Eyebrows

Question 1

Where is the eyebrow located?

Answer 1

Between the superior orbital rim (margin) and superior nuchal line

Question 2

What are the 4 layers of the eyebrow?

Answer 2

Skin
Connective tissue (dense)
Aponeurosis (muscle)
Loose connective tissue
Periosteum

Question 3

What is the function of the skin in the eyebrow?

Answer 3

Barrier to the outside environment - prevent microbes from causing infections in underlying tissue

Question 4

What are the 3 layers of skin in the eyebrow?

Answer 4

Epidermis: outermost layer
Dermis
Hypodermis: innermost layer

Question 5

What cells make up the epidermis?

Answer 5

Keratinocytes
Melanocytes
Langerhan cells
Merkel cells

Question 6

What are the characteristics and function of keratinocytes?

Answer 6

Epithelial cell; 90% of cells.
Produce fibrous protein - keratin.
Provide structure and water-resistant properties

Question 7

What are the 4 layers of keratinocytes in progressive stages of differentiation?

Answer 7

1. Stratum basale: undergo mitosis and migrate through the other layers
2. Stratum spinosum
3. Stratum granulosum: cells lose their nucleus and become more flattened (aka dying)
4. Stratum corneum: dead, flattened cells filled w keratin

Question 8

What is desquamation?

Answer 8

Cells are shed every few weeksW

Question 9

What is the function of melanocytes?

Answer 9

Produce pigment (melanin) that filters UV light

Question 10

What is the function of Langerhan cells?

Answer 10

WBC that plays a role in immune response

Question 11

What is the function of Merkel cells?

Answer 11

Attach to nerve endings to form “light touch” receptors.
Ex. feeling a piece of hair on you

Question 12

Is the epidermis vascular or avascular? If avascular, what does it rely on for nutrient supply?

Answer 12

Avascular; relies on dermis for blood supply

Question 13

What is the epidermis attached to?

Answer 13

Basement membrane - connects epithelial cells to underlying surface

Question 14

What type of barrier does the basement membrane have?

Answer 14

Partial barrier - allows only water and small molecules to pass into the dermis

Question 15

What is the dermis composed of?

Answer 15

Connective tissue, WBCs, and adnexal structure

Question 16

What are fibroblasts?

Answer 16

Cells that produce collagen and elastin?

Question 17

What is the function of collagen?

Answer 17

Structure and tensile strength

Question 18

What is the function of elastin?

Answer 18

Elasticity and enabling movement

Question 19

What is ground substance?

Answer 19

Transparent gel composed of water, glycosaminoglycans, and proteoglycans

Question 20

What is embedded in ground substance?

Answer 20

Connective tissue elements

Question 21

What are the adnexal structures found in the dermis?

Answer 21

Hair follicles, hair, sebaceous glands, sweat glands

Question 22

What is the hypodermis composed of?

Answer 22

Aka subcutaneous tissue.
Mainly composed of adipose and loose connective tissue, which allows the upper layers to move as one

Question 23

What is dense connective tissue composed of?

Answer 23

Fibroblasts, collagenous fibers, elastic fibers, adhesive proteins, ground substance

Question 24

What is the function of dense connective tissue?

Answer 24

Connect skin to underlying muscle

Question 25

What are the 4 muscles that influence eyebrow contour and position?

Answer 25

1. Frontalis 2. Corrugator 3. Procerus 4. Orbicularis oculi

Question 26

What nerve innervates all 4 muscles that influence eyebrow contour and position?

Answer 26

CN VII (facial nerve)

Question 27

Where is the frontalis muscle located and what is its function?

Answer 27

Location: Vertical fibers originate high on the scalp and insert near supraorbital margin. Function: elevates brow --> surprised look

Question 28

Where is the corrugator muscle located and what is its function?

Answer 28

Location: oblique fibers originate from the supraciliary arch and insert into the medial forehead. Function: depresses medial brows --> vertical wrinkles in glabella--> confused/concentrated look

Question 29

Where is the procerus muscle located and what is its function?

Answer 29

Location: vertical fibers originate from nasal bone and insert into medial forehead. Function: depresses medial brows --> horizontal wrinkles across bridge of nose --> aggressive/mad look

Question 30

Where is the orbicularis oculi muscle located and what is its function?

Answer 30

Location: oblique fibers originate from medial orbital rim to encircle the eye and insert into lateral palperal ligament. Function: depresses the brows & protracts eyelids

Question 31

What is loose connective tissue composed of?

Answer 31

Fibroblasts Collagenous fibers Elastic fibers Adhesive proteins Ground substance

Question 32

What is the function of loose connective tissue?

Answer 32

Connects top 3 layers (tightly bound to each other) to the underlying periosteum

Question 33

What is the "danger zone?"

Answer 33

Loose CT - pus and blood spread easily and infections can pass into cranial cavity through veins. Get very bad very quick

Question 34

What is the function of the periosteum?

Answer 34

Point of connection; covers bone

Question 35

What is the periosteum composed of?

Answer 35

Dense, irregular connective tissue. Osteogenic cells. Osteoblasts

Question 36

What are osteogenic cells?

Answer 36

Stem cells that divide and differentiate into osteoblasts

Question 37

What do osteoblasts form?

Answer 37

Bone matrix

Question 38

What are the functions of eyebrows?

Answer 38

Shield liquids from dripping into the eye and from bright light above. Facial expressions