Unit 7 - 4 Histology

Front 1

peritrichial cells

Back 1

innervate hair follicles

Front 2

merkel cells

Back 2

neuroendocrine cells

Front 3

interpapillary peg

Back 3

useful for resisting shear stress along the dermis

several rows of dermal papillae work up into epidermis (secondary dermal ridge demaracation)

Front 4

layers from dermis out to stratum corneum

Back 4

point: a continual differentiation process constantly occuring from a set of stem cells located in the stratum vasal; undergo mitosis; differentiate as they transit to surface; die by apoptosis leaving the keratin layer (protein/lipid layer)

stratum basal (stem cells);

at granulosum layer you show granular elements, lamellar bodies, nucleoli flatten out;

Front 5

stratum lucidum

Back 5

only present in thicker skin

Front 6

stratum spinosum

Back 6

lots of desmosome junctions along the stratum spinosum

Front 7

Back 7

thick skin (back, palmsl soles of feet); convuluted interface; lack of hair, sweat glands are deep in dermis;

Front 8

Back 8

thin skin

dense irregular connective tissue; thinner epidermis; dermis contaisn dense connective tissue; shallow epidermal ridges; thin keratin layer; hair follicles present (not in thick skin); sebaceous and sweat glands present

Front 9

keratinocyte

Back 9

dominant cell composing stratified squamous epithelium itself;

Front 10

melanocytes

Back 10

sit down on basal laminae, generate melanin, have dendritic projections out through spinosum layers; communicate with keratinocytes (epidermal-melanin unit); keratinocytes take up melanin secreted by melanocytes = mechanism of skin pigmentation

Front 11

merkel cells

Back 11

neural crest derived; form a nerve plate w myelinated axon at the basal lamina; form mechanoreceptors

Front 12

langerhans cells

Back 12

dendritic APC that survey keratinocyte layers and are focused on the basal layer; can migrate out and make it down to a lymph organ to stimulate T cells

Front 13

Back 13

two adjacent cells linked by desmosomes showing tonofilaments projecting in towards the cell; the intracellular space expresses cadherin proteins

INTEGRINS used to attach the basal layer to the basement membrane

Cadherins are higher up

"spines" o fstratum spinosum are cytoplasmic extensions with desmosomes

Note melanocytes at basal level, melanin granules in keratinocytes

Front 14

Back 14

note nucleus in basal cell vs granulosum layer (bottom); cell in granulosum layer is in final stage of differentiation producing lamellar bodies and apoptotic mechanisms

Front 15

Back 15

basal keratinocyte with anchoring filament; hemidesmosomes tie down basal layer to the dermis

Front 16

bullous pemphigold proteins

Back 16

form an aggregate structure that sits down through membrane and projects into extracellular space; in combo w integrins into basal laminae;

autoimmune dz; antibodies target BP180 and BP230 disrupts hemidesmosomes -> loss of epidermal integrity = complemtn activation, mast cell & eosinophil degranulation

Front 17

L-DOPA pathway is precursor for..

Back 17

melanin & catecholamine synthesis

Front 18

UVB

Back 18

causes sunstan or sunburn; bleaches pre-existing melanin in keratinocytes by inducing synthesis of new melanin by melanocytes

Front 19

induction of melanin in melanocytes via melaoncyte stimulating hormone

Back 19

GPCR binds to stimulating hormone -> transcription factor activated (kreb) -> passed our of nucleus -> activates genes important for melanin synthesis

MITF; key player in inducing melanin synthesis; lack of functioning MITF = albinism and premature aging; also found in excess in melanoma

Front 20

Turning on MITF

Back 20

Turns on genes to synthesis tyrosine hydroxylase important for the synthesis of melanin and catecholamines

Front 21

Gricellae Syndrome

Back 21

mutation in myosin 5a gene important for final transport step

Front 22

Langerhans cells

Back 22

monocyte derived; no desmosomes; can leave epidermis to lymphatic system;

Front 23

merkel cells

Back 23

nerve "twig" cut in section at the bottom of the dermis;

Front 24

point: express different kinds of keratin as you go from the basal layer to keratin layer

Back 24

along basal level of stratum; mutations in keratin 5 and 14 is a cause of epidermolysis bullosa simplex; in spiny layer stratum spinosum keratin 1 and 10 (mutations here = epidermolyitc hyperkeratosis); in stratum granulosum keratin 2e and 9 + protein filaggrin (= aggregation of keratin) - lemellar bodies express lipids responsible for cell envelope; defects in2e and 9 (epidermolytic palmoplantar keratoderma)

Front 25

point: different components fall together as cells move upwards; retain claudin-1 and claudin-4;

Back 25

structure of cornified cell envelope is a lipid layer on outersurface generated by lamellar bodies; beneath is involucrin; beneath in small proline rich proteins and loricrin; these are all cross linked together into a weave called transmutaminase; mutations in that causes specific diseases

Front 26

defects in loricrin

Back 26

vohwinkel syndrome and progressive symmetric erythrokeratodermia; lead to structural disruption of corneal layer

Front 27

Back 27

in granulosum layer lamellar bodies and keratinohyaline granules = conc aggregates of granules that are secreted and cross linked