Chapter 5 The IntegumentarySystem Flashcards
Skin Structure
-Account for 10-15% of total body weight
-Largest organ in body
Cutaneous membrane (skin)
- Epidermis
- Dermis
Epidermis
Superficial layer
-keratinized stratified squamous epithelium resting on basement membrane
Dermis
Deep to epidermis and basement membrane
-loose connective tissue and dense irregular connective tissue
Accessory Structures
Embedded in cutaneous membrane
Ex: sweat glands, sebaceous glands, hair, and nails
Arrector pili muscles
Small bands of smooth muscle associated with hair
Epidermis (avascular)
–Relies on diffusion of oxygen and nutrients from blood vessels in deeper dermis; limits epidermal thickness
–About 50% of epidermal cells are too far from adequate blood supply to sustain life; superficial layers are made up entirely of dead cells
Hypodermis
(superficial fascia or subcutaneous fat) deep to dermis
–Not part of skin; anchors skin to deeper structures like muscle and bone
–Made of loose connective and adipose tissues; has abundant blood supply
Cellulite
Dimpled or “orange peel” appearance of skin when collagen bands form around adipose tissue in hypodermis.
- Influenced by ; genetics, gender and amount and distribution of adipose tissue, and age
Functions of the Integumentary System
Critical for protecting underlying organs or maintaining homeostasis:
-Protection
-Sensation
-Thermoregulation
-Excretion
-Vitamin D synthesis
Protection
From mechanical trauma, pathogens, and environment:
–Stratified squamous, keratinized epithelium provides durable but flexible surface; protects body from mechanical trauma (stretching, pressure, or abrasions)
–Contains cells of immune system that destroy pathogens before they invade deeper tissues
-Provides protection from environmental hazards
Glands
(Protection)
secrete anti microbial substances
-sebaceous gland secretions give surface of skin slightly acidic pH (acid mantle)
-inhibits growth of many pathogens
Sensation
Enables nervous system to perceive changes in body’s internal or external surroundings; critical to homeostasis:
-Receptors detect potentiallyharmfulstimuli (heat, cold, and pain); could lead to tissue damage
Thermoregulation
–Relies on negative feedback loops for maintenance of stable internal temperature
–Internal body temperature is determined mostly by ▪Muscle activity
▪Chemical reactions (metabolism)
When body temperature rises above normal range
▪Sensory receptors (thermoreceptors) detect increase in temperature in skin and internal body fluids
▪Control center in hypothalamus acts as thermostat (thermoregulatory center); receives input from thermoreceptors; processes and responds to inputs
▪Control center stimulates sweating
▪Control center stimulates cutaneous vasodilation; dermal blood vessels widen (dilate); increased blood flow through vessels increases heat radiated from body
▪Body temperature returns to normal range and cooling mechanisms decline by negative feedback
When body temperature drops below normal range
▪Thermoreceptors detect body temperature below normal range; relay information to thermoregulatory center in hypothalamus
▪Blood vessels in dermis narrow (vasoconstrict), reducing blood flow
▪Vasoconstriction redirects blood flow to deeper tissues; conserves heat
▪When body temperature returns back to normal range, thermoreceptors stop signaling hypothalamus; heat conservation ends; feedback loop is closed
Excretion
Elimination of waste products and toxins from body
Vitamin D Synthesis
The Epidermis
The most superficial layer; composed of several cell types
Keratinocytes
Make up about 95% of epidermis. make epidermis stronger and less susceptible to mechanical trauma:
▪Keratin – tough fibrous protein
▪Linked together by desmosomes; intercellular junctions that hold cells together
Epidermal Strata Layers
-Stratum Basale
-Stratum Spinosum
-Stratum Granulosum
-Stratum Lucidum
-Stratum Stratum Corneum
Stratum Basale
(stratum germinativum) single layer of stem cells resting on basement membrane
▪Closest cells to dermal blood supply; most metabolically and mitotically active strata
▪Responsible for Vitamin D synthesis and replacement of dead keratinocytes (lost from superficial layers
Stratum Spinosum
Thickest layer
-on top of stratum basale -metabolically and mitotically active
Stratum Granulosum
▪Three to five layers of cells; prominent cytoplasmic granules with keratin bundles or lipid-based substance; secreted by exocytosis
▪Hydrophobic lipids provide waterproofing; maintains internal fluid and electrolyte homeostasis; leads to isolation and death of cells in layer and more superficial layers
Stratum Lucidum
Narrow layer of clear, dead keratinocytes; only in thick skin
Stratum Corneum
Outermost layer; several layers of dead, flattened keratinocytes with thickened plasma membrane
Keratinocyte life cycle
–Keratinocytes begin life in stratum basale or spinosum; pass through each epidermal layer; shed from stratum corneum
–Migration from deepest strata to stratum corneum takes 40−50days to complete
Dendritic (Langerhans) cells
