Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Meibomian glands are specialized sebaceous glands located within the eyelids that produce an oily substance called meibum. This oily secretion is an essential component of the tear film, helping to prevent tear evaporation and maintain eye health.
5 Must Know Facts For Your Next Test
Meibomian glands are located along the inner edge of the eyelids, with approximately 30-40 glands in the upper lid and 20-30 glands in the lower lid.
The oily secretion from the meibomian glands, known as meibum, helps prevent tear evaporation and maintains the stability of the tear film.
Dysfunction or blockage of the meibomian glands can lead to a condition called meibomian gland dysfunction (MGD), which is a leading cause of dry eye disease.
Meibomian gland secretions contain a complex mixture of lipids, including wax esters, cholesterol esters, and triglycerides, which contribute to the tear film's protective properties.
Regular blinking helps express the meibomian gland secretions onto the eye surface, ensuring the proper composition and distribution of the tear film.
Review Questions
Describe the role of meibomian glands in maintaining the tear film and eye health.
The meibomian glands produce an oily secretion called meibum that forms the outermost lipid layer of the tear film. This lipid layer helps prevent excessive tear evaporation, stabilizes the tear film, and contributes to the overall health and lubrication of the eye surface. Proper functioning of the meibomian glands is crucial for maintaining a healthy tear film and preventing conditions like dry eye disease.
Explain how the anatomical location and structure of meibomian glands relate to their function.
Meibomian glands are strategically located along the inner edge of the eyelids, allowing their oily secretions to be easily distributed across the eye surface during blinking. The glands are structured as specialized sebaceous glands, producing a complex lipid-rich substance that is essential for the tear film's composition and stability. The number and distribution of meibomian glands in the upper and lower eyelids contribute to their ability to effectively cover the entire eye surface with the protective lipid layer.
Discuss the potential consequences of meibomian gland dysfunction and its impact on overall eye health and visual function.
Disruption or blockage of the meibomian glands, known as meibomian gland dysfunction (MGD), can lead to an imbalance in the tear film composition and instability. This can result in increased tear evaporation, dry eye disease, inflammation, and potentially visual impairment. MGD is a leading cause of dry eye syndrome, which can cause symptoms like eye irritation, redness, and discomfort. Untreated MGD can also predispose individuals to other ocular surface disorders and may even affect visual acuity if the condition progresses. Understanding the critical role of meibomian glands in maintaining a healthy tear film is essential for preventing and managing various eye-related problems.
Related terms
Tear Film: The tear film is the thin layer of fluid that covers the surface of the eye, composed of three layers: the outer lipid layer produced by the meibomian glands, the middle aqueous layer produced by the lacrimal glands, and the inner mucin layer produced by goblet cells.
Sebaceous glands are specialized exocrine glands that produce an oily/waxy substance called sebum, which lubricates and waterproofs the skin and hair.
Lacrimal Glands: The lacrimal glands are the primary producers of the aqueous layer of the tear film, responsible for continuously secreting the watery component that helps maintain eye lubrication and wash away foreign particles.