Quick Facts
The medulla is a tiny area of material in some hairs, running up the middle of the hair shaft, surrounded by the cortex (Dorland, 2011).
Structure/Morphology
The hair shaft is a rigid cylindrical structure which extends from the dermis or subcutaneous tissue through to the skin surface. The hair is composed of three concentric layers, the medulla, cortex, and cuticle of the hair, originating from the hair bulb at the base of the follicle.
The medulla is the innermost central portion of the hair shaft, composed of moderately keratinized cells, making it less rigid and weaker than its surrounding layers. It can be described as the ‘marrow’ of the hair shaft. The medulla is typically found within thicker hairs and is often missing from finer hairs (Young, 2006).
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Young, B. (2006) Wheater's Functional Histology: A Text and Colour Atlas. Student consult: Churchill Livingstone/Elsevier.
