SM 255: Structure and Function of the Skin

Question 1

What are the major functions of Skin?

Answer 1

Barrier, Repair, Immunologic, Sensation, Thermoregulation, and Appearance

Question 2

How does skin contribute to a Barrier function?

Answer 2

Skin resists mechanical stress, limits water loss, blocks entry of pathogens and acts as a UV shielf

Question 3

How does skin contribute to Repair?

Answer 3

Wound healing

Question 4

How does skin contribute to the immune system?

Answer 4

Skin can both alert the immune system and temper it’s response

Question 5

How does skin contribute to Thermoregulation?

Answer 5

Skin plays a role in insulation and absorption

Question 6

How does skin contribute to appearance?

Answer 6

Appearance influences quality of life

Question 7

What are the 3 layers of skin?

Answer 7

Epidermis, Dermis, and Hypodermis

Question 8

Which layer of skin is highly cellular?

Answer 8

Epidermis

Question 9

Which layer of skin has lots of Collagen?

Answer 9

Dermis

Question 10

Which layer of skin do hair follicles originate from?

Answer 10

Dermis

Question 11

What are the appendages of skin?

Answer 11

Hair, Sebaceous Glands, Sweat Glands, Nails

Question 12

What type of cells are found in the Epidermis?

Answer 12

Keratinized Stratified Squamous Epithelium

Question 13

What types of tissue are found in the Dermis?

Answer 13

Connective Tissue and Stroma

Question 14

What separates the Dermis from the Epidermis?

Answer 14

A Basement Membrane

Question 15

What layer of skin makes up most of skin?

Answer 15

Dermis

Question 16

What is found in the Subcutaneous layer of skin?

Answer 16

Under the Dermis - high fat content

Question 17

Describe the vascular supply of the Dermis and Epidermis?

Answer 17

The Dermis has a vascular supply, the Epidermis does not

Blood vessels from the Dermis must travel up to the Epidermis

Question 18

What are the 4 layers of the Epidermis?

Answer 18

BSGS:

Basal Layer
Spinous Layer
Granular Layer
Stratum Corneum

Question 19

Describe the cells of the Basal Layer of the Epidermis?

Answer 19

Basal Layer has Stem Cells for proliferation as well as Adhesion proteins to anchor to the Basement Membrane/Dermis

Question 20

Describe the cells of the Spinous Layer of the Epidermis?

Answer 20

First step of differentiation, contains lots of Desmosomes to provide adhesive integrity to the skin

Question 21

What layer of the Epidermis is responsible for the adhesiv integrity of the skin?

Answer 21

The Spinous Layer of the Epidermis

Question 22

Describe the cells of the Granular Layer of the Epidermis?

Answer 22

Highly differentiated, with lots of Keratin Filaments and Lamellar bodies to exude Lipids

Question 23

Describe the cells of the Stratum Corneum of the Epidermis?

Answer 23

Cells here die to form a superficial, Keratinized layer

Question 24

What do Epidermal Basal layer cells look like on Histology

Answer 24

A single layer of Columnar cells

Question 25

What do Epidermal Spinous layer cells look like on Histology?

Answer 25

Multiple layers of rounded cells

Question 26

What do Epidermal Granular layer cells look like on Histology?

Answer 26

A few layers of granulated cells

Question 27

What do Epidermal Stratum Corneum layer cells look like on Histology?

Answer 27

Layers lacking nuclei

Question 28

What cell type is dominant in the Epidermis?

Answer 28

Keratinocytes

Question 29

What are Corneocytes?

Answer 29

Terminally differentiated Keratinocytes found in the Stratum Corneum

Question 30

How do Keratinocytes change as they migrate up the Epidermis from the Basal layer?

Answer 30

Their expression patterns of Keratin and other proteins vary in each layer

Question 31

What are Langerhans Cells are where are they found?

Answer 31

Langerhans cells are APCs that are found in the Stratum Spinosum

Question 32

What are Melanocytes and where are they found?

