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MSK Final Exam > Integument > Flashcards

Integument Flashcards

1
Q

What are some functions of the integument?

A

Barrier for protection, sensation and excretion, thermoregulation, and vitamin D3 synthesis

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2
Q

The integument contains epidermal derivatives including what?

A

Hair, nails and sebaceous gland

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3
Q

What is the integument composed of?

A

Epidermis and dermis

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4
Q

What is the epidermis?

A

Epithelial layer (ectoderm)

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5
Q

What is dermis?

A

Layer of CT (mesoderm)

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6
Q

What structure is deep to the dermis?

A

A loose CT layer known as the hypodermis which binds the skin to underlying tissues and corresponds to the superficial fascia

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7
Q

The epidermis consists mainly of what tissue type?

A

Stratified squamous keratinized epithelium composed of keratinocytes

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8
Q

What are examples of other less abundant cell types in the epidermis?

A

Melanocytes, Langerhans cells and Merkel cells

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9
Q

What are dermal papillae?

A

Irregular projections at epidermal-dermal junctions which interdigitate with epidermal ridges to strengthen adhesion

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10
Q

What are the two types of epidermis?

A

Thick and thin skin

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11
Q

What are characteristics of thick skin?

A 
Palms and soles + fingerprints 
Five layers (with stratum lucidum)
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12
Q

What are some characteristics of thin skin?

A

Widespread all over the body
Four layers
Ex. Glands and hair follicles

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13
Q

What are the layers of the epidermis in order from most apical to basal?

A 
Stratum corneum 
Stratum lucidum (thick skin only)
Stratum granulosum 
Stratum spinosum 
Stratum basale
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14
Q

Describe the stratum corneum

A

15-20 layers of squamous keratinized cells filled with filamentous keratin
Cells are anucleated and coated by an extracellular layer of lipids
Fully keratinized cornified cells now called squames and are continuously shed as desmosomes break down

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15
Q

Describe the stratum lucidum

A

Thin, translucent layer of flattened eosinophilic keratinocytes
Held together by desmosomes
Nuclei and organelles have been lost
Cytoplasm is almost exclusively keratin filaments

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16
Q

Describe the stratum granulosum

A

3-5 layers of flattened cells
Filled with keratohyaline granules and lamellar granules
Keratinization + lipid rich layer = an almost impenetrable skin barrier

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17
Q

What are keratohyaline granules?

A

Granules = tonofibrils + flaggrin (bundling protein)
Undergoing terminal differentiation of keratinization
Stain intensely basophilic

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18
Q

What are lamellar granules?

A

Small ovoid structures containing lipids and glycolipids

Undergo exocytosis and produce lipid rich impermeable layer that protects against water loss

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19
Q

Describe the stratum spinosum

A

Typically the thickest layer

Polyhedral cells with central nuclei and spiny processes

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20
Q

What do keratin filaments assemble into in the stratum spinosum layer?

A

Into microscopically visible bundles of tonofibrils

Associate with desmosomes —> result in spiny appearance “prickle layer”

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21
Q

Describe the stratum basale

A

Single layer of keratinocytes with stem cells interspersed
Mitotically active
Cuboidal/low columnar cells
Contain melanin

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22
Q

What is the stratum basale bound apically by?

A

Desmosomes

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23
Q

What is the stratum basale bound basally by?

A

Hemidesmosomes

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24
Q

What is the predominant cell type of the epidermis?

A

Keratinocytes

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25
Q

What do keratinocytes produce?

A

Keratins and will produce cornified cells which are full of keratin

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26
Q

What do keratinocytes participate in?

A

Epidermal water barrier

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27
Q

What processes do keratinocytes undergo?

A

Keratinization (maturation) and desquamation (being lost or shed)

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28
Q

List characteristics of melanocytes

A

Produce melanin and transfers it to keratinocytes
Neural crest cell derived
Scattered along the stratum basale

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29
Q

What is melanin?

A

Pigment protein that protects nuclei from UV radiation

30
Q

What is the epidermal melanin unit?

A

One melanocyte maintains an association with a specific number of keratinocytes (1:10)

31
Q

Describe melanin production

A

Tyrosinase converts tyrosine to DOPA
DOPA is polymerized into melanin
Reactions occur in a membrane bound pre-melanosomes but as melanin production increases they transition into melanosomes
Ends with pigment donation

32
Q

What is pigment donation?

A

The process of melanosomes being transferred to keratinocytes at the end of melanin production

33
Q

What are Langerhan’s cells?

A

APCs that provide defense against pathogens
Develop from monocyte precursors
Pale cytoplasm with long processes
Found in the stratum spinosum

34
Q

Explain epidermal differentiation and replacement

A

Epidermal cell replacement is initiated by the division of stem cells in the stratum basale
Move upward as they differentiate into keratinized cells
Eventually are lost by exfoliation on skin surface

35
Q

What is the dermal-epidermal junction?