In stratum spinosum; phagocytes of immune system; protect skin and deeper tissues from pathogens
Merkel Cells
Oval cells scattered throughout stratum basale; sensory receptors associated with small neurons in dermis:
–Detect light touch and discriminate shapes and textures
–Large numbers in regions specialized for touch: fingertips, lips, and at base of hairs
Melanocytes
In stratum basale; produce melanin (protein pigment ranging from orange-red to brown-black
Thick Skin
– about as thick as paper towel; all five epidermal layers and very thick stratum corneum; no hair follicles; many sweat glands
Thin Skin
–covers areas of body not subjected to as much mechanical stress; about as thick as sheet of printer paper; only four layers (no stratum lucidum)
–Each layer is thinner than those of thick skin
–Numerous hairs, sweat glands, and sebaceous glands present
Callus
– additional layers of stratum corneum; forms in either thick or thin skin in response to repetitive pressure
The Dermis
– highly vascular layer deep to epidermis
*Functions:
–Provides blood supply for epidermis
–Contains sensory receptors
–Anchors epidermis in place
*Composed of two distinct layers; two types of connective tissue
1. Papillary Layer
2. Reticular Layer
Papillary Layer
Thinner, most superficial of two layers
*Loose connective tissue
*Special collagen fibers at dermis-epidermal junction; extends into epidermal basement membrane; anchors epidermis to dermis
Dermal Papillae
Tiny projections at surface of papillary layer where it contacts epidermis:
–Contain tiny blood vessels (capillaries) arranged in loops; extend up into most superficial part of dermal papillae
–Allow oxygen and nutrients to diffuse into extracellular fluid of dermis, then into avascular epidermis
Tactile (Meissner) corpuscles
Also in dermal papillae; sensory receptors; respond to light touch stimuli
-skin of fingertips, lips, face, and external genital
Reticular Layer
*Collagen bundles strengthen dermis; prevent traumatic injuries from damaging deeper tissues
*Elastic fibers allow dermis to return to its original shape and size after stretching
*Rich in proteoglycans that draw water into ground substance; keeps skin firm and hydrated
*Blood vessels, sweat glands, hairs, sebaceous glands, and adipose tissue are also present
Lamellated (Pacinian) corpuscles
Sensory receptors embedded within reticular layer; respond mainly to changes in pressure and vibration
Skin Markings
Small visible lines in epidermis created by interaction between dermis and epidermis; best seen in thick skin
Dermal Ridges
Areas where dermal papillae are more prominent due to presence of thick collagen bundles
*Indent overlying epidermis to create epidermal ridges; enhance gripping ability of hands and feet:
–Occur in characteristic patterns; loops, arches, and whorls; genetically determined and unique to each person
–Sweat pores open along ridges; leave thin film or fingerprint on things touched with fingers
Tension (cleavage) lines
–indentations in epidermis from gaps between collagen bundles in dermis
Flexure Lines
–deep creases in areas of body (surrounding joints) where reticular layer is tightly anchored to deeper structure
Botox
Bacterial toxin; temporarily paralyzes facial muscles; causes skin to appear smoother
Fillers
Adipose tissue, collagen, and/or proteoglycans injected into wrinkles
Topical creams
(especially nonprescription) claim to reduce appearance of wrinkles; little to no effect
Melanin
Skin color – mostly determined by various amounts of melanin:
*Produced by melanocytes in stratum basale
*Composed of two molecules of amino acid tyrosine, occurs in stepwise fashion within special vesicle (melanosome)
*Primary function – protecting keratinocyte DNA from mutations induced by UV radiation
Tanning
Melanin synthesis increases with exposure to natural or artificial UV radiation
- has both immediate and delayed effects on skin pigmentation
Immediate Response of tanning
Oxidation of melanin already present in keratinocytes; causes melanin to quickly darken
Delayed response of tanning
UV light causes DNA damage in melanocytes; stimulates melanin production; appears within 72 hours; lasts longer than melanin oxidation
UV Radiation effects
–Amount of UV radiation melanin can absorb is limited as is the protection provided
–People of all skin pigmentations can develop sunburns and are at risk for skin cancers
Freckle
Small area of increased pigmentation; increased melanin production in local spot
Mole or Nevus
Area of increased pigmentation, caused by local proliferation of melanocytes; not an increase in melanin production
Albinism
Melanocytes fail to manufacture tyrosinase; results in lack of skin pigmentation and greatly increased risk of keratinocyte DNA damage from UV radiation
Carotene
Yellow-orange pigment in food items such as egg yolks and orange vegetables
–Lipid-soluble molecule; accumulates in stratum corneum
–Imparts slight yellow-orange color; particularly visible in stratum corneum of thick skin
Hemoglobin
In red blood cells; iron-containing protein; binds to and transports oxygen throughout body
