By the End of the Lecture, the Student Should Be Able To

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INCLUSIONS AND SECRETORY GRANULES

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LEARNING OBJECTIVES:

By the end of the lecture, the student should be able to:

• Identify Cytoplasmic inclusions with example of each.

• List the Types of glycogen particles.

• Differentiate between Exogenous and endogenous pigments.

• Recognise Crystals and crystalloids

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Cytoplasmic Inclusions

•The inclusions are small particles of insoluble substances suspended in the Cytosol

•Inclusions are

•– stored nutrient

•– secretory products,

•– Pigment granules.

•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,

•Water containing vacuoles.

• Intranuclear inclusions (INI) and cytoplasmic inclusions (CI) in the motor cortex of Huntington's disease

•Previously, inclusions were considered as non living accumulations of metabolites, cell products resulting from synthesis, or materials from outside taken into the cell.

• 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:

•Bodies such as secretory granules or droplets formerly considered

•Secretory Granules or Droplets:

•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.

•Carbohydrates as a food material is absorbed from the intestine mainly as glucose and stored in the form of polysaccharide glycogen.

•Glycogen:

• 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.

•GLYCOGEN IN LIVER CELLS Stained with carmin, nuclei are stained with haematoxylin

•1 - Glycogen (red or magenta staining) 2 – nuclei.

•Types of glycogen particles

•Two types of glycogen particles visible under transmission electron microscopy .

•– Beta particles

•– Alpha particles

•Beta particles :

•– Round, average diameter of 15 to 30 nm .

•Alpha particles

• 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

•Stored mainly in connective tissue as fat cells.

• Isolated in cytoplasm as membrane bound vacuoles and droplets containing neutral fats (triglycerides), fatty acids, cholesterol and cholesterol esters.

•Fat droplets:

•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 .

•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

•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

•Formed in the organism.

•– 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

•Yellowish brown granules.

• Now considered to be membrane bound, indigestible residue of lysosomal activity.

• Amount of lipofuscin in cells increases with age.

•Cell is not able to get rid of lipofuscin by exocytosis, it accumulate in the form of residual bodies.

•Crystals and Crystalloids

•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).

•Occasionally within mitochondria associated with cristae