Hair Flashcards
How does hair grow?
Hairs grow from the skin (epidermis) from the base of the follicle upward
What is a hair follicle?
The follicle is the structure within which hair grows; it is a cylindrical tube with a larger pit at the bottom. At the base of the follicle hair is very soft and as the hair proceeds up the follicle it begins to harden and dry out
What are the three phases of hair growth
- Anagen Phase
- Catagen Phase
- Telogen Phase
What is the Anagen Phase in hair growth?
- Actively growing
- The follicle produces new cells and pushes them up the hair shaft
- 80-90% of hairs are in the anlagen phase
What is the Catagen Phase in hair growth?
- Resting phase
- The follicle begins to shut down production of cells, the cells begin to shrink and the root condenses into a bulb-shaped structure called a root bulb
- Approximately 2% of hair
What is the Telogen Phase in hair growth?
- Resting phase
- Cell production has ceased completely; the root has condensed into a bulb and is head in place only by a mechanical connection at the base of the root/follicle
- When mechanical connection breaks (through combing, brushing etc) the follicle is triggered into the anlagen phase and the cycle renews
- Approximately 10-18% of hair
How can one tell if hair has been forcibly removed?
- Hair that is forcibly removed often has follicular tissue adhering to its root
What is the root of the hair?
The portion that formerly was in the follicle
What is the shaft?
The main portion of the hair
What is the tip of the hair?
The distal (direction away from the body)
What are the three components of hair?
The cuticle, cortex and medulla
What is the cuticle?
- An outer/protective covering of overlapping scales
- Humans have a scale pattern called imbricate
What is the cortex?
The cortex makes up the bulk of the hair, consists of spindle-shaped cells called fusiform that contain other structures e.g. pigment granules are found in cortex
What is the medulla?
The central portion of hair and consists of air or fluid filled cells
What are the types of animal hairs?
- Guard/shield hairs: large stiff hairs that make up the outer part of the animals coat
- Fur hairs: thinner and softer hairs which fill the rest of the coat providing warmth and bulk
- Vibrissa (whiskers): the short to long stiff, often white hairs around the snout and muzzle
