Case 3 Histology

Question 1

what do the secretory units of the salivary glands consist of?

Answer 1

a branched tubule-acinar structure

Compound tubuloacinar glands
- Branching duct system (number of ducts that interconnect)
- Secretory component – tubular (elongated) and acinar (grape-shaped)
(you have ducts and then coming of this you have tubular-shaped glands and grape-shaped glands)

Question 2

what do the acinar cells produce?

Answer 2

either serous, mucous or a mixed saliva

Question 3

in some cases, what do the serous cells form?

Answer 3

caps around the mucous secreting acini = serous demilunes

Question 4

which cells stain darker, serous or mucous secreting cells?

Answer 4

cells which produce serous saliva stain much darker with H&E stain compared to mucous secreting cells

Question 5

what is the route of saliva from the acini cells? epithelium?

Answer 5

the acini cells secrete saliva into small intercalated ducts which, in turn, drain into large striated ducts and then into even larger excretory ducts

EXCRETORY DUCTS
Series of ducts that increase in size
- Intercalated ducts – small, tiny lumen – simple low cuboidal epithelium (look bit flatter than square shaped (because low) but not like squamous epithelium)
- Striated ducts – formed by merging intercalated ducts – simple columnar epithelium (appears striped on high magnification)
- Intralobular ducts – formed by merging striated ducts – gradually increase in size and become surrounded by CT (big collections of lobules make a lobe) (as ducts get bigger, they get more CT around them – more support)
- Interlobular ducts – epithelium may be pseudostratified
- Interlobar ducts – may possess cilia – may be stratified or pseudostratified – epithelium eventually convey saliva into oral cavity (e.g. submandibular duct)

Question 6

what surrounds the parotid gland? what does this form? what seen here?

Answer 6

• Surrounded by a (dense) connective tissue capsule
• Septa extend from the capsule into the gland (white & pink), dividing it into lobules (glandular tissue is lobulated)
• Blood vessels (simple squamous epithelium is a sign it’s a blood vessel), nerves and excretory ducts (enlarged ones) (stratified/pseudostratified columnar epithelium is a sign of this) can be seen running through the septa

Question 7

what type of saliva do parotid glands produce?

Answer 7

• serous saliva

- therefore the secretory units are stained quite dark (likely to be parotid if consistent dark staining)

Question 8

what do the serous-secreting acini cells look like?

Answer 8

• serous cells tend to be pyramidal in shape, with their broad base on the basement membrane and their narrow apical surface facing the lumen
• their nuclei are round in shape and the lumina of the acini tend to be very small
• (clusters of dark cells also secrete into one lumen in the middle)

Question 9

what may you be able to find inside the basal lamina surrounding the base of the serous cell in parotid gland?

Answer 9

• myoepithelial cells
• these cells have a flattened nucleus
• they are contractile and help to expel the secretory product

Question 10

what will you see amongst the acini cells in the parotid gland?

Answer 10

• small intercalated ducts – the cells of these ducts are cuboidal in shape and their nuclei round
• you may also see striated ducts – the cells are columnar in shape and the cytoplasm may appear to be striated
• (intralobular duct or striated duct if got quite tall cells)

Question 11

what can be seen in the dense irregular connective tissue of the septa in the parotid gland?

Answer 11

• blood vessels (muscle tissue can look quite similar to the simple squamous on the inside of lumen – therefore don’t assume that appears thick isn’t a blood vessel) and nerves
• excretory ducts can be seen within the septa – the cells of these ducts may be stratified or pseudostratified cuboidal or, as they increase in size, stratified columnar (tall cells and look like lots of nuclei)

Question 12

what surrounds the submandibular gland? what does this form? what seen here? what acinar cells like? what mucous cells look like?

Answer 12

• Like the parotid gland, this gland is surrounded by a connective tissue capsule
• Septa extend from the capsule into the gland, dividing it into lobules
• Blood vessels, nerves and excretory ducts can be seen running through the septa
• Acinar cells – round nuclei (normally associated with cuboidal cells) – some transitioning but probably low cuboidal epithelium
• Mucous acinar appears paler – only around the edge and nuclei around edge appear dark

Question 13

what type of saliva does the submandibular gland secrete?

