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Digestive System II Associate Glands Chiaia Anatomy Block II Unit II


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What is an endocrine function?
Directly into blood stream.
WHat is an exocrine secretion?
Into duct
What does the liver serve as an interface between?
The blood (distrubutes nutrients) and the digestive system (extracts nutrients).
What are the 3 functions of the liver?
Vascular function
Secretory/excretory functions
Metabolic functions
What are the vascular functions of the liver?
storage and filtration of blood
What are the secretory/excretory functions of the liver?
Vitamin storage and excretion, A, B12, C, D, E, K, also blood clotting stuff, synthesis and secretion of bile
What are the metabolic functions of the liver?
-Protein synthesis (albumin, prothrombin, fibrinogen)
-lipoprotein and cholesterol synthesis
-carbohydrate metabolism (glycogenesis, glycogenolysis, gluconeogenesis)
-Metabolism of lipid-soluble drugs and steriods
-Urea formation (from ammonium ions)
Where is the liver located?
Upper right quadrant, below the diaphragm
What does the liver look like in the living state? (color)
Reddish brown
What is Glisson's capsule?
A dense irregular CT capsule that covers the liver and is itself coverd by the mesothelioum of the peritoneum.
What is the portal hepatis? What goes through it?
A short transverse fissure that serves as the site of entry and exit of blood vessels, lymphatics, nerves and ducts.
What seperates the right and left lobes of the liver?
The falciform ligament.
Approximately how much of the total cardiac output of the heart does the liver consume?
What percentage of the blood supply of the liver comes from the hepatic portal vein?
What forms the hepatic portal vein?
Capillaries of the digestive tract, spleen, and pancreas
What do the portal veins give rise to? What do these vessels carry?
Smaller diameter distributing veins andd inlet venules which radiate outward toward the sinusoids. They carry nutrient rich blood.
What percentage of the liver's blood supply comes from left and right hepatic arteries?
What is the origin of the left and right hepatic arteries? What is the origin of that origin?
Celiac trunk -> Abdominal aorta
What do hepatic arteries give rise to? What do these vessels do?
Smaller distributing arterioles and inlet arterioles. These carry oxygen rich blood to the hepatocytes.
WHat do inlet arterioles and venules empty into? What do these structures seperate?
The inlet arterioles and venules empty into endothelially line sinusoids which separate the plates of hepatocytes in the parenchyma.
What do the sinusoids of the liver empty into? Where are these structures located and what are they called?
Terminal hepatic venules at the center of each liver lobule, called central veins.
What do central veins empty into? What do these vessels eventually form/drain into?
Progressively larger veins, sublobular veins, and collecting veins that eventually form the left and right hepatic veins.
What shape are hepatocytes arranged in? What are they surrounded by?
Hexagonal shape. Surrounded by CT.
What is the area of denser connective tissue between the lobules of the liver called? What can be found here?
The portal tract which contains the major vessels of the liver (hepatic artery, hepatic portal vein, lymph vessels, bile duct).
What makes up the triad of vessels in the liver?
Hepatic artery, hepatic portal vein, bile duct.
Describe the cells lineing the bile duct.
Cuboidal cells w/ centrally located nucleus, looks like a string of pearls.
What two things separates the portal tract from the parenchyma of the lobules? Describe them.
Space of Moll (a narrow space, thought to be the site of origin of hepatic lymph)

Limiting Plate- A sleeve of modified hepatocytes.
Describe the arrangements of hepatocytes of lobules.
Plates or cords separated by sinusoids.
What pierces the center of each lobule of the liver? What does it do?
The center vein which drains blood from the sinusoids.
What are the 3 concepts of the liver lobule?
Classic lobule, portal lobule, hepatic lobule
What defines the classic lobule?
A hexogonal shaped parenchymal region and bounded by portal tracts at each corner of the hexagon with a central vein at its center.
Why is lobulation indistinct in humens?
Sparse perilobular CT
What is the basis for the classic lobule?
CT arrangement
Within the classic liver lobule where does blood flow and in what and from what?
From portal triads, centrally toward the central vein via the sinusoids
Within the classic liver lobule where does bile flow and in what and from what?
Bile flows from the hepatocytes, peripherally towards the bile ducts in the portal region.
Fill in the blank!

The __________ of each lobule collects blood from all ________ in that lobule and empties into the __________ which gives rise to a _________ which eventually joins the ___________
The CENTRAL VEIN of each lobule collects blood from all SINUSOIDS in that lobule and empties into the SUBLOBULAR VEIN which gives rise to a COLLECTING VEIN which eventually joins the RIGHT OR LEFT HEPATIC VEINS.
