Integument Flashcards
Stratum Spinosum
- second epidermal layer, several cell layers thick
- contains polyhedral keratinocytes with spiny processes
- layer thicken with pressure to produce corns & calluses
Stratum Granulosum
- third epidermal layer, thickest layer of non-keratinized cells
- layer where keratin begins to be produced, cells start to flatten out in shape (irregularly shaped, variable in size)
- basophilic, cysteine & histidine rich proteins
- are precursors to filagrin, which assemble keratin into bundles
Stratum Corneum
- fourth epidermal layer, annucleate (no nucleus and organelles)
- filled almost entirely with mature keratin
- plasma membrane coated with lipids, forming water barrier of epidermis
- continuously shed, (thick skin = 15-40 layers, thin skin = 10-20 layers)
Stratum Lucidium
- subdivision of stratum corneum
- only seen well in thick skin
- typically poorly stained, translucent band of cells (lucid = clear)
- derived from Corneum, no organelles or nuclei
What is the predominant cell type of the epidermis?
Keratinocytes
- they produce keratin, make up 85% of cells
- they participate in the epidermal water barrier
- will produce cornified cells, full of keratin, undergo keratinization and desquamation
Melanocytes
- neural crest derived, scattered along stratum basale
- produce melanin and transfer it to keratinocytes
What is an epidermal-melanin unit?
one melanocyte maintains an association with a specific number of keratinocytes (1:36)
Langerhans Cells
- antigen-presenting cells (APCs) that provide defense against pathogens
- identifiable in stratum spinosum, have pale cytoplasm with long processes
- they develop from monocyte precursors
- antigens are phagocytized and displayed on the cell surface, cell migrates to a nearby lymph node to activate T-lymphocyte
Merkel Cells
- epidermal cells that function in cutaneous sensation
- provide acute sensory perception in the fingertips (are associated with nerve endings)
- reside in stratum basale
Layers of the Dermis
- Papillary layer: loose CT immediately beneth epidermis, includes dermal papilla and ridges, contains vasculature and nerve endings
- Reticular layer: deep to papillary, thicker and less cellular, thick irregular bundles of Type I collagen and coarse elastic fibers, form Langer’s Lines (regular lines of tension, where surgical incisions should follow to allow for optimal healing)
Hypodermis
- subcutaneous fascia
- adipose tissue, varies in thickness/body region
- energy storage site, insulation
- Arrector pili muscles -> hair follicles
Meissner’s Corpuscle
- touch receptors responsive to low-frequency stimuli (like reading brail)
- tapered cylinders oriented perpendicular to the skin surface
- present in dermal papilae just beneath the epidermis
Pacinian Corpuscle
- looks like an onion, large ovoid structures found in the deeper dermis and hypodermis (numberour layers & thickness)
- found in fingertips, joints, periosteum and internal organs
- detect pressure or vibration
- myelinated nerve ending surrounded by a capsule sturucture
Free Nerve Endings
- terminate in the stratum granulosm
- “free” in that they lack connective tissue
- detect fine touch (not vibration), heat, cold and pain
- free dermal endings surround most hair follicles (sensitive to hair movement and mechanoreceptors)
Sebaceous Glands
- several glands per follicle
- adundant on face & scalp
- produce a lipid mixture, sebrum via holocrine secretion
- waxy mix of tryglycerides and cholesterol (lubricates, softens and waterproofs skin)
- sebum discharged into infundibulum (hair follicle), forming pilosebaceous canal
Types of Sudoriferous Glands?
- Eccrine (merocrine): coiled glands distributed over the entire body surface, except lips and external genetalia
- Apocrine: axilla, areola and nipple, skin around the anus and external genitalia, ceruminous glands of ear canal
Eccrine Sweat Glands
- simple, coiled glands found extensively throughout skin
- duct is stratified cuboidal
- myoepithelial cells faciliate expulsion of secretions (squeezing out sweat)
- temperature regulation (via evaporation from body surface)
- sweat subject to cholinergic regulation
Apocrine Sweat Glands
- large-lumen, tubular glands that act like modified smooth muscle
- duct is stratified cuboidal
- use merocrine secretion (protein, carb and ammonia rich secretion that is odorless until mixed with bacteria = body odor)
- subject to adrenergic regulation
Hair Follicles
Infundibulum: extends from surface opening to opening of sebaceous gland
Follicular bulge: near insertion of arrector pili m, contain epidermal stem cells
bulb: expanded inferior segment, invaginated by vascularized loose CT (the dermal papilla)
Hair matrix: consists of matrix cells, cells of rapid divide/differentiate, accounts for hair growth
What are the layers of the hair shaft?
Medulla: central part of the shaft, column of large, loosely connected keratinized cells
Cortex: largest layer, located outside of medulla, cells filled with kard keratin intermediate filaments
Cuticle: outermost layer, several layers of overlapping, keratinized squamous cells
What are the layers of a nail?
- highly keratinize cells on a bed of epidermis (nail bed)
Nail root: the most proximal region, covers nails matrix
Nail matrix: stem cells divide and form keratinocytes, nail plate remains attached to nail bed, pushed forward by continuous growth
Lunula: crescent-shaped white area near nail matrix
Cuticle: extension of skin covering nail root
