Hair shaftThe part of the hair not anchored in the follicle. Most of it is above the skin. It is dead, keratinized cells, which is why cutting it does not hurt.
Hair rootThe part of the hair anchored in the follicle. It lies below the skin surface.
Hair bulbThe swollen end of the root, deep in the dermis. It surrounds the papilla.
Hair papillaConnective tissue at the base of the bulb. It has blood capillaries and nerve endings from the dermis.
Hair follicleThe pocket of epidermis that the hair grows from. It reaches into the dermis and has a layered wall.
Arrector piliA small smooth muscle joined to the hair root. When it contracts, the hair stands up and goose bumps show.
Sebaceous glandAn oil gland, most often joined to a hair follicle. It releases sebum, which oils and waterproofs the skin and hair.
The hair: 5 1
Hair matrixThe layer of dividing basal cells in the bulb. Its new cells push the hair up as it grows.
The follicle and beside it: 5 2
Internal root sheathThe inner layer of the follicle wall, round the growing root. It comes from the matrix cells and reaches up to where the shaft begins.
External root sheathThe outer layer of the follicle wall. An extension of the epidermis that encloses the root.
The strand cut across: 3 3
CuticleThe outer layer of very hard, keratinized cells covering the hair.
CortexThe middle layer of compressed, keratinized cells. Its shape and structure help decide whether hair is straight or curly.
MedullaThe central core of the hair. Not every hair has one.
How this list was compiled: Read 2026-09-26. OpenStax Anatomy and Physiology 2e, section 5.2 Accessory Structures of the Skin, https://openstax.org/books/anatomy-and-physiology-2e/pages/5-2-accessory-structures-of-the-skin : hair growing from the hair follicle, an epidermal penetration of the dermis; the hair shaft not anchored to the follicle, the hair root anchored in it, ending at the hair bulb, with the hair matrix of dividing basal cells; the bulb surrounding the hair papilla of connective tissue with capillaries and nerve endings; the medulla as the central core, the cortex of compressed keratinized cells, the cuticle of very hard keratinized cells outside, not all hair having a medulla, and cortex and medulla shaping texture; the internal root sheath from matrix cells surrounding the root up to the shaft, the external root sheath as an extension of the epidermis enclosing the root; the arrector pili smooth muscle making the hair stand up (goose bumps); sebaceous glands as oil glands mostly joined to hair follicles, secreting sebum that lubricates and waterproofs skin and hair. Licence: own work
The drawing: Drawn for this site on 2026-10-04 by script. The section through the skin is composed after Gray's Anatomy (1918) fig. 944 (https://commons.wikimedia.org/wiki/File:Gray944.png), Section of skin showing a hair in its follicle, the arrector pili and sebaceous glands, by Henry Vandyke Carter, public domain; the cut strand follows the layers of fig. 945 of the same book (https://commons.wikimedia.org/wiki/File:Gray945.png), public domain. Nothing traced. Licence: own work
How it works
A hair diagram labeled in two views: one hair in its follicle, cut lengthwise through the skin, and the strand cut across to show its layers. It covers the homework: label the parts of the hair and hair follicle. Start with the 7 main parts.
Read the full guide
Root to shaft
The hair grows from the matrix in the bulb, which sits over the papilla and its blood supply. New cells push the hair up: the root is the part in the follicle, the shaft the part above the skin. Two root sheaths line the follicle.
Beside the follicle
The sebaceous gland oils the hair and skin. The arrector pili muscle pulls the hair upright and makes goose bumps. Cut across, a strand has a cuticle outside, a cortex, and often a medulla at its core.
Shaft above, root below: the skin surface is the line between them.
Questions and answers
What are the three layers of a hair strand?
From the outside in: the cuticle of very hard keratinized cells, the cortex, and the medulla at the core. Not every hair has a medulla.
What is the difference between the hair root and the hair shaft?
The root is the part anchored in the follicle below the skin; the shaft is the part not anchored, mostly above the skin. Both are made of dead keratinized cells.
What does the arrector pili muscle do?
It is a small smooth muscle joined to the hair root. When it contracts the hair stands up, trapping air, and in people this shows as goose bumps.