Final: Lecture 19

Question 0

Integument Epidermal ridges

Answer 0

• Primary dermal ridge: related to finger prints, found everywhere except forehead, external ear, perineum, and scrotum, formed during 3rd to 4th month of fetal life
• Secondary: occur in double rows, branched, thin collagenous, reticular, and elastic fibers
• Dermal papillae: upward projections from each secondary dermal ridge

Question 1

Integument Organization

Answer 1

• Epidermis
• Basement membrane
• Dermis: corresponds to lamina propria of a mucous membrane
• Subcutaneous tissue (synonyms): SubQ, superficial fascia, hypodermis (where you store a lot of body fat)

Question 2

Interpapillary peg

Answer 2

• Subdivides primary into two secondary dermal ridges

* Downward growth of epidermis along crest

Question 3

Think skin

Answer 3

• Occurs only on palms and soles and is hairless
• Epidermis varies from .4 to .6 mm thick
• Displays all five epidermal layers

Question 4

Thin skin

Answer 4

• Occurs over rest of body
• Epidermis varies from 75 to 150 umm thick
• Thinnest over eyelids, thickest thin skin on back
• Thicker on extensor surfaces than flexor surfaces
• Epidermal layers less distinct and lacking stratum lucidum

Question 5

Layers of Epidermis

Answer 5

• Stratified squamous epithelium
• Stratum Basale (germinativum)-deepest
• Stratum spinosum: with basale = stratum Malpighi
• Stratum granulosum: represted by only a few cells in thin skin
• Stratum lucidum: absent in thin
• Stratum corneum: most superficial

Question 6

Stratum Basale (germinativum)

Answer 6

• Deepest, columnar to high cuboidal keratinocytes
• Keratins 5 and 14
• Single layer of cells: held together by desmosomes, Hemidesmosomes hold layer to basal lamina
• High mitotic activity: affected by chemotherapeutic and radiation treatments

Question 7

Stratum spinosum

Answer 7

• Keratins 1 and 10
• Keratohyalin granules develop
• Membrane-coating granules first appear, lamellar bodies
• Tonofibrils: form intercellular bridges

Question 8

Stratum Granulosum

Answer 8

• Mulilayered, keratins 2e and 9
• Flattened nucleated keratinocytes
• Keratohyalin granules: no limiting membrane, provide matrix for keratin granule (filaggrin)
• Membrane-coating granules (lamellar bodies): Acylglucosylceramide–>intercellular spaces
• Tonofilaments

Question 9

Stratum Lucidum

Answer 9

• Only found in thick skin

* Contains eleiden

Question 10

Stratum corneum

Answer 10

• Multilayered, thicker in thick skin
• Enucleated, flattened, dead keratinocytes
• Cytoplasm replaced by keratin, contains keratin cross-linked with filaggrin–>cornified cell envelope

Question 11

Cornified cell envelope

Answer 11

• Extracellular: multi-lamellar lipid layer covalently linked to involucrine
• Intracellular: involucrine, small proline-rich proteins, loricrin, fillagrin and keratin complexes

Question 12

Dermis

Answer 12

• Induces development of epidermis and epidermal derivatives, supports epidermis
• Papillary layer (closest to epidermis): loose CT, separated from epidermis by basal lamina, network of fine elastic fibers and abundant capillaires
• Reticular layer: dense irregular CT, includes fibrocytes, macrophages, and adipocytes
• Capillaries located in the dermis, supply epidermis**

Question 13

Langerhans cells

Answer 13

• Dendritic cells
• From monocytes
• Antigen-presenting cells
• Migrate from epidermis to lymph nodes
• Birbeck granules

Question 14

Merkel cells

Answer 14

• Mechanoreceptors
• Usually in stratum germinativum
• Contain catecholamine-like granules

Question 15

Melanocytes

Answer 15

• Derived from melanoblasts
• Do not form desomsome attachments in epidermis
• Inject melanin granules into keratinocytes
• Pathway for melanin formation: Thyrosine–>3,4-dihydroxyphenylalanine (DOPA)–>dopaquinone–>melanin
• Requires tyrosinase

Question 16

Development of epidermis and dermis

Answer 16

• Single layer of ectodermal cells
• Divide during sixth week to form: periderm, inner cuboidal germinal layer
• Dermis is derived from mesoderm

Question 17

Sebaceous Glands

Answer 17

• Holocrine glands
• Continuously produce sebum, released into hair follicle
• Growth is stimulated at puberty by sex hormones

Question 18

Merocrine sweat glands

Answer 18

• Coiled secretory portions: lined with simple epithelium, apical dark secretory cells secrete glycoproteins, basal clear cells secrete water and electrolytes, myoepithelial cells
• Duct system consists of stratified cuboidal epithelium except in epidermis
• Cholinergic endings

Question 19

Apocrine sweat glands

Answer 19

• Found in labia majora, areola, and axillary and anal regions
• Secretions are thicker and more viscous than merocrine types
• Excretory duct opens into hair follicles
• Adrenergic innervation
• Special types: ceruminous glands and glands of Moll

Question 20

Keratinocyte Stem Cells

Answer 20

• These cells can reestablish epidermis in severely burned patients
• Migration pathway: bulb-epidermis stem cell pathway, bulb-sebaceous gland stem cell pathway, bulb-hair stem cell pathway
• Signaling pathway: Wnt signaling pathway, and Notch signaling pathway