Properties of the Hair, Skin, and Skeletal System

Vocabulary terms and definitions covering skin structure, hair anatomy, growth cycles, and the bones of the cranium based on the Paul Mitchell Schools handout.

Skin

The largest organ of the body and the only barrier against the environment.

Healthy Skin

Skin that is slightly moist, soft, and flexible.

Scalp Skin

Constructed similarly to skin elsewhere on the body, but with larger and deeper hair follicles to accommodate longer hair.

Vellus or lanugo hair

Short, fine, unpigmented, and downy hair that appears on the body, with the exception of the palms of the hands and the soles of the feet.

Terminal hair

Long, coarse, pigmented hair found on the scalp, legs, arms, and bodies of males and females.

Hair root

The part of the hair located below the surface of the epidermis.

Hair shaft

The portion of the hair that projects above the epidermis.

Follicle

The tube-like depression or pocket in the skin or scalp that contains the hair root.

Bulb

The lowest part of a hair strand; the thickened, club-shaped structure that forms the lower part of the hair root.

Dermal papilla

A small, cone-shaped elevation located at the base of the hair follicle that fits into the hair bulb.

Arrector pili

The small, involuntary muscle in the base of the hair follicle.

Sebaceous glands

The oil glands in the skin that are connected to the hair follicles.

Hair stream

Hair flowing in the same direction, resulting from follicles sloping in the same direction.

Whorl

Hair that forms in a circular pattern on the crown of the head.

Cowlick

A tuft of hair that stands straight up.

Anagen

The growth phase when new hair is produced; on average, the entire growth cycle repeats once every $4$ to $5$ years.

Catagen

The brief transition period between the growth and resting phases of a hair follicle.

Telogen

The resting phase; the final phase in the hair cycle that lasts until the fully grown hair is shed.

Skeletal system

The physical foundation of the body, made up of bone.

Bone

The hardest tissue of the body.

Skull

The skeleton of the head; divided into the cranium and the facial skeleton.

Cranium

An oval, bony case that protects the brain.

Facial skeleton

The framework of the face that is composed of $14$ bones.

Occipital bone

The hindmost bone of the skull, below the parietal bones; it forms the back of the skull above the nape.

Parietal bones

Two bones that form the sides and top of the cranium.

Frontal bone

The bone that forms the forehead.

Temporal bones

Two bones that form the sides of the head in the ear region.

Ethmoid bone

Light spongy bone between the eye sockets; forms part of the nasal cavities.

Sphenoid bone

The bone that joins all of the bones of the cranium together.

Parietal ridge

The widest area of the head, usually starting at the temples and ending at the bottom of the crown.

Apex

The highest point on the top of the head.

Mastoid process

An extension of the temporal bone located behind the ear.