Lipid Droplets-Exocrine Gland Cells

Harderian (orbital) gland from a rabbit. Several lipid droplets of different sizes 1 from an exocrine gland cell (section) after freeze-etching. Freeze-fracture makes it possible to examine cells by electron microscopy without fixation. This special procedure circumvents both the removal of water from the tissue and embedding in synthetic resin. Freeze-etching of ten brings out different structural properties for individual lipid droplets in different fracture planes 2 . These structures hold clues to the lipid composition. Lipids are pre dominantly stored as triglycerides, with cholesterol esters mixed in. In 1694, Johann Jakob Harder described a large gland in the medial upper quadrant of the orbit in the deer. Today, we know that it exists in many mammals and reptiles. Subsequently, this gland became known as the Harderian gland, although its function is still not completely elucidated.

1 Lipid droplets

2 Freeze-fracture plane of a lipid droplet

Small lipid inclusions are particularly abundant in cells from steroid hormone-producing glands. This figure shows cells from the zona fasciculata of the adrenal gland. The cells are densely populated with small vacuoles,  which correspond to small lipid droplets. With suitable fixation methods,  these lipid droplets remain intact, and they can then be stained with lipophilic dyes. At the time of preparation, other fatty substances were removed from the tissue. This accounts for the holes in these large round or polygonal cells and explains the name “spongiocytes .” Between fat vacuoles, the delicate cytoplasmic septa and cytoplasmic bridges (stained blue) are preserved  . Note the intensely stained cell nuclei (blue) 1 , their clearly visible nucleoli, and the abundance of capillaries 2 .

1 Cell nuclei

2 Capillaries

References

Kuehnel, W.(2003). Color Atlas of Cytology, Histology, and Microscopic Anatomy. 4^th edition . Institute of Anatomy Universitätzu Luebeck Luebeck, Germany . Thieme Stuttgar t · New York .