Trichology Flashcards
Define Trichology
Scientific study of hair and its diseases and care
What two parts is a mature human strand of hair divided into?
The hair root and the hair shaft
Define hair root
Is the part of hair located below the surface of the epidermis
What is the hair shaft
The portion of the hair that projects above the epidermis
What are the 5 main structures of the hair root
Hair follicle, hair bulb, dermal papilla, arrector pili muscle, sebaceous gland, and sebaceous oil glands
What is a hair follicle
The tube like depression or pocket in the skin or scalp that contains the hair root
Where is the hair follicle on the body
Distributed all over the body except palms and soles
What is the hair bulb
It’s the lowest part of a hair strand. A thickened club shaped structure that forms the lower part of the hair root.
What is the dermal papillae
Contains the blood and nerve supply that provides nutrients needed for hair growth
What is the erector pili muscle
Small involuntary muscle in the base of the hair follicle
What does the erector pili muscle do
Strong emotions or a cold sensation cause it to contract which makes the hair strand straight up?
Is the sebaceous glands
Oil glands in the skin that are connected to the hair follicles. The glands secrete a fatty or oily substance called sebum. Sebum lubricates the skin
What are the three main layers of the hair shaft
Cuticle, cortex, medulla
Define hair cuticle
Outermost layer of the hair
What does the hair cuticle look like
Single overlapping layers of transparent scale like cells that look like shingles on a roof
What does the hair cuticle provide
It provides a barrier that protects the inner structure of the hair as it lies tightly against the cortex
What is the hair cuticle responsible for
Responsible for creating the shine and smooth silky feel of healthy hair
What is the cortex
Is the middle layer of the hair. It’s a fibrous protein core formed by cells containing melanin pigment. The elasticity of the hair and its natural color are the result of the unique protein structures located within the cortex
What percent of total weight of hair comes from the cortex
About 90
What is the medulla
The innermost layer of the hair. Generally only thick hair contains a medulla
What is melanin
Tiny grains of pigment in the cortex that give natural color to the hair
What is the melanin
Tiny grains of pigment in the cortex that give natural color to the hair
What are the two types of melanin
Eumelanin and pheomelanin
What is eumelanin
The melanin that lends black and brown colors to hair
What is pheomelanin
Red yellow pigment
What are the two main types of hair on the body
Vellum and terminal hair
Define vellus hair
Short fine unpgmented and downy hair
What does vellus hair do
Helps with the evaporation of perspiration
Define terminal hair
Long, coarse, pigmented hair found on the scalp, legs, arms, and bodies of males and females
What are the 3 phases of the hair growth cycle
Anagen, catagen, telogen
Define the anagen phase
(AKA growth phase) new hair is produced. During this phase, hair is produced. During this phase hair cells are produced faster than any other call in the human body.
Define catagen phase
The brief transition period between the growth and resting phases of a hair follicle. The resting follicle canal shrinks and detaches from the dermal papilla. The hair bulb disappears and the shrunken root end forms a rounded club
How long does the catagen phase last?
1-2 weeks
Define the telogen phase
(AKA the resting phase) is the final phase in the hair cycle and lasts until the fully grown hair is shed.
How long does the telogen phase last
3-6 months
How often does the growth cycle repeat itself
Once every 4-5 years
