1. Accessory Structures of Skin
Epidermal derivatives
Cells sink inward during development to form:
hair
oil glands
sweat glands
nails
Fig. 5.1

2. Structure & Fxn. of Hair Shaft -- visible medulla, cortex & cuticle
straight hair  X-sec round
wavy hair  X-sec oval
curly hair  x-sec kidney shaped
Root -- below the surface
Follicle surrounds root
external root sheath
internal root sheath
base of follicle is bulb
blood vessels
germinal cell layer
3.Hair (pili) have a number of important characteristics:
i.hair is composed of dead, keratinized epidermal cells
ii.each hair consists of:
a. shaft which projects above the surface of the skin
b. root which penetrates into the dermis
c. hair follicle which surrounds the root
iii. hair grows due to cell division occurring in the matrix of the bulb, located at the base of a hair follicle; there is a growth cycle that includes a growth stage and resting stage
v. the color of hair is determined primarily by the amount and type of melanin
Result of melanin produced in melanocytes in hair bulb:
Dark hair contains true melanin
Blond and red hair contain melanin with iron and sulfur
Graying hair is result of decline in melanin production
White hair has air bubbles in the medullary shaft
vi. the primary functions of hair are: prevention of heat loss, protection  decreases sunburn, eyelashes help protect eyes, & touch receptors (hair root plexus) senses light touch
Fig. 5.5

3. Hair Growth Growth cycle = growth stage & resting stage Growth stage
lasts yrs.
matrix base of hair root produce length
Resting stage
lasts 3 mths.
matrix cells inactive & follicle atrophies
Old hair falls out as growth stage begins again
normal hair loss = hairs/day

4. Hair Related Structures
Arrector pili muscle
smooth muscle in dermis contracts w/ cold or fear.
forms goosebumps as hair is pulled vertically
Hair root plexus
detect hair movement
associated with hairs are sebaceous (oil) glands, arrector pili muscles, and hair root plexuses
Arrector pili [ = hair, as in depilatory ] Mm originate on the top of the dermis & insert near the base of the follicle to erect the hair. When the Arrector pili M contracts, hair is straightened & is pulled upwards, forming a little bump (“goose bump,” or “chicken flesh,” as the Germans say; the medical word is horripilation or ‘scary hair’). This reaction is mostly a leftover when our ancestors had more hair for insulation & communication; it provides little air-trapping insulation for humans.
Fig. 5.5

5. Glands of the Skin Specialized exocrine glands found in dermis
Sebaceous (oil)
Sudiferous (sweat)
Ceruminous (wax)
Mammary (milk)
Fig. 5.1

6. Sebaceous (oil) glands
Sebum
Comb. of cholesterol, proteins, fats & salts
keeps hair & skin soft & pliable
inhibits growth of bacteria & fungi (ringworm)
Acne
bacterial inflammation of glands
secretions stimulated by puberty
Fig. 5.6
4.Sebaceous (oil) glands have several important characteristics:
i.they are typically connected to hair follicles
ii.they secrete an oily substance called sebum which prevents dehydration of hair and skin, & inhibits growth of certain bacteria
Sebaceous glands develop from hair follicles & empty into them; these holocrine glands produce sebum, an oily substance that prevents drying of the skin & hair [ sebum = grease ] & contains lysozymes (bactericide). In a few sensitive regions of the skin, such as on the lips, sebaceous glands may be found independently of hair follicles. Sebaceous glands lubricate the nipple for nursing & the female’s vestibule for coitus. Sebum contains pheromones too.
What type of secretion (class of glands) do sebaceous glands exhibit? Holocrine secretion  mature cell dies and becomes secretory product.
Secretory portion in the dermis
Most open onto hair shafts