Answer 13

• mixed gland with both mucous and serous secreting cells – the serous cells predominate
• some secretory units stain darkly and are totally serous secreting cells
• it is also possible to find many pale stained acini; these mucous secreting cells are capped by darkly stained serous demilunes
• (find in submandibular and sublingual glands) (sublingual glands, because they are more mucous than serous, they tend to have more demilunes in their serous component rather than whole serous acini)
• paler because mixed gland however you can’t just say it’s paler without comparing them both on same slide

Question 14

what type of saliva does the sublingual gland secrete?

Answer 14

seromucous (mainly mucous – eat your snot with tongue)

Question 15

where do the ducts of the salivary glands open into the oral cavity?

Answer 15

a slight fold called a sublingual papilla, from which the ducts of the submandibular salivary glands open.
???

• parotid -> cheek
• submandibular -> floor of mouth
• sublingual -> under tongue

Question 16

innervation of the salivary glands?

Answer 16

chorda tympani (facial nerve) -> submandibular ganglion -> sublingual & submandibular glands 
glossopharyngeal nerve -> otic ganglion -> parotid gland

Question 17

what is the pancreas surrounded by? what does this form? what found here?

Answer 17

• thin connective tissue capsule
• septa extend into the gland from the capsule, separating the pancreatic lobules
• the connective tissue septa that divide the gland into lobules are obvious
• septa - the connective tissue varies from loose irregular to areas of dense irregular
• blood vessels (simple squamous epithelium – can appear more squished), nerves and interlobular ducts are present in the septa

Question 18

describe the exocrine component of the pancreas

Answer 18

• The exocrine component of the gland is similar to the parotid gland
• It consists of closely packed secretory acini which drain into a duct system
• The smallest intercalated ducts drain into intralobular ducts which, in turn, drain into interlobular ducts
• The interlobular ducts are located in the septa of the gland
• The interlobular ducts drain into either the main pancreatic duct or the accessory pancreatic duct

Question 19

describe the endocrine component of the pancreas

Answer 19

• The endocrine component of the gland is comprised of clusters of cells known as the pancreatic islets (islets of Langerhans)
• These are scattered throughout the gland but are most numerous in the tail
• The islets vary in size and are composed of a number of different cell types, each of which is responsible for secreting one type of hormone
• Cells not going to be in a circle like the acini – nuclei don’t make a circle – they are scattered about

Question 20

are the acini and islets stained dark or pale?

Answer 20

• acini = dark

- scattered through the glandular tissue there are a few pale-stained spheres = islets (not significantly lighter)

Question 21

describe the acini

• cells of acini
• what supported by
• ducts - epithelium

Answer 21

• The cells of the acini are triangular in shape with their apex directed towards a very small lumen
• Their nuclei are basally located
• They are supported by a fine reticular network containing a rich capillary network
• Almost like a ring of pearls – in the middle would be a lumen – very small so might not be able to see it or might not have cut through the lumen
• The intercalated and intralobular ducts are formed from simple cuboidal epithelium
• interlobular = simple/stratified cuboidal/columnar (as you move along, they get taller and more stratified)
• main pancreatic ducts – tall columnar

Question 22

is it possible to distinguish between the different cells types of islets?

Answer 22

not using H&E stain

Question 23

what are the islets cells supported by?

Answer 23

fine network of collagen fibres

Question 24

what are the interlobular ducts encircled by? what are they lined with?

Answer 24

• encircled by a layer of dense irregular connective tissue which provides support to the duct and the gland
• lined with stratified cuboidal/columnar epithelium
• ducts – very tall columnar cells, fuzzy edge (could be some cilia), nuclei make it look stratified or pseudostratified – nuclei are all near the bottom
• around it organised and dense connective tissue
• ducts can be quite large

Question 25

what is the liver covered by? describe it.

Answer 25

• thin capsule = Glisson’s capsule
• capsule is thicker at the porta hepatis and it surrounds the vessels and ducts as they extend into the gland
• capsule can be seen on curved edge

Question 26

what are the hepatocytes and sinusoids surrounded by?

