GI S6 (Done) Flashcards
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
What are the two major functions of the pancreas?
Exocrine function
Endocrine function
Outline the exocrine pancreas functions
Secretes:
Alkaline juice
Enzymes:
- Chymotrypsinogen*
- Trypsinogen*
- Elastase*
- Carboxypeptidase*
- Amylases*
- Lipases*
What structural features are responsible for the exocrine functions of the pancreas?
Exocrine tissue is glandular:
Glands secrete enzymes
Ducts secrete Alkaline juice
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
What is a haematological sign of pancreatic damage?
Pancretic enzymes appearing in blood (Amylase commonly looked for)
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)
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
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
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
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)
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
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
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
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
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
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*
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
What is the problem with storing high concentration Bicle acid in the gallbladder?
High concentration increases risk of precipitation (stone formation)
Outline control of the enterohepatic circulation
CCK stimulates gall bladder muscle, ejecting bile acids along with enzymes from pancreas
What is the concequence of bile acids and pancreatic enzymes not being released in adequate amounts?
Steatorrhoea
- Pale, floating, foul smelling
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*
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
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
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
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
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
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
What structure is found within the falciform ligament?
Ligamentum teres
Round ligament, the embryonic remnant of the umbilical vein
What are the subhepatic spaces?
Portions of the Supracolic compartment of the peritoneal cavity directly infeior to the liver
Describe the distribution of visceral peritoneal covering of the liver
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)
What are the left and right triangular ligaments?
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
Label the diagram
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
What are the lobes of the liver and how are they divided?
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
Label this diagram
Top right anticlockwise:
Right sagittal fissure
Caudate lobe
Left lobe
Left sagittal lobe
Porta Hepatis
Quadrate lobe
Right lobe
Label this diagram
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
Where is the gallbladder found?
Describe the gallbladder
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
Describe the biliary tree
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
Label the diagram
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
Describe the differences in symptoms experienced from gall stones based on where they lodge
Gall bladder:
Asymptomatic
Cystic duct:
Acute cholecystitis
Common bile duct:
Biliary obstruction
Terminal duct (Post pancreatic duct joining):
Pancreatitis
Describe the arterial supply of the Gallbladder
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)
Label the Diagram
From top centre clockwise:
Gallbladder
Right hepatic artery
Left hepatic duct
Common hepatic duct
Bile duct
Cystic duct
Cystic artery
Describe the anatomical position of the pancreas
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
Label the diagram
Left to right:
Head
Neck
Body
Tail
Describe the head of the pancreas and its surrounding structures
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)
Describe the neck of the pancreas
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
Describe the body of the pancreas and its surrounding structures
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
Describe the tail of the pancreas and its surrounding structures
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
What is the main pancreatic duct?
Begins at the tail and runs through the gland to the head where it turns inferiorly and joins the common bile duct
Describe the blood supply of the pancreas
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*
Describe the venous drainage of the pancreas
Neck, Body, Tail:
Pancreatic veins drain into the Splenic vein
Head:
**Inferior Pancreaticoduodenal vein **and Superior Pancreaticoduodenal veins drain into the SMV
Describe the spleen and it’s location
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
Describe the relations of the spleen:
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
Describe Arterial supply of the Spleen
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
Describe venous drainage of the spleen
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
Label the diagram
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
Label the diagram
From top centre clockwise:
Hepatic portal vein
Pancreatic vein
Splenic vein
IMV
Inferior pancreatico-duodenal vein
SMV
Superior pancreatico-duodenal vein
