Kyynelrauhaset

Kyynelrauhaset, or lacrimal glands, are a pair of exocrine glands responsible for producing the aqueous component of the tear film. The primary lacrimal gland is located in the orbit, in the upper outer quadrant, and is divided into orbital and palpebral parts. In addition to the main gland, several accessory lacrimal glands contribute to tear production, notably the Krause glands in the fornices of the eyelids and the Wolfring glands along the upper edge of the tarsal plate. Secretions from these glands drain through small ducts into the conjunctival sac, helping to keep the ocular surface moist.

The tears produced by kyynelrauhaset form the aqueous layer of the tear film, which sits atop a mucin layer produced by conjunctival goblet cells and a lipid layer secreted by meibomian glands. This layered tear film lubricates the cornea, provides nutrients, reduces friction during blinking, and contains antimicrobial components such as lysozyme, lactoferrin, lipocalins, and immunoglobulins (notably IgA) to protect the ocular surface.

Innervation of the lacrimal glands is primarily parasympathetic, mediated by pathways from the facial nerve (CN VII) through the greater petrosal nerve and the pterygopalatine ganglion to the lacrimal nerve. Sympathetic inputs modulate glandular blood flow and secretion.

Clinically, dysfunction of kyynelrauhaset can lead to tear film instability and dryness (keratoconjunctivitis sicca), or to reflex tearing if drainage pathways are obstructed. Acute dacryoadenitis refers to inflammation of the gland itself. Obstruction of the nasolacrimal drainage system can cause epiphora (excessive tearing). Autoimmune conditions, such as Sjögren’s syndrome, may involve lacrimal function and contribute to chronic dry eye.