i want 20 mcq with their model answer below each question that covers different aspects of Objectives Identify types of salivary glands
Describe histological structure of major salivary glands & compare between them
Describe the histological structure of the exocrine part of the pancreas
Compare between histological structure of parotid gland and pancreasSalivary glands
• They are exocrine glands that produce saliva, which
perform the following functions:
1- Moistening and lubrication of ingested food and the oral
mucosa.
2- Initiation of carbohydrate digestion with amylase enzyme.
3- Containing immune components such as
lysozyme, lactoferrin & immunoglobulins (IgA).Types of salivary glands
Paired glands
Major
Parotid
Submandibular
Sublingual
Secrete 90% of total
volume of saliva.
Minor
Found in the lamina
propria of oral
mucosa of:
Lips (Labial)
Tongue (Lingual &
von Ebner glands)
Cheeks (Buccal)
Palate (Palatine)
Secrete 10% of total
volume of saliva.Histological Structure of
Major salivary glands
Stroma
(= Connective tissue)
Capsule
Dense irregular C.T.
Trabeculae
(septa)
Reticular
C.T.
- C.T. septa descend from the capsule
- Divide the gland into lobes & lobules
- Carry blood vessels, nerves & ducts.
-Reticular cells & fibers that support
cells of the parenchyma.
-Can be demonstrated by silver stain
Parenchyma
(= Functional part)
Secretory
units
Duct systemConnective tissue stromaParenchyma
➢ 1- Secretory units (acini)
✓Acinus [grape]
✓Three types of acini: serous, mucous, mixed.
Serous acini, which contain only serous cells.
Mucous acini, which contain only mucous cells.
Mixed acini, which contain both serous and mucous
cells.
Cells of all acini are surrounded by basal lamina
that encloses contractile myoepithelial cells.Myoepithelial cells (basket cells)
Shape: stellate shaped cells with several
long contractile processes rich in actin &
myosin filaments.
Site:
▪ Surrounding the acini (mainly mucous
acini) and the proximal ends of the duct
system.
▪ They are found between the basal lamina
and the base of the cells.
Function: they are contractile cells.
Their contraction squeezes and propels
secretory products from acini into the duct
system.Serous acini
• Shape: small & spherical
• Lumen: narrow
• Cells: only serous cells
• Myoepithelial cells: few
Structure of serous cells:
LM:
Shape: pyramidal, with a wide basal
surface and a small apical surface.
Nuclei: rounded, lightly stained & near the
base of the cells.
Cytoplasm: basal basophilia and apical
acidophilia [apical acidophilic secretory
(zymogen) granules].
LM
EMEM: (characters of protein-secreting cells)
Cytoplasm: contains
-Large amounts of basal RER.
-Prominent supranuclear Golgi apparatus.
-Numerous mitochondria.
-Apical electron dense secretory granules.
Nucleus: euchromatic (extended chromatin).
• Function of serous acini:
Secretion of serous watery fluid rich in
enzymes (amylase) and other proteins.EM of serous acini
secretory
granules
Golgi apparatus
Nuclei
RERMucous acini
• Shape: large & more tubular.
• Lumen: wide.
• Cells: only mucous cells.
• Myoepithelial cells: numerous
Structure of mucous cells:
LM:
Shape: columnar.
Nuclei: flattened & basal.
Cytoplasm: pale stained (vacuolated or
foamy). As it contains granules filled with
mucin that dissolves during H&E preparation.
LM
EMEM: [mucous (glycoprotein) secreting
cells]
-Less extensive basal RER.
-Supranuclear Golgi apparatus.
-Mitochondria.
-Numerous membrane bound mucin
granules.
Function of mucous acini:
Secretion of mucous (viscous) that provide
lubricating properties in saliva.Mixed (seromucous) acini
➢They contain both serous and
mucous cells.
➢In routine H&E preparations,
mucous acini have a cap of
serous cells called serous
demilunes [half-moon].Serous acini are darkly stained
(basal basophilia & apical acidophilia)
Mucous acini are pale stained
(vacuolated cytoplasm)Mixed acini
Mucous acini
Serous
demilunesParenchyma
➢ 1- Secretory units (acini)
➢ 2- Duct system
➢ 2- Duct system
Their
cells
modify
serous
secretion
of acini
Secretory ducts
Intercalated
duct
Striated
duct
Interlobular
duct
Excretory ducts
Interlobar
duct
convey or
transport the
secretion
Main duct
Intralobular
ductsI- Intralobular ducts:
(include Intercalated & Striated ducts)
A) Intercalated ducts:
➢They represent the initial part of duct
system that drain the secretory acini.
➢They are lined by simple cubical
epithelium.
