Week 3- Integumentary System Flashcards
Integument
-Skin covering your body
-body’s largest organ
-surface epithelium protects underlying body layer
-connective tissue that is deep to epithelium provides strength and resilience
-also contains smooth muscle associated with hair follicles (arrector pili)
-nervous tissue detects and monitors sensory stimuli (touch, pressure, temp, and pain)
-7-8% of body weight and about 1.5-2 square meters
-2 layers:
1) epidermis
2) dermis
Cutaneous membrane
Another word for skin
Integumentary System
-Consists of the skin and its derivatives: nails, hair, sweat glands, and sebaceous (oil) glands
What does every square inch of skin contain on average?
up to 20 feet of blood vessels, 650 sweat glands, 100 sebaceous glands, and over 100 nerve endings
What can the skin do?
-acts as barrier to outside world
-subjected to trauma, harmful chemical, pollutants, microbes, and damaging sunlight
-changes in color may reflect body disorders or anomalies
-skin changes and lesion sometimes reflect systemic infections or disease
Dermatology
Scientific study and treatment of integumentary system
Epidermis
-keratinized, stratified squamous epithelial tissue
-0.075-0.6 mm thick
Layers of epidermis (Superficial to deep)
1) Stratum corneum
2) Stratum lucidum (only in thick skin)
3) Stratum granulosum
4) Stratum spinosum
5) Stratum basale
Stratum corneum
-“horny layer”
-most superficial layer of epidermis
-20-30 layers of dead, scaly, interlocking, keratinized cells
-dead keratinocytes are anucleated (lacking nucleus) and tightly packed
-cells contain large amount of keratin
-keratinocytes are made in stratum basale and move up to stratum corneum where they are sloughed off
-thickened surface as well as exocrine secretions help prevent growth of microorganisms
Stratum lucidum
-“clear layer”
-2-3 keratinocyte layers, cells are pale and flattened
-deep to stratum corneum
-ONLY IN THICK SKIN
-helps protect from UV light
Stratum granulosum
-“granular layer”
-3-5 layers of keratinocytes superficial to stratum spinosum
-process of keratinization begins (keratinocytes synthesize significant amounts of keratin)
-accumulation of keratin causes both nucleus and organelles to disintegrate which results in death of these cells
Stratum spinosum
-keratinocytes attach to their neighbors by many membrane junctions called desmosomes (which provide structural support between cells of epidermis)
-also contains epidermal dendritic cells
Epidermal dendritic cells
-immune cells are immune cells that help fight infection in epidermis
-present in stratum spinosum and stratum granulosum
-phagocytic activity initiates immune response to protect body against pathogens that have penetrated superficial epidermal layers as well as epidermal cancer cells
Stratum Basale
-deepest epidermal layer
-“basal layer”
-single layer of cuboidal/columnar cells attached to underlying basement membrane that separates epidermis from dermis
3 Cell Types of Stratum Basale
1) Keratinocytes
2) Melanocytes
3) Tactile/Merkel cells
Keratinocytes
-most abundant cell type in epidermis
-stem cells divide to generate new keratinocytes that replace dead ones shed from surface
-gives skin its strength and makes epidermis water resistant
Melanocytes
-have long branching processes
-produce and store the pigment melanin in response UV light exposure
-tanning is result of melanocytes producing melanin to block UV light from causing mutations in DNA in keratinocytes and fibroblasts
Tactile Cells
-few in number and scattered about
-sensitive to touch and when compressed they release chemicals that stimulate sensory nerve endings
-more common in sensitive areas like fingertips
How is skin classified as thick or thin?
