Skin And Appendages

Front 1

What are the layers of the skin?

Back 1

1.) epidermis

2.) dermis

Front 2

What are the characteristics of the epidermis?

Back 2

1.) made of stratified squamous keritinied epithelium

2.) has 5 layers in thick skin

Front 3

What are the characteristics of the dermis?

Back 3

1.) made of connective tissue

2.) has 2 identifiable layers

Front 4

What is the origin of the epidermis and what are the layers?

Back 4

origin = ectoderm

layers = stratum germinativum (malphigian layer)

stratum spinosum (malphigian layer)

stratum granulosum

stratum lucidum (most prominent in thick skin has acidophilic cells that are dont have nuclei or organelles)

stratum corneum (horny cells or squams)(flatened keratin-filled cellsdevoid of any organelles includingthe nucleus)

Front 5

(Cutaneous burn)

1st degree burn

Back 5

Damage tosuperficial epidermis

Cells ofstratum germinativum remainviable and regenerate epidermis

Front 6

(Cutaneous burn)

2nd degree burn

Back 6

Epidermiscompletely destroyed

Remnants ofsweat glands and hair follicles in the dermis are able to regenerate theepidermis

Front 7

(Cutaneous burn)

3rd degree burn

Back 7

Full-thicknessburn

Destroysepidermis and dermis

Skin graftsare typically necessary

Loss ofbody fluids can cause hypovolemia and shock With 15% ofbody area in adults and With 10% ofbody area in children

Front 8

Cells found in the epidermis

Back 8

1.Keratinocytes (Ectodermal origin) 2.Melanocytes (Neuralcrest origin)

3.Langerhanscells (Dendritic, antigen presenting cells)

4.Merkel Cells (Specializedkeratinocytethat is involved in touch.)

Front 9

Keratinocytes

Back 9

predominant cell type in the epidermis. They go through a very specializeddifferentiation to give rise to the protective dead cell layer, the stratum corneum.

Front 10

Basal Cell Carcinoma

Back 10

(70% of skin cancers)

They only arise in regions of skin containing sebaceous glands.

They typically occur after the age of 40 in fair skinnedindividuals and are usually found on the eyelids and bridge of nose.

Histologically basal cell carcinoma cells form discrete nests or islands ofcells that resemble normal basal cells.

Basal cell carcinoma seldom metastasize.

Front 11

Squamous Cell Carcinoma

Back 11

(20% of skin cancers).

Fair-skinned blonds with outdooroccupations are particularly prone to this form of cancer.

Histologically, there is a complete replacement of normalepithelium with pleomorphic cells.

In laterstages, the cells penetrate the dermis. The prognosis depends more on location, size and depth of penetrationthan on the degree of anaplasia.

Relatively few squamous cell carcinomas (2-5%)metastasize to regional lymph nodes

Front 12

Langerhans Cells

Back 12

dendritic cells mainly found in thestratum spinosum.

They are similar to dendritic cells seen in lymphoid tissues

They are responsible forengulfing invading micro-organisms in the epidermis and presenting antigens tolymphoid cells

*not attached to adjacent cells by desmosomes

Front 13

Melanocytes

Back 13

neural crest origin -

specialized cells located in stratum germinativum that replicate slowly throughout life,

thereby maintaining epidermal-melaninunits (one melanocyteassociates with a fixed number of keratinocytes).

Epidermal-melanin units vary regionally.

Epidermal-melanin units are not determined by race orgender.

not connected to surrounding cells by desmosomes but can be connected to lamina but hemidesmosomes

Front 14

what do Melanocytes contain?

Back 14

Melanocytes contain large amount of theenzyme, tyrosinase. Tyrosinase is responsible for conversion of tyrosine through a series ofsteps to melanin

Front 15

cytocrine secretion

Back 15

process whereMelanin granules are injectedinto keratinocytes. This is where melanin seen in the skin is actually found. The melanocytes have the fewest melanin granules

Front 16

What is the role of melanocytes and where are they found within the keratinocytes?

Back 16

Melanin granules take positionabove the nuclei of keratinocytes in the strata germinativum and spinosum. The role of thegranules is to protect the dividing cells from UV radiation (think of them asforming an umbrella over the nucleus)

*Lysosomal degradation of melanin granules is slower in darker-skinnedraces and melanin granules may be evident in the upper strata of the epidermis.

Front 17

Malignant Melanoma

Back 17

2% of skin cancers

Because of their neural crest origin (i.e. highly migratorycells), they are very metastatic. Melanoma appears as nests of pigmented melanocytes that penetrate theepidermis.

The cells also invadethe dermis where they have access to blood vessels and lymphatics.