What defines a lobule in the portal lobule description? What would this be in the liver?
A region of the parenchyma whose secretory units flow into a common interlobular duct. In the liver this would be the bile duct of the portal tract.
What is the portal lobule described in terms of?
Bile flow
What is the portal lobule defined as?
A triangular region of hepatocytes with a central vein at the apices of the triangle and the portal triad (with the accompanying bile duct) at the center.
Where does bile flow in the portal lobule?
Bile flows from teh periphery to the center of the portal lobule into the interlobular bile duct.
Describe the size of the hepatic portal acinus.
Smallest functional unito f the liver
Give the arrangement of veins and hepatocytes within the hepatic portal acinus.
A diamond-shaped mass of hepatocytes lying between two central veins at the apices of its long axis and two portal tracts at apices its short axis.
What transverses the meridian of the diamond of hepatocytes in the hepatic portal acinus model?
Preterminal branches of a distributing arteriole which supplies blood to the sinusoids.
In the portal acinus model hepatic cords are supplied by each arterial branch are divided into how many zones?
3 functional zones.
Describe zone 1 of the portal acinus model, where are its cells, what sort of blood does it recieve and what is its exposure to waste?
Cells closest to the arteriole and meridian
Recieves an excellent supply of oxygenated blood and nutrients
Minimally exposed to metabolic waste
Describe zone 2 of the portal acinus model, where are its cells, what sort of blood does it recieve and what is its exposure to waste?
Cells further from vessels than zone 1, receive only moderately oxygenated blood, intermediate exposure to metabolic waste.
Describe zone 3 of the portal acinus model, where are its cells, what sort of blood does it recieve and what is its exposure to waste?
Cells closest to cental vien, recieves poorly oxygenated blood, high exposure to metabolic waste.
Which zone is the primary site of alcohol and drug detox? What are they more vulnerable to?
Zone 3 hepatocytes are more vulnerable to toxic damage than zone 1, liver disease usually shows degeneration of zone 3 cells first.
Within each lobule hepatocytes are arranged in thin cords or plates 1 or 2 cells thick. These are separated by what?
Thin endothelially lined sinusoids.
What sort of structure do the hepatic plates form?
A continuously anastomosing labyrinth of cells.
What do the sinusoids form within the lobule? Where do they ultimately empty?
A continuosu vascular channel within the lobule that ultimately empties in the central vein at the center of the lobule.
Are hepatocytes in direct contact with the sinusoids?
What separates hepatocytes from sinusoids?
A thin perisinusoidal space (space of Disse)
What does the space of Disse contain? (fluid)
Blood plasma but not blood cells or platelets.
What sort of structures are there many of in the space of disse?
Numerous microvilli protruding from the surface of hepatocytes.
What are perisinusoidal cells of Ito? Where are they found? What do they do?
Irregular cells with long cytoplasmic processes which concentrate vitamin A.
What sort of cell type form the wall of hepatic sinusoids?
Simple squamous endothelial cells.
Describe the endothelial cells of the wall of the hepatic sinusoids.
Discontinuous without a continuous basal lamina.
Describe the membrane of endothelial cells of hepatic sinusoids.
Riddled with clusters of small holes (Sieve plates)
What sort of things cannot pass through hte endothelial wall and into the space of disse?
Plasma only, cells and other larger structures cannot pass.
What supports the sinusoid epithelium?
A network of reticular fibers.
What sort of cells do the lumens of sinusoids often contain and where are they derived from?
Large branched phagocytic cells (Kupffer cells), derived from the mononuclear phagocyte line.
What do Kupffer cells do?
These cells phagocytose damaged red blood cells and plasma debri.
Describe what liver hepatocyts do to the end-products of absorption. WHere do these endproducts come from? What are they stored as and when are they released?
Hepatocytes metabolize the end products of absorption from the ailementary canal, stores these as cellular inclusions and releases them into sinusoids in response to hormonal or neural signals.
Describe the shape/ organization of hepatocytes.
Large polygonal shaped cells which are packed together to form thin plates or cords of the liver parenchyma.
Descibe the nucleus of hepatocytes.
Bi nucleated occasionally and of variable size.
How many mitochondria do hepatocytes have?
Numerous mitochondria.
Describe the RER of liver hepatocytes.
Abundant due to much protein synthesis
Describe the golgi of hepatocytes.
Describe the quantities of peroxisomes, lysosomes and endosomes in hepatocytes.
Hepatocytes contain lipid droplets (VLDL) when are they increased?
After a fatty meal.
What is the SER of the hepatocytes responsible for?
Drug metabolism and detox.
What happens to the SER of hepatocytes when lipid-soluble toxin levels rises?