number of layers and thickness of stratified squamous epithelium
Thick skin
-palms of hands and soles of feet
-has all 5 epidermal strata
-0.4mm-0.6mm thick
-houses sweat glands but no hair follicles or sebaceous glands
Thin skin
-covers most of body
-has 4/5 layers of epidermis (lacks stratum lucidum)
-contains hair follicles, sebaceous glands, and sweat glands
-0.075-0.150mm thick
Skin color
-normal skin color results from colors of hemoglobin, melanin, and carotene
Hemoglobin
-exhibits a bright red color upon binding oxygen, thus giving blood vessels in dermis a reddish tint that is most easily seen in light pigmented individuals
Melanin
-pigment produced and stored in melanocytes
-2 types: eumelanin (brown and black) and pheomelanin (light tan, yellow, and red)
-all people have same number of melanocytes
-melanocyte activity, type of melanin present, and color of melanin produced by
these cells result in different color skin tones
Carotene
-yellow-orange pigment that is acquired from various yellow-orange veggies (carrots, corn, and squashes)
-accumulates inside keratinocytes of stratum corneum and in subcutaneous fat
-several forms (alpha, beta, ect)
-beta is most common and is converted to vitamin A in liver
Albinism
-inherited recessive condition where enzyme needed to produce melanin is nonfunctional
-melanocytes are unable to produce melanin
-individuals have white hair, pale skin, and pink irises
Nevus
-commonly called a mole
-harmless, localized overgrowth of melanocytes
-may become malignant melanoma due to excessive UV light exposure
Freckles
-yellowish or brown spots that represent localized areas of increased melanocyte activity, not an increase in number
Hemangioma
-anomaly that results in skin discoloration due to blood vessels that proliferate to form a benign tumor
Capillary hemangiomas
-strawberry colored birthmarks
-appear in the skin as bright red to deep purple nodules that are usually present at birth and disappear in childhood
-development may occur in adults
Cavernous hemangiomas
-port wine stains
-involve larger dermal blood vessels and may last lifetime
Friction ridges
-ridge patterns follow contours of skin
-found on palms, fingers, soles, and toes
-help increase friction on contact, so hands can firmly grasp items and feet don’t slip when barefoot
-some suggest they also provide flexibility to skin and allow it to be deformed without damage
-when sweat glands and oil glands release secretions, noticeable fingerprints may be left on surfaces
-unique identifier because no 2 people have same fingerprint (not even identical twins)
Dermatoglyphics
study of friction ridge patterns
Dermis
-deep to epidermis and ranges in thickness from 0.5-3mm
-composed of connective tissue proper
-contains mostly collagen fibers, with some elastic and reticular fibers too
-contains dendritic cells, blood vessels, sweat glands, sebaceous glands, hair follicles, nail roots, sensory nerve ending, and smooth muscle associated with hair follicle (arrector pili)
Two regions of dermis
1) Superficial papillary layer
2) Deeper reticular layer
Papillary layer
-superficial part of dermis
-composed of areolar tissue
-derives name from projections called dermal papillae
-dermal papillae and epidermal ridges work together to increase area of contact between 2 layers and interlock them
Dermal papillae
-contains capillaries that supply nutrients to cells of epidermis
-contain sensory nerve endings that serve as tactile receptors (monitor touch on surface of epidermis)
Reticular layer
-forms deeper, major portion of dermis that extends from papillary layer to underlying subcutaneous layer
-consists primarily of dense irregular connective tissue
-collagen fibers are interwoven into meshwork that surrounds structures in dermis
Lines of cleavage
-identify predominant orientation of collagen fiber bundles
-surgical incisions should be made parallel to lines of cleavage to ensure incision remains closed, rapid healing, and prevention of scarring
Striae
-Stretch marks
-caused by tearing of collagen fibers when skin is stretched beyond capacity (exceeds elastic capacity)
Subcutaneous layer
-NOT considered part of integument
-deep to integument
-areolar and adipose tissue
-reticular layer of dermis is interwoven with it to stabilize skin position and bind it to underlying structures
-pads and protects body, acts as energy reservoir, and provides thermal insulation
-high vascularized (many drugs injected here)
-thickness and distribution influenced by sex hormones
-testosterone=fat accumulates at neck, upper arms, abdomen, lower back, and
butt
-estrogen=layer is thicker overall and accumulates in mammary regions, butt, hips,
and thighs
Functions of Integument
-Protection from external environment
-Prevention of water loss and gain
-Vitamin D synthesis
-Secretion
