Exam 3: Integument Flashcards
Integument
Covering
includes skin, sweat glands, sebaceous glands, hair, and nails
Largest organ
Skin functions
Protection from microorganisms and dehydration
Regulation of body temperature - sweat
Reception by sensory nerve endings for touch, pressure, pain, temperature, and proprioception
Absorption of UV radiation to form vitamin D
Excretion by sweat glands
Thick skin
Covers palms and soles
Does not have hair follicles, arrector pili muscles, or sebaceous glands; does have sweat glands
Thin skin
Covers most of body
Has hair follicles, arrector pili muscles, sebaceous glands, and sweat glands
Thickness of skin refers to
thickness of the epidermis layer
Skin layers
Epidermis and Dermis
Epidermis is the
epithelial layer of skin
Epidermis arises from
ectoderm
Epidermis consists of
stratified squamous keratinized epithelium
Epidermal ridges (rete ridges)
project into dermis to increase epidermal surface area and adhere it to dermis
Epidermis contains
sensory nerve endings, but no vasculature - gets nutrients from dermal capillaries
Cell types present in epidermis
Keratinocytes, Nonkeratinocytes (Langerhans Cells, Merkel Cells, Melanocytes)
Keratinocytes
Epithelial cells in epidermis
Most common cell type
Mitotic activity in basal layers allow for skin renewal
Fill with keratin filaments as approach surface
Langerhans Cells (Dendritic Cells)
Defense cells in epidermis
Reside mainly in stratum spinosum
Have long, thin cytoplasmic processes which extend into intercellular space - form white halo around nucleus
Langerhans cells are derived from
precursors in the bone marrow
They pass into bloodstream and travel to skin
When reach epidermis they differentiate into Langerhans cells
Langerhans cells function by
Processing antigens that enter skin - antigen is phagocytized, and attached to surface of cell
Cell travels to lymph node where antigen-presenting cells interact with lymphocytes
Birbeck granules
look like rods and vesicles
Unique to Langerhans cells
Involved in defense
Langerhans cells are mostly found in
Stratum spinosum
Merkel Cells
mechanoreceptors in epidermis
Relay fine touch sensation - texture and shape of objects
Merkel cells are found mainly in
Keratinocytes of stratum basale
Numerous in fingertips
Merkel cell-neurite complexes
unmyelinated nerve terminals approach merkel cells to take away touch sensation
Melanocytes
protect DNA of skin
synthesize pigment melanin and share it with neighboring keratinocytes
Melanocytes arise from
neural crest cells
Melanocytes reside between
cells in the stratum basale and superficial dermis
Their processes extend into the intercellular space of the stratum spinosum
Melanocytes synthesize
tyrosinase in their rER, which is packaged by the Golgi into melanosomes. Tyrosine is transported into melanosomes where tyrosinase converts it to melanin
Pigmentation of the skin is due to
tyrosinase activity, number of melanin granules, size, distribution, and rate of breakdown - not numbers of functional melanocytes (total number is same for all races)
Strata of thick skin (outermost to innermost)
Stratum Corneum, Stratum Lucidum, Stratum Granulosum, Stratum Spinosum,
Stratum Basale
Vitiligo
decrease or complete loss of melanocytes
Autoimmunity or self-destruction of melanocytes
Albinism
Melanocytes are present but do not synthesize melanine - defect or absence of tyrosinase
Stratum Corneum
Outermost layer of thick skin epidermis
Flattened, desiccated, keratinized, dead cells. Thick layer - becomes thicker in areas that have an unusual amounts of friction = callus formation
Stratum Corneum functions
as protection
Stratum Corneum contain
Keratin filaments and amorphous matrix
No nuclei or organelles in cells
No desmosomes between cells of surface layers = at surface cells can come off (desquamate)
Deeper cells have desmosomes
Stratum Lucidum
Layer under Stratum Corneum Subdivision of stratum corneum Light staining layer No organelles or nuclei - dead cellular material Contain keratin filaments Not visible in thin skin
Function of stratum lucidum
protection
Stratum Granulosum
middle layer of epidermis
3 - 4 layers Diamond shaped cells contain nuclei, but nuclei are starting to die
Contain many granules (Keratohyalin and Membrane coating granules)
Keratohyalin granules
consist of soft keratin proteins
Membrane coating granules (lamellar bodies)
contain lipids
Exocytosis of lipid substance forms sheets of waterproof material - barrier that prevents water from entering, but also prevents diffusion of nutrients in extracellular space from reaching superficial layers of cells - die of starvation
Function of Stratum Granulosum
Waterproof body
Stratum Spinosum
Deep to stratum granulosum
Thickest stratum
Cells have interdigitating processes (intercellular bridges) with desmosomes
Contain membrane-coating granules and Langerhans cells
Tonofilaments
bundles of intermediate filaments make of cytokeratin.
