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Module 2: MSK > Skin (integumentary system) > Flashcards

Skin (integumentary system) Flashcards

To learn about the skin...

1
Q

What are the functions of the integumentary system?

A
  1. Maintain internal environment
  2. Protection from invaders and gross physical units
  3. Receive stimuli from environment
    4 Thermoregulation via sweat glands, fat deposits, blood vessels
  4. Excretory and photochemical functions
  5. Good source of diagnostic info
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2
Q

What is the embryonic origin of the epidermis?

A

Surface ectoderm.

- Initially a single layer, the epidermis reaches full thickness at birth

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3
Q

What is the embryonic origin of the dermis?

A

mesoderm

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4
Q

What is the embryonic origin of accessory structures (hair, sweat glands, mammary glands, etc)?

A

They are derivatives of epidermal cells and the epidermis originates in the surface ectoderm

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5
Q

What are the layers of the skin?

A

From the top:

  • Epidermis
  • Dermis
  • Hypodermis
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6
Q

Describe the structure of the epidermis?

A
  • Composed of keratinized, stratified squamous epithelium
  • forms outer layer of skin
  • predominantly keratinocytes and melanocytes (pigment cells)
  • Langerhans and Merkel cells also found there
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7
Q

What are Melanocytes?

A
  • Melanocytes are cells that create skin and hair pigmentation.
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8
Q

What are Langerhans Cells?

A

epidermal dendritic cells involved in signaling the the immune system

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9
Q

What are Merkel cells?

A

Cells associated with sensory nerve endings

  • They contain dense core neurosecretory granules
  • believed to be sensitive to tactile stimuli
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10
Q

From the dermis outward, what are the 5 layers of epidermis?

A
  1. Stratum basale (germinativum)
  2. Stratum spinosum
  3. Stratum granulosum
  4. Stratum lucidum (thick skin only)
  5. Stratum corneum
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11
Q

Describe the cells of the stratum basale (germinativum)

A
  • Basopihlic keratinocytes that are cuboidal to columnar
  • Cells have hemidesmosomal junctions with underlying basement membrane
  • Desmosomes bind cells to lateral and upper surfaces
  • mitotic figures are common as these cells are continuously renewing epidermal cells
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12
Q

Describe the cells of the stratum spinosum

A
  • polygonal or slightly flattened cells
  • prominent desmosomal attachments to adjacent cells
  • appear “spiny” in light microscope
  • cells contain abundant keratin filaments
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13
Q

Describe the cells of the stratum granulosum

A
  • Cells contain keratohyalin granules (not membrane bound)
  • these are basophilic granules, not to be confused with melanin granules (mostly found in basal layers of epidermis)
  • Cells have lamellar bodies
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14
Q

What are lamellar bodies?

A

Contribute to the formation of the intercellular epidermal water barrier
- ovid-shaped membrane bound organelles that hold a mixture of pro-barrier lipids and proteases used to form the epidermal water barier

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15
Q

Describe the cells of the stratum lucidum

A
  • thin layer of weakly eosinophilic, flattened cells specific to thick skin only
  • very few organelles or nuclei
  • abundant filaments in an electron dense amorphous matrix with no keratohyalin granules
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16
Q

Describe the cells of the stratum corneum

A
  • flattened, keratinized cells
  • plasma membranes are thickened by deposition of secretions from membrane-coating granules
  • strong barrier to movement of material across skin
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17
Q

Where is thin and thick skin present?

A

Thick skin: palms and soles of feet

Thin skin: everywhere else

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18
Q

What are the layers of the dermis?

A

Papillary layer

Reticular layer

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19
Q

Where are melanocytes found in the epidermis?

A

Beneath or between epithelial cells of the stratum basale and in hair follicles attached to basement membrane

20
Q

What is the origin of melanocytes?

A

They come from the neural crest and are responsible for synthesizing melanin granules

21
Q

What is albinism?

A

no melanin produced, usually due to absence of the enzyme tyrosinase

22
Q

How is melanin produced?

