List of abbreviations		 Vocabulary
of micros-
copic
anatomy
specialist terms
explained in
English +
German

Every attempt was made to provide correct information and labelling, however any liability for eventual errors or incompleteness is rejected!
dieser Seite

Editor:
Dr. med.
H. Jastrow
Conditions
of use
Overview primary lysosomes (Lysosoma primaria):
Pages with explanations are linked to the text below the images if available! (Labelling is in German)
lysosome of a
pinealocyte (rat)		 alveolar macrophage with lyso-
somes + heterolysosomes (rat)		 lysosome of an
alveolar macrophage (rat)
macrophage of the Tela
submucosa gastrici (rat)		 detail: lyso-
somes (rat)
human segmentonuclear
neutrophilic granulocyte
 eosinophilic
granulocyte (rat)		 "granules" of an eosinophil are
in fact lysosomes (rat)		 lysosomes + mitochondria
heart muscle cell (monkey)		 exocytosis of a zy-
mogen vesicle (monkey)		 lysosomes of a baso-
philic granulocyte (rat)
RER and lysosomes
of a human plasma cell		 dictyosomes form lysosomes
human plasma cell		 lysosomes
of a human plasma cell		 lysosomes of a human
eosinophilic granulocyte		 lysosome of a human
eosinophilic granulocyte
Lysosomes (Terminologia histologica: Lysosomae), which are also called prelysosomes and primary lysosomes in former days, are relatively electron-dense organells homogenously filled with very tiny granules and usually spheres in three-dimensional shape. Lysosomes have median diameters of 25 to 200 nm and thus on average are considerably smaller than heterolysosomes. Lysosomes are enzyme filled vesicles originating from terminal cisterns of the trans-side of Golgi-apparatuses. They contain a high concentration of digestive, i.e. lytic enzymes which were synthetised in rough endoplasmic reticulum transferred via small vesicles to cis-sides of Golgi-apparatuses and packed there into lysosomes. Lysosomes are present in all cells of animals with exception of red blood cells (erythrocyten). Their number is high in microphages (e.g. neutrophilic granulocytes) and macrophages as well as in other phagocyting cells of the reticulohistiocytic and reticuloendothelial systems. Further they are numerous in cells of the liver and kidney as well as in nerve-, gland-, and muscle cells.
The specific "granules" of neutrophilic, eosinophilic or basophilic granulocytes are lysosomes as well (see images above).
More than 50 different enzymes have been demonstrated inside lysosomes most of which are acid hydrolases. The most important lysosomal enzymes are: acidic phosthatase (most characteristic enzyme), alpha-aminopeptidase and other proteases, beta-glucuronidase, esterases, sulfatases, desoxyribonucleases, ribonucleases, cathepsin D, collagenases, triglyaridlipases, neuraminidases, phospholipases, sphingomyelinase, glucosidase, N-acetyl-hexosaminidase and hyaloronidase. These enzymes have optimal effectiveness under acidic pH 4-5. For this reason an ATP driven protone pump is located inside the double membrane which borders the lysosomes in order to pump H+ ions into their lumen.
Lysosomes serve for degradation of foreign organic substances (heterophagy / foreign body defense) internalised by endocytotic processes. Further they are responsible for destruction of cell own material (autophagy of organells).
Since during endocytosis  (pinocytosis or phagocytosis) the membranes of lysosomes fuse with the internalised material lysosomes decrease in number. The term degranulation of lysosomes means that the electron-dense content of the lysosomes fuses with endosomes. Thereby the enzymes are released and attack the content of the endosome which now is called heterolysosome (Terminologia histologica: Heterolysosoma). Heterolysosomes are the second stage of lysosomes in which intracellular digestion takes place. Some lysosomes are secreted from cells by exocytosis (e.g. as zymogen vesicles in the pancreas; see above or as mast cell vesicles). In this case they release their enzymes to help in extracellular digestion or to reduce viscosity of secretions. Glucocorticoids (like Cortison) "stabilise" the membranes of lysosomes and thus inhibit inflammatory processes.

--> secondary- - telo- or tertiary lysosomes, cytoplasm, Golgi-apparatus, macrophages, blood cells
--> Electron microscopic atlas Overview
--> Homepage of the workshop

Two images were kindly provided by Prof. H. Wartenberg; other images, page & copyright H. Jastrow.