Integument I

Question 1

Primary Dermal Ridge

Answer 1

• Related to finger prints
• Found everywhere except forehead, external ear, perineum, and scrotum
• Formed during 3rd to 4th months of fetal life
• Subdivided into 2 secondary dermal ridges by interpapillary peg

Question 2

Interpapillary peg

Answer 2

Downward growth of epidermis along crest

Question 3

Secondary dermal ridge

Answer 3

Occur in double rows, branched

Thin collagenous, reticular, and elastic fibers

Question 4

Dermal papillae

Answer 4

Upward projections from each secondary dermal ridge

Question 5

Function of Integument

Answer 5

Protection from mechanical injury, prevents desiccation, protects against foreign substances and microorganisms, protects against UV radiation, thermoregulation, regulation of bp (via dermal capillary network), excretion of metabolic waste products, synthesis of provitamin D

Question 6

Thick skin

Answer 6

Occurs only on palms and soles and is hairless
Epidermis varies from 0.4 to 0.6 mm thick
Displays all 5 epidermal layers

Question 7

Thin Skin

Answer 7

Occurs on rest of body
Epidermis varies from 75-150 micrometers thick
Thinnest thin skin - eyelids
Thickest thin skin - back
Thicker on extensor surfaces than flexor surfaces
Epidermal layers less distinct and lacking stratum lucidum.

Question 8

Dermis

Answer 8

Corresponds to lamina propria of a mucous membrane; .5 to 3mm thick

Question 9

List the epithelial layers of thick skin in the correct order.

Answer 9

Stratum Basale (germinativum) 
Stratum spinosum 
Stratum granulosum 
stratum lucidum 
stratum corneum

Question 10

Stratum Basale (germinativum)

Answer 10

Columnar to high cuboidal keratinocytes - keratins 5 and 14 (low molecular weight)
Only layer with hemidesmosomes. High mitotic activity.

Question 11

Stratum Spinosum

Answer 11

Polyhedral shaped (prickle cells). Keratins 1 and 10 (high molecular weight). Keratohyalin granules, membrane coating granules, and tonofibrils.

Question 12

Stratum Granulosum

Answer 12

Keratins 2e and 9. Flattened nucleated keratinocytes. Tonofilaments.

Question 13

Stratum Lucidum

Answer 13

Flat keratinocytes lacking nuclei and organelles; only found in thick skin. Contains eleiden

Question 14

Stratum Corneum

Answer 14

Thicker in thick skin. Enucleated, flattened, dead keratinocytes. Cytoplasm replaced by keratin. Cornified cell envelope.

Question 15

Thick skin

Answer 15

occurs only in palms and soles and is hairless; epidermis varies from 0.4-0.6 mm thick. Displays all 5 epidermal layers.

Question 16

Thin skin

Answer 16

Epidermis varies from 75-150 um thick. Thicker on extensor surfaces than flexor surfaces. Epidermal layers are less distinct and lacking stratum lucidum.

Question 17

Where is the thinnest thin skin?

Answer 17

eyelids

Question 18

Where is the thickest thin skin?

Answer 18

back

Question 19

Keratinization

Answer 19

1. lipids are covalently linked to involucrin forming epidermal permeability barrier.
2. Cornified cell envelope is a specialized structure that reinforces the plasma membrane of keratinocytes when reaching final stage of differentiation. Contains involucrin, small proline rich proteins, and loricrin.
3. Keratin filaments, aggregated by fillagrin interact w/ the inner side of pm to form cell envelope.
4. Tight juntions in the stratum granulosum (w/ claudins 1 and 4) are also components of the permeability layer.

Question 20

Dermis Characteristics

Answer 20

Dense fibrous irregular CT beneath epidermis; induces development of epidermis and epidermal derivatives - supports epidermis

Question 21

What is dermis derived from?

Answer 21

embryonic mesoderm

Question 22

Hypodermis characteristics

Answer 22

Loose CT that underlies dermis - corresponds to superficial fascia - technically not part of skin. May contain fat cells that can form panniculus adiposus.

Question 23

2 layers of the dermis

Answer 23

papillary and reticular layer

Question 24

Papillary layer (closest to epidermis)

Answer 24

Loose CT; separated from epidermis by basal lamina. Network of fine elastic fibers and abundant capillaries.

Question 25

Reticular Layer

Answer 25

Dense irregular CT; include fibrocytes, macrophages, and adipocytes.

Question 26

Langerhans cells

Answer 26

dendritic cells (antigen presenting cells); from monocytes - primarily in the stratum spinosum - migrate from epidermis to lymph nodes - birbeck granules

Question 27

Merkel Cells

Answer 27

Mechanoreceptors; may also act as diffuse neuroendocrine cells; usually in germinativum; contain catecholamine-like granules

Question 28

Melanocytes

Answer 28

Derived from melanoblasts; do not form desmosome attachments in epidermis so somewhat mobile; inject melanin granules into keratinocytes; the pathway for melanin formation is tyrosine -> DOPA -> dopaquinone -> malanin.

Question 29

Epidermis starts as?

Answer 29

single layer of ectodermal cells

Question 30

What week of embryonic development does the epidermis divide?

Answer 30

6th week - forms periderm and inner cuboidal germinal layer

Question 31

What is dermis derived from?

Answer 31

mesoderm