Histology of the Pancreas & Liver: Week 1 Flashcards
General details about the pancreas are…
Location: lies against posterior abdominal wall; retroperitoneal
Anatomical regions: uncinate process, head, body, tail
Division: septa (CT) subdivides pancreas into lobules; septa contains nerves & vessels
Function: exocrine and endocrine
The exocrine pancreas produces ___ ml of fluid per day, and the fluid contains digestive ____
1200, proenzymes
The functional unit of the exocrine pancreas is the___
pancreatic acinus
Each pancreatic acinus is formed of __ to __ acinar cells and each acinus usually contains 3-4 ____ cells
40 -50
centroacinar
*centroacinar cells are the beginning of the duct system
Features of acinar cell,for example shape etc.
Shape: pyrimidal shape
location: sits on basal lamina
cytoplasm: basophilic & apical secretory granules
Basal membrane: receptors for cholecystokinin
abundant in rER, polysomes, mitochondria
Well developed Golgi
Acinar cells are stimulated by …
secretin to produce fluid high in HCO3-
cholecystokinin to secrete proenzymes
What type of innervation stimulates both acinar and centroacinar cells?
Parasympathetic
Pancreatic enzymes include…
- pancreatic amylase
- pancreatic lipase
- ribonuclease and DNase
- trypsinogen, chymotrypsinogen, procarboxypeptidase, elastase
Centroacinar cell features
- Squamous to low cuboidal cells
- have receptors for secretin
- form the intra-acinar portion of intercalated ducts
Intercalated ducts begin __, and are named based on__ ? What kind of epithelium do they have?
- Begin in acini
- named for location between acini
- simple cuboidal epithelium
Interlobular ducts are made up of what kind of epithelium and cells?
simple low columnar epithelium, with
enteroendocrine and goblet cells
Main pancreatic duct joins__ __ duct. What kind of epithelium and cells make up this duct?
- joins the common bile duct
- simple columnar epithelium with goblet cells
Features of Pancreatic Islets (of Langherhans)…
- ~ 1,000,000 islets per pancreas
- richly vascularized spherical groupings of ~ 3,000 cells
- most abundant in the tail region of the pancreas
- surrounded by and pervaded by reticular fibers
Cells of Pancreatic Islets
β - cells: produce insulin and amylin
α - cells: produce glucagon
δ - cells: produce somatostatin
G cells: produce gastrin
PP cells (F cells): produce pancreatic polypeptide
Pancreatic hormone: Insulin…steps of formation
- produced as pre-proinsulin in RER
- converted to proinsulin in RER cisternae
- converted to insulin in Golgi, packaged for export
Insulin…why is it released and what does it do?
released due to increase in blood glucose
increases cell permeability to glucose; cell uptakes and stores glucose
Pancreatic hormone: Glucagon…why is it released and how is it produced?
- released in response to low blood glucose
- produced as a prohormone which undergoes proteolytic cleavage
Glucagon acts on ____ to activate what?
hepatocytes, glycogenolysis
Glucagon causes what mechanism to help remove glucose?
hydrolytic enzymes, released into the bloodstream, break down glucose
Glucagon activates what process in the liver?
gluconeogenesis
Pancreatic hormone: Somatostain… why is it released?
released due to increases in blood glucose, aa’s or
chylomicrons
What are the functions of somatostatin/what does somatostatin do?
- inhibits the release of hormones by α - cells and β –cells
- suppresses exocrine secretion of pancreas
- reduces motility of smooth muscle in digestive tract & gallbladder (inhibits secretion of digestive hormones)
Pancreatic hormone: Gastrin
realsed by G cells
Gastrin stimulates what 3 functions?
- gastric release of HCl
- gastric motility and emptying
- cell division of gastric regenerative cells
Pancreatic hormone: pancreatic polypeptide…what is it released by and what does it regulate?
- released by PP cells
- helps regulate both endocrine and exocrine secretions of the pancreas
Liver: General things to consider
- weighs ~ 1500 g
- located in upper right quadrant of abdominal cavity
- has both endocrine and exocrine function
- site of detoxification of drugs and toxins
Glisson’s capsule functions in what way in relation to the liver?
is dense irregular CT that covers the liver
The hilum of the liver is called ___ and it is where ___, ___,and ___ enter.
Porta hepatis; blood, lymph vessels, bile ducts
The primary cell type of the liver is ___ and they form ___
Hepatocytes, lobules
What are the 3 types of liver lobules?
- Classical Liver Lobule (aka Classic Hepatic Lobule)
- Portal Lobule
- Portal Acinus (Hepatic Acinus)
What are the features of the classic liver lobule?
