Integument Histology Flashcards
Layers of the epidermis (5)
Statum corneum Stratum lucidem Statum granulosum Stratum spinosum Stratum basale
Epidermis is comprised of (4)
Keratinocytes
Melanocytes
Merkel cells
Langerhans cells
Thick vs. thin skin
Thick only on palms and soles. Has 5 layers.
Thin is widespread but only has 4 layers (no stratum lucidem).
Stratum basale
Bottom layer. Single layer of keratinocytes.
Mitotically active layer of cuboidal/low columnar cells.
Bound apically by desmosomes and basally by hemidesmosomes.
Stratum spinosum
Several cell layers thick.
Layer thickens with pressure to produce corns and calluses.
Stratum granulosum
Thickest layer of non-keratinized portion of epidermis.
Has keratinocytes with keratohyalin granules.
Irregularly shaped and variable in size.
Keratohyalin granules
Found in keratinocytes.
Basophilic, cysteine and histidine-rich proteins.
Precursor to filaggrin.
Stratum corneum
Anucleated w/o organelles.
Filled with mature keratin.
PM forms water barrier.
Continuously shed.
Stratum lucidem
Subdivision of stratum corneum.
Seen well only in thick skin.
Poorly stained.
No organelles or nuclei.
Keratinocytes
Produce keratin and participate in the epidermal water barrier.
Will produce cornified cells full of keratinization.
Undergo keratinization and desquamation.
Basal cells
Synthesize intermediate filaments. Grouped into bundles called tonofibrils.
Spinous cells
Keratin synthesis coninues, begin synthesis of keratohyalin granules and glycolipid containing lamellar bodies.
Granular cells
Discharge lamellar bodies to form water barrier.
Keratohyalin granules w/ flaggrin present, which promotes production of tonofibrils.
Now cells are cornified.
Epidermal differentiation and replacement
Initiated by division of stem cells in SB.
New cells undergo divisions in SB.
Move upward as the differentiate into keratinized cells.
Eventually lost by exfoliation.
Epidermal-melanin unit
One melanocyte maintains association with a specific number of keratinocytes (1:36).
Langerhans cells
APCs thet provide defense against pathogens.
Found in stratum spinosum.
Merkel cells
Cutaneous sensation (fingertips). Found in stratum basale.
Dermal-epidermal junction
Dermal papillae project into epidermis, complemented by epidermal ridges.
Layers of dermis (2)
Papillary layer: loose CT beneath epidermis.
Includes dermal papilla and ridges.
Has vasculature and nerve endings.
Reticular layer: deep to papillary layer.
Thicker and less cellular.
Forms regular lines of tension.
Hypodermis
Subcutaneous fascia.
Meissner’s corpuscle
Sensitive touch receptors.
Present in dermal papillae just beneath epidermis.
Pacinian corpuscle
Large ovoid structures that detect pressur or vibration.
Found in fingertips, joints, periosteum, internal organs.
Free nerve endings
Terminate in SG.
Does not have CT.
Modalities in fine touch, heat, cold, and pain.
Surround most hair follicles.
Sebaceous glands
Produce sebum via holocrine secretion.
Sebum discharged into infundibulum forming pilosebaceous canal.
Eccrine (merocrine) sweat glands
Found throughout skin.
Myoepithelial cells facilitate exulsions of secretion.
Duct is stratified cuboidal.
Apocrine sweat glands
Uses merocrine secretion to secrete proteins, carbs, ammonia.
Has myoepitheial cells.
Duct is stratified cuboidal.
Subject to adrenergic regulation.
Melanin production
Reactions occur in premelanosomes in melanocyte. Once enough melanin is produced, they become melanosomes. Melanin is donated to keratinocytes via phagocytosis.
