Hair follicles and nails

Hair color

Blonde: Little black-brown melanin Jet black: Has the most melanin Red hair: Varying amounts of a red type of melanin Hair sometimes contains both black-brown and red melanin

Nail bed

Nail also attaches to this structure, which is located between the nail matrix and the hyonychium Visible through the clear nail and appears pink because of blood vessels in the dermis

Hair

One of the characteristics of all mammals; found everywhere on the human skin except for the palms, soles, lips, nipples, parts of the external genitalia, and the distal segments of the fingers and toes

Nail groove

The edges of the nail fold is then held in place by this structur

Nail matrix

The nail root extends distally to this structure Thicker than the nail bed and produces nearly all of the nail

Growth stage

in this stage of hair growth, the hair grows longer as cells are added at the base of the hair root, and then eventually, the hair stops growing where the hair follicle shortens and holds the hair in place

Growth stage

A hair increase in length as new matrix cells are produced, differentiate, become keratinized, and die

Lunula

A small part of the nail matrix which is seen through the nail body as whitish, crescent-shaped area at the base of the nail Best seen through the thumb because the blood vessels do not show through the thick nail matrix

Nails

A thin plate consisting of layers of dead stratum corneum cells that contain a very hard type of keratin Located at the distal ends of our digit fingers

Hair follicle

A tubelike invagination of the epidermis that extends into the dermis Hair grows and develops within this structure

Shaft and root

Are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers: medulla, cortex, and cuticle

Nail growth

As the nail forms in the nail matrix and bed, it slides over the nail bed toward the distal end of the digit Nails grow an average rate of 0.5-1.2 mm per day, and fingernails grow more rapidly that toenails

Nail matrix and bed

Composed of epithelial tissue, with a stratum basale that gives rise to the cell that form the nail

Nail root

Covered by the skin

Cuticle

Covers the cortex, a single layer of cells also containing hard keratin; edges of this cell overlap like shingles on a roof

Hair papilla

Dermis of the skin projects into the hair bulb as this structure where there are blood vessels that provide nourishment to the cells of the matrix

Epithelial root sheath

Divided into external and internal parts At the opening of the follicle, this structure has all the strata found in thin skin, the deeper in the hair follicle, the number of cells decrease until, at the hair bulb, only the stratum basale is present

Resting stage

Follows the growth stage, after which a new cycle begins and a new hair replaces the old hair, which falls out of the hair follicle

Hair shaft

Hair is divided by this, which protrudes above the surface of skin

Hair structure

Hair shaft, root hair bulb, medulla, cortex, cuticle, hair follicle, dermal root sheath, and epithelial root sheath

Matrix

Inside the hair bulb is a mass of undifferentiated epithelial cells

Hair growth cycle

Involves a growth stage and resting stage The length of each stage in this cycle depend on the hair: eyelash - grows aprox. 30 days and rest for 105 Scalp - grows for 3 years and rest of 1-2 years

Hair root

Located below the surface

Hyponychium

Located beneath the free edge of the nail body is a thickened region of the stratum corneum

Hair color

Melanocytes within the hair bulb matrix produce melanin and pass it to keratinocytes in the hair cortex and medulla. Varying amounts and types of melanin cause different shades of hair color

Cortex

Surround the medulla and forms the bulk of the hair, cells contain hair keratin

Hair bulb

The base of the root is expanded to form this structure

Medulla

The central axis of the hair, and it consists of two or three layers of cells containing soft keratin

Nail fold

The lateral and proximal edges of the nail are covered by skin

Dermal root sheath

The portion of the dermis that surrounds the epithelial root sheath

Nail body

The visible portion of the nail

Cuticle

This structure allows the stratum corneum of the nail fold to to grow onto the nail body AKA eponychium

Hair follicle

This structure consists of a dermal root sheath and an epithelial root sheath

Hair color

With age, the amount of melanin in hair can decrease, causing hair color to fade or become white