-Gives blood characteristic color
Erythema
blood flow in dermis increases; makes skin more reddish
-Other conditions causing erythema include trauma, fever, and infection
Pallor
Blood flow in dermis decreases; results in loss of normal pinkish hue; most visible in pale-skinned individuals; epidermis takes on whitish color of collagen in dermis
Cyanosis
Sign that someone needs immediate attention; hemoglobin has very low levels of bound oxygen; blood turns reddish purple; skin takes on faint bluish hue; can occur when:
–someone has difficulty breathing
–hemoglobin or red cell levels are low in blood
–hemoglobin is unable to bind to oxygen
ACCESSORY STRUCTURES OF THE INTEGUMENT: HAIR, NAILS, AND GLANDS
Accessory structures or appendages
Include hair, nails, and glands
Hair (pili)
Small filamentous structures; protrude from surface of skin over entire body except in regions with thick skin, lips, and parts of external genitalia
Hair functions
–Provides protection by preventing substances and organisms from entering eyes and nose
–Protects underlying skin of scalp from UV radiation and mechanical trauma
–Associated with small sensory neuron; plays role in detecting changes in environment
Hair Structure
Composed of Shaft and Root. Made of:
stratified squamous keratinized epithelial cells
Hair Shaft
▪Portion of hair projecting from skin’s surface
▪Made of columns of dead keratinized epithelial cells that have completed keratinization process
Hair Root
▪Segment of hair embedded in dermis; surrounded by small sensory neuron
▪Indented at base by projection of blood vessels from dermis (hair papilla)
▪Root and hair papilla collectively known as hair bulb
▪Many epithelial cells in root are still alive; have not completed keratinization process
Hair Matrix
Small number of keratinocytes at base of root; actively divide
Hair Strands
-Inner Medulla
-Middle Cortex
-Outermost cuticle
Inner medulla
Soft core only found in thick hair (head); composed of soft keratin
Middle cortex
Highly structured and organized with several layers of keratinocytes containing hard keratin; provides strength
Outermost cuticle
Single layer of over lapping keratinocytes containing hard keratin; provides mechanical strength
Dermal root sheath
surrounds epithelial root; consists of connective tissue; supports follicle and keeps it separate from dermis
Arrector pili muscles
Small bands of smooth muscle; attach to dermal root sheath on one end and dermal papillary layer on other
Contraction of arrector pili
Causes hair to:
-stand up (piloerection), gives skin dimpled appearance (“goosebumps”)
Hair Growth Stages
- Growth stage
- Resting stage
Growth stage
Mitosis occurs in matrix
▪Cells divide and push cells above them farther away from blood supply; keratinize and die
▪Stage varies in duration from a month to as long as six years; depends on location of hair
Resting stage
Mitosis in matrix ends as cells die
▪Follicle shortens; hair is pushed toward surface where it remains dormant for a month or two
▪Falls out on its own or is pushed out by new hair in growth stage
Lanugo
Thin, non pigmented hair covering nearly entire body of fetus; generally fall out around birth; replaced with one of two hair types:
▪Terminal hair
▪Vellus hair
Terminal Hair
Thick, coarse, and pigmented hair; surrounding eyes and on scalp
-replaces much of vellus hair after puberty; varies by gender; more hair replacement occurs in males than female
Vellus Hair
Thinner non pigmented hair; over remaining regions of body
Hair Pigmentation
▪Blond hair – little melanin ▪Black hair – contains lots of melanin
▪Red hair – special reddish pigment containing iron
–Melanocytes produce less melanin with aging so hair eventually turns gray or white
Nails
Hard accessory structures at ends of digits; composed of stratified squamous epithelium filled with hard keratin
Nail plate
Most visible component of nail; on top of underlying epidermal nail bed; divided into:
1. Nail Body
2. Nail root
Nail body
visible portion of nail plate
Nail root
portion of plate under skin; location of nail matrix containing actively dividing cells
Proximal nail fold
on proximal edge covering nail root; distal edge of fold is eponychium (cuticle); consists of only stratum corneum
Medial & lateral nail folds
on medial and lateral edges of nail plate respectively
Distal or free edge nail plate
attached to underlying nail bed by accumulation of stratum corneum called hyponychium
Nail Growth
Occurs at nail matrix
–Actively dividing cells push neighboring cells distally
–Die once keratinization is completed and have been cut off from blood supply
–Grow an average of 0.5mm per week; toenails grow more slowly
Nails
*Do not contain melanocytes; mostly translucent except at lunula; half-moon shaped region of proximal nail plate; represents accumulation of keratin
*Primary function – protection of underlying tissue (distal tips of fingers and toes) from trauma; can be used as tools; enables more precise gripping of items
Glands
Derived from epidermal cells; located deeper in dermis:
*Sweat (sudoriferous) glands – produce sweat
*Sebaceous glands – produce oily sebum