-Absorption
-Temperature regulation
-Assisting immune system
-Sensory perception
Protection from external environment
-protects against harmful chemicals, toxins, microbes, and excessive heat or cold
-protects deeper tissues from solar radiation, especially UV
Prevention of Water Loss or Gain
-epidermis is water resistant not waterproof
-some water is lost through sweat but more is lost through transpiration
-prevents major absorption of water (don’t swell up when taking a bath)
Transpiration
Process in which fluids slowly penetrate through epidermis and evaporate into surrounding air
Vitamin D Synthesis
-at exposure to UV light keratinocytes converted steroid molecule to vitamin D3 (cholecalciferol)
-vitamin D3 is them transported to liver/kidneys where it becomes calcitriol (active from of vitamin D)
-increased absorption of Ca and phosphate from small intestine, which results in more calcium being absorbed in foods we eat
Secretion
-Sweat releases excess heat from body
-also alters electrolyte level (excretes water, urea, and salts0
-Sebum lubricates epidermis and hair
-helps make skin water resistant
Absorption
-taking in of a gas, liquid, light, or heat
-skin can absorb certain chemicals and drugs such as estrogen from birth control patch or nicotine from nicotine patch
-skin is selectively permeable
-skin can absorb small, nonpolar molecules
Transdermal administration
-drugs that are soluble in oil or lipid-soluble carriers may be administered by patch on skin
-drug slowly penetrates epidermis and can be absorbed into blood vessels of dermis
-allows for continual, slow absorption of drug over extended period of time
Temperature regulation
-Dermal blood vessels can vasoconstrict (colder temps) and vasodilate (warmer temps)
-sweating from sweat glands also cools body
Immune function
-epidermal dendritic cells and dendritic cells of dermis
Sensory reception
-ability of tactile sensory receptors to detect stimuli such as touch or pressure
-seven major types of sensory receptors are housed within skin to detect, distinguish, and interpret stimuli from external environment
Epidermal derivatives
Nails, hair, and exocrine glands
Nails
-scalelike modifications of stratum corneum
-protect distal tips of digits during jumping, kicking, or catching
-fingernails also assist in grasping objects
Parts of nail
-each nail has a free edge, nail body, nail root, nail plate, nail bed, nail matrix, lunula, nail folds, cuticle, and hyponychium
Free edge
Part of finger nail that you would clip
Nail body
-Actual nail
-Appears darker/pinkish because of bloodflow in underlying capillaries
Nail root
Proximal part embedded in skin
Nail plate
Composed of free edge, nail body, and nail root
Nail bed
Contains the deeper, living cell layers of epidermis and is covered by the nail body
Nail matrix
-Actively growing part of nail
-formed at nail root and proximal end of nail body, where nail bed thickens
Lunula
Whitish, senilunar area of proximal end of nail body
Nail folds
Folds of skin along the lateral and proximal borders of nail that overlap nail
Eponychium
-Cuticle
-narrow band of epidermis extending from margin of nail wall onto nail body
Hyponychium
Area of thickened epithelium underlying free edge of nail
Brittle nails
-prone to vertical splitting and separation of nail plate layers at free edge
-overexposure to water or certain household chemicals can cause this
Ingrown nail
-occurs when edge of nail digs into skin around it
-characterized by pain and inflammation
-may result from overly tight shoes and improper trimming of nails
Nail pitting
-refers to tiny depressions or shallow holes in nail body
-usually a symptom of another disorder like psoriasis, alopecia areata, dermatitis, or connective tissue disorder
Nail clubbing
-tip of finger enlarges and edges of nail grow and curve around tip
-occurs over period of years and is indicative of hypoxia (inadequate blood flow to tissue)
-often seen in conditions associated with hypoxia (smoking, cardiovascular disease, and diabetes)
Onychomycosis
-fungal infection that occurs in nails constantly exposed to warmth and moisture
-fungus starts to grow under nail and eventually causes yellow discoloration, a thickened nail, and brittle, cracked edges
Spoon nail (Koilonychia)
-outer surface if nails are concave instead of convex
-usually sign of iron deficiency and treating deficiency should alleviate condition
Beau’s lines
-run horizontally across nail and indicate temporary interference with nail growth at time portion of nail was formed
-caused by injury to nail, severe illness, or chronic malnutrition
Vertical ridging
-common and usually doesn’t indicate any serious medical problem
-occurs more frequently as we age
Hair
-found almost everywhere on body except palms of hands, palmar surface of fingers, sides and soles of feet/toes, lips, and portions of external genitalia
