2/3 Skin Function

Question 1

How long does epidermal turn over take?

Answer 1

Every 3 weeks

Question 2

What germ layers form the skin?

Answer 2

Ectoderm and mesoderm

Question 3

The epidermis, follicles, sweat glands, sebaceous glands, and modified glands come from the ____ (germ layer)

Answer 3

Ectoderm

Question 4

The dermis, subcutis, vasculature, lymphatics, nerves, subQ fat, and the arrector pili muscles come from the ______ (germ layer)

Answer 4

Mesoderm

Question 5

Hair follicles are an extension of the _______.

Answer 5

Epidermis

Question 6

Which layer determines the thickness of the skin?

Answer 6

Dermis

Question 7

Skin is thick in the _____ and _____, and thinnest in the ______ and _____ regions.

Answer 7

Dorsal neck & back; inguinal & axillary

Question 8

What can lead to increases in skin thickness?

Answer 8

-Inflammatory infiltrate
-Neoplastic infiltrate
-Matrix deposition/fluid

Question 9

The majority of cells in the epidermis are _______.

Answer 9

Keratinocytes

Question 10

From outermost to innermost, what are the layers of the epidermis?

Answer 10

1. Stratum corneum
2. Stratum lucidum**
3. Stratum granulosum
4. Stratum spinosum
5. Stratum basale

Not visible in haired areas

Question 11

What is the stratum lucidum?

Answer 11

An eosinophilic layer of keratin between the granular and keratinized layers. Evident on nasal planum or paw pads (not visible on haired areas).

Question 12

Which layer of the epidermis to germinal/dividing cells reside?

Answer 12

Stratum basale (basal layer)

Question 13

What three structures are used to connect keratinocytes?

Answer 13

1. Desmosomes
2. Tight junctions
3. E-cadherins

Question 14

Describe the function of desmosomes in keratinocytes.

Answer 14

Connect cells via attachment to cytoplasmic structures (ex. cytokeratins) within the cytoplasm of the keratinocytes.

Question 15

What is spongiosis?

Answer 15

Intercellular edema that makes the desmosomes very apparent on histology.

Question 16

Define acantholytic cells.

Answer 16

Skin cells that do not undergo the normal desquamation process.

Keratinocytes used to be called acanthocytes.

Question 17

Describe the function of E-cadherin in keratinocytes.

Answer 17

Connects keratinocytes to each other, and keratinocytes to intra-epidermal melanocytes and Langerhans cells.

Question 18

What is glabrous skin?

Answer 18

Hairless skin.

Question 19

Define acanthosis.

Answer 19

Epidermal hyperplasia (usually due to chronic irritation).

Question 20

What is the envelope?

Answer 20

Lipids (fatty acids, cholesterol etc.) and antimicrobial peptides (iNOS) surrounding the keratinocytes.

Question 21

How does the epidermis respond to insult or injury?

Answer 21

Epidermal hyperplasia–basal cells divide faster (decreased transit time), the spinous layer gets thicker, and acanthosis occurs. Leads to decreased cell differentiation and changes to the granular & keratin layers.

Question 22

Histologic features of acute/subacute insult or injury to the epidermis include _____ and _____.

Answer 22

Hypogranulosis and parakeratosis.

Question 23

Histologically, chronic irritation to the epidermis can lead to ________ and ________.

Answer 23

Hypergranulosis and compact hyperkeratosis.

Question 24

What are some immune functions or strategies of keratinocytes?

Answer 24

1. Normal flora/microbiome
2. Antimicrobial peptides (defensins etc.)
3. Fatty acid barrier in envelope
4. Release of cytokines and chemokines
5. Expression of MHCII on injury.

Question 25

Where are melanocytes found?

Answer 25

The epidermis (between basal keratinocytes), hair bulb, and dermis.

Question 26

How do melanocytes create pigment?

Answer 26

Melanocytes carry melanin via melanosomes. The melanosomes travel to the dendritic processes to surrounding cells.

Question 27

Describe the pathologic process that causes hyperpigmentation.

Answer 27

Irritated keratinocytes produce melanin-stimulating hormone (MSH) --> activation of melanocytes --> increased pigmentation

Question 28

Define leukoderma.

Answer 28

Loss of pigment of the epidermis.

Question 29

Define leukotrichia.

Answer 29

Loss of pigment of the hair coat.

Question 30

Describe the pathologic process of pigmentary incontinence.

Answer 30

Injury to the junction between the dermis/epidermis and basal cells (skin) or the matrical cells of the hair bulb leads to damaged melanocytes, which release melanin into the dermis where it is phagocytized by dermal macrophages (melanophages).

Question 31

What are Merkel-Ranvier cells, and where do you find them?

Answer 31

Nervous cells in the epidermis of vertebrates with touch receptors for shape/texture and neuroendocrine functions. Located between basal keratinocytes.

Question 32

What are Langerhans cells, and where do you find them?

Answer 32

Professional intraepithelial dendritic antigen presenting cells. Located throughout epidermis and hair follicle epithelium.

Question 33

What is the function of the dermis?

Answer 33

Support for all other skin structure--contains vasculature, lymphatics, and nerves.

Question 34

What are the main components of the dermal extra-cellular matrix?

Answer 34

Collagen (major component; tensile strength), elastin fibers (elasticity), and mucopolysaccharides (pliability).

Question 35

What is the function of dermal dendritic cells?

Answer 35

Essentially the same as Langerhans cells, but they are in the dermis surrounding vasculature to encounter antigens from blood or wounds.

Question 36

What are the results of defects in the basement membrane zone?

Answer 36

Separation of the epidermis from the dermis --> subepidermal clefting, vesicles, or bullae)

Question 37

From outermost to innermost, what are the various layers/components of the hypodermis?

Answer 37

1. Pannicular fat 2. Pannicular muscle 3. Subcutaneous fat | The hypodermis is also called the subcutis.

Question 38

Define cellulitis.

Answer 38

Inflammation of subcutaneous fatty tissue due to infectious agents.