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MS Week 1 > Histology of the Skin > Flashcards

Histology of the Skin Flashcards

1
Q

What are the three components of the skin?

A

Epidermis, dermis and hypodermis

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2
Q

What are the 4 (5) epidermal layers?

A

Stratum germinativum (deepest) aka basal right up against the BM, these are mitotically active
Stratum spinosum, also divide
Stratum granulosum, begin to see basophilic keratohyaline granules migrate toward sunny side of nuc
*Stratum lucidum, thick skin only
Stratum corneum (most superficial), fully keratinized dead cells

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3
Q

What are characteristics of the stratum germinativum (basal)?

A
  • Basal layer right up against BM
  • Mitotically active
  • Contain hemidesmosomes (cell to ECM- along basal lamina) and desmosome (cell to cell)
  • Polyribosomes
  • Intermediate filaments (keratin type) in cytoplasm
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4
Q

What are the two major mitotic levels?

A

Stratum germinativum (basal) and stratum spinosum

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5
Q

What are characteristics of the stratum spinosum?

A
  • “Prickle”, spiny cell layer
  • Mitotically active
  • Desmosomes at cell-cell junctions
  • Polyribosomes
  • IF (keratin type) and tonofibrils
  • Membrane coating granules (keratinosomes)
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6
Q

mnemonic for the epidermal layers

A

GSGLC

Germ-Spin-Granular-Lucid-Corn

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7
Q

What are lamellar bodies? Where are they localized in the cell? In which layer do they first appear

A

Derived from the golgi apparatus, contain lipid and lipid processing enzymes –> first appear in the spinous cell and migrate to sunny side of nucleus. When granulosum, they exocytose their content and provide a lipid coating aka water barrier for neighboring cells

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8
Q

What are characteristics of the stratum granulosum?

A

Contain keratohyalin granules (dark staining)! No mitotic activity, nuclei become pyknotic (shrivel, dying)

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9
Q

What are the characteristics of the stratum lucidum? Where is it located?

A

Present only in thick skin (palms of hands/feet), appears “glassy”, nuclei gone

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10
Q

What are characteristics of the stratum corneum?

A

The outermost layer of the epidermis! Cells totally dead and flat, completely keratinized.

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11
Q

What are the characteristics of thick/thin/back skin?

A

Thick- thick epidermis (and sometimes stratum lucidum)
Thin- thin epidermis
Skin of back- thin skin but with a thick dermis

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12
Q

What is keratin composed of?

A

Keratin consists of fibers and proteinaceous material- IFs (keratin) and interfilamentous matrix – complex.

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13
Q

Describe the process of keratinization and its two phases

A

Synthetic phase- IFs, membrane coating granules (lamellar bodies) and keratohyalin granules (gran layer only) which contain filaggrin and trichohyalin

Degradative phase- lamellar granules discharge, lysosomes degrade organelles, filaments and keratohyalin form a fibrous mass

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14
Q

What is the function of filaggrin?

A

As cell begins to break down (gran layer), filaggrin binds all IFs into an enormous mass called keratin

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15
Q

What is the difference between hard/soft keratins? Where are they found? Which is most common?

A

Hard- NO granulosar cell layer phase, found in hair/nails
Soft- granular cell layer phase, epidermis and internal root sheath of hair
*Soft is most common!

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16
Q

What is psoriasis?

A

An itching rash like- due to increase in the number of dividing cells in the basal and spinosum layers. There is more mitosis and increase in the rate of cell turnover.

Great epidermal thickness and continuous turnover!

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17
Q

What is pemphigus vulgaris?

A

An autoimmune blistering disorder, caused by disruption of desmosomes linking cells of the epidermis (specifically keratinocytes)
Antibodies made against desmogleins!

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18
Q

What is bullous pemphigoid?

A

Autoimmune blistering disorder at the dermis-epidermis junction, due to an antibody against an antigen in the dense plaque of the hemidesmosome. Leads to sep or epidermis and dermis leading to fluid build up in the lamina lucida region of the BM.

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19
Q

What type of cells are present in the epidermis?

A

Keratinocytes**, Melanocytes, Langerhan’s cells (APC) and Merkel cells

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20
Q

What is the function of the merkel cell?

A

A variation of epithelial cells found in the epidermis that are associated with a nerve for light touch

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21
Q

What are dermal papillae?

A

Projections of dermis into the epidermis- Can be broken up by ridge or pegs of further epidermal growth especially prominent in thick skin.

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22
Q

What are the two types of dermal papillae?

A

Vascular- with loops of capillaries that run in/out of papillae
Nervous- innervated by a sensory nerve fiber

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23
Q

What are the layers of the dermis?

A

The papillary layer (superficial) and reticular layer made of elastic fibers that start thin and then increase in size as they move deep.

24
Q

What are Langer lines? Why are they significant?

A

They are characterized by the prevailing direction of collagen in the dermis, made of DENSE IRREGULAR tissues with prevalent lines or RETICULAR fibers. This is important for incisions because they heal better.

25
Q

What cells are found in the dermis?

A

Fibroblasts* (made of connective tissues), mast cells, macrophages

less common: smooth muscle, skeletal muscle and fat

26
Q

What is the hypodermis composed of?

A

Loose connective tissue and lots of FAT cells!

27
Q

What three factors give the skin its color?

A

Carotenes (yellowish color), blood capillaries (redish) and varying amounts of melanin (brown to black)

28
Q

What cell type produces melanin? Where are they typically found?

A

Melanocytes produce melanin in little membrane bround organelles called malonosomes. Commonly found in stratum germintivum or spinosum cells of epidermis with long arms.