7. Sudoriferous (sweat) glands
Eccrine (sweat) glands
most areas of skin
secretory portion in dermis with duct to surface
regulate body temperature
H2O, NaCl, urea, uric acid, A.A., glucose, & lactic acid
5.Sudoriferous (sweat) glands produce sweat (perspiration) which helps to cool the body by evaporating, and also eliminates small amounts of wastes; there are two types of sweat glands (see Table 5.3):
i.numerous eccrine sweat glands which have an excretory duct that opens at a pore at the surface of the epidermis
1. eccrine sweat glands are coiled tubes that directly empty their product onto the epidermal surface. Eccrine sweat glands excrete mostly water with a little salt & wastes [ about 99% water with a little salt, metabolites, & waste products, such as urea ] and are a powerful cooling adaptation. Evaporation of water from your skin surface cools the blood in the dermal layer, and this cooled blood then circulates to cool the remaining body. Sweat also functions to inhibit bacterial growth—it has lysozymes.
ii.apocrine sweat glands which are located mainly in the skin of the axilla, groin, areolae, and bearded facial regions of adult males; their excretory ducts open into hair follicles
apocrine sweat glands are larger and are concentrated in the axillary, anal, & inguinal regions, and the areola of the nipple. They usually empty into a hair follicle. Apocrine sweat is more viscous, providing a feast for bacteria. Bacterial wastes from the more viscous apocrine sweat adds to one's body odor, so “you might better communicate with your fellow human beings.” Surprise!: Apocrine sweat glands become active in puberty & are concentrated where there’s pubic hair! Apocrine sweat glands are stimulated during emotional stress & sexual arousal; this secretion is commonly referred to as “cold sweat.” Their secretion contains pheromones.
Eccrine glands release sweat via merocrine secretion, and apocrine glands through apocrine secretion (see previous section on epithelial tissue & secretory modes). However, new thoughts and studies have pointed to the idea that these are actually, merocrine glands, too!!! Eccrine glands are for thermoregulation, and apocrine glands are for chemical & visual communication.
Fig. 5.6
Apocrine (sweat) glands
Armpit & pubic regions
Also around areolae & bearded regions of adult males
Secretory portion in dermis w/ duct that opens onto hair follicle
Secretions more viscous & milky (lipids & protein)

8. Ceruminous glands
6.Ceruminous glands are modified sweat glands located in the ear canal;
they are involved in producing a waxy secretion called cerumen (earwax)
Provides a sticky barrier that prevents entry of foreign bodies into the ear canal.
Ceruminous Glands produce cerumen (ear wax) in the auditory canal, which functions along with sebum & ear hair to trap intruders from reaching the ear drum & middle ear. [ Ceruminous glands are modified sweat glands ]
Fig
Modified sweat glands produce waxy secretion in ear canal
Cerumin contains secretions of oil & wax glands
Helps form barrier for entrance of foreign bodies
Impacted cerumen may reduce hearing

9. Structure of Nails Tightly packed keratinized cells Nail root
Fig. 5.7
Each nail consists of:
a.free edge
b.transparent nail body with a whitish lunula at its base
c.nail root embedded in a fold of skin
Associated with a nail are:
a.hyponychium (located under the free edge) attaches the nail to the fingertip
b.eponychium (cuticle) attaches the margin of nail wall to neighboring epidermis
c.nail matrix below nail root produces growth in which cell division occurs
Cells transformed into tightly packed keratinized cells 1 mm per week
iii.The functions of nails include helping to grasp and manipulate objects, providing protection against trauma to the ends of the digits, and scratching various body parts.
Tightly packed keratinized cells
Nail body
visible portion pink due to underlying capillaries
free edge appears white
Nail root
buried under skin layers
lunula is white due to thickened stratum basale
Eponychium (cuticle)
stratum corneum layer

10. Thin Skin vs. Thick Skin Thick skin only on palms and soles
thick epidermis (.6 to 4.5 mm.) with distinct stratum lucidum & thick stratum corneum
lacks hair follicles and sebaceous glands
ii. thick skin covers the palms, palmar surfaces of digits, and soles

11. Thin Skin vs. Thick Skin Thin skin covers most of body
thin epidermis (.1 to .15 mm.) that lacks stratum lucidum
lacks epidermal ridges, has fewer sweat glands & sensory receptors
i. thin skin covers all body regions except the palms, palmar surfaces of digits, and soles