Answer 26

a fine, supportive reticular network

Question 27

describe the hepatic lobule (epithelium) (how identify different parts)

Answer 27

• Capsule can be seen on the curved edge
• Central vein found in the middle of the lobule
• Plates of hepatocytes lead away from the central vein
• The spaces between the cells are sinusoids which have been cut in various planes
• Blood cells can be seen in some of the sinusoids
• One type of cell located in the sinusoid is the Kupffer cell which is the macrophage of the liver
• On the periphery of the lobule there are a number of portal triads
• Each portal triad contains three structures; a branch of the hepatic artery, a branch of the portal vein and a bile duct
• terminal branch of hepatic artery (blood from aorta – rich in oxygen)
• terminal branch of portal vein (blood from intestines – low in oxygen but rich in nutrients) (70% of blood)
• bile ductule (brings bile out the other way)
• The artery and vein are lined with simple squamous epithelium and the duct with simple cuboidal epithelium
• The shape of the nuclei will help you distinguish between structures
• Central vein (simple squamous epithelium)
• Plates of hepatocytes – row of hepatocytes (not really straight line)
• Sinusoids (very leaky capillaries) – between the plates (may contain blood cells)(may see Kupffer cells)
• Portal triad/tract – at each corner of hexagon
• 3 white circles – not always nice round circle depending on plane cut in
• nuclei around the white space suggests it’s a duct instead of a blood vessel

Question 28

what are the 3 types of surface of hepatocyte?

Answer 28

• sinusoidal; between cell and blood sinusoids (70%) – surface of hepatocytes facing the sinusoids/blood
• canalicular; between cell and bile canaliculi (15%) – surface of hepatocytes facing the bile
• intercellular; between adjacent cells (15%) – adjacent to one another hepatocyte – form like rows (not always straight) = plates of hepatocytes

Question 29

describe the flow of blood and bile

Answer 29

• Blood from hepatic portal vein and hepatic artery passes down the sinusoid until it gets to the central vein -> IVC
• On its way down, it will drop off any oxygen and nutrients it’s brought with it
• At the same time, the hepatocytes will be secreting bile -> bile canaliculi -> bile ductule
• Blood and bile don’t mix – they’re going opposite directions in different channels

Question 30

how easy is it to see the structures in liver and why?

Answer 30

• Human liver doesn’t have so much connective tissue so the structure is no so clear
• Don’t always see clearly the central vein and portal triad with connective tissue between

Question 31

what is the wall of the gall bladder like?

Answer 31

similar to that of the gastrointestinal tract but it lacks the submucosal layer
- No MM (muscularis mucosa) or submucosa (because no MM, no submucosa either because it’s the MM that causes the distinction between lamina propria and submucosa, so therefore we just have a lamina propria)

Question 32

what does the mucosa of the gall bladder consist of?

Answer 32

• a layer of simple columnar epithelium
• nuclei of epithelial cells are elongated and basally located
• Type of epithelium – lots of cytoplasm before get to nucleus – simple columnar – lots of lymphocytes, which make cause the look of many nuclei – many around the basement membrane of the epithelium (but some epithelium may be pseudostratified)
• luminal surface appears uneven; this is due to the presence of microvilli (absorbing fluid)
• mucosa thrown into many folds (rugae - folds like stomach - not thick like in stomach but quite big in comparative size – need them for expansion – store about 150ml bile)
• a supporting lamina propria
• lamina propria is made of loose irregular connective tissue and contains many blood vessels
• thick, highly vascularised lamina propria (because the fluid that’s being absorbed needs somewhere to go)

Question 33

describe the other layers of the wall of gall bladder

Answer 33

• There is no distinct submucosa
• Only one muscularis is evident – this is a thin layer which is composed of muscle fibres orientated in many directions that encircles the mucosa
• The fibres of the muscle layer are arranged in longitudinal, transverse and oblique direction but they do not form distinct layers like elsewhere in the tract
• The outer layer is serosa in parts (when covered by peritoneum but some areas its stuck up against the liver – embedded in liver tissue) and adventitia in others (on underside of the liver) (serosa = on part not touching liver)
• The outer adventitial layer is thick and contains numerous vessels and nerves
• The large circular structure is the gallbladder which is surrounded by liver tissue on one half

Question 34

what is the lumen of gall bladder like?

Answer 34

large - store about 150ml bile