Medulla (hair)

Medulla (hair)

The medulla is the innermost layer of the hair shaft, located beneath the cortex. This layer is not always present, especially in hairs with a fine texture. The medulla is primarily composed of round cells, two to five rows across.

Structure

The medulla is made up of a series of cells that look like a string of beads in a cross-section. These cells are filled with air and keratin, a type of protein. The medulla's structure can vary depending on the type of hair and species. In humans, the medulla can be continuous (unbroken), interrupted (broken at intervals), or fragmented (sporadic). It can also be absent, particularly in naturally blonde or fine hair.

Function

The exact function of the medulla is not well understood. Some theories suggest that it may play a role in the transport of nutrients to the cells of the hair shaft. Others propose that the medulla may contribute to the hair's ability to withstand force and prevent breakage.

Medulla in Different Types of Hair

The medulla's appearance can vary significantly between different types of hair. For example, in human hair, the medulla is generally thin and fragmented, while in animal hair, it is often thick and continuous. This difference can be used in forensic science to distinguish human hair from animal hair.

Medulla and Hair Color

The medulla can also influence the color of hair. The air-filled cells of the medulla can scatter light, which can contribute to the hair's overall color. This is particularly noticeable in gray or white hair, where the lack of pigment in the cortex and medulla can result in a transparent or translucent appearance.

See Also

• Hair follicle
• Hair anatomy
• Hair shaft