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Skin: Function & Interaction with other systems in the body

Antonia Tanzil Imelda Rosalyn Sianipar

Physiology Department Faculty of Medicine, University of Indonesia

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THE INTEGUMENTARY SYSTEM

•  Integumentary System (inte = whole; -gument = body covering )

•  Two major components: – Cutaneous membrane / skin – Accessory structure: hair, nails, & multicellular

exocrine glands

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SKIN (CUTANEOUS MEMBRANE)

•  Largest organ of the body, both surface area & weight •  In adults,

–  covers an area of about 2m2 –  weighs 4.5 – 5 kg (16% of total body weight)

•  Has 2 components:

– Epidermis – Dermis

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EPIDERMIS

•  Functions - As barrier that prevents water loss and entry of

chemicals & microorganism - protects against abrasion and UV light radiation - synthesis of vitamin D - gives rise to hair, nails and glands

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DERMIS

•  Functions -  Give structural strength and flexibility of

the skin -  The epidermis exchanges gases,

nutrients, and waste products with blood vessels in the dermis

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ACCESSORY SKIN STRUCTURES

•  1. Hair and hair follicles •  2. Smooth muscle arrector pilli •  3. Cutaneous glands •  4. Nails

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General Function of The Integumentary System

Protection Excretion

and Absorption

Sensation Maintenance

of Body Temperature

Synthesis of Vitamin D3

Storage of lipids

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GENERAL FUNCTION A. Protection

Factors that play roll in this function: - keratin - lipids - oily sebum - acidic pH of perspiration - pigment melanin - epidermal Langerhans cells and macrophages in the

dermis

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GENERAL FUNCTION B. Excretion and Absorption - Sweat excretion - Absorption of water soluble substances, certain lipid soluble materials, certain drugs and gases

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GENERAL FUNCTION C. Sensation of touch, pressure, pain and

temperature stimuli

Variety of nerve endings and sensory receptors are distributed in the epidermis and dermis

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GENERAL FUNCTION

D. Maintenance of body temperature - Thermoreceptors - Sweat production and evaporation - Alterations in cutaneous blood flow conserve or release heat * Local control * Neural control (primary determining

factor)

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GENERAL FUNCTION Maintenance of body temperature

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GENERAL FUNCTION

E. Synthesis of vitamin D3 - Action of UV rays in sunlight to the

molecule in the skin. - The role of liver and kidneys to produce

the most active form of vitamin D3

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GENERAL FUNCTION

F. Storage of lipids – In adipocytes in the dermis and

adipose tissue in the subcutaneous layer

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RELATIONS OF THE INTEGUMENTARY SYSTEM WITH OTHER SYSTEM IN THE BODY

MUSCULOSKELETAL SYSTEM •  Synthesizes vitamin D3, essential for:

–  Calcium & Phosphorus absorption (bone maintenance and growth)

–  Calcium absorption (muscle contraction) –  Skeletal system provides support for skin

•  Contraction of skeletal muscles pull against skin of

face, producing facial expressions, important in comunication

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NERVOUS SYSTEM •  Nerve endings in skin and subcutaneous tissue

provide input to the brain for touch, pressure, thermal and pain sensations

•  Control blood flow and sweat glands activities for thermoregulation

•  Stimulates contraction of arrector pili muscles to elevate hair

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ENDOCRINE SYSTEM

•  Keratinocytes in skin help activate vitamin D to calcitriol, a hormone that aids absorption of dietary calcium and phosphorus

•  Sex hormones

–  Stimulate sebaceous glands activities –  Influence hair growth, distribution of subcutaneous fat,

and apocrine sweat glands activities •  Adrenal hormone

–  Alter dermal blood flow and help mobilize lipids from adipocytes

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CARDIOVASCULAR SYSTEM

•  Local chemical changes in dermis cause widening and narrowing of skin blood vessels, which help adjust blood flow to the skin, prevents fluid loss, serves as blood reservoir

•  Provides oxygen and nutrients to skin; delivers hormones and cells of immune system

•  Carries away carbon dioxide, waste products and toxins from skin

•  Provides heat to maintain normal skin temperature

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LYMPHATIC SYSTEM & IMMUNITY

•  Discourage penetration and growth of microbes:

– Provide mechanical barriers – Langerhans cells in epidermis : recognizing &

processing foreign antigens – Macrophages in the dermis : phagocytize

microbes that penetrate the skin surface – Mast cells trigger inflammation and initiate the

immune response •  Defending the integument by providing additional

macrophages and mobilizing lymphocytes

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RESPIRATORY SYSTEM

•  Hairs in nose filter dust particles from inhaled air •  Stimulation of pain nerve endings in skin may

alter breathing rate •  Provide oxygen and eliminates carbon dioxide via

gas exchange with blood

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DIGESTIVE SYSTEM

•  Helps activate vitamin D to the hormone

calcitriol, which promotes absorption of dietary calcium and phosphorus in the small intestine

•  Provides needed nutrients to the skin, and

lipids for storage by adipocytes

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URINARY SYSTEM

•  Assists in excretion of water and solutes •  Keratinized epidermis limits fluid loss through

skin •  Excretes waste products of skin metabolism

•  Activates vit.D precursor made by keratinocytes

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REPRODUCTIVE SYSTEM

•  Nerve endings in skin and subcutaneous tissue respond to erotic stimuli à contributing to sexual pleasure

•  Mammary glands (modified sweat glands) produce milk •  Suckling of a baby stimulates nerve endings in skin à

leading to milk ejection •  Skin stretches during pregnancy as fetus enlarges

•  Sex hormones affect hair distribution, adipose tissue distribution in subcutaneous layer, and mammary gland development

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Effects of Aging on The Integumentary System

•  The skin becomes thinner and very pale

•  The integument becomes weaker and less resilient, and sagging and wrinkling occur

•  The skin becomes dry and often scaly

•  How does this conditions occurs

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Effects of Aging on The Integumentary System

•  The skin becomes cool

•  The hairs are gray or white

•  Prolonged skin wound-healing

•  How does this conditions occurs

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References

•  Marieb EN. Essentials of human anatomy and Physiology. 9th ed;Pearson:2009.

