Lecture 26: Integument

Question 1

Primary dermal ridge

Answer 1

Related to finger prints, found everywhere except forehead, external ear, perineum, scrotum

Question 2

Interpapillary peg

Answer 2

Downward growth of epidermis along crest

Question 3

Secondary dermal ridge

Answer 3

Occurs in double rows, branched; made up of thin collagenous, reticular, and elastic fibers

Question 4

Dermal papillae

Answer 4

Upward projections from each secondary dermal ridge

Question 5

Thick skin

Answer 5

Occurs only on palms, soles and is hairless - displays all five epidermal layers

Question 6

Thin skin

Answer 6

Occurs everywhere besides where thick skin is, thinnest on eyelids/thickest on back; thicker on extensor surfaces than flexor surfaces; epidermal layers less distinct and lacking stratum lucidum

Question 7

Stratum basale

Answer 7

deepest layer of epidermis; columnar to high cuboidal epithelium; single layer of cells containing keratins 5 and 14; high mitotic activity

Question 8

Stratum spinosum

Answer 8

Polyhedral-shaped prickle cells containing keratins 1 and 10; appearance of lamellar bodies and tonofibrils

Question 9

Stratum granulosum

Answer 9

Multilayered flattened nucleated keratinocytes with keratins 2e and 9; contain fillagrin, lamellar bodies, tonofilaments

Question 10

Stratum lucidum

Answer 10

Flat keratinocytes w/o nuclei and organelles; ONLY in thick skin, contain eleiden

Question 11

Stratum corneum

Answer 11

Multilayered - thicker in thick skin, enucleated/flattened/dead keratinocytes, cytoplasm replaced by keratin; cytoplasm contains keratin and cross-linked fillagrin

Question 12

Cornified cell envelope

Answer 12

Extracellular layer has multi-lamellar lipid layer covalently linked to involucrine; intracellular layer contains involucrine, small proline-rich proteins, loricrin, fillagrin and keratin complexes

Question 13

Papillary layer of dermis

Answer 13

Closest to epidermis, loose connective tissue; network of elastic fibers and capillaries

Question 14

Reticular layer of dermis

Answer 14

Deeper, dense irregular connective tissue containing fibrocytes, macrophages, and adipocytes

Question 15

Hypodermis

Answer 15

Loose connective tissue underlying dermis which is technically not part of the dermis, may contain panniculus adiposus layer of fat cells

Question 16

Langerhans cells

Answer 16

Resident dendritic cells derived from bone marrow precursor which act as antigen presenting cells working with CD8+ cells; primarily present in stratum spinosum, migrate to lymph nodes

Question 17

Birbeck granule

Answer 17

Part of the Langerhans cell which contains langerin and CD1a which take up and deliver antigens

Question 18

Merkel cells

Answer 18

Mechanoreceptors that act as diffuse neuroendocrine cells and contain catecholamine-like granules; occur usually in stratum germinativum/basale

Question 19

Melanocytes

Answer 19

Derived from melanoblasts, inject melanin granules into keratinocytes

Question 20

Melanin formation

Answer 20

Tyrosine to 3,4-dihydroxyphenylalanine to dopaquinone to melanin - requires tyrosinase

Question 21

What embryonic germ layer is the dermis derived from?

Answer 21

Mesoderm

Question 22

Periderm

Answer 22

Formed from division of ectodermal cells in the sixth week; sloughs off to form vernix caseosa

Question 23

Inner cuboidal germinal layer

Answer 23

Proliferates to form adult layers of epidermis and derivatives such as fingernails, hair buds and toenails