Skin Appendages and Integument Function

What are the major appendages of the skin?

• Sweat glands• Sebaceous glands• Hairs• Nails

What are the types of glands found in the skin?

• Sweat glands-sudoriferous– Merocrine/Eccrine- most common sweat glands, regulates body

temperature (most areas of the skin)• Their secretory portion can be located in the dermis or hypodermis• Produce sweat (a watery mixture of salts), antibodies and metabolic wastes

– Prevents overheating

– Apocrine- produce sweat plus a milky or yellowish substance composed of fat and protein.

• Found in the arm pits, genitalia and the areola of the breasts• Thought to be scent glands.• Their secretory portion can be located in the dermis or hypodermis• Their excretory ducts open into hair follicle• Start secreting at puberty

– Ceruminous- produce cerumen (ear wax), modified apocrine glands– Mammary glands- produce milk, modified apocrine glands

What are the types of glands found in the skin?

• Sebaceous glands- oil glands (sebum)– Softens and lubricates hair and skin, helps hair from

becoming brittle– Slows water loss and kills bacteria– Connected to hair follicles (absent in palms and soles)– A natural skin cream, keeps skin soft

Accessory Structures of the Skin• Hair

– Found almost everywhere on the body EXCEPT the palms, sides/soles of feet, lips and sides of fingers/toes

– Made from hair follicles– Made of dead keratinized skin cells

Parts of Hair

– Shaft-visible part• Medulla(central core)• Cortex (bulky layer)• Cuticle (heavily keratinized; protects hair)

– Root-below the surface– Cuticle– Follicle (surrounds the root)

• External root sheath• Internal root sheath• Base of the follicle is the bulb (where new hair develops)

Hair Related Structures

• Arrector Pili-smooth muscle where dermis contracts with cold or fear, also forms goosebumps, – This muscle inserts with one end to the papillary

layer of the dermis and with the other end to the dermal sheath of the hair follicle.

• Hair root plexus-detects hair movements• Seaceous glands-oil glands

Why is hair useful?

• Senses insects that land on the skin.• Hair on the head protects the head from a

blow, sunlight and heat loss.• Eyelashes shield the eye• Nose hairs filter the air

More about Hair

• Growth cycle is in two stages: growth stage (lasts 2-6 years) and resting stage (3 months); old hair falls out as growth stage begins again (normal hair loss is about 70-100 hairs a day)

• Hair color is due to type and amount of melanin (dark hair-true melanin, blond/red hair-melanin with iron and sulfur, gray-reduction in melanin and white-air bubbles in medullary shaft)

• Hair growth and color

Hair Follicle

Hair Color and Texture• Hair color is determined by the amount and type of melanin

present.• Melanocytes become less active with age. Gray hair is a

mixture of pigmented and non-pigmented hairs.• Red hair results from a modified type of melanin that

contains iron.• The shape of the hair shaft determines texture.

– Round shaft – straight hair– Oval shaft – wavy hair– Flat shafts – curly or kinky hairPerms use chemicals to flatten shafts and makes hair curly.Alopecia is the term for hair loss.

Accessory Structures of the Skin

• Nails made up of tightly packed keratinized cells– Nail body-visible pink portion, free edge appears white– Nail root-buried under skin layers, lunula is white due to

thickened stratum basale– Eponychium (cuticle)-stratum corneum layer

• A nail is a scalelike modification of the epidermis• Useful tools to pick up small objects or scratch an

itch.• Nail matrix is the region responsible for nail growth.

Nails

FUNCTION OF INTEGUMENT!!!!

Thermoregulation- skin contains sweat glands that secrete watery fluid, that when evaporated, cools the body.Sensation- Skin contains sensory receptors that detect cold, touch, and pain.Vitamin D synthesis- cholesterol in the skin is bombarded by sunlight and converted to vitamin D (calcium cannot be absorbed from digestive tract)Blood reservoir- blood will be moved from skin to muscles during strenuous activity.Excretion- Sweating is an important outlet for wastes such as salt and nitrogen containing compounds. (urine)

Physiology of the Skin• Protection - the epidermis provides a barrier to fluid loss

from the body (this protective function is impaired in patients with burns).

• Barrier function - intact skin prevents the entry of micro-organisms into the body. Antimicrobial proteins are produced by the epidermis - they act by piercing holes in the outer membranes of micro-organisms.

• Resistance to wear and tear - continuous replacement of the outer epidermal cells that wear off - new cells are produced in the deepest layer of the epidermis and gradually migrate towards the surface

• The skin provides a barrier to ultraviolet light. The melanocytes contain melanin, which absorbs UV radiation, and also distribute the pigment to neighboring cells. Skin exposed to sunlight becomes wrinkled and creased. Changes seem to be due to disruption of collagen and elastin in dermis, and loss of fibroblasts which make new proteins.

Barriers

• Three types of skin cancer corresponding to three major types of skin cells: basal cells, squamous cells, and melanocytes.

• Cancer of melanocytes - malignant melanoma - is the most lethal variety, but also the least common.

• If caught early, most cases of non-melanoma skin cancer are easily treated under local anaesthetic

• Whites in Australia have the highest rates of skin cancer of all types in the world.

• The damaging effects of sunlight can occur many years before tumors appear.

• Ultraviolet light causes mutations at points on a DNA strand.

Skin Cancer

Fun Facts• House dust is mainly skin flakes! • If you laid out all your skin on a flat surface, it would have

an area of about 2 square meters. • Skin weighs about 2.5 kilograms - the largest organ in the

body. • What hurts if you pull it, but doesn't hurt if you cut it?

Your hair, of course! • Skin is elastic - it springs back into shape when stretched.

Some medicines (estrogen, nicotine) can pass through the skin, but others cannot (insulin). Why is that? Because only fat-soluble substances can enter the skin, not water-soluble ones.

• Your hair stands on end and you develop 'goose bumps' because there are tiny muscles attached to the hair follicles and they contract when you are frightened or cold.

Additional Online Activities

• Click here to go to McGraw-Hill - Essential Study Partner

• Choose the Unit : Support & Movement• Choose Topic : Integumentary System

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