1. Chapter 6 Skin and the Integumentary System
Composed of several tissues
Maintains homeostasis
Protective covering
Retards water loss
Regulates body temperature
Houses sensory receptors
Contains immune system cells
Synthesizes chemicals
Excretes small amounts of waste

2. Types of Epithelial Membranes
Mucous
line tubes and organs that open to outside world
lining of mouth, nose, throat, etc.
secrete mucus
Serous
line body cavities that do not open to the outside
reduce friction
inner lining of thorax and abdomen
cover organs of thorax and abdomen
secrete serous fluid
Cutaneous
covers body
skin
Synovial
composed entirely of connective tissue
lines joints
Secretes synovial fluid

3. Skin Cells
help produce Vitamin D needed for normal bone and tooth development
some cells (keratinocytes) produce substances that simulate development of some WBCs

4. Layers of Skin Epidermis Dermis Subcutaneous layer beneath dermis
not part of skin

5. Epidermis lacks blood vessels keratinized
thickest on palms and soles ( mm)
melanocytes provide melanin
rests on basement membrane
stratified squamous

6. Production of new cells is balanced with the loss of dead cells
Protects underlying tissues against water loss, mechanical injury, and the effects of harmful chemicals
Epidermal cells keratinize and die as they are pushed to the surface

7. Epidermis Layers of Epidermis stratum corneum (dead cells)
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale (reproduce and grow)

9. Dermis on average 1.0-2.0mm thick contains dermal papillae
binds epidermis to underlying tissues
irregular dense connective tissue
muscle cells
nerve cell processes
specialized sensory receptors
blood vessels
hair follicles
glands

11. Subcutaneous Layer hypodermis loose connective tissue adipose tissue
insulates
major blood vessels
binds skin to
underlying organs

12. Hair Follicles epidermal cells tube-like depression
extends into dermis
hair root
hair shaft
hair papilla
dead epidermal cells
melanin
arrector pili muscle

13. A hair usually grows for a while, rests, and then is replaced by a new hair.
Hair color is determined by genes that direct the type and amount of pigment epidermal melanocytes produce
A bundle of smooth muscle cells forms the arrector pili muscle and attaches to each hair follicle
One or more sebaceous glands are attached to each hair follicle

15. Nails protective coverings nail plate nail bed lunula
made of specialized
Epithelial cells that
keratinize

16. Sebaceous Glands usually associated with hair follicles
holocrine glands
secrete sebum
Excess sebum causes acne
absent on palms and soles

17. Sweat Glands sudoriferous glands widespread in skin
originates in deeper dermis
or hypodermis
Types
eccrine glands
apocrine glands
ceruminous glands
mammary glands

18. Eccrine sweat glands Most numerous
Found on the forehead, neck, back, palms, and soles
Respond to elevated body temp or emotional stress
Sweat and sebaceous gland activity decreases with advancing age
Sweat is mostly water with salts and waste products

19. Apocrine Sweat Glands Become active at puberty
Located in the axillary regions (armpit), groin, and around the nipples

20. Ceruminous glands are modified sweat glands that secrete earwax
Mammary glands are modified sweat glands that secrete milk

22. Regulation of Body Temperature
Regulation of body temperature is vital because heat affects the rates of metabolic reactions. Normal temperature of deeper body parts is close to a set point of 37°C (98.6°F). Skin plays a key role in body temperature homeostasis.

23. Heat production and loss
Heat is a by-product of cellular respiration.
The most active cells are skeletal and heart muscle cells and the liver.
If body temperature rises above normal:
-more blood enters dermal blood vessels (vasodilation).

24. If body temperature rises above normal:
more blood enters dermal blood vessels (vasodilation).
deeper blood vessels contract (vasoconstriction) diverting blood
to the surface and the skin reddens

25. heat is lost to the outside by:
radiation - rays move from warmer to cooler surroundings (primary way)
conduction - heat moves from warmer objects to cooler objects it is touching
convection - heated air moving away from the body
evaporation - fluid evaporates from the surface carrying heat away (sweating)

26. If the body temperature drops below normal:
dermal blood vessels constrict, causing the skin to lose color
sweat glands become inactive
if heat is lost excessively, skeletal muscles involuntarily contract increasing cellular respiration and producing additional heat.

