Hair

Definition

Hair is a protein filament that grows from follicles found in the dermis. It is a defining characteristic of mammals, providing insulation and sensory functions.

5 Must Know Facts For Your Next Test

1. Hair is primarily composed of keratin, a fibrous structural protein.
2. The growth cycle of hair includes three phases: anagen (growth), catagen (transitional), and telogen (resting).
3. Hair helps regulate body temperature by providing insulation.
4. It also serves as a sensory organ through its association with nerve endings in the skin.
5. Specialized hair structures, such as whiskers in some mammals, are adapted for enhanced tactile sensing.

Review Questions

Related terms

Keratin: A fibrous structural protein that makes up hair, nails, and the outer layer of skin.

Follicle: A small secretory cavity or gland where hair grows from within the dermis.

Whiskers: Longer, specialized hairs typically found on mammals that serve primarily as tactile sensors.