Pilus
-a single hair
-composed of keratinized cells growing from hair follicles that extend into dermis and often subcutaneous layer too
-differences in density due to texture and pigmentation
3 Kinds of Hair
1) Lanugo
2) Vellus
3) Terminal
Lanugo
-fine, unpigmented, downy hair that first appears on fetus in last trimester
-at birth, most has been replaced vellus
Vellus
-fine, unpigmented/light pigmented
-primary human hair
-found on upper and lower limbs
Terminal hair
-Coarser, pigmented, and longer than vellus
-grows on scalp, eyebrows, and eyelashes
-at puberty, replaces vellus hair in axillary and pubic regions
-under influence of testosterone, forms beard
Three zones of hair
1) Hair bulb
2) Root
3) Shaft
Hair bulb
-consists of epithelial cells and is a swelling at the base where hair originates in dermis
-epithelium at base of bulb surrounds a small hair papilla (composed of small amount of connective tissue containing tiny blood vessels and nerves)
Root
Zone of hair extending from bulb to skin surface
Shaft
-portion that extends beyond skin surface
-contains living epithelial cells whereas root and shaft consist of dead epithelial cells
Hair matrix
-structure immediately adjacent to hair papilla in hair bulb
-epithelial cells near center divide, producing new cells that are gradually pushed toward surface
-specialized type of keratinization occurs here
Medulla
-remnant of soft core of matrix
-composed of loosely arranged cells and air spaces
-contains soft, flexible keratin
-not found in all hair types
Cortex
Several layers of flattened cells closer to outer surface of developing hair form relatively hard cortex
Cuticle
A single cell layer around the cortex that coats the hair
Hair follicle
-oblique tube that surrounds hair root
-extends into dermis/subcutaneous layer
-2 concentric layer:
1) outer connective tissue root sheath (originates from dermis)
2) inner epithelial tissue root sheath (originates from epidermis)
-arrector pili extend from hair follicle to dermal papillae
Arrector pili
-thin ribbons of smooth muscle
-stimulation is usually result of an emotional state (like fear or rage) or response to cold temperatures
-upon stimulation by nervous system, arrector pili contract, pulling on hair follicle and elevating hair creating goosebumps
Functions of Hair
1) Protection
-protects scalp from sunburn and injury
-hair within nostrils entrap particles and prevent entry deeper into respiratory
system
-hair in external ear canal protect ear from insects and foreign particles
-eyelashes protect eye
2) Heat retention = prevents loss of conducted heat from scalp to surrounding air
3) Sensory reception = follicles have associated tactile receptors that detect light touch
4) Visual identification = important in determining age and identifying individuals
Hair color
-determined by melanin synthesized in matrix adjacent to hair papillae
-variations in hair color = genetic differences in structure of melanin
-also influenced by environmental and hormonal factors
-grey hair=reduction in melanin production in hair follicle
-white hair= complete stoppage of melanin production
3 Stages of Hair Growth Cycle
1) Anagen
2) Catagen
3) Telogen
Anagen Phase
-Active phase of hair growth where living cells in hair bulb are rapidly growing, dividing, and transforming into hair
-longest part of cycle and lasts 18 months-7 years depending on location on body and individual’s genetics
-each hair strand grows 0.5-1cm/month
-on scalp, 80-95% of follicles are in this stage
Catagen phase
-Brief regression period where cell division ceases and follicles undergo involution
-Lasts about 3-4 weeks
Telogen phase
-Resting phase and usually when hair is shed
-after 3-4 months in phase, cells of hair bulb start regrowing and follicle reenters anagen phase
Alopecia areata
-“spot baldness”
-circular bald patches develop on scalp/body
-autoimmune disorder where body mistakes selected hair follicles as foreign and attacks them
Diffuse hair loss
Hair is shed from all parts of scalp
Male pattern baldness
-causes hair loss first from only crown region of scalp rather than uniformly
-Baldness allele is dominant in genetic males and is expressed only in presence of testosterone
-in genetic females, baldness allele is recessive
Hirsutism
-excessive hairiness in body areas that normally do not have terminal hair (face, chest, and back)
-affects all individuals regardless of sex
-most commonly caused by excess of male sex hormones either through medical condition (like PCOS) or certain medications (like anabolic steroids)
Exocrine glands in skin
1) Sweat glands
2) Sebaceous glands
Sweat glands
-2 types: merocrine(eccrine) and apocrine
