chapter 5 - integumentary system

skin consists of 2 part

epidermis and dermis

epidermis

outermost superficial region

dermis

middle region

hypodermis

superficial fascia, deepest region (NOT part of the skin)

subcutaneous layer deep to the skin

mostly adipose tissue

four cell types of the epidermis

keratinocytes

melanocytes

dendritic cells

tactile epithelial cells

five distinct layers of the epidermis

stratum basale

stratum spinosum

stratum granulosum

stratum lucidum (only found in thick skin, palms + soles)

stratum corenum

epidermis

keratinized stratified squamous epithelium

made keratinocytes, melanocytes, dendritic (langerhans), and tactile (Merkel) cells

keratinocytes

produce fibrous protein keratin

melanocytes

10-25% in lower epidermis

produce pigment melanin

dendritic (Langerhans) cells

macrophages that help activate immune system

tactile (Merkel) cells

touch receptors

stratum basale

bottom, deepest single-celled epidermal layer

also called stratum germinativum

stem cells, melanocytes, merkel cells

stratum spinosum

mutliple layers

keratinocytes, melanin granules, dendritic (langerhan’s) cells

stratum granulosum

thin; three to five cell layers

cells flattened

keratinocytes keratohyalin, and lamellated granules accumulated

stratum lucidum

a few rows of flat cells

thin, transparent band

ONLY IN THICK SKIN, PALMS and SOLES

dead keratinocytes

stratum corneum

top layer, 20-30 rows of dead, flat cells

dead keratinocytes (keratinized membranous sacs)

dermis

strong and flexible connective tissue

has two layers papillary and reticular

papillary layer of dermis

areolar connective tissue, collagen and elastic fibers, blood vessels

dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings (touch receptors)

reticular layer of dermis

80% of the thickness of dermis

collagen fibers provide strength and resiliency

ex: stretches with pregnancy

skin markings

friction ridges, cleavage lines, and flexure lines

friction ridges

epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints

ex: identical twins, still don’t have the same

cleavage lines

collagen fibers arranged in bundles for cleavage (tension) lines

incisions made parallel to cleavage lines heal more readily

flexure lines

of reticular layer are dermal folds at or near joints

sensory receptors in the dermis

Pacinian corpuscles, Meissner’s corpuscles, and free nerve endings

Pacinian corpuscles

stimulated by heavy pressure

Meissner’s corpuscles

tactile sense to light touch

free nerve endings

respond to temperature

hypodermis

subcutaneous layer deep to the skin

composed of adipose and areolar connective tissue

melanin

yellow to reddish-brown to black pigment

responsible for dark skin colors

produced in melanocytes, which migrate to keratinocyte to form “pigment shields” for nuclei

freckles and pigmented moles = local accumulations of melanin

carotene

yellow to orange pigment

most obvious in palms and soles

hemoglobin

responsible for pinkish hue of skin

blueness or cyanosis

low oxygenation of hemoglobin

sign of respiratory or cardiovascular issues

pallor or blanching

emotional stress, low blood pressure, anemia (decreased ability of blood to carry oxygen)

redness or erythema

embarrassment, fever, inflammation, or allergy

yellowness or jaundice

liver disorders

red/purple/green/yellow marks

bruises, ecchymoses or hematomas

result from blood leakage from damaged blood vessel beneath skin

brown or black patches

hyperpigmented, thickened skin in folds may be a sign of an endocrine disorder

derivatives of the epidermis

sweat glands

oil glands

hairs and hair follicles

nails

two main types of sweat (sudoriferous) glands

eccrine (merocrine) sweat glands

apocrine sweat glands

eccrine (merocrine) sweat glands

all over the body

active from birth, sweat = 99% water

merocrine (exocrine secretion)

thermoregulation and ducts open to the surface of the skin

apocrine sweat glands

axillary and anogenital areas (limited)

active from puberty, sweat = fatty

apocrine

function as sexual scent glands

ducts open to the hair follicle

sebaceous glands

widely distributed

associated with hair follicle

active from puberty

sebum = oily holocrine secretion (debris of dead cells), bactericidal which softens hair and skin

ducts open to the hair follicle

hair

consists of dead-keratinized cells and contains hard keratin

hair pigments

melanin (yellow, rust brown, and black)

gray and white hair = decreased melanin production, increased air bubbles in shaft

functions of hair include

helping to maintain warmth

alerting the body to presence of insects on the skin

guarding scalp against physical trauma, heat loss, and sunlight

hair is distributed over the entire skin surface except…

palms, soles, and lips

nipples and portions of the external genitalia

two-layered follicle wall

outer connective tissue root sheath

inner epithelial sheath

parts of hair follicle

shaft

hair root

hair bulb (expanded deep end)

hair follicle receptor (root hair plexus)

arrector pili

hair follicle receptor (root hair plexus)

sensory nerve endings around each bulb

stimulated by bending a hair

arrector pili

smooth muscle attached to follicle

responsible for “goosebumps” (involuntary NS)

types of hair

vellus and terminal

vellus

pale, fine body hair of children and adult females

terminal

coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)

functions of the integumentary system

protection (chemical, physical and mechanical, and biological barriers)

body temperature

cutaneous sensations

metabolic functions

blood reservoirs

excretion

chemical barrier

low pH secretions (acid mantle) and defensins limit bacterial activity

physical and mechanical barriers

keratin and glycolipids block most water and water-soluble substances

biological barriers

dendritic cells, macrophages, and DNA

body temperature regulation

~500 ml/day of routine insensible perspiration at a normal body temperature

increased temp = dilation of dermal vessels and increased sweat gland activity (sensible perspirations) to cool the body

cutaneous sensations

temperature, touch, and pain

metabolic functions

synthesis of vitamin D precursor and collagenase

blood reservoir

up to 5% of body’s blood volume

excretion

nitrogenous wastes and salt in sweat

most skin cancers are…

benign (do not spread)

risk factors of skin cancer

overexposure to UV radiation

frequent irritation of the skin

metastasis

spread to other tissues

three major types of skin cancer

basal cell carcinoma

squamous cell carcinoma

melanoma

basal cell carcinoma

least malignant, most common

exposed surfaces and easy to manage

stratum basale cells proliferate and slowly invade dermis and hypodermis

cured by surgical excision in 99% of cases

squamous cell carcinoma

second most common and can spread if not treated early

involves keratinocytes of stratum spinosum

common on scalp, ears, lower lip, and hands

good prognosis is treated by radiation therapy or removed surgically

melanoma

malignoma and most dangerous

can enter into blood stream and then can travel to the lungs

involves melanocytes

highly metastatic and resistant to chemo

wide surgical excision and immunotherapy

burns can be caused by…

heat, electricity, radiation, and certain chemicals

burns

tissue damage, denatured protein, cell death

immediate threat of burns

dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock

rule of nines

used to estimate the volume of fluid loss from burns

a/p head and neck = 9%

a/p upper limbs = 18%

a/p trunk = 36%

perineum = 1%

a/p lower limbs = 36%

first degree burns

epidermal damage only

localized redness, edema (swelling), and pain

second degree burns

epidermal and upper dermal damage

blisters appear

third degree burns

entire thickness of skin damaged

gray-white, cherry red, or black

no initial edema or pain (nerve endings destroyed)

skin grafting usually necessary