Lecture 19 Flashcards
Pancreas Histology
2x different cell populations with ducts inbetween
-similar to salivary glands
-dark staining - exocrine pancreas cells making enzymes
-light staining- aggregates - endocrine hormone secreting cells (embedded among exocrine cells) - can see with Increase magnification that exocrine arranged similar to acini/collective groups/sac of cells
CT with duct
Endocrine Pancreatic Cells
Islets of Langerhans
Pale staining
Clusters- embedded in exocrine
Produce hormones- insulin
Exocrine Pancreatic Cells
Arranged in Pancreatic Acini (similar to serous acini of submandibular glands) Acini- cells arranged around lumen Secretions released into ducts Dark staining (zymogen granules) Granular appearance Secretions: 1. Digestive Enzymes 2. Fluid 3. Electrolytes Ductal cells secrete Bicarbonate (key for keeping enzymes appropriately activated in lumen of duodenum)
Acini
contain 5-8 pyrmaid shaped cells
surround tiny lumen (lumen often too small to see with light microscope) (small in pancreas- smaller than slaivary glands)
Acinar cells have large spherical nucleus in basal position;
mitochondria orientated perpendicular to the basal surface
Protein secretory products are synthesized in the basal rER, packaged in the golgi, and accumulated as zymogen granules in the apical cytoplasm
Acini produce a small volume of enzyme-rich fluid (contribute towards pancreatic juice)
Ducts of Pancreas
Ducts begin with the smallest intercalated ducts which are inserted into the acini
Duct cells produce bicarbonate and a large volume of alkaline fluid (~1 Litre daily)
Centro-acinar cells
Intercalated duct cells which penetrate the lumen of the acini
Ductal Flow of substance through pancreas
- Intercalated ducts –>
- Intralobular ducts –>
- Interlobular ducts –>
- Pancreatic duct –>
- Common Bile duct =Hepato-pancreatic Ampulla of Vater –>
- Duodenum
Exocrine pancreas gland
Tubulo-acinar gland
with highly branched ducts (similar to the parotid gland-serous)
Some Liver functions
- Endocrine
- Exocrine
- Synthesis
- albumin, prothrumbin, bile/bile acids - Detox
- Storage (glycogen molecules)
What is the structural problem of hepatocytes
Artery: get blood to hepatocytes
Vein: blood away from hepatocytes
Duct: transport the bile
CT septa
separates lobules-hexagonals
- Collage
- BV- nutrients, taking away wastes
- Nerves
- Lyphatics
Portal areas
Contains portal triad
6x (at every edge) of hexagonal lobule
-not same as porta hepatis
Hepatocyte
Not randomly arranged
- arrange in radiating columns
- columns can branch freely, but are in a radiating pattern
- well supplied and nourished, supplied with substrate through sinusoids
Sinusoids
BV between adjacent columns of hepatocytes
- therefore each hepatocyte has 2x sources of BV - maximal contact with blood supply
- strategic -allows liver to do all functions, having free access to substrates
- have endothelial cells
- contains mixed bloods. Its mix of nutrients and oxygen diffuse down a concentration gradient.into hepatocyte –> eventually draining into central vein in centre of lobule
Why arent histological sections not containing perfectly hexagonal lobules of the liver
As plane of section is not perfect
“Hepatic Lobule”
Classical/Anatomical classification of liver portion
hexagonal shape
-has portal space at each space
-contains radiating columns of hepatocytes
-b/w which have sinusoids
Branch of Portal Vein
- Thin walled. Large lumen. –> Low pressure (not coming from heart, coming from gut) 75% of blood supply to liver. Nutrient rich contents.
- intermediate branches before feeding into lobule’s sinusoids
Branch of Hepatic Artery
- Thick muscle walled. Rel. Small lumen –> High pressure (coming from heart/systemic). 25% of blood supply to liver. Oxygen rich.
- no intermediate branches. Feeds straight into lobule’s sinusoids.
Central vein
Centre of Hepatic lobule
- contains mixed bloods. Its mix of nutrients and oxygen diffuse down a concentration gradient.into hepatocyte –> eventually draining into central vein in centre of lobule
- Branches and then Eventually returns to heart via IVC Inferior Venacava
Diffusion gradient of Function diamond Hepatic Acinus
Nutrient Rich blood: Portal vein –> Central vein
-Gradient of rich –> as nutrients diffuse into hepatocytes, nutrient richness decreases as reaching central vein
Oxygen rich Blood: Hepatic Artery –> sinusoids –> Central Vein
-Creates differentiate zones of nutrient and oxygen enrichment
Zone 1 Hepatocytes: recieve both nutrient and oxygen rich blood
Zone 3 hepatocytes, after diffusion has taken place, have relatively nutrient and oxygen poorer blood
Hepatocytes at different region of the liver will have :
1. Different enzyme profiles
-as they have different functions
-affected differentially by diseases (dependant on disease type)
“Liver Acinus”
Function classification of liver unit
- contains 3x zones
- both nutrient and oxygen rich blood flowing away from Triad –> central vein
Sinusoid cytologically
Poligonal structures
Separated by Sinusoidal Capillary
1. Sinusoid=capillary
- normal capillary only hold 1x RBC. Sinusoid Lumen much wider, accomodating more than one RBC(up to 10)
-faster/greater proportionate amount of substrate
-increased rate of diffusion
Endothelium between hepatocytes
Leaky Endothelium
- lines the sinusoids
- IntErcellular openings (gaps between adjacent endothelial cells)
- good or substrates to diffuse
- Fenestrated
Kupffer cells
Luminal Macrophage like -if want to maximise diffusion, want to minimise potential barrier -prevent obstruction of lumen -antibacterial
Stellate Cells
located in Space of Disse- lymphatic space b/w endothelium and microvilli of hepatocytes
Fat storing
Role in Vitamin A metabolism
-implicated in scarring when there is liver damage
Hepatocyte microvilli
increases SA available for transport and metabolic processes
-hepatocytes have enriched border of microvilli
Cytosolic contents of hepatocytes
contains lots/abundance of organelles - as expected for such a metabolically active cell
-abundance of organelles will depend on whether in Zone 1, 2 or 3
-due to undergoing high rate of replacement (due to liver’s importance)
=lots of cell Division and Regeneration
=Not unusual to see a) bi-nucleate (abnormal for normal cells-pathological) , b) polyploidal nuclei (one big nucleus containing multiple copies of DNA material (abnormal for normal cells-pathological)
Bile Canilliculi of Hepatocyte
Membranous infoldings that create channel-like-structure
- not a cell
- proteins help to create an occluding junction, sealing off bile canaliculus so channel doesnt leak
- b/w adjacent hepatocytes
arranged. Converge and feed into –> bile ductles –> which then feed into bile duct - continuous version, canaliculi join to form Bile ductle that join to form bile duct. Canciculi between adjacent canaliculi towards portal space :Direction of Bile flow
Portal Lobule
Triangular border
Formed by the flow of bile
continuous version, canaliculi join to form Bile ductel that join to form bile duct. Canaliculi between adjacent canaliculi towards portal space :Direction of Bile flow
