Example Answer
to the Question about the Structure of Hair Follicles

a.

1. dermal root sheath
2. hair bulb
3. medulla of hair
4. cortex of hair
5. cuticle of hair
6. arrector pili muscle
7. sebaceous gland
8. external epithelial root sheath
9. internal epithelial root sheath
10. germinal matrix
11. papilla
12. melanocyte

b.

Name of structure : arrector pili muscle

• The arrector pili muscle is usually at rest so relaxed and at its maximum length.
  In this case the hair shaft lies close to the skin, forming a small angle with the surface of the skin.
• When the body is under some form of stress, e.g. due to fear or low temperatures, nerve endings stimulate the arrector pili muscles to contract and so pull on the hair bulb, causing the shaft of the hair to move away from the surface of the skin towards a higher angle (e.g. up to 90^o, so perpendicular) to the surface of the skin. This can also cause the skin around the emerging hair shaft to rise, resulting in the effect known as "goose pimples" or "goose bumps".

c.

Name of structure : sebaceous gland

Name of secretion: sebum

A function of sebum: Any ONE of

• prevents the hair from becoming too dry
• prevents surrounding skin from becoming too dry
• helps to keep the surrouding skin soft
• protects the skin by inhibiting the growth and reproduction of some bacteria

d.

Name of structure : germinal matrix

Name of process of cell division that happens here: mitosis