OPT 114 EYEBROWS

SCALP

skin

connective tissue (sense)

aponeurosis (muscle)

loose connective tissue

periosteum

superior nuchal line

runs horizontally from external occipital protuberance

skin

functions as a barrier to the outside environment by preventing microbes from causing infections in underlying tissues

Three layers of skin

epidermis, dermis, hypodermis

Epidermis

outer layer of skin, mostly composed of keratinocytes (90% of cells in epidermis)

Keratinocytes

produce keratin- provides structure and water resistant properties

4 layers of keratinocytes

stratum basale, stratum spinosum, stratum granulosum, stratum corneum

stratum basale

innermost layer, only these cells undergo mitosis and then migrate through the other layers

Stratus Granulosum

cells lose their nucleus and become more flattened

stratus corneum

dead, flattened cells filled with keratin. these cells are shed every few weeks in desquamation

Melanocytes

produce melanin that filters UV light

Lamgerhans cells

considered a type of white blood cell and play a role in immune response

Merkel cells

attach to nerve endings to form "light touch" receptors

The epidermis is avascular

relies on dermis for blood supply

basement membrane

Cells at the base of an epithelial layer are attached to this.

Dermis

middle layer of skin, composed of connective tissue

Fibroblasts

cells that produce collagen and elastin

Collagen

proteins that provides structure and tensile strength

Elastin

protein that provides elasticity , enabling movement

ground substance

transparent gel composed of water, glycosaminoglycans and proteoglycans

white blood cells

involved in immune response

Adnexal structures include:

hair follicles, hair, sebaceous glands, sweat glands

first body hairs formed during embryological development?

eyebrow hairs

Hypodermis

the layer of skin beneath the dermis, which is primarily composed of adipose and loose connective tissue

dense connective tissue

connects the skin to underlying muscle and contains arteries, veins, and nerves supplying the eyebrows

4 muscles innervating eyebrows

-Frontalis

-Corrugator

-Procerus

- Orbicularis Oculi

Frontalis

vertical fibers originate high on the scalp and insert near supraorbital margin

-elevates the brows

What muscle is associated with the look of surprise?

Frontalis

What nerve innervates the frontalis muscle?

CN VII (facial nerve )

Corrugator

oblique fibers originating from the supracilliary arch and insert into the medial forehead

- depresses medial brows forming vertical wrinkles

What muscle is associated with the look of trouble/confusion?

Corrugator

What nerve innervates the corrugator?

CN VII (facial nerve)

Procerus

vertical fibers originating from the nasal bone and insert into the medial forehead

-depresses medial brows furrowing horizontal wrinkles across bridge of nose

What muscle is associated with the look of menace or anger?

Procerus

What nerve innervates the procerus muscle ?

CN VII (facial nerve)

orbicularis oculi

Oblique fibers originating from the medial orbital rim to encircle the eye and insert into the lateral palpebral ligament

-depresses the brows and protracts the eyelids

What nerve innervates the orbicularis oculi?

CN VII (facial nerve)

What is loose connective tissue composed of?

fibroblasts, collagen fibers, elastic fibers, adhesive proteins, ground substance

What is the function of loose connective tissue In the skin?

connects the skin, dense connective tissue and the muscles to the underlying periosteum

Why is connective tissue considered the danger zone?

pus and blood can easily spread causing infections to pass into the cranial cavity through veins

What is the periosteum composed of?

dense irregular connective tissue that cover bone

Osteogenic cells

stem cells that divide and differentiate into osteoblasts

osteoblast

form the bone matrix

What are the primary functions of the eyebrows?

- shield liquids from dripping into the eye

-shield from bright light above

-plays role in aging (atrophy and drooping)

-crucial to facial expressions