gland of Harder
Definition A structure first described in 1694 by Johann Jacob Harder (1656-1711), which is found in most terrestrial vertebrates within the orbit where, in some species, it is the largest structure.
Histology Compound tubular or compound tubuloalveolar; its secretory duct is usually morphologically distinct only after leaving the substance of the gland to open on the surface of the nictitating membrane. The tubules of the gland are formed of a single layer of columnar epithelial cells surrounded by myoepithelial cells.
Products of the gland Varies among vertebrate groups. Epithelial cells have vacuoles whose contents may be mucous, serous or lipid. It is unclear whether the gland can act both as an exocrine and endocrine organ. Gland structure and synthesis are controlled by gonadal, thyroid and pituitary hormones and nerves–e.g., by a network of autonomic nerves and neuropeptides.
Reference J Anat. Aug 1994; 185(Pt 1): 1–49