Integument I Flashcards
What is the general organization of the integument?
epidermis, basement membrane, dermis, subcutaneous tissue
What are some synonyms for subcutaneous tissue?
SubQ, superficial fascia, hypodermis
What are the types of epidermal ridges?
primary dermal ridge, interpapillary peg, secondary dermal ridges, dermal papillae
Describe primary dermal ridges
• Related to finger prints • Found everywhere except forehead, external ear, perineum, and scrotum • Formed during 3rd to 4th months of fetal life • Subdivided into two secondary dermal ridges by interpapillary peg
What is the interpapillary peg?
Downward growth of epidermis along crest
describe secondary dermal ridges
• Occur in double rows, branched • Thin collagenous, reticular, and elastic fibers
What are dermal papillae
Upward projections from each secondary dermal ridge
List the integument functions
• Protection from mechanical injury • Prevents dessication • Protects against foreign substances and microorganisms • Protects against UV radiation • Thermoregulation • Regulation of blood pressure (via dermal capillary network) • Excretion of metabolic waste products • Synthesis of provitamin D
Describe thick skin
• Occurs only on palms and soles and is hairless • Epidermis varies from 0.4 to 0.6 mm thick. • Displays all five epidermal layers
Describe thin skin
• Occurs over rest of body • Epidermis varies from 75 to 150 μmm thick. • Thinnest thin skin is on eyelids • Thickest thin skin is on back • Thicker on extensor surfaces than flexor surfaces • Epidermal layers less distinct and lacking stratum lucidum
What are the layers of the stratified squamous epithelium of the epidermis?
• Stratum basale (germinativum) • Stratum spinosum • Stratum granulosum: • Stratum lucidum • Stratum corneum
Which is the deepest layer of the epidermis?
stratum basale
Which layer of the epidermis is represented by only a few cells in thin skin?
stratum granulosum
Which layer of the epidermis is absent in thin skin?
stratum lucidum
Which layer of the epidermis is most superficial?
stratum corneum
Describe stratum basale.
(germinativum) • Deepest • Columnar to high cuboidal keratinocytes • Keratins 5 and 14 (low-molecular weight keratins) • Single layer of cells • Held together by desmosomes • Hemidesmosomes hold layer to basal lamina • High mitotic activity: • Mitotic activity produces stem cells differentiating keratinocytes. • Affected by chemotherapeutic and radiation treatments
Describe stratum spinosum
• Polyhedral-shaped cells (prickle cells) • Keratins 1 and 10 (high molecular weight keratins) • Keratohyalin granules develop • Membrane-coating granules first appear: • Lamellar bodies • Contain lipid, carbohydrate, and hydrolytic enzymes • Tonofibrils • Form intercellular bridges
Describe stratum granulosum
• Multilayered • Keratins 2e and 9 • Flattened nucleated keratinocytes • Keratohyalin aggregates: • Fillagrin induces cross-linkage of keratin filaments by disulfide bonds • No limiting membrane • Membrane-coating granules (lamellar bodies) • Acylglucosylceramide → intercellular spaces • Tonofilaments
Describe stratum lucidum
• Flat keratinocytes lacking nuclei and organelles • Only found in thick skin • Contains eleiden
Describe stratum corneum
• Multilayered (5-50 layers) • Thicker in thick skin • Enucleated, flattened, dead keratinocytes • Cytoplasm replaced by keratin • Cytoplasm contains: • Keratin cross-linked with filaggrin • → cornified cell envelope
List and describe the layers of the cornified cell envelope.
• Extracellular: • Multi-lamellar lipid layer covalently linked to involucrine • Intracellular: • Involucrine • Small proline-rich proteins • Loricrin • Fillagrin and keratin complexes
What are the characteristics of the dermis?
• Dense fibrous irregular connective tissue layer beneath epidermis • Derived from embryonic mesoderm • Induces development of epidermis and epidermal derivatives • Supports epidermis
What are the characteristics of the hypodermis?
• Loose connective tissue that underlies dermis • Corresponds to superficial fascia of gross anatomy • Technically not part of skin • May contain fat cells that can form a thick layer called the panniculus adiposus.
List and describe the two layers of the dermis.
• Papillary layer (closest to epidermis): • Loose CT • Separated from epidermis by basal lamina • Network of fine elastic fibers and abundant capillaries • Reticular layer • Dense irregular CT • Includes fibrocytes, macrophages, and adipocytes