•  Martini FH. Fundamentals of Anatomy and Physiology. 7th ed; Pearson:2006

•  Tortora GJ. Principles of Anatomy and Physiology. 11th ed; John Wiley: 2006

•  Tate P. Principles of Anatomy and Physiology;McGrawHill. 2009

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THANK YOU

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Synthesis of vitamin D3 UV radiation

Epidermal cells

7-dehydrocholesterol Cholecalciferol/vitamin D3

liver

intermediary products

kidneys hormone calcitriol

Absorption of calcium & phosphorus by the small intestine

Bone maintenance & growth

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SYNTHESIS OF VITAMIN D

•  UV LIGHTà MOLECULE IN THE SKIN •  (7-DEHYDROCHOLESTEROL) IS CONVERTED •  àVIT.D PRECURSOR MOL.

(CHOLECALCIFEROL)à BY THE BLOOD à •  LIVERà MODIFIED à TO THE KIDNEY à

•  MODIFIED TO FORM ACTIVE VITAMIN D (CALCITRIOL) à STIMULATE CALCIUM AND PHOSPHATE UPTAKE IN THE INTESTINE

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EFFECTS OF AGING ON THE INTEGUMENTARY SYSTEM

•  Most changes occur in the dermis •  Collagen fibers begin to ↓ in number, stiffen,

break apart and disorganize à shapeless •  Elastic fibers lose some of their elasticity •  Fibroblast (produce collagen and elastic fibers) à ↓ in number à skin forms wrinkles

•  Langerhans cells ↓, macrophages à less –efficient phagocytes à skin immune responsiveness ↓

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EFFECTS OF AGING ON THE INTEGUMENTARY SYSTEM

•  Size of sebaceous glands↓à dry and broken skin, more susceptible to infection

•  Production of sweat diminishes à ↑incidence to heat stroke

•  Number of functioning melanocytes↓à gray hair and atypical skin pigmentation.

•  Size of some melanocytes↑ à pigmented blotching (age spots)

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EFFECTS OF AGING ON THE INTEGUMENTARY SYSTEM

•  Walls of blood vessels in the dermis become thicker and less permeable, subcutaneous adipose tissue is lost.

•  Aged skin is thinner than young skin, migration of cells from the basal layer to the epidermal surface slows considerably.

•  Skin heals poorly and becomes more susceptible to pathological conditions: skin cancer and pressure sores

•  Growth of nails and hair slows, nailsà brittle due to dehydration

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SKIN COLOR

•  Melanin: responsible for skin, hair, and eye color.

•  Most melanin molecules : brown to black pigments, some are yellowish or reddish.

•  Melanin : protection against UV light •  Melanin >> :freckles, moles, nipples, areolae of

the breast, axillae and genitalia •  Melanin <<: lips, palms of the hands, soles of

the feet

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SKIN COLOR

•  Melanin production is determined by genetic factors,exposure to light and hormones

•  Skin colors are not determined by the number of melanocytes

•  Exposure to UV light darkens melanin and stimulates melanin productionà additional protection

•  During pregnancy à estrogen and melanocyte stimulating hormon à ↑ melanin production in the mother

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GLANDS IN THE SKIN

•  Skin à 2 types of exocrine glands: •  Sebaceous glands and sweat glands

•  Sebaceous (oil) glandsà oily lipid secretion àsebumà inhibits bacteria growth, lubricates and protects the keratin of the hair shaft and conditions the surrounding skin.

•  Sebaceous follicles ( not associated with hair follicles) discharge sebum directly onto the epidermis: on the face, back, chest, nipples and external genitalia

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GLANDS IN THE SKIN

•  Sweat glands/ sudoriferous glands: apocrine sweat glands and merocrine sweat glands.

•  Apocrine sweat gland •  - Armpits; around the nipples and pubic region à hair foll •  - Secretion: sticky, cloudy and odorous •  - Secreting at puberty à nutrient source for bacteria •  - Controlled by nervous system and circulating hormones

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GLANDS IN THE SKIN

•  Merocrine (Eccrine) sweat glands •  - More numerous than apocrine s.g (adult : 2-5 million) à palms and soles >> •  - Sweat produced = sensible perspiration •  - 99% water + electrolites (NaCl), organic nutrients, peptide (AB properties), waste products. •  - pH 4.0 -6.8

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GLANDS IN THE SKIN

•  Functions of merocrine sweat glands •  - Cooling the surface of the skin •  - Regulated by neural and hormonal •  - Excreting water and electrolytes (+ ingested drugs) •  - protection from Environmental Hazards

* Dilution harmful chemicals; inhibition growth of microorganisms by flushing and action of dermicidin

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GLANDS IN THE SKIN

•  Specialized glands •  Mammary glands

- Anatomically related to apocrine glands - Controlled by interaction between sex hormones and pituitary hormones

•  Ceruminous glands - modified sweat glands in the passageway of external ear - secretions + sebaceous glands à cerumen