Digestive 4 Flashcards
Liver functions
o Produces and secretes bile.
o Receives substances absorbed by the intestines
through portal circulation.
o Processes/stores nutrients, minerals, and glucose
(glycogen); controls when to put these into blood.
o Detoxifies ingested toxins (e.g. alcohol, drugs).
o Breaks down old RBCs & produces blood proteins.
ANTERIOR liver
o Anteriorly, liver is divided into left and right lobes.
o Lobes separated by a falciform ligament, which connects liver to anterior abdominal wall.
o Inferiorly, falciform ligament is continuous with round ligament (ligamentum teres), which is remnant of umbilical vein. Connects to umbilicus.
o Superiorly, falciform ligament turns into coronary ligament, which attaches to diaphragm.
SUPERIOR liver
o Coronary ligament reflects superiorly onto diaphragm.
o Bare area of liver: Area bounded by the coronary ligament and triangular ligaments, not covered by peritoneum (liver directly touching diaphragm).
o Triangular ligaments: formed at left and right angles of coronary ligament.
POSTERIOR liver
o Two more lobes:
• Caudate lobe (between inferior vena cava and venous ligament of the liver (ligamentum venosum)
• Quadrate lobe (between gallbladder and round ligament)
Porta hepatis: site where portal triad enters/exits the liver. The portal triad consists of:
o Hepatic artery (supplies oxygenated blood to liver)
o Hepatic portal vein (brings nutrient-rich blood from intestines to liver)
o Common hepatic duct (carries bile away from liver toward duodenum).
Lesser omentum
double-layer of peritoneum connecting liver with lesser curvature of stomach and first part of duodenum.
The portal triad runs within the lesser omentum to get to the porta hepatis.
BLOOD
Blood from portal vein (3/4, nutrientrich) and hepatic artery (1/4, O2-rich) percolate through hepatocyte plates (via large capillaries called sinusoids).
Cleaned blood then reaches a central vein in middle of lobule. Central veins empty into hepatic veins that drain
liver (into inferior vena cava).
BILE
o Bile produced by hepatocytes is secreted into bile canaliculi (channels between hepatocytes), which merge to form biliary ducts.
o Biliary ducts unite to form left and right hepatic ducts, which drain bile from left and right lobes of liver.
o Left and right hepatic ducts converge at porta hepatis to form the common hepatic duct.
CIRRHOSIS
o Destruction of hepatocytes, replaced by tough scar tissue. Liver becomes hard and nodular due to scar tissue.
o Blood flow through liver becomes inefficient, leading to portal hypertension.
o Causes:
• Alcohol (most common)
• Viruses (hepatitis C)
• Drugs/medications
• Autoimmune disease
JAUNDICE
o Hepatocytes decompose old RBCs. Convert heme
(protein in hemoglobin) into a yellow-green substance called bilirubin, which is excreted in bile.
o Bilirubin gives bile its yellow/green colour and is oxidized in intestines to give feces its brown colour.
o A diseased liver cannot process and excrete bilirubin
efficiently, leading to high bilirubin in circulation.
o Jaundiced patients have yellowish skin and eyes,
and clay-coloured feces.
The gallbladder has 3 parts:
o Fundus (rounded inferior part) o Body (middle part) o Neck (narrow superior part)
cystic duct
connects neck of gallbladder with hepatic duct. Bile drains into and out of the gallbladder by this duct.
runs in layers of lesser omentum to join common hepatic duct.
bile duct
Once cystic duct and common hepatic duct unite, the bile duct is formed. Bile duct transports bile from liver/gallbladder to duodenum.
Bile:
yellow/green alkaline solution that emulsifies (breaks down) fats.
Gallstones
o Gallstones form when cholesterol, bilirubin, and other substances in bile crystallize to make stones.
o May not cause any pain; but if lodged in cystic or bile duct, can cause severe abdominal pain and block bile
from reaching the duodenum.
o If recurrent, may need to have gallbladder removed (cholecystectomy).
Pancreas:
an elongated, flat gland found in the upper left abdomen behind the stomach and between the
duodenum and spleen.
ANATOMY pancreas
o Five parts:
1) Head (expanded part close to duodenum)
2) Uncinate process (hook-shaped projection of head of pancreas)
3) Neck (small part adjacent to pylorus)
4) Body
5) Tail (left-most part close to spleen)
The pancreas performs two major functions:
o Exocrine function: produces pancreatic juice, which contains enzymes essential for digestion.
o Endocrine function: produces hormones (insulin and glucagon) that control blood glucose levels.
EXOCRINE
o Most (~95%) of pancreas is acinar cells arranged in acini (sacs). o Acinar cells make pancreatic juice containing: • Enzymes (amylase, trypsin, chymotrypsin) that break down starch and protein. • Bicarbonate, which neutralizes gastric acid. o Enzymes are stored and secreted as zymogens (inactive enzymes). Zymogens move from acinus via intralobular ducts to main pancreatic ducts. o Zymogens are active once they reach acidic environment of duodenum.
ENDOCRINE
o Endocrine pancreas comprises 5% of thec ells arranged in islets (of Langerhans).
o These cells produce:
• Insulin (decreases blood glucose).
• Glucagon (increases blood glucose).
• Somatostatin (slows down digestion, inhibits insulin and glucagon production).
o Islet cells secrete these hormones directly into the bloodstream.
Insulin
is the hormone that lowers blood glucose (facilitates glucose entry into cells).
Diabetes
absence or insufficient insulin production, or an inability of cells to properly use insulin, leading to high blood sugar levels
pancreatic ducts
Main pancreatic duct + Bile duct => hepatopancreatic ampulla (of Vater). => major duodenal papilla.
hepatopancreatic ampulla (of Vater).
Main pancreatic duct joins with bile duct, and together they form hepatopancreatic ampulla (of Vater).
Hepatopancreatic ampulla drains into duodenum at major duodenal papilla.
Hepatopancreatic sphincter (of Oddi)
surrounds this duct and controls flow of bile and pancreatic juice into duodenum.
Controls entry of bile and pancreatic juice through major duodenal papilla.
PANCREATITIS
o Pancreatitis is inflammation of pancreas, often due to premature release/activation of pancreatic juice that eats away at acini.
o Causes:
• Blockage of bile duct/hepatopancreatic ampulla (e.g. gallstones)
• Alcohol
• Viruses
• Trauma (injury to pancreas)
o Can be sudden (acute) or chronic, and very painful!
Pancreatic duct summary
oLeft and right hepatic ducts combine to form common hepatic duct, which carries bile from liver.
oCystic duct carries bile to/from gallbladder.
oBile duct is formed after cystic duct joins common hepatic duct.
oMain and accessory pancreatic ducts drain pancreas.
oMain pancreatic duct joins with bile duct to form hepatopancreatic ampulla. It empties into duodenum at major duodenal papilla. oAccessory pancreatic duct empties into duodenum separately at minor duodenal papilla.
PANCREATIC
CANCER
o Uncontrolled proliferation of cells in pancreas.
o Most commonly associated with: smoking, pancreatitis/inflammation, diabetes, age (70+).
o Most common: adenocarcinoma (acinar cells).
o Difficult to detect until advanced stage. Thus, when detected it has usually spread to other tissues, so has a high mortality rate.
o In Canada: 12th highest incidence, 4th deadliest.