A

Uneven boundary with finger like dermal papillae that project into the dermis
Complemented by epidermal protrusions known as epidermal ridges
Hemidesmosomes provide tight interface
Focal adhesions are also present

36
Q

The dermal-epidermal junction increases in size/number at sites of what?

A

Mechanical stress

37
Q

What are the two layers of the dermis?

A

Papillary and reticular layer

38
Q

Describe the papillary layer of the dermis

A

Loose CT immediately beneath the epidermis

Contains vasculature and nerve endings

39
Q

Describe the reticular layer of dermis

A

Deep to papillary layer
Dense irregular CT with coarse elastic fibers
Form regular lines of tension called Langer’s lines

40
Q

What is the subpapillary plexus?

A

Rich, nutritive capillary network located between the papillary and reticular layers

41
Q

What is the deep plexus?

A

Lies near dermis-subcutaneous layer interface

42
Q

Describe the hypodermis

A

Loose CT that binds the skin loosely to adjacent organs

Adipocytes vary in number and size based on body regions/nutritional state

43
Q

The extensive vasculature within the hypodermis promotes what?

A

Rapid uptake of insulin or drugs injected into this tissue

44
Q

Sensory receptors of the skin include?

A

Non-encapsulated and encapsulated receptors

45
Q

What are Merkel’s cells?

A

Epithelial tactile cells that function as low threshold mechanoreceptors essential for sensing gentle touch
Abundant in sensitive skin (ex. Fingertips and hair follicles)

46
Q

List characteristics of Merkel’s cells

A

Resemble surrounding keratinocytes but lack melanosomes

Contain small golgi derived granules concentrated near the basolateral surface

47
Q

What are characteristics of Merkel cell carcinoma (MCC)?

A

Rare and aggressive
Difficult to treat
40x less common than malignant melanoma but 2x mortality rate

48
Q

What are free nerve endings of the skin?

A

Located in the papillary dermis and extend into the lower epidermal layers
Respond primarily to high and low temperatures, pain and itching
May also function as tactile receptors

49
Q

What are Meissner’s corpuscle?

A

Encapsulated receptors responsive to light touch or low frequency stimuli
Perpendicular to the epidermis in the dermal papillae
Numerous in the fingertips, palms and soles

50
Q

What are lamellated (Pacinian) corpuscles?

A

Large encapsulated oval structures found deep in the reticular dermis and hypodermis
Specialized for sensing coarse touch, pressure (sustained touch) and vibration

51
Q

What are some other locations where Pacinian corpuscles are found?

A

CT of visceral organs

Wall of the rectum and urinary bladder where they produce pressure sensations when distorted

52
Q

Describe sebaceous glands

A

Produce a lipid mixture known as sebum via holocrine secretion (apoptosis) and is discharged into a hair follicle

53
Q

Where are sebaceous glands abundant?

A

Face and scalp

54
Q

Describe characteristics of the sebum produced by sebaceous glands

A

Waxy mix of triglycerides and cholesterol that lubricates, softens and waterproofs the skin

55
Q

Describe eccrine sweat glands

A

Simple coiled glands with a stratified cuboidal duct
Found extensively throughout the skin
Method of secretion is merocrine which is facilitated by myoepithelial cells

56
Q

What process do eccrine sweat glands participate in?

A

Temperature regulation via cooling

Evaporation of H2O from sweat on the body surface

57
Q

What are the components of sweat?

A

H2O, salt, ammonia, uric acid and mucinogen granules

58
Q

What are apocrine sweat glands?

A

Tubular glands with a large lumen and stratified cuboidal duct
Method of secretion is merocrine which is facilitated by myoepithelial cells

59
Q

Explain the merocrine secretion of apocrine sweat glands

A

Protein, carb and ammonia rich secretion
Odorless until mixed with bacteria
Become functional at puberty

60
Q

Describe the hair bulbs of hair follicles

A

The terminal dilation of a hair follicle

Dermal papilla insert into it providing nutrients via capillaries

61
Q

What forms the hair matrix?

A

Keratinocytes which are continuous with the epidermis

Divide and differentiate leading to hair growth

62
Q

Describe the follicular bulge of a hair follicle

A

Contains epidermal stem cells

Near insertion of the arrector pilli muscle

63
Q

What are arrector pilli muscle?

A

A small bundle of smooth muscle that extends from mid point of the hair root to the papillary layer of the dermis

64
Q

What causes goose bumps?

A

Contraction of the arrector pilli muscle which distorts the attached dermis

65
Q

What are nails?

A

Highly keratinized cells on a bed of epidermis known as the nail bed

66
Q

What is the nail root?

A

The most proximal region of the nail and covers the nail matrix

67
Q

What is the nail matrix?

A

Contains stem cells that divide and form keratinocytes
Nail plate remains attached to nail bed
Pushed forward by continuous growth

68
Q

What is the lunula of a nail?

A

Crescent shaped white area near the nail matrix

69
Q

What is the cuticle of a nail?

A

Extension of the skin covering the nail root

70
Q

What does it mean if a nail is black or purple that is not due to bruising?

A

Could be a sign of melanoma

MSK Final Exam (26 decks)

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