Block 1: Skin

Question 1

What are the functions of the skin?

Answer 1

Protection: physical barrier against thermal and mechanical insults
sensory: many receptors; monitor environment
thermoregulatory: insulating to maintain body temp
metabolic: synthesize vitamin D3
sexual signaling

Question 2

Difference b/w thick and thin skin

Answer 2

thickness of the epidermal layer; thin skin lacks the stratum lucidum

Question 3

Epidermis origin

Answer 3

epithelial layer of ectodermal origin

Question 4

Dermis origin

Answer 4

mesodermal connective tissue

Question 5

Function of “waviness” of the epidermis and dermis contact layer

Answer 5

dermal papillae and epidermal ridges provide strength to the 2 layers

Question 6

Describe the construction and histological appearance of the epidermis

• epithelium type
• cells present
• nutrients

Answer 6

stratified squamous epithelium composed of keratinocytes and a few other cell types (located in the stratum basale). The cells of the top most layer are keratinized (anucleate). Lacks vasculature, receiving nutrients via diffusion from the dermis

Question 7

Melanocyte
origin
f(x)

Answer 7

origin: neural crest cells

f(x): protect the nucleus of keratinized cells

Question 8

Merkel Cells
location
f(x)

Answer 8

stratum basale

f(x): light touch

Question 9

Langerhan’s Cells
location
f(x)

Answer 9

location: stratum spinosum

f(x): antigen presenting cells derived from monocytes that bind, process, & present antigens to T lymphocytes

Question 10

Describe the construction of the dermis

Answer 10

papillary layer: loose CT; contains meissner corpuscles

reticular layer: dense irregular CT; contains pacinian corpuscles (also in the hypodermis)

Question 11

Stratum Corneum
f(x)
morphology

Answer 11

f(x); prevent against desiccation and friction
morphology: squamous, keratinized cells (anucleate)

cells are flattened bags of keratin-fillagrin complexes surrounded by a cell membrane

Question 12

Stratum Basale
f(x)
how are cells joined?
appearance

Answer 12

appearance: closely spaced nuclei, basophilic appearance
cells joined: desmosomes and hemidesmosmes
appearance: basophilic appearance

Question 13

Epidermolysis Bullosa
defect
result

Answer 13

defect: in the anchoring fibrils that anchor the epidermis to the dermis
result: friction causes the epidermis to separate; fluid builds up b/w epidermis and dermis, causing blistering & skin erosion

Question 14

Stratum Lucidum
location
appearance

Answer 14

found only in thick skin

appearance: thin, transulcent layer of flattened eosinophilic keratinocytes, held together by desmosomes

Question 15

Stratum Granulosom
morphology
f(x)
releases

Answer 15

morphology: cytoplasm filled w/ extremely basophilic keratohyaline granules
f(x): cells undergoing the terminal differentiation process of keratinization
releases: fiaggrin into cytoplasm, resulting in cornification

Question 16

Stratum Spinosum

cells

Answer 16

cells: several keratinocyte layers joined w/ desmosomes; langerhans cells are present

Question 17

Stratum Basale
f(x)
cell types
appearance

Answer 17

f(x): basal/regenerative layer for all layers of epidermis
cell type: keratinocytes, merkel cells, melanocytes
appearance: cuboidal or columnar cells

Question 18

Describe the difference b/w the layers of the dermis

Answer 18

papillary layer: superficial, loose connective tissue that forms dermal papillae to add strength to the skin, interlocking with epidermal ridges

reticular layer: deep, dense irregular connective tissue; surrounds hair follicles, sebaceous glands, and sweat glands, etcs.

Question 19

Why are granules in some keratinocytes necessary?

Answer 19

keratohyaline granules (located in stratum granulosom) are masses of filaggrin that help link the keratinocytes together

Question 20

Which layer creates the waterproof barrier that exists in the stratum corneum?

Answer 20

stratum granulosum

Question 21

Describe the relationship b/w melanosomes and keratinocytes

Answer 21

melanosomes are melanin pigment stored in vesicles; keratinocytes take in melanosomes and accumulate them as a supranuclear cap that, prior to keratinization, absorbs and scatters sunlight to protect DNA of the living cells from the ionizing, mutagenic effects of UV radiation

Question 22

Do melanocytes have desmosomes?

Answer 22

no; only hemidesmosome like attachement to the basal layer

Question 23

Describe the mechanism of melanin synthesis

Answer 23

melanin synthesis is catalyzed by tyrosinase, which converts tyrosine to DOPA which is further transformed and polymerized to different melanin forms The pigment is packaged in melanosomes. Keratinocytes engulf melanosomes, and they accumulate within the cell as an extranuclear cap that, prior to keratinization, absorbs and scatters sunlight to protect the DNA of living cells

Question 24

What’s the relationship b/w PKU and melanosomes?

Answer 24

patients w/ PKU can experience lighter skin b/c of decreased melanocyte activity.

Question 25

Hair Follicles extensions of what layer? associated w/ important parts

Answer 25

extensions of epidermis | associated w/ sebaceous glands

Question 26

Focal Adhesions

Answer 26

anchor actin to the basal lamina

Question 27

Hemidesmosomes vs. Focal Adhesions

Answer 27

focal adhesions: actin filaments and integrins linking the cell to the basement membrane hemidesmosomes: use integrins and intermediate filaments to link the cell to basal lamina

Question 28

Describe sebaceous glands

Answer 28

sebaceous glands are embedded in the dermis; branched acinar glands that release sebum into the upper hair follicle secrete contents via holocrine secretion (the entire cell dies and contributes to the secretory product)

Question 29

pilosebaceous unit

Answer 29

hair follicle + sebaceous gland also associated w/ arrector pili muscle

Question 30

In which layer are sweat glands located?

Answer 30

the dermis holds the acinar section; the epidermis holds the ductal section

Question 31

Two Plexi

Answer 31

deep plexus of BV's b/w hypodermis and dermis that nourishes the skin

Question 32

Subcutaneous Tissue/Hypodermis composition f(x)

Answer 32

composition: loose CT | f(x): loosely binds skin to adjacent organs to allow for movement

Question 33

Free Nerve Endings f(x): location

Answer 33

location: located in the deep (reticular) dermis or subcutaneous layer f(x): for more coarse touch, pressure, and vibrations

Question 34

Difference b/w eccrine and apocrine gland. Similarity?

Answer 34

eccrine: widely distributed apocrine: skin of axillary and perineal region that produce phermornes similar b/c both secrete by merocrine secretion