12. Photodamage UVA & UVB light can damage skin
Acute overexposure causes sunburn
UVA produces oxygen free radicals that damage collagen & elastic fibers  leads to wrinkling
DNA damage in epidermal cells can lead to skin cancer
UVA:
Can pass through window glass.
Is not affected by a change in altitude or weather.
Is present all day and every day of the year.
Penetrates deep into skin layers.
Is 5% of the sun's rays.
Is 20 times more abundant than UVB rays.
Affects long-term skin damage.
UVB:
Cannot pass through window glass.
Causes sunburn.
Causes tanning.
Helps the body with normal vitamin D production.
Varies with the season. It is more intense in the summer than in the winter.
Varies with weather conditions.
Is more intense at midday than in the morning or late afternoon.
Is more intense at high altitudes and near the equator.
Is 0.5% of the sun's rays.
Is protected against by the sun protection factor (SPF) in sunscreens.
Is related to more than 90% of nonmelanoma skin cancer.
Is related to cataracts.
Sunscreens that say "broad-spectrum" can protect the skin from both UVA and UVB rays. Sunscreens come in lotions, gels, creams, and ointments

13. Skin Cancer 3 common forms of skin cancer
basal cell carcinoma (rarely metastasize)
squamous cell carcinoma (may metastasize)
malignant melanomas (metastasize rapidly)
most common cancer in young women
arise from melanocytes ----life threatening
key to treatment is early detection watch for changes in symmetry, border, color and size
risks factors include-- skin color, sun exposure, family history, age & immunological status
1 million cases diagnosed per year

14. Epidermal Wound Healing
1. Epidermal wound healing- (e.g. 1st degree abrasion or 2nd degree burn) central portion of wound usually extends deep down to the dermis >
whereas the wound edges usually involve only superficial damage to the epidermal cells.
epidermal wounds are repaired by enlargement & migration of basal cells contact inhibition, & division of migrating & stationary basal cells.
Abrasion or minor burn
Basal cells migrate across the wound
Contact inhibition w/ other cells stops migration
Epidermal growth factor stimulates cell division
Full thickness of epidermis results from further cell division

15. Deep Wound Healing
If an injury reaches dermis, healing occurs in 4 phases:
inflammatory phase has clot unite wound edges and WBCs arrive from dilated and more permeable blood vessels
migratory phase begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblasts
proliferative phase is a completion of tissue formation
maturation phase sees the scab fall off
Deep wound healing- injury extends to tissues deep to the epidermis, the repair process is more complex & scar formation results
during inflammatory phase, a blood clot unites the wound edges, epithelial cells migrate across the wound, vasodiation & increased permeability of blood vessels delivers phagocytes, and fibroblasts form
migratory phase - epithelial cells beneath the scab bridge the wound, fibroblasts begin to synthesize scar tissue, & damaged b.v.’s begin to grow.
in this phase the tissue filling the wound is called granulation tissue
proliferative phase - the events of the migratory phase intensify
maturation phase - scab sloughs off, epidermis is restored to normal thickness, collagen fibers become more organized, fibroblast begin to disappear, & b.v.’s restored
Scar formation
remains within the boundaries of the original wound
keloid scar extends into previously normal tissue
collagen fibers are very dense and fewer blood vessels are present so the tissue is lighter in color
4 phases:
Inflammatory
Migratory
Proliferative
Maturation
Scar formation
Hypertrophic
Keloid
Which phases have been left out of this illustration?

16. Burns Types of burns: 1st 2nd 3rd Problems that result
shock due to water, plasma & plasma protein loss
circulatory & kidney problems from loss of plasma
bacterial infection
First-degree
only epidermis (sunburn)
Second-degree burn
destroys entire epidermis & part of dermis
fluid-filled blisters separate epidermis & dermis
epidermal derivatives are not damaged
heals without grafting in 3 to 4 weeks & may scar
Third-degree or full-thickness
destroy epidermis, dermis & epidermal derivatives
damaged area is numb due to loss of sensory nerves
Destruction of proteins of the skin
chemicals, electricity, heat

17. Skin Grafts
New skin can not regenerate if stratum basale and its stem cells are destroyed
Skin graft is covering of wound with piece of healthy skin
To ensure no tissue rejection occurs transplantations are:
Autografts (from self)
Isografts (from twin)
Autologous skin used
transplantation of patients skin grown in culture
 for more info.
Serial documentation of healing skin grafts following burns in an 18 month old child.
Photographer: Gigi William's                        

18. Pressure Sores Decubitus ulcers
Caused by constant deficiency of blood flow to tissue
Areas affected is skin over bony prominence in bedridden patients
Preventable w/ proper care