursa and anterior to the left kidney along the superior border of the pancreas Splenic artery divides into 5 or more branches before entering the splenic hilum

Question 55

Describe venous drainage of the spleen

Answer 55

Splenic vein drains the spleen Splenic vein is joined by the IMV posterior to the body of the pancreas Splenic vein unites with the SMV behind the nech of the pancreas to form the hepatic portal vein

Question 56

Label the diagram

Answer 56

**From top left anticlockwise:** Celiac artery Common hepatic artery Gastroduodenal artery Right Gastro-omental artery Anterior and posterior superior pancreatico-duodenal arteries SMA Uncinate process of the head of the pancreas Inferior pancreatico-duodenal artery (divides into posterior and anterior superior pancreatico-duodenal arteries) Splenic artery Greater pancreatic artery

Question 57

Label the diagram

Answer 57

**From top centre clockwise:** Hepatic portal vein Pancreatic vein Splenic vein IMV Inferior pancreatico-duodenal vein SMV Superior pancreatico-duodenal vein