Answer 32

Melanocytes are Melanin producing cells that are found in the Basal Layer of the Epidermis

Question 33

What are Merkel Cells and where are they found?

Answer 33

Merkel cells are mechanoreceptors found in the Basal Layer of the Epidermis

Question 34

What is the primary function of the Epidermis?

Answer 34

Forming a semi-permeable barrier

Question 35

How long does it take for the Epidermis to turn over?

Answer 35

30 days

Question 36

What is Desquamation?

Answer 36

The sloughing off of cells on the outer layer of skin, which are replenished by Stem cells in the Basal Layer of the Epidermis

Question 37

How does Psoriasis relate to Keratinocyte proliferation?

Answer 37

Psoriasis is an inflammatory skin disease with increased Keratinocyte proliferation and turnover driving abnormal differentiation and the formation of hypercellular plaques

Question 38

How does the Epidermis function as a semi-permeable barrier by replenishing cells?

Answer 38

Replenish cells constantly through stem cells in the basal layer of skin giving rise to new Keratinocytes in a continuous cycle

Question 39

How do Keratinocytes maintain shape?

Answer 39

They build cytoskeleton networks made of Microtubules, Actin-based microfilaments, and Keratin-based intermediate filaments

Question 40

How is the Epidermis connection to the Dermis mediated by Keratinocytes?

Answer 40

Keratinocytes from the Basal Layer of the Epidermis are linked to the Dermis with Hemidesmosomes

Question 41

What are Desmosomes?

Answer 41

Specialized junctions that Anchor Keratin to sites of cell-cell contact

Question 42

What allows for selective permeability in the Epidermis?

Answer 42

Tight junctions from proteins like Occludin

Question 43

What is the function of Lamellar Bodies?

Answer 43

Lamellar Bodies excrete lipids to form water proof seals

Question 44

What is the "brick and mortar" model of the Stratum Corneum?

Answer 44

Bricks are Corneocytes and Mortar is Lamellar Membrane

Question 45

What role do Corneocytes play in the organization of the Stratum Corneum?

Answer 45

Corneocytes are anucleated keratin-filled dead Keratinocytes that form a crosslinked membrane

Question 46

What role does the Lamellar Membrane play in the organization of the Stratum Corneum?

Answer 46

The Lamellar Membrane consists of Lipids extruded by Lamellar Bodies in Keratinocytes to forma hydrophobic seal

Question 47

How is the Dermis able to maintain the pliability of skin?

Answer 47

Fibroblasts in the Dermis secrete Collagen, Elastic, and Ground Substance to build a strong but flexible matrix

Question 48

What is Ground Substance?

Answer 48

Hydrophilic connective tissue gel made of GAGs secreted by Fibroblasts in the Dermis

Question 49

What type of fiber provides tensile strength to skin?

Answer 49

Collagen

Question 50

What type of fiber provides flexibility to skin?

Answer 50

Elastic fibers

Question 51

What cells can be found in the Dermis?

Answer 51

``` Fibroblasts Dermal Papilla Cells Mast Cells Monocytes Lymphocytes ```

Question 52

What role do Dermal Papilla cells play?

Answer 52

Specialized fibroblasts that maintain the hair growth cycle

Question 53

What role do Mast cells in the Dermis play?

Answer 53

Release Heparin and Histamine to trigger Immediate Hypersensitivity reactions and Urticaria

Question 54

What role do Monocytes play in the Dermis?

Answer 54

Phagocytic debris clearance

Question 55

What role do Lymphocytes play in the Dermis?

Answer 55

Immunoregulation of the skin in both the Dermis and Epidermis

Question 56

What is a Pilosebaceous Unit?

Answer 56

Arrector Pilori + Hair shaft + Sebaceous Glands in Dermis

Question 57

What are Sebaceous glands?

Answer 57

Glands lined with Sebocytes that secrete lipids into a duct

Question 58

What are Apocrine and Eccrine glands?

Answer 58

Apocrine and Eccrine glands are sweat glands that are associated with hair and not associated with hair respectively