Integumentary System I

Question 1

General organization of integument

Answer 1

• epidermis
• basement membrane
• dermis (corresponds to lamina propria of mucous membrane)
• subcutaneous tissue
• epidermal ridges

Question 2

Primary dermal ridge

Answer 2

• related to finger prints
• everywhere except forehead, exter ear, perineum, scrotum
• formed 3-4 months of fetal life
• divided into two secondary dermal ridges by interpapillary peg

Question 3

Interpapillary peg

Answer 3

• downward growth of epidermis along crest

Question 4

Secondary dermal ridges

Answer 4

• occur in double rows, branched
• thin collagenous, reticular, and elastic fibers
• dermal papillae are upward projections from each secondary dermal ridge

Question 5

Integumentary funx

Answer 5

protection from: mechanical injury, foreign subs, UV radiation

• prevents dessication
• thermoregulation
• regulation of BP (via caps)
• excretion of metabolic waste products
• Vitamin D synth

Question 6

Thick skin

Answer 6

• occurs only on palms/soles; hairless
• epidermis between 0.4-0.6 mm
• displays all 5 epi layers

Question 7

Thin skin

Answer 7

• occurs everywhere except palms/soles
• thinnest on eyelids
• thickest on back
• thicker on extensor surfaces than flexor surfaces
• epi layers less distinct, lacking stratum lucidum

Question 8

Layers of epidermis

Answer 8

(stratified squam epi)
deepest --> most superficial
-  STRATUM BASALE 
(germinativium)
-  STRATUM SPINOSUM
-  STRATUM GRANULOSUM
-  STRATUM LUCIDUM
-  STRATUM CORNEUM

Question 9

Stratum basale (germinativium)

Answer 9

• columnar to high cuboidal keratinocytes
• low molecular weight Keratins 5 and 14
• single layer of cells held together by desmosomes
• hemidesmosomes hold layer to basal lamina
• high mitotic activity producing stem cells that differentiate keratinocytes; affected by chemo/radiation

Question 10

Stratum spinosum

Answer 10

• polyhedral shaped “prickle cells”
• high molecular weight Keratins 1 and 10
• keratohyalin granules develop
• membrane coating granules first appear; lamellar bodies containing lipid, carb, hydrolytic enzymes
• tonofilaments from intercellular bridges

Question 11

Stratum granulosum

Answer 11

• multilayered
• Keratins 2 and 9
• flattened nucleated keratinocytes
• keratohyalin aggregates: fillagrin induces x-linkage of keratin filaments by disulfide bonds; no limiting membrane
• membrane coating granules (lamellar bodies): acylglucosylceramide – > intercellular spaces
• tonofilaments

Question 12

Stratum lucidum

Answer 12

• flat keratinocytes lacking nuclei and organelles
• only in thick skin
• contains eleiden

Question 13

Stratum corneum

Answer 13

• multilayered (5 - 50 layers)
• thicker in thick skin
• enucleated, flattened, dead keratinocytes
• cytoplasm replaced by keratin
• cytoplasm contains: keratin x-linked w/fillagrin – > cornified cell envelope

Question 14

Cornified cell envelope

Answer 14

extracellular: multi-layered lipid layer covalently linked to involucrine
intracellular: involucrine, small proline-rich proteins, loricrin, fillagrin and keratin complexes

Question 15

Dermis characteristics

Answer 15

• dense fibrous irregular connective tissue layer beneath epidermis
• derived from embryo mesoderm
• induces development of epidermis and derivatives
• supports epidermis

Question 16

Hypodermis characteristics

Answer 16

• loose connective tissue that underlies dermis
• corresponds to superficial fascia of gross anatomy
• not technically part of skin
• may contain fat cells that can form a thick layer called panniculus adiposus

Question 17

Layers of dermis

Answer 17

• papillary layer (closest to epi): loose CT, separated from epi by basal lamina, network of elastic fibers and abundant capillaries
• reticular layer: dense irregular CT, includes fibrocytes, macrophages, and adipocytes

Question 18

Langherans cells

Answer 18

= dendritic cells

• from monocytes
• antigen-presenting cells
• primarily found in stratum spinosum
• migrate from epidermis to lymph nodes
• Birbeck granules

Question 19

Merkel cells

Answer 19

• mechanoreceptors
• act as diffuse neuroendocrine cells
• usually in stratum basale (germinativium)
• contain catecholamine-like granules

Question 20

Melanocytes

Answer 20

• derived from melanoblasts
• do not form desmosome attachments in epidermis
• inject melanin granules into keratinocytes
• pathway for melanin formation:
  Tyrosine –> 3,4-DOPA –> dopaquinone –> melanin
  *requires tyrosinase