Form bundles in cells of upper layers of stratum spinosum
Function of stratum spinosum
binding of stratum, protection against invasion (by preventing fissures and Langerhan cell activity)
Stratum Basale (Germinativum)
Deepest layer of epidermis
Single layer of columnar cells with oval nuclei
Desmosomes bind cell membrane to all neighboring cells
Most intense mitotic activity in this layer
Rests on basement membrane - attach to basement membrane via hemidesmosomes
Function of stratum basale
cell renewal, and anchors epidermis to basement membrane
Strata of thin skin
Stratum corneum, stratum spinosum, and stratum basale
Dermis
Connective tissue layer of skin
Provides strength & structure - protein collagen
Provides defense, nutrition, themoregulation, sensation, stretch
Dermis arises from
mesoderm
Dermal papillae
extend into epidermis - interdigitate with epidermal ridges projecting into dermis
Areas subject to increased mechanical stress (feet, hands - Thick skin) have prominent epidermal ridges, dermal papillae, and true dermal ridges
True dermal ridges
in thick skin - hands, soles of feet
Oriented parallel to and lie in between dermal papillae
Genetically unique - form pattern of fingerprints and footprints
Layers of Dermis
Papillary layer and reticular layer
Papillary Layer of dermis
superficial layer consisting of thin loose CT - defense against invasion
Forms dermal papillae
Papillary layer contains
Loose connective tissue
Type III collagen fibers (reticular fibers)
Elastic fibers
Anchoring fibrils (Type VII collagen) - anchors epidermis to dermis
Fibroblasts, macrophages, plasma cells, mast cells
Capillary loops (nutrition and themoregulation)
Meissner corpuscles (mechanoreceptors)
Krause end bulbs
Partial thickness burns
extend into papillary layer of dermis - superficial second degree burns
Extend into reticular layer of dermis - deep second degree burns
Superficial burns
involve epidermis, first degree burns
Reticular layer of dermis
Thickest layer of dermis
Made of dense irregular collagenous connective tissue
Type I collagen fibers form bundles with regular lines of tension - tensile strength
Reticular layer consists of
Type I collagen fibers
Thick elastic fibers
Proteoglycans
Fibroblasts, mast cells, lymphocytes, macrophages, fat cells
Hair follicles, arrector pili muscles, sebaceous glands, sweat glands
Pacinian corpuscles, Ruffini corpuscles
Pacinian corpuscles
detect pressure and vibrations
Found in reticular layer of dermis
Ruffini corpuscles
tensile forces
Many in soles of feet
found in reticular layer of dermis
Full thickness burns
third degree burns, extend into subcutaneous tissue (hypodermis) and may damage underlying muscle tissue
Hypodermis
deep to dermis, superficial fascia
subcutaneous connective tissue with adipose tissue
Not part of skin
Meissner’s corpuscles
tucked away in dermal cap - in papillary layer of dermis
Mechanoreceptor - fine touch
Eccrine Sweat glands
Scattered throughout skin, secrete sweat for thermoregulation
Simple coiled tubular glands - duct opens into pore on surface of epidermis
Located deep in dermis or hypodermis
Eccrine gland secretes via
merocrine secretion - squirts out only secretory product
Eccrine gland is innervated by
postganglionic sympathetic fibers
Secretory segment of eccrine gland
simple cuboidal to low columnar cells
Myoepithelial cells of eccrine gland
surround secretory unit
covered by basal lamina
contain actin and myosin filaments - squeeze out secretory product
Duct segment of eccrine gland
Stratified cuboidal epithelium
two layers
Apocrine sweat glands
found in axilla, areola of nipple, and anal region
Larger than eccrine glands
Located in deep dermis and hypodermis
Duct opens into canal of hair follicle, superficial to the entry of the sebaceous gland duct
Release of secretory product via merocrine secretion
Modified apocrine glands
Ceruminous (wax) glands of external auditory meatus
Glands of Moll in the eyelids
Secretory unit of Apocrine glands
simple cuboidal to low columnar
Lumen is larger than eccrine glands
Secretory product is viscous and odorless when released
Myoepithelial cells surround secretory unit
Apocrine glands innervated by
postganglionic sympathetic fibers
influenced by hormones
Sebaceous glands
in dermis and hypodermis, throughout body
Secrete sebum
Appendages of hair follicles - empty sebum into canal of hair follicle
Influenced by hormones
Duct is stratified squamous epithelium
Secretory unit is acinus - sits on basal lamina
Sebaceous glands secrete via
holocrine secretion
Hair follicles
Hair bulb encloses hair root, external root sheath, internal root sheath, and hair shaft
Hair root is made of
matrix and dermal papilla - at bottom of hair follicle
Hair shaft is made of
Medulla (inner layer)
Cortex (middle)
Cuticle (outer)
Cortex and cuticle are keratinized, medulla is moderately keratinized
Internal root sheath layers
Henle’s layer (outer)
Huxley’s layer (middle)
Cuticle (inner)
Has some keratinization
Arrector pili muscles
smooth muscle attached to hair follicle
When contract, raise hair
Cradle sebaceous glands
Sympathetically inervated
Nails consist of
Nail plate (hard keratin)
Nail bed - stratum basale and spinosum
Nail root - matrix where nail growth occurs, forms keratin of nail plate
Proximal nail fold - eponychium (cuticle)
