Eyebrows Flashcards

1
Q

Where is the eyebrow located?

A

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

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2
Q

What are the 4 layers of the eyebrow?

A

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

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3
Q

What is the function of the skin in the eyebrow?

A

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

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4
Q

What are the 3 layers of skin in the eyebrow?

A

Epidermis: outermost layer
Dermis
Hypodermis: innermost layer

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5
Q

What cells make up the epidermis?

A

Keratinocytes
Melanocytes
Langerhan cells
Merkel cells

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6
Q

What are the characteristics and function of keratinocytes?

A

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

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7
Q

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

A
  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
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8
Q

What is desquamation?

A

Cells are shed every few weeksW

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9
Q

What is the function of melanocytes?

A

Produce pigment (melanin) that filters UV light

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10
Q

What is the function of Langerhan cells?

A

WBC that plays a role in immune response

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11
Q

What is the function of Merkel cells?

A

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

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12
Q

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

A

Avascular; relies on dermis for blood supply

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13
Q

What is the epidermis attached to?

A

Basement membrane - connects epithelial cells to underlying surface

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14
Q

What type of barrier does the basement membrane have?

A

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

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15
Q

What is the dermis composed of?

A

Connective tissue, WBCs, and adnexal structure

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16
Q

What are fibroblasts?

A

Cells that produce collagen and elastin?

17
Q

What is the function of collagen?

A

Structure and tensile strength

18
Q

What is the function of elastin?

A

Elasticity and enabling movement

19
Q

What is ground substance?

A

Transparent gel composed of water, glycosaminoglycans, and proteoglycans

20
Q

What is embedded in ground substance?

A

Connective tissue elements

21
Q

What are the adnexal structures found in the dermis?

A

Hair follicles, hair, sebaceous glands, sweat glands

22
Q

What is the hypodermis composed of?

A

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

23
Q

What is dense connective tissue composed of?

A

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

24
Q

What is the function of dense connective tissue?

A

Connect skin to underlying muscle

25
What are the 4 muscles that influence eyebrow contour and position?
1. Frontalis 2. Corrugator 3. Procerus 4. Orbicularis oculi
26
What nerve innervates all 4 muscles that influence eyebrow contour and position?
CN VII (facial nerve)
27
Where is the frontalis muscle located and what is its function?
Location: Vertical fibers originate high on the scalp and insert near supraorbital margin. Function: elevates brow --> surprised look
28
Where is the corrugator muscle located and what is its function?
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
29
Where is the procerus muscle located and what is its function?
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
30
Where is the orbicularis oculi muscle located and what is its function?
Location: oblique fibers originate from medial orbital rim to encircle the eye and insert into lateral palperal ligament. Function: depresses the brows & protracts eyelids
31
What is loose connective tissue composed of?
Fibroblasts Collagenous fibers Elastic fibers Adhesive proteins Ground substance
32
What is the function of loose connective tissue?
Connects top 3 layers (tightly bound to each other) to the underlying periosteum
33
What is the "danger zone?"
Loose CT - pus and blood spread easily and infections can pass into cranial cavity through veins. Get very bad very quick
34
What is the function of the periosteum?
Point of connection; covers bone
35
What is the periosteum composed of?
Dense, irregular connective tissue. Osteogenic cells. Osteoblasts
36
What are osteogenic cells?
Stem cells that divide and differentiate into osteoblasts
37
What do osteoblasts form?
Bone matrix
38
What are the functions of eyebrows?
Shield liquids from dripping into the eye and from bright light above. Facial expressions