Skin

Question 1

Keratinocytes are of what embryological tissue origin? What are they?

Answer 1

Ectoderm

They are keratinizing epidermal cells (they produce keratin) that are the main cells in all 5 layers of the skin

Question 2

What do keratinocytes produce?

Answer 2

• In spinosum - keratin
• Blue & in stratum granulosum
  
  • Keratohyalin granules (filaggrin), which organize keratin into keratin-filaggrin protein complexes
  • Lipid-rich lamellar bodies/granules

Question 3

Keratohyalin granules turn the cell what color on an h&e stain?

Answer 3

Blue!

Recall: Hematoxylin is a basic dye that stains acidic structures (nucleus, keratohyalin granules, calcified material)

Question 4

Formation of a water-protective layer of skin requires

Answer 4

• Cells undergo apoptosis and extrude their nucleus as well as their lipid-rich lamellar granules, creating the water-protective barrier
• The cells become stratified squamous (keratinized) epithelium: flattened bags of keratin-filaggrin complexes surrounded by a cell membrane

In stratum granulosum

Question 5

Stratum spinosum holds the cells that

Answer 5

Are filled with keratin bundles called tonofilaments that converge into small, spiny cellular extensions and insert on desmosomes to strengthen cell-to-cell adhesion

Question 6

Stratum granulosum cells make

Answer 6

Keratohyaline granules and Lamellar granules ; purplish-blue

Question 7

Stratum corneum cells

Answer 7

have no organelles; they are cornified (filled with keratin, extruded organelles, and flattened)

Question 8

Stratum basale

Answer 8

One-cell thick layer of cells bound to the basement membrane below by hemidesmosomes

Contains stem cells

Question 9

Melanocytes are from neural crest cells. Where are they? How do you recognize them?

Answer 9

Sits on the basal layer alongside keratinocytes; have a pale cytoplasm

Question 10

Melanin funciton

Answer 10

Protect keratinocytes from UV radiation

Question 11

Langerhans cells - what is their function and where are they? Origin?

Answer 11

• What: Engulfs foreign antigens, goes to lymph nodes, and presents antigen to an active lymphocyte
• Where: Stratum spinosum
• Origin: monocytes in bone marrow

Question 12

Merkel corpuscle

Answer 12

• Merkel cell + nerve ending
• Tactile discrimination
• In the stratum basale, but not seen in an H& E

Question 13

Epidermolysis Bullosa is a dysfunction in what cell junciton?

Answer 13

Hemidesmosomes anchor basal cells to the basal lamina

Friction can cause the epidermis to separate and fluid builds up between the dermis & epidermis –> blister

Question 14

Keratin tonofibrils made by stratum spinosum keratinocytes insert onto..

Answer 14

Desmosomes

Question 15

Outer layer of the dermis

Answer 15

Papillary layer: sticks up with dermal papillae into the epidermal ridge

• Loose connective tissue, lots of collagen 3, blood vessels

Question 16

Deeper layer of the dermis - what is it called? what type of tissue is it/describe its characteristics

Answer 16

Reticular layer

• Dense irregular connective tissue
• Fewer cells, more fibers such as collagen1 and elastic fibers

Question 17

What are these wavy dark lines?

Answer 17

Elastic fibers of the reticular dermis

Question 18

Hypodermis/subcutaneous tissue is made of what kind of connective tissue? What does it have a lot of?

Answer 18

Loose connective tissue that loosely binds skin to adjacent organs to allow for movement

Has a lot of blood vessels

Question 19

Melanocyte produciton of melanin - what are the two steps and where does is occur?

Answer 19

1. Tyrosinase oxidizes tyrosine to DOPA
2. DOPA turns into melanin

Occurs in premelanosomes: membrane-bound structures derived from golgi

Question 20

How do mealnocytes “donate” their melanin pigment to keratinocytes?