➢They are surrounded by myoepithelial
cells.
➢They modify serous secretion.
➢They join each other to form striated
ducts.B) Striated ducts:
Lined by simple columnar epithelium (low
columnar cells).
Nuclei of striated duct cells: central
Cytoplasm: acidophilic with basal striations
By EM: the basal striations are due to many
infoldings of their basal cell membrane, with
numerous mitochondria in-between.
Function of striated ducts:
Striated ducts are ion transporting cells that
modify serous secretion by:
reabsorption of Na+ from the primary
secretion.
secretion of K + and HCO3
- into the secretion.EM of a striated duct cell
Mitochondria
Central
nucleus
Infoldings of
basal cell
membraneII) Excretory ducts:
Include:
A- Interlobular ducts:
Present in the C.T. septa between the lobules.
Lined with simple columnar epithelium (tall
columnar cells).
B- Interlobar ducts:
Present in the C.T. septa between the lobes
Lined by pseudostratified columnar
epithelium.
C-Main duct:
Initially lined by stratified columnar epithelium
that changes into stratified squamous
nonkeratinized epithelium at it opening in the
oral cavity.Major salivary glands
Parotid
Submandibular
SublingualParotid gland
• It is the largest major salivary gland
• The parotid gland is purely serous.
• Histological structure:
Stroma: is well developed.
Capsule & trabeculae are thick and rich
in fat cells.
Parenchyma:
Secretory units: purely serous acini.
Duct system: well developed.
The main duct (Stensen’s duct) opens on
the oral cavity opposite the second
upper molar tooth.
Capsule
Capsule
Fat cells
adipose cells are usually distributed in C.T. capsule &
septa and between acini of the gland.Parotid glandSubmandibular gland
• The submandibular glands are mixed
glands that are mostly serous in humans.
• Histological structure:
Stroma: thick C.T. capsule & thin trabeculae
containing less fat cells.
Parenchyma:
Secretory units: The acini are predominantly
serous (90%) with few mucous and mixed acini
(10%).
Duct system: well developed.
The main duct (Wharton’s duct) opens on the
floor of the oral cavity.Submandibular gland
Serous
acini
Mucous
acini
Striated
duct
Serous
demiluneSublingual glands
➢The smallest of the major glands.
➢They are mixed glands that are mostly
mucous secreting in humans.
➢Histological structure:
Stroma: thin.
Parenchyma:
Secretory units: The acini are
predominantly mucous with some mixed
acini (mucous with serous demilune).
•No purely serous acini.
Duct system: is the same as major salivary
glands.
The main duct opens on the submandibular
main duct or directly opens on the floor of
the mouth.Mixed salivary glands
Submandibular gland
(mainly serous)
Sublingual gland
(mainly mucous)PancreasThe pancreas is a mixed exocrine-endocrine gland
Histological structure
C.T. Stroma
Capsule
(thin)
Trabeculae
(thin)
Reticular
C.T.
Secretory
units
Purely
serous
hormones
digestive enzymes
Parenchyma
Exocrine part
Duct system
Endocrine part
Islets of
LangerhansPancreasSerous acini of pancreas
(Pancreatic acinar cells)
The same structure of serous acini of salivary glands
but No myoepithelial cellsDuct system
Intercalated
ducts
The initial cells of
intercalated ducts
extend into the
lumen of the acinus
as small pale-
staining centroacinar
cells that are unique
to the pancreas.
Proximal part lined by
simple squamous
Remaining part by low
cuboidal epithelium.
Interlobular
ducts
Lined by simple
columnar
epithelium.
Main pancreatic
duct
Lined by simple
columnar epithelium
with goblet cells
(similar to that of
duodenum where it
opens).
No striated
ductSerous acini of pancreas
apical acidophilic zymogen granules
Centroacinar
cells
basal
basophiliaPancreas
Islets of
LangerhansPancreas & parotid are purely serous glands.
Histological features that distinguish the pancreas from the parotid gland:
1) Presence of centroacinar cells
2) Presence of islets of Langerhans
3) Absence of myoepithelial cells
4)Absence of striated ducts
Centroacinar
cellsParotid gland
Pancreas
Islet of
LangerhansParotid Type Exocrine gland Capsule & trabeculae Thick
Serous acini Myoepithelial cells Centroacinar cells
Duct system: Intercalated ducts
Striated ducts Main duct
Present Absent
Not invaginated into acinar lumen Present
Lined by stratified columnar then stratified squamous nonkeratinized epithelium
Islets of Langerhans Absent
Pancreas Mixed Thin
Absent Present
Its initial part invaginates into acinar lumen
Absent
Lined by simple columnar epithelium with goblet cells
Present