Follicular lumen

Follicular lumen is a term used in anatomy and histology to describe the space within a follicle. The term is most commonly used in the context of the thyroid gland, where the follicular lumen is filled with colloid, a substance that is used in the production of thyroid hormones.

Etymology

The term "follicular lumen" is derived from two Latin words. "Folliculus" means "small bag" and "lumen" means "light" or "opening". In the context of anatomy and histology, a lumen is the inside space of a tubular structure, such as an artery or intestine.

Anatomy

In the thyroid gland, the follicular lumen is the space within each follicle. The follicles are spherical structures that are lined by follicular cells. These cells produce and secrete colloid into the follicular lumen. The colloid serves as a reservoir for the thyroid hormones thyroxine (T4) and triiodothyronine (T3), which are essential for many bodily functions, including growth and metabolism.

Histology

Under the microscope, the follicular lumen appears as a clear space within the follicle. The colloid within the lumen can be stained with certain dyes, such as hematoxylin and eosin, to make it more visible. The follicular cells that line the lumen can also be seen. These cells are usually cuboidal or columnar in shape, and they have a large, round nucleus.

Related Terms

• Follicle: A small secretory cavity, sac, or gland.
• Colloid: A substance microscopically dispersed evenly throughout another substance.
• Thyroid gland: A large ductless gland in the neck that secretes hormones regulating growth and development through the rate of metabolism.
• Thyroxine (T4): The main hormone secreted into the bloodstream by the thyroid gland.
• Triiodothyronine (T3): A thyroid hormone that plays vital roles in the body's metabolic rate, heart and digestive functions, muscle control, brain development and function, and the maintenance of bones.

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