-have coiled tubular secretory portion that is located in reticular layer of dermis and a sweat gland duct that transports secretions to surface of epidermis or into hair follicle
-contain myoepithelial cells (specialized epithelial cells with contractile proteins like muscle)
-in response to nervous system, contract to squeeze gland, causing it to discharge
its accumulated secretions
Sweat pore
indented region where sweat gland duct opens on epidermal surface
Merocrine (Eccrine) Sweat Glands
-most numerous and widely distributed sweat glands
-3-4 million on integument
-simple coiled tubular glands that discharge secretions (sweat) directly into surface of skin
-major function is thermoregulation
-provide means for loss of both water and electrolytes, as well as some protection from environmental hazards by diluting harmful chemicals and preventing growth of microorganisms
Sweat
-clear secretion released by exocytosis
-99% water
-1% other chemicals including electrolytes (Na and Cl), metabolites (ex. lactate), and waste products (urea and ammonia)
Apocrine Sweat Glands
-coiled, tubular glands that release secretions into hair follicles in axillae, around nipples, in pubic region, and in anal region
-has larger lumen than merocrine gland and secretions are different
-secretions are viscous and cloudy, containing proteins and lipids that are acted upon by bacteria to produce a distinct odor
-glands become active around puberty
Sebaceous Glands
-holocrine glands that produce an oily, waxy secretion called sebum that is usually discharged into a hair follicle and onto hair itself
-sebum acts as lubricant to keep skin and hair from becoming dry, brittle, and cracked
-sebum also has some bactericidal properties
-secretions of sebum is stimulated by hormones, especially male sex hormones
-sebaceous glands relatively inactive in childhood and are activated during
puberty
Acne
-Plugged ducts of sebaceous glands
-Types of acne lesions:
-comedo
-papule/pustule
-nodule
-cyst
Comedo
-Sebaceous gland plugged with sebum
-Open comedo = blackhead, plugged material is dark, blackish color
-Closed comedo = whitehead, top surface is whitish color
Papule and Pustule
-both are domed shaped lesions
-papules are fluid filled, form red elevations on skin, and do not contain pus
-papules may become pustules which are filled with a mixture of white blood cells, dead skin cells, and bacteria (called pus)
Nodule
Similar to pustule but extends into deeper into skin layers, usually rupturing hair follicle wall; prone to scarring
Cyst
Large fluid filled nodule that can become severely inflamed and painful and can lead o scarring
Ceruminous glands
-modified apocrine sweat glands only located in external acoustuc meatus (ear canal)
-secretions from a waterproof earwax called cerumen
-cerumen and tiny hairs in meatus help trap foreign particles or small insects and keeps them from reaching eardrum
-cerumen also helps lubricate external acoustic meatus and eardrum
Mammary glands
-modified apocrine sweat glands
-present in both males and females but glands only functional in pregnant and lactating females when they produce breast milk (a secretion that nourishes offspring)
-development of glands and its secretions are controlled by complex interaction between gonadal and pituitary hormones
How do damaged tissues repair themselves?
Regeneration or fibrosis
Regeneration
-Replacement of damaged or dead cells with same cell type by cell division
-restores tissue function
-when regeneration is not possible because part of the organ is too severely damaged or cells lack capacity to divide, body fills gap with scar (fibrous) tissue
Fibrosis
-process of scar tissue deposition in connective tissue during healing
-binds damaged parts together
-replacement scar tissue is composed mostly of collagen fiber and produced by fibroblasts of connective tissue
-some structural restoration occurs but functional activities not restored
Psoriasis
-chronic autoimmune disorder that has periods of flare-ups and remissions throughout a person’s lifetime
-T-lymphocyte mistakenly attacks keratinocytes, causing rapid overgrowth and overproduction of new skin cells
-normal sloughing off cycle is thrown out of balance and proliferation of cells develops into patches of whitish, scaly skin (called plaques) on epidermal surface
Steps of Wound Healing
1) Cut blood vessels release blood into wound; blood brings in clotting proteins, numerous leukocytes, and antibodies
2) Blood clot forms; macrophages and neutrophils clean wound of cellular debris
3) Cut blood vessels regenerate and grow; soft mass deep in wound becomes granulation tissue; macrophages within wound begin to move clotted blood; fibroblasts produce new collagen fibers
4) Epithelial regeneration; new epithelial cells migrate over wound, moving internally to now superficial remains of clot/scab; connective tissue is replaced by fibrosis