A

by oxidation of dihydroxy-phenylalanine (DOPA). DOPA is made from tyrosine by the enzyme tyrosinase

23
Q

How are melanin granules produced?

A

By the deposition of melanin onto a fibrous lattice, called the melanosome

24
Q

Why does pigment vary in individuals?

A

Pigment is determined by melanosome size, distribution, and density of pigment.

25
Q

What is the process of melanin distribution throughout epidermal cells?

A

Melanin granules, made in melanocytes, are “injected” into keratinocytes.
- melanocytes don’t accumulate melanosomes, they continually transfer them. This process is known as cytocrine secretion.

26
Q

What are free nerve endings?

A

Terminals of thinly myelinated or unmyelinated nerve fibers that penetrate the epidermis
- responsible for sensing pain and temp changes

27
Q

Describe the papillary layer

A

More cellular connective tissue than the reticular layer

  • contains fibroblasts, macrophages, mast cells, fine collagen fibers
  • Outstanding features: vascular papillae and Meissner’s corpuscles
28
Q

What are vascular papillae

A

In dermis, complementary to epidermal projections (rete ridges)

29
Q

What are Meissner’s corpuscles?

A

In dermis, encapsulated sensory receptors for light touch

30
Q

Describe the reticular layer

A

In dermis, thick layer containing irregular dense connective tissue which has more fibers (and thicker ones) and fewer cells than papillary layer

31
Q

Describe the subcutaneous tissue

A

Known as the hypodermis:

  • binds skin to subjacent organs
  • often contains adipose tissue, blood vessels, lymph vessels, and pacinian corpuscles
32
Q

What are pacinian corpuscles?

A

endcapsulated, ovoid sensory receptors

  • sensitive to deep pressure
  • together with Meissner’s corpuscles, they are responsible for vibratory sensation
33
Q

What are the functions of blood supply in the skin?

A
  • nourish epidermal structures

- termp regulation

34
Q

Where are blood vessels found in the skin?

A

In dermis and hypodermis (few vessels found in reticular layer of dermis)

35
Q

What are the structures of hair follicles?

A

Layers from inside out:

  1. Matrix cells (including melanocytes)
  2. Inner root sheath
  3. Outer root sheath (source of new epidermal cells in wound healing)
  4. Connective tissue sheath
36
Q

What are the structures of a hair shaft after emerging from follicle?

A
  1. Medulla - forms central axis
  2. Cortex - multilayered structure containing pigment granules
  3. Cuticle - thin protective covering
37
Q

What are arrector pili?

A

bundle of smooth muscle fibers obliquely attached to hair follicle

38
Q

What are sebaeous glands?

A

alveolar glands with excretory duct opening into hair shaft

  • secretes sebum (made of lipid rich cell debris)
  • these glands have no myoepithelial cells
39
Q

What are nails composed of?

A

Keratinized plates which form a protective covering over the distal ends of digits

40
Q

What is the nail bed?

A

the nail plate rests on the nail bed which consists of epithelial cells continuous with the epidermis

41
Q

What is the nail matrix?

A

These cells produce the nail plate

42
Q

What are myeoepithelial cells?

A

Cells that surround secretory cells and their contractions aid in movement of secretions toward the duct

43
Q

What are dark cells?

A

Cells that border the lumen of secretory tubules and produce a mucoid substance

Have abundant rER

44
Q

What are clear cells?

A

Cells that rest on the basal lamina of secretory tubules and are involved in secretion of water and electrolytes

Have abundant smooth ER

45
Q

Describe sweat gland ducts.

A

Lined by stratified cuboidal epithelium, they recover sodium as sweat passes through the duct

46
Q

Where does new growth occur when epidermis is removed by trauma (blisters, burns, scrapes…)?

A

From hair follicles and sweat glands

47
Q

Where are stem cells located for the epidermis?

A

Midway along the hair follicle

Module 2: MSK (11 decks)

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