homeostasis

HomeostasisHomeostasis

How the body maintains a constant How the body maintains a constant internal environmentinternal environment

Levels of organizationLevels of organization

From smallest to largest:From smallest to largest: CellsCells TissuesTissues OrgansOrgans Organ SystemsOrgan Systems OrganismsOrganisms

Organ systems work together to maintain a Organ systems work together to maintain a constant internal environment. (homeostasis)constant internal environment. (homeostasis)

Levels Beyond OrganismLevels Beyond Organism

There are higher There are higher levels of organization levels of organization above organismsabove organisms PopulationPopulation CommunityCommunity EcosystemEcosystem BiosphereBiosphere

What are the major organ What are the major organ systems?systems?

IntegumentaryIntegumentary MusculoskeletalMusculoskeletal CardiovascularCardiovascular RespiratoryRespiratory NervousNervous EndocrineEndocrine ImmuneImmune

Integumentary SystemIntegumentary System

The skin is the largest The skin is the largest organ in the body, 12-organ in the body, 12-15% of body weight. 15% of body weight.

Two distinct layers occur Two distinct layers occur in the skin: the in the skin: the dermisdermis and and epidermisepidermis. .

The dermis is a The dermis is a connective tissue layer connective tissue layer under the epidermis, and under the epidermis, and contains nerve endings, contains nerve endings, sensory receptors, sensory receptors, capillariescapillaries, and elastic , and elastic fibers fibers

Follicles and GlandsFollicles and Glands

Hair follicles are lined Hair follicles are lined with cells that synthesize with cells that synthesize the proteins that form the proteins that form hair hair

sebaceous gland (that sebaceous gland (that secretes the oily coating secretes the oily coating of the of the hair shafthair shaft), ), capillary bedcapillary bed, nerve , nerve ending, and small ending, and small muscle are associated muscle are associated with each hair follicle with each hair follicle

EWWWW!EWWWW!

If the sebaceous If the sebaceous glands becomes glands becomes plugged and plugged and infected, it becomes infected, it becomes a skin blemish (or a skin blemish (or pimple)pimple)

Sweat!Sweat!

2 types of sweat 2 types of sweat glandsglands All sweat glands open All sweat glands open

to the surface through to the surface through pores. pores.

The two types are The two types are Eccrine (all over the Eccrine (all over the body), Apocrine (the body), Apocrine (the smelly ones)smelly ones)

Hair and NailsHair and Nails

Hair, scales, feathers, Hair, scales, feathers, claws, horns, and nails claws, horns, and nails are animal structures are animal structures derived from skin. derived from skin. Genetics controls Genetics controls several features of hair: several features of hair: baldness, color, texture.baldness, color, texture.

Nails consist of highly Nails consist of highly keratinized, modified keratinized, modified epidermal cells. The nail epidermal cells. The nail arises from the nail bed. arises from the nail bed.

How does it help in How does it help in homeostasishomeostasis

The integumentary The integumentary system has multiple system has multiple roles in homeostasis, roles in homeostasis, including protection, including protection, temperature temperature regulation, sensory regulation, sensory reception, reception, biochemical biochemical synthesis, and synthesis, and absorption.absorption.

Skin and HomeostasisSkin and Homeostasis

The skin's primary functions are to serve as a The skin's primary functions are to serve as a barrier to the entry of microbes and viruses, barrier to the entry of microbes and viruses, and to prevent water and extracellular fluid loss and to prevent water and extracellular fluid loss

Melanocytes form a second barrier: protection Melanocytes form a second barrier: protection from the damaging effects of ultraviolet from the damaging effects of ultraviolet radiation radiation

When a microbe penetrates the skin (or when When a microbe penetrates the skin (or when the skin is breached by a cut) the the skin is breached by a cut) the inflammatory responseinflammatory response occurs. occurs.


When the body temperature rises, the When the body temperature rises, the hypothalamus sends a nerve signal to the hypothalamus sends a nerve signal to the sweat-producing skin glands, causing them to sweat-producing skin glands, causing them to release about 1-2 liters of water per hour, release about 1-2 liters of water per hour, cooling the body cooling the body

The hypothalamus also causes dilation of the The hypothalamus also causes dilation of the blood vessels of the skin, allowing more blood blood vessels of the skin, allowing more blood to flow into those areas, causing heat to be to flow into those areas, causing heat to be convected away from the skin surface. convected away from the skin surface.


When body temperature When body temperature falls, the sweat glands falls, the sweat glands constrict and sweat constrict and sweat production decreases. If production decreases. If the body temperature the body temperature continues to fall, the continues to fall, the body will engage in body will engage in thermiogenesis, or heat thermiogenesis, or heat generation, by raising generation, by raising the body's metabolic rate the body's metabolic rate and by shivering. and by shivering.

Skin and HomestasisSkin and Homestasis

Water loss occurs in the skin by two routes.Water loss occurs in the skin by two routes. evaporation evaporation sweating sweating

In hot weather up to 4 liters per hour can be In hot weather up to 4 liters per hour can be lost by these mechanisms. lost by these mechanisms.

Skin damaged by burns is less effective at Skin damaged by burns is less effective at preventing fluid loss, often resulting in a preventing fluid loss, often resulting in a possibly life threatening problem if not treatedpossibly life threatening problem if not treated

Sensors in the skinSensors in the skin

Sensory receptors in the Sensory receptors in the skin include those for skin include those for pain, pressure (touch), pain, pressure (touch), and temperature. and temperature.

Deeper within the skin Deeper within the skin are Meissner's are Meissner's corpuscles, which are corpuscles, which are especially common in especially common in the tips of the fingers the tips of the fingers and lips, and are very and lips, and are very sensitive to touch.sensitive to touch.

Sensors in the skinSensors in the skin

Pacinian corpuscles Pacinian corpuscles respond to pressure. respond to pressure.

Temperature Temperature receptors: more cold receptors: more cold ones than hot onesones than hot ones

Synthesis in the skinSynthesis in the skin

Skin cells synthesize melanin and Skin cells synthesize melanin and carotenes, which give the skin its color. carotenes, which give the skin its color.

The skin also assists in the synthesis of The skin also assists in the synthesis of vitamin D. vitamin D.

Children lacking sufficient vitamin D Children lacking sufficient vitamin D develop bone abnormalities known as develop bone abnormalities known as rickets.rickets.

RicketsRickets

SummarySummary

The skin plays an important role in the The skin plays an important role in the maintenance of homeostasis.maintenance of homeostasis.

It is an important barrier to infections and It is an important barrier to infections and diseases. diseases.

It plays a part in the feedback loop that It plays a part in the feedback loop that regulates body temperature.regulates body temperature.

It also synthesizes important vitamins for It also synthesizes important vitamins for our bodies. our bodies.

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