Histo - Skin Flashcards

1
Q

What are the 5 Functions of Skin?

A
  1. Protection from…
    • abrasion, water loss/gain, bacterial invasion, sunlight
  2. Sensory
  3. Thermoregulatory
    • Either insulation or mechanism for heat loss
  4. Metabolic
    • Vitamin D
  5. Sexual signaling
    • Visual or pheromones
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2
Q

What are the 3 Layers of Skin (Integument)?

A
  1. Epidermis
    • Keratinized SS
      • Epidermal ridges
  2. Dermis
    • Papillary dermis (loose CT)
    • Reticular dermis (dense irregular CT)
      • Dermal papillae
  3. Hypodermis
    • Loose CT
    • Abundant fat
      • Subcutaneous tissue = superficial fascia
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3
Q

What are the 2 Types of Skin?

A
  1. Thick skin
    • Example: palm/foot
      • thicker keratin
      • no hair follicles
  2. Thin skin
    • Example: arms/legs
      • thinner keratin
      • hair follicles
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4
Q

What type of skin is this?

A

Thin skin

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5
Q

What type of skin is this?

A

Thick skin

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6
Q

Identify the 3 layers of skin

A
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7
Q

What are the 5 Layers of Epidermis?

A

Basics:

  • Main cells = keratinocytes

Layers:

  1. Stratum Basale = cuboidal or columnar cells
    • Proliferative
    • Binds BL via hemidesmosomes & integrins
    • Binds BL vs anchoring fibrils of Type VII collagen
  2. Stratum Spinosum
    • Lower layer = proliferative
    • Numerous desmosomes & tight junctions
  3. Stratum Granulosum
    • Filled w/ keratohyline granules
      • Filaggin/cytokeratin
      • Lamellar granules (exocytosed)
      • Lipids/glycolipid
  4. Stratum Lucidum (Anucleated)
    • only in THICK skin
  5. Stratum Corneum (Anucleated)
    • form the keratin layer
    • dead squames filled w/ cytokeratin
    • surrounded by protective layer
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8
Q

What are the layers can you see in this image?

A
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9
Q

What is this?

A

Keratinocytes in Stratum Spinosum

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10
Q

What can we see in this picture?

A
  • C = Stratum corneum
  • L = Stratum lucidum
  • G = Stratum granulosum
  • S = Stratum spinosum
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11
Q

What are the 5 Main Issues with the Skin that can arise?

A
  1. Blisters
    • Friction blisters
    • Blistering diseases
      • bullus pemphigoid (hemidesmosome disruption)
      • pemphigus (autoimmune–> damage to keratinocyte jxns)
  2. Cancers
    • Basal cell carcinoma
    • Squamous cell carcinoma
    • Merkel cell (tactile) carcinoma
  3. Psoriasis
    • increased proliferation & differentiation
  4. Pigment disorders
    • albinism
    • vitiligo (loss of pigment)
  5. Moles or Nevi
    • from melanocytes
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12
Q

What are the 3 other cells found in the Epidermis?

A
  1. Melanocytes
    • Derivative: Neural crest
    • Location: Stratum Basale
      • 1 per 5-6 keratinocytes
      • Pale staining
    • Structure: Long Projections/granules
      • Extend into invaginations of keratinocytes
    • Function: cytocrine secretion
      • inject melanin –> keratinocytes
      • cluster over nucleus & protect from UV
  2. Langerhans Cells
    • Derivative: Monoocytes
    • Location: Stratum Spinosum (mostly)
      • Rare/difficult to see
    • Structure: Dendritic cells
    • Function: Ag presenting cell
  3. Merkel Cells
    1. AKA: Epithelial tactile cells
    2. Location: Stratum Basale
    3. Structure: look like keratinocytes (but no melanin)
      1. dense core granules
      2. mechanoreceptors
    4. Fucnction: light touch/texture
      1. base interacts w/ unmyelinated sensory fibers
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13
Q

What cell type is this?

A

Langerhans Cells​

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14
Q

What cell type is this?

A

Merkel Cells

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15
Q

What cell type is this?

A

Melanocytes

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16
Q

What are the 2 Layers of the Dermis?

