Skin Functions

what is the main function of the skin

maintaining homeostasis

how does the skin maintain homeostasis

• protective covering

• prevents some water loss

• contains sensory receptors

• excretes some wastes

• helps produce vitamin d

• helps regulate body temperature

what is the skin a protective covering against

harmful substances and microorganisms

what are the three types of ways the skin provides protection

• physical barriers

• chemical barriers

• biological barriers

why is the skin a good physical barrier

it is continuous so bacteria cannot breach to get in

what contributes to the skin’s physical barrier

flat, dead cells of stratum corneum surrounded by lipids

what blocks most water and water soluble substances

keratin and glycolipids

what is a slight weakness of keratin and glycolipids

fat soluble things might be able to get in

what are some things that can penetrate the skin

• lipid soluble substances

• plant oils (ex: poison ivy

• organic solvents

• some drugs

why is it good that some drugs can penetrate the skin

transdermal drug delivery has made an important contribution to medical practice as an alternative to oral delivery and hypodermic injections

what are the ways that the skin acts as a chemical barrier

• skin secretions

• melanin

what are skin secretions

low pH (acidic) controls bacterial multiplication

acid mantle

low pH skin secretions to control bacterial multiplication

what are some things that kill bacteria on the skin

sebum and natural antibiotics like defensins

how does melanin act as a chemical barrier

defense against UV radiation damage

what are the ways that the skin acts a biological barrier

• dendritic cells of epidermis

• macrophages of dermis

what are biological barriers in place in case of

if there is a breach

how do dendritic cells of the epidermis act as a biological barrier

present foreign antigens to white blood cells

how do macrophages of the dermis act as a biological barrier

present foreign antigens to white blood cells

how does the skin contribute to the regulation of body temperature

sweat glands are adjusted accordingly via a negative feedback loop

why is it important to regulate body temperature

a slight shift can disrupt rates of metabolic reactions

what is the set point of body temperature monitored by

the hypothalamus

what is the set point of deep body temperature

98.6 degrees Fahrenheit

what is the negative feedback loop process for when body temperature rises

• thermoreceptors signal hypothalamus

• vasodilation of dermal blood vessels

• sweat glands are activated

what is the negative feedback loop process for when body temperature falls

• thermoreceptors signal hypothalamus

• vasoconstriction of dermal blood vessels

• sweat glands are inactive

• muscles contract involuntarily → shivering

how does vasoconstriction increase body temperature

when the blood vessels constrict it preserves the heat that your body already has by reducing blood flow to the skin

how does vasodilation decrease body temperature

by widening the blood vessels near the surface of the skin so excess heat escapes into the air

what is heat a product of

cellular metabolism

what are the most active body cells that are major heat producers

• skeletal muscle

• cardiac muscle

• cells of the liver

what are the methods of heat loss

• radiation

• conduction

• convection

• evaporation

radiation

primary method of heat loss, where infrared heat rays escape

conduction

heat moves from skin to cooler objects

convection

heat loss into circulating air currents

evaporation

sweat changes into a gas and carries heat away

what are two problems in temperature regulation

• hyperthermia

• hypothermia

hyperthermia

abnormally high body temperature

what can cause hyperthermia

a hot humid day when sweat cannot evaporate, because when air temperature is high, radiation is less effective so body may gain heat from hotter air

what are the symptoms of hyperthermia

• skin becomes dry

• weakness

• dizziness

• nausea

• headache

• rapid pulse

what causes hypothermia

prolonged exposure to cold or illness

shivering

involuntary skeletal muscle contraction

what initiates shivering

hypothalamus

what are the symptoms of hypothermia

• confusion

• lethargy

• loss of reflexes

• loss of consciousness

if hypothermia is not treated what happens

organs shut down

hypothermia

abnormally low body temperature

what can extreme vasodilation result in

collapse of the cardiovascular system which can be fatal

fever

set point of body temperature is elevated by the immune system to fight infection

what is the process that occurs that results in a fever

in response to the presence of bacteria phagocytes release pyrogens, so the hypothalamus increases the set point and thus raises body temperature

what helps destroy pathogens

elevated body temperature

how does the body actually cause an increase in its temperature

• shivering

• no sweat

• dermal blood vessels constrict

why do you sweat when your fever breaks

your body no longer needs to raise its temperature to fight off a virus

when is hypothermia intentionally induced

during certain surgeries to prevent organ damage from decreased oxygen supply body temperature is lowered to between 79 and 89 degrees farenheit

what are a few additional functions of the skin

• cutaneous sensation

• metabolic functions

• excretion

cutaneous sensation

receptors in the skin respond to external stimuli

what system is the cutaneous sensation part of

nervous system

examples of cutaneous sensation

• touch receptors

• deep pressure

what produces the vitamin D precursor

metabolic functions

what is excreted

some nitrogen contain wastes (urea)

what are the types of skin cancer

• basal cell carcinoma

• squamous cell carcinoma

• melanomas

where do basal and squamous cell carcinoma arise from

epithelial cells in skin

where do melanomas arise from

melanocytes

what type of skin caner is the least common but the most deadly

melanomas