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Sertoli cell (rat)
|macrophage with large autophagolyso-
somes in connective tissue (rat)
phagolysosome 1 (rat)
lysosome 2 (rat)
lysosome 3 (rat)
|heterolysosome + primary lyso-
somes human pharyngeal tonsil
Heterolysosomes (Terminologia histologica: Heterolysosoma)
are no longer called secundary lysosomes. They are relatively large
heterogenous more or less spherical organelles of variable electron-density.
The diameter of cut heterolysosomes ranges from 0.3 to 2 µm
thus it is considerably larger than that of lysosomes
proper which were called primary lysosomes before. Heterolysosomes are
bordered by a double, i.e. unit membrane and derive from lysosomes
when fusing with other material.
|large phagolysosome of
a Kupffer cell in liver (rat)
|heterolysosome with tu-
bules parotid gland (rat)
There are two possible ways of this process:
1. Heterolysosomes which originate from lysosomes
when fusing with endocytotic vesicles
in a process termed heterophagy (which means uptake of material
from outside the cell for further degradation) are called phagolysosomes
phagosomes (Terminologia histologica: Phagosomae = Heterophago[lyso]somae).
These large organells are formed in case phagocyting cells draw very large
particles with diameters of several micrometers like bacteria or other
whole cells into their cytoplasm. This happens for example when old or
misformed erythrocytes are degraded by macrophages.
A special phagosome is a phagophore
which is characterized by several layers of its bordering membrane.
2. Heterolysosomes which originate from lysosomes
when fusing with cell organells or other cytoplasmatic material
in a process termed autophagy (self-degradation for destruction
of cell-own material) are named auto(phago)lysosomes
(Terminologia histologica: Autophago[lyso]somae.
Heterolysosomes are present in all cells of animals with exception
of erythrocytes. Their number is high in microphages
(e.g. neutrophilic granulocytes) and macrophages
as well as other phagocyting cells of the reticulohistiocytic and reticuloendothelial
systems and Sertoli-cells of the testis.
Heterolysosomes are the intracellular compartment of digestion, i.e.
over 50 different enzymes of the fused (primary)
lysosomes work on the internalized and mixed-up material. Heterolysosomes
are important for destruction of foreign organic substances and
which were internalized by phagocytosis/pinocytosis
or they serve for destruction of cell-own materials/organells. The appearance
of heterolysosomes is very variable since it depends on the material which
is destroyed. Multivesicular bodies seem to be
a special form of heterolysosomes which destroy small vesicles. Some heterolysosomes
show remainings of attacked cell organells or lipid
droplets. The intracellular digestion process is able to rewin
a lot of important basic components (e.g. amino acids) from protein degradation.
Thus a very considerable amount of different substances is transported
through the membrane of heterolysosomes for recycling in the cytoplasm.
Other (smaller) substances of which the cell wants to get rid are transported
into the heterolysosomes. During time heterolysosomes get smaller more
condensed and filled with indigestible products like lipofuszin and finally
they become residual bodies = telolysosomes
(Terminologia histologica: Telolysosomae = Corpuscula residualia).
--> (primary) lysosomes - telolysosomes,
--> Electron microscopic atlas Overview
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Images, page & copyright H. Jastrow.