A
  1. Papillary layer
    • Loose CT
    • Made from:
      • Collagens I & III
      • Elastic fibers
      • Fibroblasts
      • Other cells
  2. Reticular layer
    • Dense Irregular CT
    • Made from:
      • Collagen I
      • Elastic fibers

Notes:

  • Highly innervated
    • Tactile receptors
  • Can include:
    • Sweat glands
    • Hair follicles
    • Blood vessels
    • Immume cells
17
Q

What are the 3 Plexi of the Dermis/Hypodermis?

A
  1. Subpapullary plexus
    • Btw papillary & reticular layers
    • Extends INTO papillary layer
    • Thermoregulatory
      • AV shunts
  2. Dermal/Cutaneous plexus
    • within the Dermis
  3. Deep plexus
    • Btw Dermis & Hypodermis
18
Q

What features of the dermis can you see?

A
  • Dermis showing Elastic Fibers
    • Elastic stain w/ fibers darkly stained
    • Diameter decreases closer to epidermis
    • Insert into BL
19
Q

What are the 7 Tactile Receptors in Skin?

A
  1. Free nerve endings
    • Tactile
    • Light touch
    • Pain
    • Temp extremes
    • Itching
  2. Nerve fibers w/ tactile discs
    • interact w/ Merkel cells
  3. Root hair plexus
    • Nerve senses movement of hair & touch
  4. Krause end bulbs
    • Nerve senses low freq. vibration or movement
    • Mainly on penis/clitoris
  5. Ruffini corpuscles
    • Tissue distortion
  6. *Meissner’s corpuscle
    1. Light touch
    2. Papillary dermims
    3. Most numerous in fingertips, palms, feet
      1. how we use braille
  7. *Pacinian corpuscle
    1. Pressue & high-freq vibration
    2. In deep dermis/hyperdermis

* = only tactile receptors that can be easily identified histologically

20
Q

What are the Characteristics of Hair?

A

Basics:

  • Long, keratinized structures
  • Made via hair follicles
    • Location: thin skin (w/ exceptions)
    • Originates: in the Dermis –> Epidermis
  • Arrector pili (smooth muscle)
    • make hair “stand on end”

Hair Follicles:

  • Dermal papilla = hair
  • Root + bulb
    • Matrix, medulla, cortex of root
  • Have stem cells
    • can regenerate keratinocytes
  • Melanocytes = cause hair pigmentation
21
Q

What are the 3 Stages of Hair Growth?

A
  1. Anagen
    • Growing hair (length)
  2. Catagen
    • Arrests growth
    • Hair regresses
  3. Telogen
    • Hair is lost
    • Causes alopecia (baldness)
22
Q

What are the Characteristics of Nails?

A

Basics:

  • Nail root
    • covered by eponychium (cuticle)
  • Nail plate
    • Hard keratin
    • Has lunula (white semi-circle)
  • Nail bed
    • Has only basal & spiny layers of dermis

Growth:

  • Fom nail matrix
    • most proximal part of nail
  • Hyponychium
    • “Free” nail is no longer connected to the skin
23
Q

What parts of the nail can we see?

A
24
Q

What are the 3 Glands in the Skin?

A
  1. Sebaceous glands (aka Sebocytes)
    • Thin skin (mostly)
    • Secrete = Sebum
      • Holocrine secretion
      • Looks like clusters of squamous cells (fried eggs)
    • Secreted into hair follicles
    • Can be antibacterial/antifungal
    • Gland can look scalloped
  2. Eccine sweat glands
    • Round/Oval acinar organization of cells
      • around central lumen
      • can be stratified
    • Secretory part
      • Merocine section
      • Dermis/Hypodermis
      • More lightly stained than ducts
    • Duct part
      • secretory part to surface of the skin
      • open at sweat pore
  3. Apocrine sweat glands
    • Round/oval acinar organization
      • cells around central lumen
    • Larger lumen than eccrine sweat glands
      • develop in presense of sex hormones (after puberty)
    • Secretory part
      • MEROCRINE secretion
    • Apical part of duct = opens into hair follicles
      • not skin surface
25
Q

What is this?

A

Apocrine Sweat Glands

26
Q

What is this?

A

Eccrine Sweat Glands

27
Q

What is this?

A

Sebaceous Glands