Page 11 - Headlines Histology2024_Neat

or endogenous material (e.g., damaged organelle) and it is called
autophagosome.
• Multivesicular bodies are spherical forms of heterophagosomes. They are
membrane-bounded vesicles containing a number of smaller vesicles.
• Residual bodies are debris containing vacuoles representing the terminal
stage of lysosomal activities. Their contents may either be extruded from
the cell by exocytosis or accumulate in the cytoplasm as lipofuscin
pigments.
Functions

• Degradation of any exogenous macromolecules (phagocytosis and
pinocytosis).

• Disposition of any organelles or cell constituents that are no longer useful to
the cell (autophagy).

PEROXISOMES

• Peroxisomes are spherical, membrane-bounded organelles containing
peroxide forming enzymes and catalase that are involved in the formation
and degradation of intracellular hydrogen peroxide.

• With LM, it does not appear. With EM, they are membrane-bounded
vacuoles, vary in size and appearance depending on species and cell types.

• They are relatively large in hepatocytes and kidney cells and small in
intestinal cells (microperoxisomes).

• In human cell, they contain finely granular matrix of moderate density.
• In many other species, they have crystalline core called a nucleoid. Such

nucleoid is absent from liver peroxisomes from reptiles, birds, and human
being which are species that lack urate oxidase, an enzyme that degrades
urates.
Functions

• Peroxisomes contain at least three oxidase (D-amino acid oxidase, urate
oxidase and catalase).

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