Integument Histo Flashcards
Integument
Largest organ in the body Epidermis and dermis Protection Secretion/absorption Makes vitamin D3 Thermoregulation
Epidermis
Keratinized Stratified squamous ET Stratum corneum Stratum lucidum (thick skin) Stratum granulosum Stratum spinosum Stratum basale Keratinocytes Melanocytes Langherhan’s cells Merkel cells
Stratum basale
Deepest epidermal layer 1 row of keratinocytes with stem cells interspersed Contains melanocytes Contains Merkel cells Mitotically active Bound apically via desmosomes Bound basally via hemidesmosomes
Stratum spinosum
Many cell layers thick
Has keratinocytes
Gets thickened to form calluses and corns
Stratum granulosum
Thickest nonkeratinized layer
Keratinocytes have keratohyaline granules, the precursor to filaggrin
Filaggrin makes keratin into bundles
Irregularly shaped, variable in size
Stratum lucidum
Only in thick skin
No organelles or nuclei
Stains very light (almost transparent)
Right under stratum corneum
Stratum corneum
Thickest layer with keratin No organelles or nuclei Form water barrier of epidermis via lipids on plasma membrane Continuously shed Thicker in thick skin
Keratinocytes
Contain keratin
Participate in the epidermal water barrier
Participate in keratinization and desquamation (shedding)
Keratinization
Basal cell: contains intermediate keratin filaments held together in tonofibrils
Spinous cell: keratin synthesis still occurring; keratohyaline granules are being produced and lamellar bodies
Granular cells: discharge of lamellar bodies—>water barrier
Filaggrin further promotes aggregation of keratin filaments
Now cornified cells—>keratinized
Process is pH dependent: more superficial, lower pH
Melanocytes
Produce melanin, an enzyme that protects cells from UV radiation
Start out in premalanosomes—>melanosomes
Melanosomes extend into the cell processes and melanin is transferred to keratinocytes via phagocytosis “pigment donation”
Tyrosine—>DOPA via tyrosinase
DOPA—>melanin
Epidermal-melanin unit: 1 melanin per 36 keratinocytes
Langerhan’s cells
APC’s that are derived from monocytes
Most noticeable in the stratum spinosum layer
Antigen is phagocytized and displayed on the cell surface
Activates lymphocytes
Merkel cells
In stratum basale
Acute sensory perception
Associated with nerve endings
Merkel cell carcinoma: uncontrolled proliferation of merkel cells
Dermal-Epidermal junction
Dermal papillae
Epidermal ridges
Hemidesmosomes
Focal adhesions
Layers of the dermis
Reticular layer
Papillary layer
Papillary layer
Right underneath the epidermis Most superficial is loose areolar CT Rest is dense irregular CT Thinner collagen fibers, elastic fibers Vasculature and nerve endings
Reticular layer
Dense irregular CT
Deep to papillary layer
Thicker and less cellular
Langer’s lines-regular lines of tension
Hypodermis
Subcutaneous fascia
Deepest layer
Not true Integument
Adipose tissue
Meissner’s corpuscles
In dermal papillae
Touch receptors responsive to low frequency stimuli
Pacinian corpuscles
In dermis or hypodermis
Round (looks like onion)
Responsive to pressure and vibrations
Fingerprints, joints, internal organs
Free nerve endings
Free in that they are not surrounded by CT
Stop in the stratum granulosum
Fine touch, heat, cold, pain
By hair follicles
Sebaceous glands
Near hair follicles
Holocrine secretion
Secrete sebum made of triglycerides and cholesterol
Lubricate and soften skin
Water barrier
Pilosebaceous canal-sebum discharged into the hair follicle
Sweat (sudoriferous) glands
Eccrine (merocrine) and apocrine
Eccrine sweat glands
All around body except for lips and external genitalia Small lumen Secrete via merocrine/eccrine secretion Myoepithelial cells cause secretion Water, uric acid, ammonia in secretion Coiled glands Ducts are stratified cuboidal Temp regulation via cooling Cholinergic regulation
Apocrine sweat glands
Areola, anus, axilla Large lumen Nervous sweat Contains salt, proteins, carbs in secretion Myoepithelial cells Secrete via merocrine secretion Andrenergic regulation
Infundibulum
Hair follicle
From sebaceous gland to opening of surface
Follicular bulge
Contains stem cells
Near arrector pili muscle
Bulb
Deepest part of hair follicle
Contains invagination where dermal papillae are
Hair matrix
Contain matrix cells that divide rapidly
Count for hair growth
Medulla of hair shaft
Loose arrangement of keratin fibers
Innermost part
Cortex of hair shaft
Surrounds medulla
Hard intermediate keratin filaments
Largest layer
Cuticle
Outermost layer of hair shaft
Several layers of overlapping keratinized squamous cells
Nail
Highly keratinized cells on a bed of epidermis
Nail root
Most proximal region, covers nail 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 are near nail matrix
Cuticle
Extension of skin covering nail root