Front 18

Merkel Cells

Back 18

They are primarily found in thick skin where touch is acute. They appear to be mechano-receptive cells as suggested by their association with nerveendings. These specialized keratinocytes contain 80nm neurosecretory granules. They cannot be distinguished from keratinocytes in H and E preparations.

Front 19

2 layers of the dermis

Back 19

1.) Papillary- loose CT containing fibroblasts, mastcells and macrophages as well assome leukocytes - major part of the dermal papillae or pegs

2.) Reticular- dense irregular CT - composed of collagen fibers (type I) and fewer cells thanthe papillary layer

Front 20

How is the distinction between thick and thin skin made?

Back 20

The distinction is dependent on the thickness of theepidermis only

Front 21

Thick (Glabrous) Skin

Back 21

Found in areas exposed to greater wear and abrasion.

The palms of the hands and the soles of the feet have classicexamples of thick skin.

Thick skin has allfive epidermal layers with a prominent stratum lucidum and a thick stratum corneum.

Thick skin ishairless and, as such, has no sebaceous glands.

Front 22

Thin (Hairy) Skin

Back 22

found covering all the rest of the body that is not thick skinned

It typically has no distinct stratum lucidum and a quite thin stratum corneum

Front 23

HYPODERMIS

Back 23

lies deep to the dermis, but not considered part ofthe skin.

It is also called superficial fascia or subcutaneous CT.

- loose CT withvarying numbers of fat cells. The fat cells vary in size according to the degree of obesityof the individual

Front 24

APPENDAGES OF THE SKIN

Back 24

Hair follicles

Sweat glands

Sebaceous glands

Mammary glands

nails

Front 25

Hair Follicles

Back 25

invaginations of epidermis which during periods of growth have bulbous terminal dilations-the hair bulb.

The bulb rests upon a dermal papilla that contains thecapillaries that nourish the hair follicle.

The cells of the hair bulb arelike those of the stratum germinativum

Front 26

Sweat Glands

Back 26

Two types of sweat glands. (1. Eccrine sweat glands2. Apocrine sweat glands)

They develop asinvaginations of epidermis into the underlying connective tissue.

Front 27

Eccrine Sweat Glands

Back 27

simple, coiled tubular glands - secrete a non-viscous fluid. Evaporation of the fluid coolsskin. Eccrine sweat glands are alsoexcretory. Sweat contains catabolites

Front 28

Myoepithelialcells

Back 28

are specialized cells thatsqueeze the secretions from the sweat acini.They are epithelial, notsmooth muscle cells.They are acidophilicbecause they contain actin filaments.

Front 29

Apocrine Sweat Glands

Back 29

Specialized glands located in the axillary, areolar and anal regions. The ducts open into hair follicles and secrete a viscous,odorless fluid. The secretionattains a distinctive odor by the action of bacteria that reside on theskin. In more "primitive" mammals, secretions of the apocrine glands have sexual function, i.e. attract the oppositesex. Interestingly, in humans, theapocrine sweat glands become active atpuberty. The mammary gland is believed to be a highly modified apocrine sweat gland.

Front 30

Nails

Back 30

plates of keratinized epithelial cells. Nail plates are transparent and therebyprovide a quick assessment of oxygenation of blood. Blue indicates poor oxygenation (cyanosis). 1. nail root - germinal region 2. underlying the nail plate is the nail bed which consists of stratum germinativum and stratum spinosum only (the malpighian layer) 3. the epithelium ofthe nail bed arises from the nail matrix. The matrix extends deep to the root. 4. nail grows fromproximal end and slides over the nail bed. The bed does not contribute to the nail plate.

Front 31

SKIN AS A SENSORY ORGAN

Back 31

A majorfunction of the skin is to serve as a sensory receptive organ. As such, the skin has a number ofspecialized sensory receptors associated with i

Front 32

Free Nerve Endings

Back 32

Unmyelinated axons that penetrate the basal lamina of the epidermis toenter the stratum germinativum and spinosum. Ramify among the epithelial cells. Involved in temperature and pain perception.May also functionin crude touch as evidenced by the fact that they are the only type of receptor found in the cornea.

Front 33

Meissner’s Corpuscles

Back 33

most abundant in thick (glabrous) skin as well as in the skin of the lips and nipples. These specialized encapsulated receptors can be found within the dermal papillae of thickskin.Involved in discriminative touch,ability to discriminate two points

Front 34

Pacinian Corpuscles

Back 34

This encapsulated receptor is found in thedermis and often, the hypodermis, of both thick and thin skin.Pacinian corpuscles are especially abundant in theskin of the fingertips. The corpuscle is traditionally described as apressure sensor, but its rapid adaptation has lead some to believe the pacinian corpusclesignals a vibratory sense, i.e. it responds to a tuning fork placed against theskin.