Sweat Glands
Differ structurally and in products secreted; all secrete products via exocytosis (merocrine secretion):
- Eccrine
- Apocrine
- Ceruminous
- Mammary Glands
Eccrine sweat glands
▪Most prevalent type
▪Simple coiled tubular glands in dermis
▪Sweat contains mostly water, waste products, and electrolytes
▪Exits from duct through sweat pore onto epidermal surface
Apocrine sweat glands
▪Found in specific regions of body such as axillae, anal area, and areola
▪Large glands; release protein-rich secretion into hair follicle
▪Secretions become odoriferous once skin bacteria metabolize contents
▪Influenced by sex hormones; become active after puberty
Ceruminous sweat glands
▪Modified apocrine glands ▪Release thick secretion called cerumen (ear wax) into hair follicles in ear
▪Cerumen traps incoming particles along tube leading to tympanic membrane; also lubricates
Mammary sweat glands
highly specialized sweat glands; produce modified sweat (milk)
Sebaceous glands structure
Branched with clusters of secretory cells (acini) surrounded by small ducts; converge to form central duct that empties into hair follicle or small pore; make and secrete sebum
Sebaceous glands
–Everywhere on body except palms and soles; greatest number on face and scalp
–Secretion is influenced by sex hormones, especially male hormone (testosterone)
–Dramatic increase in sebum production occurs after puberty
–Contains cellular fragments and debris in addition to lipids
–Coats hair, providing it with hydrophobic barrier; inhibits water loss
–Also inhibits growth of or kills certain bacteria
Sebum
Waxy, oily mixture of mostly lipids; released by holocrine secretion; secretory cells accumulate sebum until cell ruptures
Acne
Accumulation of sebum and dead cells within sebaceous glands; produces comedone (blackhead); occasionally becomes infected by Propionibacterium acnes; causes inflammation and formation of pustule (pimple)
Wounds
Common skin pathology; defined as any disruption in skin’s integrity; includes
–Lacerations (cuts)
–Burns
–Skin cancers
Burns
Wounds caused by heat, extreme cold, electricity, chemicals, and radiation; classified according to extent and depth of tissue damage:
- First degree
- Second degree
- Third degree
First degree burn (superficial)
–Minor wounds; only damage epidermis
–Skin may develop erythema (redness) and some mild pain without any permanent damage
Second degree burn (partial thickness)
–Involve epidermis and part or all of dermis
–Can result in pain, blistering, and scarring
Third degree burn (full thickness)
–Most damaging wounds
–Involve epidermis, dermis, hypodermis, potentially even deeper tissue (muscle or bone)
–Not generally painful at first because nerves too are destroyed
–Typically major tissue damage and significant scarring; loss of hair follicles; diminished or absent keratin production
–Problems with dehydration due to massive fluid loss from swelling; also great risk for infection
Rule of nines
*Method for estimating how much of body has been affected by burn
*Body is divided into 11 areas; each represents 9% of total body area
*Useful clinical tool for grading extent of burn; severity and extent of burn are used to direct treatment options
Skin Cancer
One of the most common diseases in the world; caused by mutations in DNA; induces cell to lose control of cell cycle
Tumor
Unchecked cell division eventually leads to formation of large population of undifferentiated cells
Metastasize
Tumor cells spread through blood or lymphatic vessels to other tissues and continue to divide
Factors that increase risk of developing cancer
–cancer-inducing chemicals, toxins, or agents called carcinogens
–forms of radiation
Basal cell carcinoma
–Most common of all cancer types–Arises from keratinocytes in stratum basale of epidermis
–Skin regularly exposed to UV radiation is at risk for developing these tumors
–Appears as nodule with a central crater
–Rarely metastasizes to other tissues
–Can be resolved successfully with surgical removal
Squamous cell carcinoma
–Second most common skin cancer–Cancer of keratinocytes of stratum spinosum
–Scaly plaques may ulcerate and bleed; usually on head and neck
–Tumors are more likely to metastasize than basal cell carcinoma; surgical removal is still useful
Malignant melanoma
Cancer of melanocytes
–Early detection of melanoma is critical due to tendency to metastasize
–“Arms” of cancerous melanocytes extend down into dermis and access dermal blood vessels; enables cells to spread to other tissues via bloodstream
–Treated with surgical removal; possibly radiation therapy and chemotherapy
–Prognosis depends on size of tumor, depth to which it extends into dermis, and whether it has metastasized to other tissues
ABCDE rule of Malignant melanoma
Can distinguished from other skin cancers and normal moles using ABCDE rule:
–(A): Asymmetrical shape (two sides do not match)
–(B): Border irregularity
–(C): Color, usually blue-black or a variety of colors
–(D): Diameter generally larger than 6 mm (size of a pencil eraser)
–(E):Evolving (changing) shape and size