Number increases.
What does the lumen of SER of hepatocytes contain?
Microsomal mixed-function oxidase system".
What are the 3 most common methods of drug inactivation and detoxifaction? Where are these peformed?
In hepatocyte SER, methylation, conjugation, oxidation.
What 2 types of surfaces do polygonal hepatocytes within hepatic plates contain?
Those which border other hepatocytes (lateral domain)

And those that border the sinusoids (sinusoidal domain).
What are the bile canaliculus? What domain are they a part of?
The lateral domain contains a tubular space between hepatocytes that form the bile canaliculus which are initial portions of the bile duct system.
What is the lateral domain formed from?
Solely from the hepatocyte membranes.
What surrounds membranes adjacent to the canaliculi in the lateral domain of hepatocytes? What do they do?
The membranes adjacent to the canaliculi are surrounded by tight junctions which isolate the bile space from the extracellular space.
From what surface do microvilli protrude from the canaliculi of hepatocytes in the lateral domain?
Short microvilli.
What do bile caniculi form relative to hepatocytes? What do they connect with? Where do they converge?
Bile canaliculi form a ring around hepatocytes and connect with those of adjacent hepatocytes to fmorm a complex branched network which converges on the portal region of the lobule.
What do bile canaliculi empty into? In what region? Where do they lead?
Bile canaliculi empty into bile ductals (Canals of Herring) in the portal region which lead to the portal bile ducts. These lead then do larger ducts wich eventually fuse with the left and right hepatic ducts.
What type of epithelium lines bile ductules and bile ducts?
Cuboidal epithelium.
What seperates the sinusoid epithelia from the hepatocytes in the sinusoidal domain?
The space of Disse.
What enzymes are particularly active in the sinusoidal domain of the liver? Why?
Na+/K+ ATPase and adenylate cyclase wich facilitate membrane transport.
What is the major secretion of the liver?
What sort of digestive enzymes does bile contain?
NO digestive enzymes.
What functions does bile have? (3)
Diluting and neutralizing acid chyme in the intestines and adjucting the intestinal pH to appropriate levels for pancreatic enzymes to function. Also to emulsify fat.
What are the major compounds of bile?
Bile salts (Taurocholate, glycocholate), bilirubin, electrolytes, cholesterol, phospholipids, lecithin, IgA
Where do the bile salts in bile come from?
80% reabsorbed from small intestine
10% synthesized
What is bilirubin?
Yellowish green toxic product of hemoglobin degradation.
Describe the shape/location of the gall bladder.
The gall bladder is a hollow pear-shaped organ attached to the posterior-inferior surface of the liver.
What is the major function of the gall bladder?
Store, concentrate and release bile.
Is the gallbladder a gland?
What are the 5 layers of the gallbladder wall? (from interior to exterior) Be sure to mention what they are composed of (cell type etc.)
1. Simple columnar epithelium composed of clear and brush cells.
2. Lamina propria composed of vascularized loose CT
3. Muscularis externa composed of smooth muscle of mixed orientation
4. A layer of perimuscular CT
5. A thin outer simple squamous epithelium (serosa)
How does bile reach the gall bladder from the liver?
Via the common hepatic duct.
What are the 3 functions of bile?
Emulsification of fat
Excretion of waste products from dead RBCs
Excretion of excess choloesterol synthesized in the liver.
How is bile concentrated in the gall bladder?
Removal of water and ions (concentrated 5-10 times)
How much bile does the gallbladder release into the liver every day? What triggers its release?
Up to 1200 mL of bile. Occurs in response to contraction of the gall bladder's smooth muslce layer.
What is the signal for gallbladder contraction? Where is this produced?
The signal is the hormone cholecystokinin-pancreozymin produced by the enteroendocrine cells of intestinal epithelium.
What controls the flow of bile? At what junction?
The flow of bile is controlled by the sphincter choledochus, at the junction of the common bile duct and the duodenum.
What causes the duodenum and bile duct to releax?
CCK (cholecystokinin)
What is the junction of the common bile duct and the duodenum called?
Ampulla of Vater.
What forms gallstones? Where do they frequenly lodge?
Cholesterol precipitating, fequently lodge in the cystic of common hepatic ducts.
Describe the type of gland the pancreas is and where it is.
An oblong tubuloacinar gland that nestles within the curvature of the duodenum.
What are the 4 regions of the pancreas?
The Uncinate process, head, body and tail.
What drains the secretions of the pancreas?
The pancreatic duct.
What envelopes the pancreas? What does it form?
A thin connective tissue capsule which forms delicate septae within the parenchyma to divide the organ into lobules.