Answer 20

The premelanosomes mature into melanosomes, which eventually become colored pigments. They move to the tip of the melanocytes, where a keratinocyte will engulf it along with part of the cell membrane (cytocrine secretion)

Question 21

Hair production is just like keratin production, it’s just a harder keratin.

Hair follicles are associated with what other two structures?

Answer 21

• Sebaceous gland: Produces sebum to lubricate the skin and hair; protect against infections
• Arrector pili: autonomically innervated smooth muscle; when cool, it causes the hair to stick straight up

Question 22

Oblique and cross section of hair follicle - which part is continuous with teh surface of teh skin?

Answer 22

External root sheath is the only part continuous with the surface of the skin

Note the dermal papilla in the center giving the hair follicle nutrients

Question 23

Nail matrix makes the keratin and then gets pushed out

Answer 23

Question 24

Sebaceous gland

Answer 24

Holocrine secretion of sebum

Question 25

Eccrine sweat glands

Answer 25

* All over your body; note how the duct opens onto the skin's surface * Innervated by cholinergic nerve endings * Small secretory portions & ducts * Can modify their products on their way to the surface of the skin (sebaceous & apocrine don't)

Question 26

How are apocrine sweat glands visibly different from eccrine sweat glands? Where are they? What do they produce? How are they innervated?

Answer 26

* **Bigger lumen** * Only located in the skin of **axillary and perineal** regions * Produces **pheromones** * Innervated by **adrenergic** nerve endings

Question 27

**Meissner corpuscles** - location, composition, and detection

Answer 27

Location: Dermal papilla & papillary layer of fingertips, palms, soles Composition: modified Schwann cells with a nerve axon exiting at its base Detection: light touch

Question 28

Pacinian Corpuscles are where?

Answer 28

Look like onions in the hypodermis Touch, pressure, vibration

Question 29

**Free nerve endings** are unencapsulated. Can you see them in an H&E stain?

Answer 29

NO.

Question 30

**Ruffini corpuscles** have ___ fibers sticking through it, so as collagen gets pulled it, it stimulates these to respond to *stretch & torque.* **Krause end bulbs** can respond to l*ow frequency vibration* because they're penetrated by a ___ fiber.

Answer 30

Ruffini, collagen fiber Kraus, sensory fiber

Question 31

What layer of skin is this?

Answer 31

Hypodermis

Question 32

Answer 32

Reticular layer of dermis

Question 33

What is the region highlighted in yellow?

Answer 33

Stratum granulosum

Question 34

What's the function of this structure?

Answer 34

Pacinian corpuscle - to respond to vibration stimuli

Question 35

What layer of the integument thas a decent amt of vasculature within the tissue (choose all that apply)? * Epidermis * Papillary layer of dermis * Reticular layer of dermis * Hypodermis * Subcutaneous tissue

Answer 35

Everything but the epidermis. Epidermis is avascular

Question 36

The **ducts** of both eccrine and apocrine sweat glans use what kind of epithelial cells?

Answer 36

Stratified cuboidal . (Note: myoepithelial cells are in the *secretory* part of only eccrine sweat glands)

Question 37

Identify the region indicated by the arrows

Answer 37

Granulosum

Question 38

Answer 38

Epidermal ridge

Question 39

**Ehlers' danos syndrome** (defect in collagen production) would affect which the most? * Dermis * Hypodermis * Arteriovenous shunts * Hair follicles * Sweat glands

Answer 39

**Dermis** - connective tissue supporting epithelium; collagen, elastin, reticular fibers

Question 40

Answer 40

Bulb of hair follicle

Question 41

What gland is this?

Answer 41

Apocrine sweat gland, secretory portion; because it has a big lumen

Question 42

Decrease in tyrosinase would do what to your skin?

Answer 42

Decrease skin pigment becasue tyrosinaes is crucial for melanin produciton

Question 43

Which is most prevalent on the surface of a melanocyte? * Gapjunctions * hemidesmosomes * tight junctions * microvilli * cilia

Answer 43

**Hemidesmosomes** holds it down

Question 44

What sensation stimulate a ruffini corpuscle?

