Download INCLUSIONS AND SECRETORY GRANULES

INCLUSIONS AND SECRETORY GRANULES
LEARNING OBJECTIVES:
By the end of the lecture, the student should be able to:
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Identify Cytoplasmic inclusions with example of each.
List the Types of glycogen particles.
Differentiate between Exogenous and endogenous pigments.
Recognise Crystals and crystalloids
Cytoplasmic Inclusions
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The inclusions are small particles of insoluble substances suspended in the
Cytosol.
a | Intranuclear inclusions (INI) and cytoplasmic inclusions (CI) in the motor cortex of
Huntington's disease
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Inclusions are
– stored nutrient
– secretory products,
– Pigment granules.
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Examples of inclusions are
– glycogen granules in the liver and muscle
cells,
– lipid droplets in fat cells,
– pigment granules in certain cells of skin and
hair,
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Water containing vacuoles.
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Previously, inclusions were considered as non living accumulations of
metabolites, cell products resulting from synthesis, or materials from outside
taken into the cell.
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Now it is known that many of them participate in the normal functioning of cell
now.
Liver section from a patient
with glycogen-storage disease
type IV stained with
hematoxylin and eosin.
Hepatocytes are typically
enlarged 2-fold to 3-fold, with
faintly stained basophilic
cytoplasmic inclusions.
Secretory Granules or Droplets:
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Bodies such as secretory granules or droplets
formerly considered as cytoplasmic inclusions , but
these are membrane bound packets of enzymes.
Examples of Inclusions
1. Stored foods in the form of carbohydrates and fats, which are stored in the
cytoplasm as energy reserves.
Electron micrograph of a lipid droplet in the cytoplasm;
the droplet contains triacylglycerols, the main form of stored fat.
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Carbohydrates as a food material is absorbed from the intestine mainly as
glucose and stored in the form of polysaccharide glycogen.
Glycogen:
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Water soluble.
Gives a “moth – eaten” appearance to the
cytoplasm.
GLYCOGEN IN LIVER CELLS
Stained with carmin, nuclei
are stained with haematoxylin.
1 - Glycogen (red or magenta staining)
2 – Nuclei.
Under electron microscope:
• Seen as free electron dense particles 20 to 30 nanometers in diameter, often
lying between agranular endoplasmic reticulum.
GLYCOGEN IN
LIVER CELLS
Stained with
carmin,
nuclei are
stained with
haematoxylin
1 - Glycogen
(red or magenta
staining)
2 – nuclei.
Types of glycogen particles
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Two types of glycogen particles visible under transmission electron microscopy
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Beta particles
Alpha particles
Beta particles :
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Round, average diameter of 15 to 30
nm .
Alpha particles
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Complexes of beta particles in the
form of rosettes or alpha particles
About 50 to hundred nanometers in
diameter.
Glycogen alpha particles in human liver
Fat Cells :
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Stored mainly in connective tissue as fat
cells.
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Isolated in cytoplasm as membrane bound
vacuoles and droplets containing neutral fats
(triglycerides), fatty acids, cholesterol and
cholesterol esters.
FAT CELLS
Panniculus adiposus
Fat droplets:
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Fat droplets appear to arise in the golgi apparatus
and in relation to agranular reticulum and are
bounded by a membrane 6 to 7 nanomertes thick
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Pigments
Materials that display colour without having been
stained.
May be:
• Exogenous.
• Endogenous.
High power stain is positive for melanin pigment at the
basal cell layer and superficial lamina propria.
Exogenous Pigments :
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Taken in by the organism from the environment.
Include carotenes, yellowish red pigments of vegetables that are fat
soluble ( lipochromes) ;
Include dusts that is carbon which is particularly prominent in the cells of
the lungs and associated lymph nodes;
And minerals such as lead and silver.
Endogenous Pigments
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Formed in the organism.
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Most imp endogenous pigment is
hemoglobin.
Melanin is an endogenous dark – brown
or black pigment found in the skin and
eye.
Melanin is produced in sun tanning and is
produced in large amounts in the epidermis of negroid races.
Lipofuscin:
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Yellowish brown granules.
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Now considered to be membrane bound, indigestible
residue of lysosomal activity.
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Amount of lipofuscin in cells increases with age.
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Cell is not able to get rid of lipofuscin by exocytosis, it
accumulate in the form of residual bodies.
Crystals and Crystalloids:
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Occur in few cell types.
Seroli’s cells (sustentacular) and interstitial cells of
the testis store these in the cytoplasm as non –
membrane bound packets.
Also occur in some microbodies (peroxisomes).
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Occasionally within mitochondria associated with cristae.
Reference:
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Basic Histology by Junqueira Page # 48-50.
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