1.0 OTW: Histology of Skin

how can you remember the four layers of the epidermis?

"Can't Get SunBurned": strata corneum, granulosum, spinosum, basale

stratum granulosum

-1-3 cell layers -basophilic keratohyalin granules; aggregate keratin filaments

what are Langerhans' cells?

-dendritic APCs derived from monocytes -after phagocytizing antigen, they leave the epidermis and migrate to lymph nodes to present antigen to T lymphocytes

merocrine

-exocytosis of vesicles -most classical -serous glands (exocrine pancreas, salivary glands, goblet cells)

stratum basale

-one cell thick -anchors to dermis via hemidesmosomes -stem cells (mitosis) -pigmented (melanin)

stratum spinosum

-several cells thick; varies -anchor to adjacent cells via desmosomes on cell processies -differentiated keratinocytes

eccrine sweat glands

-simple coiled glands, not associated w/ hair follicles -regulate body temperature; secrete hypotonic sweat -consists of secretory segment located deep in dermis or upper part of hypodermis and a directly continuous, less coiled duct segment that leads to epidermal surface of thick & thin skin

sebaceous glands - sebum secreting cells

-store oily secretion; secrete sebum for moisture -undergo apoptosis; release sebum by disintegration -holocrine secretion

compare thick vs. thin skin

-thick s. corneum & thick s. granulosum of epidermis vs. thin s. corneum, single layer or no prominent s. granulosum

stratum corneum

-thickness varies widely in thick vs. thin skin -filaggrin aggregates keratin & lipids from lamellar bodies form extra coat around cells; water barrier -entirely filled with keratin filaments; eosinophilic

apocrine sweat glands

-tubular glands associated w/ hair follicles at the: axilla, external genitalia, skin around anus -secretory coil w/ large lumen, merocrine secretion -protein-rich secretion w/ stinky odor produced by bacterial breakdown of secretion i.e. pheromones

what are the 6 functions of the skin?

1. barrier 2. water/temperature homeostasis 3. sensory information 4. vitamin D 5. excretion 6. immunologic functions

layers of the skin

1. epidermis: stratified squamous keratinized epithelium with 4 strata 2. dermis: connective tissue with papillary layer (loose CT) & reticular layer (dense CT) 3. hypodermis: adipose tissue (loose CT); sensory nerve endings and skin appendages

melanocyte UV protection

1. melanocytes produce melanin granules called melanosomes 2. melanosomes are transported on melanocytes cytoplasmic processes 3. keratinocytes "eat the hand that feeds them": phagocytose tips of melanocyte processes 4. keratinocytes internalize granules 5. melanosomes released into cytoplasm of keratinocytes 6. melanin protects the nuclear DNA from UV radiation

dermis layers

1. papillary layer (LCT) *sensory receptors* 2. reticular layer (DICT)

multicellular exocrine glands may be:

1. simple (unbranched) 2. compound (branched ducts)

Which of the following describes the function of a Langerhans cell in the epidermis?

A. Anchoring cell to the basement membrane B. Protective cell against UV radiation C. Touch receptor cell between cells of the stratum basale D. Cell that produces keratohyalin granules for the stratum granulosum E. Antigen presenting cell in the epidermis

A 5-year-old boy is seen by a dermatologist after experiencing a series of unexplained blisters and scars that often become infected. A diagnosis of bullous pemphigoid, a genetic skin condition that results from inadequate adhesion at the dermoepidermal junction was made after examination. Abnormalities in which of the following structures would most likely be associated with bullous pemphigoid?

A. Desmosomes of cells at the stratum spinosum B. Hemidesmosomes of cells at the stratum basale C. Keratohyalin granules of cells at the stratum granulosum D. Lysosomes of Langerhans's cells at the stratum spinosum E. Pigment granules of melanocytes in the stratum basale

An 18-year-old woman comes to the office due to a slowly enlarging, irregularly shaped mass on her left auricle. She had an ear piercing at this site 6 months ago but there were no immediate complications such as bleeding. It's likely that the mass was caused by keloids, formed after excessive growth and thickening of the dense connective tissue layer of the skin. Which of the following skin layers would most likely exhibit abnormal thickening during keloids?

A. Epidermis stratum corneum B. Dermis papillary layer C. Superficial cortex D. Hypodermis E. Dermis reticular layer

In an experimental subject, the stratum corneum is progressively removed using adhesive tape. Which of the following is most likely to occur at the site of stripping?

A. Increased accumulation of keratohyalin granules B. Increased accumulation of keratin C. Increased water loss D. Decreased blood flow E. Decreased diffusion of lipids F. Decreased melanin production

A friend of yours returns home following a 4-week summer vacation at the beach. You notice that her skin has become much darker in colour. Which of the following biological processes accounts for this change in skin coloration?

