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Histology > Skin > Flashcards

Skin Flashcards

1
Q

Epidermis type and origin

A

It is an epithelial layer of ectodermal origin

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2
Q

Dermis type and origin

A

It is connective tissue of mesodermal origin

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3
Q

Skin appendages

A

Sweat glands
Sebaceous glands
Hair
Nails

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4
Q

Types of skin

A

Thick skin

This skin

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5
Q

Epidermis cell types

A

It is formed of Stratified squamous keratinized epithelium

Has keratinocytes and non-keratinocytes

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6
Q

Keratinocytes are:

A 
Arranged in 5 layers 
Stratum basale
Stratum spinosum 
Stratum granulosum
Stratum lucidum 
Stratum corneum
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7
Q

Stratum basale

A

Germinal layer
Single layer of columnar cells
Cytoplasm is basophilic due to high ribosomal content
Many mitotic figures
EM:
Contains IF (tonofilaments)
There are desmosomes between cells and hemidesmosomes at the basment membrane

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8
Q

Stratum spinosum

A

Prickle cell layer
Several layers of polygonal cells with central nuclei
Some mitotic figures
Has many spinous interdigitating processes and intercellular bridges ending with desmosome
Many tonofilaments in the cytoplasm

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9
Q

Stratum granulosum

A

Granular layer
3-5 layers of polygonal cells with central nuclei
The cytoplasm contains basophilic non-membranous granules called keratohyaline granules
EM:
There are membrane coated lamellar granules that reease lipid-containing substance in the intercellular space. This forms a barrier against invasion with foreign materials resembling intercellular cement

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10
Q

Stratum lucidum

A

Clear layer
It is translucent thin layer of eosinophilic flattened cells containing eledin
EM:
Cells have no organelles, no nuclei and the cytoplasm is mainly formed of closely packed tonofilaments embedded in an electron dense matrix
desmosomes are still present

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11
Q

Stratum corneum

A

Horny layer
Superficial cells are shed
Consists of many layers of flattened non-nucleated keratinized cells
Cytoplasm is filled with filamentous scleroprotein called keratin

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12
Q

Malpighian layer

A

Stratum basale + stratum spinosum

Renewal occurs every 15-30 days

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13
Q

Non-keratinocytes examples

A
  • Melanocytes
  • Langerhan’s cells
  • Merkel’s cells
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14
Q

Melanocytes origin

A

Derived from the neural crest

Ectodermal

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15
Q

Melanocytes

Sites

A

Between cells of stratum basale and in hair follicles

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16
Q

Melanocytes

LM

A

They have rounded cell bodies with central nuclei

They long cytoplasmic processes extend between cells of Malpighian layer

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17
Q

Melanocytes

EM

A

Cytoplasm contains numerous smal mitochondria, well-developed Golgi and rER
Not attatched to keratinocytes by bind to the basal lamina by hemidesmosomes

18
Q

Epidermal-melanin unit

A

One melanocyte maintains an association with a given number of keratinocytes

19
Q

Epidermal-melanin unit

A

One melanocyte maintains an association with a given number of keratinocytes

20
Q

Function of melanin

A

Fuse with lysosomes and occupy a supranuclear position protecting the dividing nucleus from UV rays

21
Q

Albinisim

A

Genitic defect in tyrosinase enzyme so no melanin is produced

22
Q

Melanocytes are DOPA +ve or -ve

A

DOPA +ve

23
Q

Keratinocytes are DOPA +ve or -ve

A

DOPA -ve

24
Q

Melanophages/Melanophore cells are DOPA +ve or -ve

A

DOPA -ve

25
Q

Langerhan’s cells

Origin

A

Derived from the mesenchyme from the bone marrow

26
Q

Langerhan’s cells

Site

A

Inbetween cells of stratum spinosum

27
Q

Langerhan’s cells

Structure

A

Branched star-shapped cells with intended nuclei and clear cytoplasm
Have characteristic rod-shapped granules called Birbeck’s granules

28
Q

Langerhan’s cells

Function

A

Antigen-presenting cells for lymphocytes

29
Q

Merkel’s cell

Sites

A

They are present in thick skin

30
Q

Merkel’s cell

Structure

A

Large dark cells
Resemble keratinocytes but cytoplasm contains small dense granules
Associated with nerve endings

31
Q

Merkel’s cell

Function

A

May act as mechanoreceptors or may heave DNES-cell like activity

32
Q

List layers of dermis.

A

Papillary layer

Reticular layer

33
Q

Mention components of reticular layers of dermis in thick skin

A

It consists of dense connective tissue that contains the following:

  1. Abundant collagen fibers type I and elastic fibers.
  2. Sweat glands.
  3. Sympathetic nerve fibers, free nerve endings and encapsulated sensory organs (e.g. Pacinian corpusles).
34
Q

Papillary layer

A

Outer layer beneath the epidermis

It consists of loose CT rich in cells, free nerve endings and blood capilaries for nutrition of the epidermis

35
Q

The dermis contains

A

Sweat glands, hair folicles and sebaceous glands

36
Q

Dermo-epidermal junction

A

Interdigitations between the dermal papillae and epidermal ridges

37
Q

Sites of thick skin

A

Covers palms of hand and soles of feet

38
Q

Thin layer sites

A

Covers everywhere except palms and soles

39
Q

LOOK AT THE TABLE OF THICK SKIN AND THIN SKIN

A
40
Q

Soft keratin

A

Tonofilament –> keratohyaline –> eleidin –> soft keratin

41
Q

Hard keratin

A

Tonofilaments –> hard keratin

42
Q

Pigment of red hair

A

Pheomelanin

Histology (5 decks)

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