29
Q

Describe the process of melanin production in a melanocyte:

A

Rough ER makes tyrosinase and pinched off in granule called pre-melanosome, takes up tyrosine and gradually makes the melanosome more pigmented. As they migrate, melanin formed inactivates tyrosinase making a mature melanin granule. Keratinocytes get melanin in their cytoplasm as it is pinched off of arms of melanocyte through cytokine secretion.

30
Q

What is the difference between white/black individuals?

A

NOT NUMBER OF MELANOCYTES- INSTEAD LOCATION AND DEGREDATION OF MELANIN.
In white people, melanin granules are smaller and localized near nucleus and degraded more rapidly. In black, they are larger, more isolated and scattered so less degraded.

31
Q

How does tanning work?

A

Immediate darkening in existing melanin, gradual increase in tyrosinase activity (long term, delayed tan).

32
Q

What is albinism?

A

The inability to produce melanin due to lack of tyrosinase activity

33
Q

What is vitiligo?

A

Autoimmune disease where melanocytes are destroyed, leading to depigmentation.

34
Q

Where is the vascular supply to skin?

A

Most is subcutaneous, send branches up toward the skin and make a network called the rete cutaneum. From there send branches to the epidermis or hypodermis. If go to dermis/epidermis side, they make a second network called the rete subpapillare between the papillar and reticular layers of the dermis.

35
Q

Mnemonic for vascular supply to skin

A

Subcute- Cute- Subpap (between papillary and reticular layers of dermis)

36
Q

Where are AV shunts typically found?

A

In the reticular layer of the dermis. If cold they will OPEN and if warm they will CLOSE (blood gets to capillaries to lose heat)

37
Q

What are the major components of hair?

A

The hair shaft (hard/soft keratin) and the hair follicle (derived from epidermis)

38
Q

What are the major associated structures with hair

A

Sebaceous glands
Apocrine sweat glands (nerves)
Arrector pili muscles (pull up if goose bumps)

39
Q

What is the function of the arrector pili muscle? What nervous system controls them? Where does it run?

A

Attached to the papillary layer of dermis and to the hair follicle- Controlled by sympathetic nervous system.
If contracted, will pull the epidermis down which gives good bumps on the skin.

40
Q

Why is hair how to pull out?

A

Free edge of hair points up and free edge of follicle points down- thick like velcro- its hard to pull them against each other.

41
Q

What is the basis for different hair colors? Black? Brown/blond? Red? Gray?

A

Oxidation of tyrosine and amount of pigment.
Black: well oxidized tyrosine
Brown/blonde: Same quality pigment, less of it
Red: pigment with limited oxidation
Gray: mix of white/black hair

42
Q

Mnemonic for types of hair

A

Lan- fetal
Vel- most body hair
Ter- scalp/brow etc.

43
Q

Function of sebaceous gland? What are they typically associated with?

A

Produce oils that lubricate the skin and hair through HOLOCRINE secretion– pushed out by contraction of the arrector pili muscle. Typically associated with hair follicles.

44
Q

What is the lunula of the nail?

A

A crescent shape at the base of the nail. Matrix of mitotically active cells is thick and blood vessels cannot show through.

45
Q

How is the sebaceous gland related to acne?

A

During puberty, androgens are increased which causes for increased activity of sebaceous glands –> oily skin leading to acne and blackheads (plugged sebaceous gland open to surface)

46
Q

Describe the function of an eccrine and apocrine sweat gland? Which is more numerous?

A

Eccrine has a coiled duct and secretory region that opens to pore of epidermal surface.
Apocrine also has a coiled secretory region but duct opens to lumen of the hair follice –> associated with hair!
Eccrine (heat) > apocrine (nervous)

47
Q

What cell types line eccrine and apocrine sweat glands?

A

Secretory portion: simple cuboidal of clear and dark cells to secrete things.
Duct portion: coiled with STRATIFIED CUBOIDAL CELLS that may reabsorb things

48
Q

Where do you find myoepithelial cells?

A

In the eccrine and apocrine sweat gland, at the secretory portion. Act to contract and push product into the lumen.
- LOOK LIKE STRIPES

49
Q

How can you tell apocrine and eccrine sweat glands a part?

A

The lumen of the apocrine sweat gland is HUGE, much larger than eccrine.

50
Q

List 3 examples of free nerve endings in the skin?

A

Peririchial nerve endings (deep portion of hair follicles), merkel (touch- located in epidermis) and pain

51
Q

Examples of encapsulated nerve endings?

A

Mechanoreceptors (corpuscles of ruffini and karuse’s)
Meissner’s corpuscles: touch (finger tips, nipples)
Pacinian corpuscles: pressure (dermis, hypodermis)

52
Q

Describe the appearance of meissner’s corpuscle, where are they found?

A

Kind of a round of pointed shape, a myelinated nerve fiber then runs into round potion where nerve is surrounded by flattened schwann cells

Found in nervous papillae of dermis

53
Q

Describe the appearance of pacinian corpuscle, where are they found?

A

Myelinated nerve fiber runs into a structure that looks like a sliced onion- of modified schwann cells around the fiber.

54
Q

What happens with cut?

A

Epidermal cells start to divide rapidly and move down, and underline the clot. Collagen production in the dermis due to fibroblasts which will push up and form a scar.

55
Q

What is the difference between a split skin graft and full-thickness graft?

A

Split skin graft leaves behind some epidermis, which means they can regenerate themselves –> don’t necessarily need to suture
Full thickness graft takes skill down to the hypodermis so there are no cells to regenerate layers –> sutured shut.

MS Week 1 (11 decks)

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