What takes on the exocrine function of the pancreas? How about the endocrine?
Pancreatic acini, Islets of Langerhans.
Describe Acini (morphology, cell types, components).
Round to oval shaped secretory units composed of 40-50 pyramidal shaped acinar cells which form secretory component and 3-4 centrally locaed low cuboidal centroacinar cells which form the beginnings of the duct system.
What do centroacinar cells of the pancreas lead to?
The initial portion of the duct system or intercalated ducts.
Intercalated ducts from neighboring acini join to form larger INTRAlobular ducts which are composed of what type of cells?
Simple cuboidal-columnar cells.
Intralogular ducts from several lobules converge to form larger INTERlobular ducts which are composed of what type of cells?
Low columnar epithelium.
What do the interlobular ducts empty into?
The main pancreatic duct.
Describe pancreatic acinar cells shape. WHy are they shaped this way?
Pyramidal-shaped cells with an ultrastucture typical of a cell polarized for protein synthesis and secretion. These cells are polarized somewhat.
Describe the basal region of pancreatic acinar cells. (4)
Their basal region rests on a basement membrane. It contais a round nucleus, an extremely well developed RER with numerous basophilic polysomes and numerous mitochondria.
Describe the apical region of pancratic acinar cells. (4)
Numerous secretory zymogen granules whose number fluctuates with the state of fasting
Well developed golgi
Numerous microvilli on the luminal surface
Tight/Adhereing/desmosomes/gap junctions connect adjacent cells and isolate the lumen form the intercellular space.
What activates proenzymes in the duodenum?
In what form are the enzymes of the pancreas released?
Inactive proenzymes.
What prevents autodigestion of the pancreas? Where do these come from?
It is protected from premature activation by a trypsin inhibitor secreted by the acinar cells.
Why are inflammatory diseases of the pancreas (pancreatitis) so dangerous?
It can result in the lysis of the acinar cells and subsequent release of active digestive enzymes into the abdominal cavity causing serious organ damage.
What occupies the lumen of each acinus? WHat do these represent?
Centroacinar cells occupy the lumen of each acinus. They represent the initial portion of the intercalated ducts.
Describe the physical appeareance of centroacinar cells.
Small, stellate with a clear cytoplasm.
What are centroacinar cells diagnostic for?
The pancrease.
What do centroacinar cells do?
Secrete bicarbonate ions which maintain duodenal pH appropriate for enzyme function.
What is trypsinogen for, what secretes it?
Proteolysis, acinar
What is chymotrypsinogen for, what secretes it?
Proteolysis, acinar
What is procarboxypepsidase for, what secretes it?
Proteolysis, acinar
What is pancreatic amylase for, what secretes it?
Hydrolyzes starch and glycogen
What is pancreatic lipase for, what secretes it?
Hydrolyzes fats
What secreates ribonuclease, deoxyribonuclease and cholseterol esterase?
Acinar cells
What regulates acinar cell enzyme secretion? What produces this?
IT is regulated by the hormone Cholecystokinin (CCK) which is produced in the epithelium of the duodenum.
Where are the receptors for CCK on acinar cells located?
The basal surface.
What regulates the secretion of centroacinar cells? What procduces this?
The secretion of centroacinar cells is regulated by levels of the hormone secretin produced by the duodenal epithelium.
What are pancratic islets of langerhans? What is their appearance? WHere are they found?
They ae multihormonal micro-organs in the form of ovoid groups of clear endocrine cells scattered throughout the exocrine pancreas. They ar most numerous in the tail region of the pancreas.
What are the 3 effects of liver failure?
Reduced protein synthesis
Reduced metabolic detoxification
Decreased bile secretion
What does reduced protein synthesis of the liver lead to?
Decreased albumin synthesis with decreased osmotic pressure in the blood causing edema.

Also increased spontaneous internal bleeding due to reduced synthesis of clotting factor.
What is the result of reduced metabolic detoxification in the liver? What pathological state can this lead to?
Increased plasma levels of biological toxis leading to hepatic coma.
What does decreased bile secretion lead to? (pathological state).
Bile accumulation in the liver and plasma manifested as a yellowish discoloration of the skin = jaundice.
What is acute hepatic failure due to? What inflammes?
Viral infection which results in inflammation of the hepatic plates (hepatitis)
What does chronic progressive liver disease result from (cirrhosis)?
Chronic alcohol or drug abuse, chronic viral hepatitis.
How does viral hepatitis damage the liver? What does this damage result in?
Destruction of hepatic plates and sinusoids which are replaced by fibrous CT scars. Thus the reorganized, damaged lobule is altered with reduced synthesis, secretion and blood flow.

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