A. Increased number of granular keratinocytes B. Increased production of melanin C. Increased thickness of the stratum corneum D. Migration of melanocytes into the stratum corneum

Which of the following histological observations would be abnormal and a sign of a possible clinical condition, select all that apply:

A. Presence of melanocytes in the stratum spinosum B. Presence of melanocytes in the stratum basale C. Absence of melanocytes in the stratum spinosum D. Absence of melanocytes in the stratum basale E. Presence of pigmentation in keratinocytes of the stratum basale F. Presence of pigmentation in melanocytes of the stratum basale G. Absence of pigmentation in keratinocytes of the stratum basale H. Absence of pigmentation in melanocytes of the stratum basale

are melanocytes pigmented?

NO! they give it away to keratinocytes for UV protection!

does thick skin have hair follicles?

No! Only thin skin does!

paracrine

Referring to a secreted molecule that acts on a neighboring cell.

Which of the following sensory receptors most likely sense temperature and pain?

a. Baroreceptors b. Pacinian Corpuscles c. Merkel Cells d. Free nerve endings e. Meissner's Corpuscles

Which of the following best describes the appearance of the stratum granulosum?

a. Basophilic b. One-cell thick c. Eosinophilic d. Anuclear e. Brown pigment

Which of the following layers contains blood vessels that provide nutrients to the epidermis?

a. Dermal reticular layer b. Stratum corneum c. Layer of dense irregular connective tissue d. Hypodermis e. Papillary layer

Which of the following best describes the function of lamellar bodies?

a. Form cell-cell desmosomes in stratum corneum b. Give rise to lighter staining stratum lucidum c. Secreted to form extracellular keratin fibers d. Found mainly in the stratum spinosum e. Form the epidermal water barrier

Which of the following sensory receptors is most likely found deep in the reticular layer next to the hypodermis?

a. Free nerve endings b. Baroreceptors c. Meissner's Corpuscles d. Pacinian Corpuscles e. Merkel Cells

Which of the following best describes the function and location of Langerhans cells?

a. Immune reactions in the stratum spinosum b. Production of melanin in the stratum basale c. Forms the epidermal water barrier in stratum granulosum d. Phagocytosis of excess keratin in the stratum corneum e. Somatic sensation of light touch in the stratum basale

Which of the following best describes the function of the hypodermis?

a. Improves effectiveness of immune reactions in dermis b. Acts as storage of energy and insulation c. Mediates passage of nutrients from blood into epidermis d. Contributes to epidermal water barrier e. Regulates temperature via sweat secretion

Which of the following best describes epidermal retes, or rete pegs?

a. Increase adhesion between stratum basale and dermal papillae b. Decreases the need for a thick stratum corneum in soles of feet c. Formed only in the epidermis of thin skin d. Increases number of sensory receptors in the deep dermis e. Stimulates migration of melanocytes into the papillary connective tissue

Which of the following cell types in the epidermis normally exhibit a pigmented appearance?

a. Keratinized cells b. Keratinocytes c. Sensory cells d. Endothelial cells e. Melanocytes

which of the following cell types have the highest rate of mitosis in the epidermis and therefore most vulnerable to acquiring mutations?

a. Keratinocytes in the stratum basale b. Fibroblasts in the dermis c. Keratinocytes in the stratum spinosum d. Endothelial cells in the papillary layer e. Epithelial cells in the stratum granulosum

Which of the following substances are secreted by melanocytes?

a. Lamellar bodies b. Melanin c. Lipofuscin d. Melatonin e. Keratin

Which of the following layers contains many lymphocytes acting as an immune surveillance system?

a. Layer of dense irregular connective tissue b. Hypodermis c. Stratum corneum d. Dermal reticular layer e. Papillary layer

Which of the following regions of the human body would have skin with a highly developed stratum corneum?

a. Lips b. Armpits c. Forearms d. Feet e. Ears

Which of the following sensory receptors is most likely found in the stratum basale?

a. Meissner's Corpuscles b. Free nerve endings c. Baroreceptors d. Pacinian Corpuscles e. Merkel Cells

Which of the following sensory receptors is most likely found in the dermis papillary layer?

a. Meissner's Corpuscles b. Pacinian Corpuscles c. Free nerve endings d. Baroreceptors e. Merkel Cells

Which of the following features are characteristic of cells in the stratum spinosum?

a. Melanin pigment in cell cytoplasm b. Highly developed hemidesmosomes c. Prominent spines with desmosomes d. Basophilic cytoplasmic granules e. Eosinophilic anuclear keratinized cells

Glands that secrete their products via traditional exocytosis utilize which of the following mechanisms of secretion?

a. Merocrine b. Endocrine c. Apocrine d. Paracrine e. Holocrine

Glands that lose their connection to the apical surface and lack a duct are best classified as:

a. Merocrine glands b. Exocrine glands c. Endocrine glands d. Holocrine glands e. Apocrine glands

The papillary layer of the dermis is composed of what type of tissue?

a. Non-keratinized epithelial tissue b. Dense regular connective tissue c. Adipose tissue d. Loose connective tissue e. Dense irregular connective tissue

Which of the following best describes the epidermis of thick skin?

a. Non-mitotic keratinocytes in the stratum basale b. Thick stratum granulosum and thin stratum corneum c. Thick stratum corneum with anuclear cells d. Non-keratinized epithelium e. Absent stratum lucidum layer