27. Problems in Temperature Regulation
Hyperthermia – abnormally high body temperature
Hypothermia – abnormally low body temperature

28. If the air is saturated with water, sweat may fail to evaporate, and body temperature may remain elevated (hyperthermia)
Symptoms may begin with headache, dizziness, nausea, muscle cramping, and may lead to major organ failure
Lack of sweating – medical emergency

29. Hypothermia is lowered body temperature.
Symptoms begin with shivering, and leads to mental confusion, lethargy, loss of reflexes and ,consciousness, and eventually major organ failure

30. Skin Color
All humans have about the same number of melanocytes. Skin color differences are due to the amount of melanin produced

31. Genetic factors Genes that control melanin production are inherited.
Dark skin is due to genes that cause large amounts of melanin to be produced
Lighter skin is due to genes that cause lesser amounts of melanin to form.
Mutant genes may cause a lack of melanin in the skin (albinism).

32. Environmental factors
Sunlight, ultraviolet light, and X rays darken existing melanin and stimulate more melanin production temporarily darkening the skin.

33. Physiological factors
If blood is well oxygenated hemoglobin (blood pigment) is bright red causing the skin of light complected people to appear pinkish.
If oxygen content of blood is low hemoglobin is dark red and the skin appears bluish (cyanosis).
Dilated blood vessels can cause skin to redden

34. Constricted blood vessels cause a loss of reddish color.
Carotene in the subcutaneous layer may cause the skin to appear yellowish.
• Disease may affect skin color.

35. Healing of Wounds and Burns
Skin injuries trigger inflammation. Blood vessels dilate forcing fluids to leave and enter the damaged tissue. The affected area becomes red, warm, swollen, and tender.

36. Cuts
A shallow cut in the epidermis is filled in by reproducing epithelial cells.
Deeper cuts into the dermis or subcutaneous layer cause a clot to form.
platelets become entrapped in protein fibers (fibrin).
tissue fluids seep into the area
blood clot and dried fluids form a scab

37. fibroblasts begin to form new collagenous fibers that bind edges of the wound together
blood vessels extend beneath the scab
phagocytes remove dead cells
a scar where connective tissue replaces skin may appear

38. granulations (new blood vessel branch & fibroblasts) may form in large open wounds

39. Healing of Cuts

40. First degree burns (superficial partial-thickness burn)
only burns the epidermis
heals quickly with no scarring
the area is warm and red.

41. Second degree burns (deep partial-thickness burn) –
destroys some epidermis and dermis
blisters appear
area becomes moist and firm and varies in color from dark red to waxy white

42. healing depends on the accessory organs that survive
skin usually recovers with no scar tissue unless an infection occurs.

43. Third degree burns (full-thickness burns)
destroys the epidermis, dermis, and the accessory organs of the skin
injured skin may appear dry and leathery and varies in color from red to black to white
healing only occurs from epithelial cells growing inward from the margin of the burn

44. may require skin grafting:
autograft - thin layer of skin from unburned area is removed and transplanted in injured area
homograft - cadaveric skin is used to cover injury
skin substitutes
- amniotic and artificial membranes human skin cultures
- grow in lab and transplant
extensive scarring

45. Rule of Nines

46. Life Span Changes Melanin production slows Skin becomes scaly
Hair thins
Number of hair follicles decrease
Nail growth becomes impaired
Sensory receptors decline
Body temperature unable to be controlled
Diminished ability to activate Vitamin D
Skin becomes scaly
Age spots appear
Epidermis thins
Dermis becomes reduced
Loss of fat
Wrinkling
Sagging
Sebaceous glands secrete less oil

47. Clinical Application Acne Vulgaris most common skin disorder
sebum and epithelial cells clog glands
produces whitheads and blackheads (comedones)
anaerobic bacteria trigger inflammation (pimple)
largely hormonally induced
androgens stimulate sebum production
treatments include antibiotics, topical creams, birth control pills