Answer 44

Stretch or torque

Question 45

What skin layer would most likely be to the origin of skin cancer?

Answer 45

Stratum basale

Question 46

What are the 3 components of the **pilosebaceous unit?**

Answer 46

* **Hair follicle**: downgrowths of epidermal epithelium * **Sebaceous glands**: outgrowths of the external root sheath * **Arrector pili**: originates in the subcutaneous layer and contracts to expel sebaceous gland secretions

Question 47

What is this region?

Answer 47

Papillary dermis

Question 48

Ichthyosis

Answer 48

Filaggrin normally binds keratin fibers to create an effective water barrier. ## Footnote **Ichthyosis**: filaggrin mutations causes scaly skin and hyperkeratosis from compensatory repair mechanisms causing increased cell proliferation

Question 49

Albinism

Answer 49

Genetic disorder that involves a defect in tyrosinase or in melanin production rate

Question 50

Which part o fthe hair follicle will become cornified (hard keratin)?

Answer 50

Internal root sheath

Question 51

What part of the hair follicle separates the connective tissue from the follicle?

Answer 51

Glassy membrane

Question 52

Which part of the nail gives rise to the nail

Answer 52

Question 53

The secretory part of the ECCRINE sweat gland vs the APOCRINE sweat gland is composed of what cell types?

Answer 53

Eccrine - clear, dark, myoepithelial cells Apocrine- simple cuboidal or columnar cells

Question 54

Which sweat gland is more involved in the physiological response to increased body temp and stress?

Answer 54

Eccrine sweat glands

Question 55

Kraus end bulbs respond to what? Where are thye?

Answer 55

Low frequency vibration in skin of penis and clitorus

Question 56

Describe the transformation of keratinocytes from the basal to the superficial layers, ultimatelyr esulting in keratinization

Answer 56

1. *Stratum basale:* Keratinocyte is a **basal cell** 2. *Stratum spinosum*: Keratinocyte starts **making keratin** and are are attached to each other by **desmosomes** (looks spiny) 3. *Stratum granulosum*: **Filaggrin** is released from keratohyalin granules and lipid rich organelles are extruded to form a **water barrier** 4. *Stratum corneum*: Lost nuclei and desmosome attachments; "**keratinized**"

Question 57

Where in the body are melanocytes?

Answer 57

In the skin and the iris

Question 58

Cutis laxa

Answer 58

Impaired elastic recoil becuase elastic fibers don't form properly

Question 59

hair follicles, hair, sweat glansd, sebaceous glands, nails, and mammary glands project from the dermis but

Answer 59

They are epidermal derivatives - they originate from ectoderm

Question 60

The **outermost papillary layer** has \_\_\_\_ anchoring the intermediate filaments to the basal lamina \_\_\_\_ anchoring actin to the basal lamina

Answer 60

**Hemidesmosomes** anchor IF to the basal lamina **Focal adhesions** anchor actin to the basal lamina

Question 61

Panniculus carnasus

Answer 61

STriated muscle deep to the subcutaneous fascia

Question 62

Subutaneous tissue contains ___ and ___ so drugs are absorbed rapidly

Answer 62

Loose connective tissue of **fat cells** and **numerous blood vessels** (drugs absorbed quickly)

Question 63

Blood vessels that nourish teh skin come from two plexi where?

Answer 63

Between the hypodermis and dermis

Question 64

Papillary layer vs deeper reticular layer of the dermis contains what kind of tissue?

Answer 64

* Papillary layer: Loost connective tissue (type 1 & 3 collagen) * Blood vessels, nerve processes, some elastic fibers * Reticular layer: Irregular dense connective tissue (type I collagen) * More fibers, fewer, cells and ELASTIC FIBERS