Which of the following sensory receptors is located in the dermis and senses light touch?

a. Pacinian Corpuscles b. Free nerve endings c. Meissner's Corpuscles d. Merkel Cells e. Baroreceptors

Which of the following best describes the epidermis depicted in the image?

a. Prominent stratum lucidum is visible b. Would be found in regions covered by thin skin c. Non-keratinized stratified squamous epithelium d. Would be found in regions covered by thick skin e. Lacks a stratum granulosum

Which of the following best describes the appearance of sebaceous glands?

a. Simple cuboidal epithelium lining a large lumen b. Lighter staining associated with hair follicles c. Simple cuboidal eosinophilic cells near the hypodermis d. Basophilic cell aggregated near the dermo-epidermal junction

Which of the following epidermal cell layers anchors directly to the dermis connective tissue?

a. Stratum corneum b. Stratum basale c. Stratum spinosum d. Stratum granulosum e. Stratum lucidum

From which of the following regions was this electron micrograph most likely obtained?

a. Stratum spinosum b. Stratum basale c. Stratum corneum d. Dermis papillary layer e. Stratum granulosum

Exocrine glands whose ducts are unbranched are best classified as:

a. Tubular glands b. Alveolar glands c. Compound glands d. Acinar glands e. Simple glands

which of the following is the deepest layer of the skin?

a. reticular layer b. stratum corneum c. dermis d. hypodermis e. epidermis

hypodermis

adipose CT; energy storage, thermal regulation

apocrine

apical portions of the secretory cell is shred along w/ lipid secretion (mammary gland, prostate)

Dermal Papilla

attachment of epidermis to dermis enhanced by increased interface btwn. the two tissues

Are eccrine sweat glands found only in thick skin, only in thin skin or both?

both

holocrine

cell undergoes apoptosis; breaks apart; releases its secretory content (sebaceous glands)

Pacinian corpuscle are found where?

dermis: deep in reticular layer

glands of thick skin

eccrine

glands of thin skin

eccrine, apocrine, sebaceous

where is thin skin found?

entire body except thick skin areas

Do the ducts of eccrine sweat glands "dump" their secretions into hair follicles or directly into the epidermal surface?

epidermal surface

free nerve endings are found where

epidermis

epidermal ridges

fingerprints; known as Epidermal Rete or "Rete Pegs"

Do the ducts of apocrine glands "dump" their secretions into hair follicles or directly into the epidermal surface?

hair follicles

Do the ducts of sebaceous glands "dump" their secretions into hair follicles or directly into the epidermal surface?

hair follicles

hair follicle

hairs composed of keratinized cells that develop from stem cells in hair follicle bulb

Merkel cells function

have nerve fibers; mechanoreceptors

endocrine glands

have no ducts, use blood vessels to distribute secretions

Which of the following mechanisms of secretion do sebaceous glands use?

holocrine

sebaceous gland MOA

holocrine secretion of oil

What is the main secretory product of eccrine glands?

hypotonic sweat

epidermis - wear and tear consists of:

keratinized stratified squamous epithelium: grows continuously but maintains normal thickness via desquamation: forming four distinct layers

You identify a pigmented cell in the stratum basale, this cell is most likely a:

keratinocyte

if melanocytes are found elsewhere, what does that indicate?

melanoma

Which of the following mechanisms of secretion do apocrine sweat glands use?

merocrine

Which of the following mechanisms of secretion do eccrine sweat glands use?

merocrine

apocrine sweat gland MOA

merocrine secretion, simple tubular, stinky

Which of the following best describes the function of sebaceous glands?

moisturize skin

How many cells thick is the stratum basale layer of the epidermis?

one-cell thick

stratum lucidum

only visible in thick skin

where is thick skin found?

palm of hand; soles of feet

Meissner's corpuscles are found where?

papillary layer

What is the main secretory product of apocrine glands?

pheromone rich sweat

Pacinian corpuscle function

pressure, vibration

where are Langerhan's cells found?

scattered among the stratum spinosum

exocrine glands

secrete into ducts connecting to a surface

eccrine sweat gland MOA

simple tubular, merocrine secretion

a 23-year-old male is diagnosed with hyperhidrosis, a condition characterized by excessive sweating in hands. Excessive secretion by which of the following glands is most likely responsible for this patient's sweaty palm of hands & soles of feet?

sodium chloride rich sweat from eccrine glands

what type of tissue is the epidermis primarily composed of?

stratified squamous keratinized epithelium

Merkel cells are found where?

stratum basale

Which of the following layers would you examine to locate normal melanocytes?

stratum basale

melanocytes are found where normally?

stratum basale ~ every 6th cell; elongated nuclei surrounded by clear cytoplasm

Ruffin corpuscles function

stretch and torque

free nerve endings function

temperature, pain

endocrine

the body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream

what skin has more sensory receptors?

thick

Meissner's corpuscles function?

touch receptors, thick skin

shape of secretory epithelium may be:

tubular or acinar/alveolar

exocrine glands can be:

unicellular or multicellular