9/ 12 Dennis_PPT_Integument Flashcards
Integument
- Largest organ in the body (15-20% of body weight)
- Provides: • Protection: physical, chemical, & biological barrier • Sensation & excretion • Thermoregulation • Synthesis of Vitamin D3
- Epidermis & dermis • Hypodermis = subcutaneous fascia
The Epidermis
The epidermis composition
What are the four main cells in the epidermis?
• Keratinocytes • Melanocytes • Merkel cells • Langerhans cells
Two types of skins, what is their distribution?
Epidermis: Stratum Basale
- Single-layer of _____ w/stem cells interspersed
- Mitotically active, cuboidal/low columnar cells
- Contains _____
- Bound apically by via _____
- Bound basally by _____
keratinocytes
melanin
desmosomes
hemidesmosomes
Epidermis: Stratum Spinosum
- Several cell layers thick
- Contains ______ with spiny processes
- Layer thickens with pressure to produce ____ and ___
polyhedral keratinocytes
corns & calluses
Epidermis: Stratum Granulosum
- Thickest layer of _____ portion of epidermis
- Keratinocytes contain keratohyalin granules
- Basophilic, cystine- & histadine-rich proteins
- Precursor to _____ , assembles keratin into bundles
- Irregularly shaped, variable in size
non-keratinized
flaggrin
Epidermis: Stratum Corneum
- Anucleate cells, lose nucleus & organelles
- Filled almost entirely with mature ____
- Plasma membrane coated w/EC layer of lipids → forms ___ barrier of epidermis
keratin
water
Epidermis: Stratum Lucidum
- Subdivision of ____
- Only well seen in ___ skin
- Typically poorly stained, translucent band of cells
- No organelles or nuclei
stratum corneum
thick
Keratinocytes
Predominant cell type of the epidermis
- Produce keratins, 85% of cells
- Participate in the _____
- Will produce ‘cornified’ cells, full of keratin
- Undergo keratinization & desquamation
epidermal water barrier
Keratinization & Desquamation
• Basal cell:
synthesize intermediate (keratin) filaments; grouped into bundles, _____
• Spinous cell:
keratin synthesis continues, begin synthesis of keratohyalin granules & glycolipid-containing lamellar bodies
- Granular cells:
- Discharge lamellar bodies → water barrier
- Keratohyalin granules w/filaggrin present
- Filaggrin further promotes aggregation of keratin filaments (tonofibrils)
- now cornified cells → keratinized
tonofibrils
Epidermal Differentiation & Replacement
- Epidermal cell replacement is initiated by the division of stem cells in the _____
- New cells undergo divisions in the stratum basale
- Move upward as they differentiate into keratinized cells
- Eventually are lost by exfoliation on skin surface
stratum basale
Melanocytes
- _____-derived, scattered along stratum basale
- Produce melanin & transfers it to keratinocytes
- Melanin: pigment protein that protects nuclei from _____
Epidermal-melanin unit: one melanocyte maintains an association with a specific number of keratinocytes ____(ratio)
Neural crest
UV radiation
(1:36)
Melanin Production
- Oxidation of _____ into DOPA (3,4- dihydroxyphenylalanine) by _____
- DOPA is polymerized into melanin
- Enzyme is UV sensitive
- Reactions occur in membrane-bound organelles, ______
- As more melanin is produced premelanosomes → _____
- Extend into cell processes
- Transferred to keratinocytes via ______→ ‘pigment donation’
tyrosine and tyrosinase
premelanosomes
melanosome
phagocytosis
Langerhans Cells
- Antigen-presenting cells (APCs) that provide defense against pathogens
- Develop from monocyte precursor
- Antigen is phagocytized & displayed on the cell surface
- Cell migrates to a nearby lymph node to activate T-lymphocytes
- Identifiable in _____
- Pale cytoplasm with long processes
stratum spinosum
Merkel Cells
- Epidermal cells that function in _____
- Provide acute sensory perception (fingertips)
- Reside in the ______
- Associated with nerve endings
- Merkel cell carcinoma (MCC): • Rare, but highly aggressive form of skin cancer • Merkel cells undergo uncontrolled proliferation
cutaneous sensation
stratum basale
Dermal-Epidermal Junction
- Uneven boundary except in the thinnest skin
- Finger-like _____, project into epidermis
- Complemented by epidermal protrusions, ______
- Increased in size at sites of mechanical stress
- Hemidesmosomes provide tight interface
- Focal adhesions are also present
dermal papillae
epidermal (rete) ridges
Layers of the Dermis
what are the two layers? Which layer has the langer’s lines?
- Papillary layer:
- Loose CT immediately beneath epidermis • Thinner collagen fibers, elastic fibers • Includes dermal papilla & ridges • Vasculature & nerve endings
• Reticular layer:
• Deep to papillary layer • Thicker & less cellular • Thick, irregular bundles of type I collagen & coarse elastic fibers • Form regular lines of tension, Langer’s lines
Hypodermis (Subcutaneous Fascia)
- Adipose tissue (panniculus adiposus)
- Varies in thickness/body region
- Energy storage site, insulation
- Arrector pili muscles → ______
hair follicles
integument summary
Meissner’s Corpuscle
- Touch receptors responsive to____
- Tapered cylinders oriented _____ to the skin surface
- Present in the _____ just beneath the epidermis
low-frequency stimuli
perpendicular
dermal papillae
Pacinian Corpuscle
- Large, ovoid structures found in the deeper ____and____
- Fingertips, joints, periosteum, & internal organs
- Detects ____or____
- Myelinated nerve ending surrounded by a capsule structure
dermis and hypodermis
pressure or vibration
Free Nerve Endings
- Terminate in the _____
- “Free” in that they lack ___
- Modalities: fine touch, heat, cold, & pain
- Free dermal endings surround most hair follicles
- Sensitive to ____ movement
- Serve as _______
stratum granulosum
CT
hair
mechanoreceptors