- central vein forms
longitudinal axis - portal areas contain portal
v, hepatic a, and bile
ductule - hepatocyte cords radiate
from center - sinusoids found between
hepatocyte cords - blood percolates from
portal areas to central vein (moving from outward to inward) - central vv –> sublobular vv
–> collecting vv –> hepatic
vv
LOBULE HAS HEXAGONAL SHAPE
drains blood from portal vein and hepatic artery to hepatic or central vein
What are the features of the portal lobule?
- describes pattern of bile
flow to interlobular bile
ducts - center of portal lobule is
portal area - periphery is imaginary
line that connects three
central veins
TRIANGULAR IN SHAPE
Drains bile from hepatocytes to bile duct
What are the features of the portal acinus lobule?
- based on blood flow
from distributing
arteries - indicates the order in
which hepatocytes
degenerate due to
toxicity or hypoxia - divided into three zones
of decreasing
oxygenation
RHOMBOIDAL IN SHAPE
Zone 3 least oxygenated, Zone 2 , Zone 1 most oxygenated
Supplies oxygenated blood to hepatocytes
What are sinusoids and their components?
large-diameter fenestrated vessels, lined by endothelium
contains Kupffer cells (macrophage-like
phagocytes)
has a perisinudoisal space
(space of Disse) separates
sinusoids from hepatocytes
* hepatic stellate cells (Ito
cells) contain vitamin A and
fat droplets
Hepatocytes, Space of Disse (perisinusoidal space), and Sinusoid
Sinusoids are surrounded by plates of ___?
Hepatocytes
Flow of bile (Hepatic ducts)
- bile canaliculi anastomose with one another
- canaliculi transition to canals of Hering (also
called cholangioles) - canals of Hering empty into interlobular bile
ducts that merge to form larger ducts - these lead to right and left hepatic ducts
Hepatocytes are __ in shape and__-__ um (micrometers
in diameter)
polygonyl,20-30
Hepatocytes have a membrane with the following lateral domains: form bile canaliculi isolated by __ __; also have gap junctions, __ increase surface area for bile secretion and its walls of canaliculi are rich in __ and __.
fasciae occludentes, microvilli, Na+-K+ATPase and
adenylate cyclase
Hepatocytes have a membrane with the following sinusoid domain: have microvilli projecting into
__ __,release __
secretions, and exchange between __ and hepatocyte
takes place.
perisinusoidal space
(of Disse), endocrine, blood
Organelles found in hepatocytes are:
- nucleus: single or double and diploid or polyploid (up to 64 N
abundant free ribosomes, RER and
Golgi
* up to 2,000 mitochondria per cell
(more abundant near central v)
- abundant endosomes, lysosomes, peroxisomes
- SER, especially rich in
zone 3, detoxifies blood - Inclusions
– lipid droplets ( mostly
VLDL)
– glycogen (β particles)
located near SER
Role of the liver is to…
manufacture bile, 600 to 1200 ml per day
Bile is made up of…
H2O, bile salts, phospholipids, cholesterol, bile
pigments, IgA
What are the 2 methods for making bile salts?
– are reabsorbed from lumen of small intestine
– or formed de novo in the SER of hepatocytes
What are the bile pigments?
– bilirubin: water-soluble, yellow-green, toxic degradation product
of hemoglobin
– biliverdin, phycobilin, phycobiliprotein, phycoerythrobilin,
stercobilin, urobilin
slide 43
Another funtion of the liver is to metabolize organic substances: Lipids…what are the steps of lipid metabolism in the liver?
– chylomicrons from digestion enter lymphatic system
– these reach the liver via hepatic artery
– broken into glycerol and fatty acids
– fatty acids used to make phospholipids and
cholesterol or acetyl CoA
– acetyl CoA used to make ketone bodies
– hepatocytes manufacture VLDLs
– phospholipids, cholesterol, ketone bodies, and VLDLs
released into space of Disse, as needed
Another funtion of the liver is to metabolize organic substances: Carbohydrates
– maintains normal blood glucose levels by:
» taking in and storing glucose as glycogen
» glucose reformed by glycogenolysis as needed
» gluconeogenesis: formation of glucose from other
molecules
Another funtion of the liver is to metabolize organic substances: Proteins
– hepatocytes manufacture ~__% of blood proteins
» blood clotting factors
» complement proteins
» transport proteins
» albumins
– hepatocytes manufacture __ (except __ __)
– hepatocytes manufacture ___
– hepatocytes convert __ to __
~90%, globulins (except gamma
globulins), non-essential amino acids, ammonia, urea
Other roles of the liver are…vitamin storage of? degradation of?
– vitamin storage: A, D, B12
– degradation of hormones by lysosomal enzymes
– degradation of drugs and toxins (in SER or peroxisomes)
* methylation
* conjugation
* oxidation
Liver has role of immune funciton…
- release of IgA in bile
- Kupffer cells phagocytose foreign particulate
matter
