2. Skin (Integument) Consists of three major regions
Epidermis—superficial region
Dermis—middle region
Hypodermis (superficial fascia)—deepest region
Subcutaneous layer- the layer deep to skin (not technically part of skin)
Mostly adipose tissue
Anchors skin to the underlying tissue (mostly muscle)
Shock absorber

3. • Hair follicle receptor (root hair plexus) Adipose tissue
Hair shaft
Dermal papillae
Epidermis
Subpapillary
vascular plexus
Papillary
layer
Pore
Appendages
of skin
Dermis
Reticular
layer
• Eccrine sweat
gland
• Arrector pili
muscle
Hypodermis
(superficial fascia)
• Sebaceous
(oil) gland
• Hair follicle
Nervous structures
• Hair root
• Sensory nerve fiber
Cutaneous vascular
plexus
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Adipose tissue
Figure 5.1

4. Epidermis Keratinized stratified squamous epithelium
Cells of epidermis
Keratinocytes—produce fibrous protein keratin
Melanocytes
10–25% of cells in lower epidermis
Produce pigment melanin
Epidermal dendritic (Langerhans) cells—macrophages that help activate immune system
Tactile (Merkel) cells—touch receptors

5. Stratum lucidum (soles of feet, palms of hands)
Apical Layer
Stratum corneum
Most superficial layer; 20–30 layers of dead
Cells, contains glycolipids.
Stratum lucidum (soles of feet, palms of hands)
Stratum granulosum
3 - 5 layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) &
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes.
Stratum basale
Deepest epidermal layer; one row of actively
mitotic stem cells; some newly formed cells
become part of the more superficial layers.
See occasional melanocytes and epidermal
dendritic cells.
(a)
Dermis
Basal Layer
Figure 5.2a

6. Layers of the Epidermis: 1. Stratum Basale (Basal Layer)
Deepest epidermal layer firmly attached to the dermis
Single row of stem cells
Function = replace the rest of the epidermis as it wears away (by means of mitosis – cell division)
Cells undergo rapid division
Journey from basal layer to surface takes 25–45 days

7. Layers of the Epidermis: 2. Middle Layers
Stratum Lucidum – visible only in thick skin (soles of feet & palms of hands)
A few rows of flat, dead Keratinocytes
Stratum Granulosum – cells flatten; thin layer
Stratum Spinosum (Prickly Layer)

8. Layers of the Epidermis: 3. Stratum Corneum (Horny Layer)
20–30 rows of dead, flat, keratinized membranous sacs
75% of the epidermal thickness
Functions:
Protects from abrasion and penetration
Waterproofs
Barrier against biological, chemical, and physical assaults

9. Dermis Strong, flexible connective tissue Richly supplied with…
Nerve fibers
Blood & lymphatic vessels
Two layers:
1) Papillary
2) Reticular

10. • Sebaceous (oil) gland
Hair shaft
Dermal papillae
Epidermis
Papillary
layer
Pore
Appendages of skin
Dermis
Reticular
layer
• Eccrine sweat gland
• Arrector pili muscle
Hypodermis
• Sebaceous (oil) gland
• Hair follicle
Nervous structures
• Hair root
• Sensory nerve fiber
Cutaneous vascular plexus
• Pacinian corpuscle
• Hair follicle receptor
(root hair plexus)
Adipose tissue
Figure 5.1

11. Layers of the Dermis: 1. Papillary Layer
Dermal papillae contain:
Capillary loops (blood supply)
Meissner’s corpuscles (touch receptors)
Free nerve endings (pain receptors)
Friction Ridges
Palms of hands & soles of feet
Patterns are genetically determined & unique
Sweat pores open along crests, leaving films of sweat (fingerprints)

12. Friction ridges
Openings of
sweat gland ducts
(a)
Figure 5.4a

13. Layers of the Dermis: 2. Reticular Layer
~80% of the thickness of dermis
Collagen fibers provide strength and resiliency
Elastic fibers provide stretch-recoil properties
Cleavage Lines
Collagen fibers are arranged in bundles
Less dense regions or separations between theses bundles form cleavage (tension) lines
*tend to run longitudinally in skin of head & limbs
*tend to run in circular patterns in skin of neck & trunk
Incisions made parallel to cleavage lines heal more readily

14. Cleavage Lines of the Skin
(b)
Figure 5.4b

15. Skin Color 3 pigments contribute to skin color: Melanin
Yellow to reddish-brown to black, responsible for dark skin colors
- Produced in melanocytes; migrates to keratinocytes where it forms “pigment shields” for nuclei
- Freckles and pigmented moles = accumulations of melanin

16. Skin Color Carotene Hemoglobin Responsible for the pinkish hue of skin
Yellow to orange - most obvious in the palms and soles
Hemoglobin
Responsible for the pinkish hue of skin

17. Skin Discoloration
Blue (cyanosis) – skin can become blue due to heart failure & severe respiratory disorders
Same thing occurs to people with dark skin, but is masked by their melanin (can see the blue in their mucous membranes & nail beds)
Red – fever embarrassment (blushing), hypertension, inflammation, allergy
Pallor (pale skin) – under emotional distress (fear,anger) some people become pale. Could also signify low blood pressure or anemia
Yellow (jaundice) – signifies liver disorder in which yellow bile pigments accumulate in the blood & are deposited in body tissue.
Bronzing (metallic appearance) –
Addison’s disease: adrenal cortex secreting inadequate amounts of steroid hormones
Presence of a pituitary gland tumor inappropriately secrete (MSH) melanin secreting hormone
Bruises (hematoma) – places where blood escaped from blood vessels & clotted beneath the skin

18. Appendages of the Skin Derivatives of the epidermis Sweat glands
Oil glands
Hairs and hair follicles
Nails

19. Sweat Glands Two main types of sweat (sudoriferous) glands
Eccrine (merocrine) sweat glands —abundant on palms, soles, and forehead
Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes
Ducts connect to pores
Function in thermoregulation

20. (b) Photomicrograph of a sectioned eccrine gland (220x)
Sweat pore
Eccrine
gland
Sebaceous
gland
Duct
Dermal connective
tissue
Secretory cells
(b) Photomicrograph of a
sectioned eccrine gland (220x)
Figure 5.5b

21. Sweat Glands
Apocrine sweat glands —confined to axillary and anogenital areas
Sebum: sweat + fatty substances and proteins
Ducts connect to hair follicles
Functional from puberty onward (as sexual scent glands?)
Specialized apocrine glands
Ceruminous glands—in external ear canal; secrete cerumen (ear wax)
Mammary glands

22. Sebaceous (Oil) Glands
Widely distributed
Most develop from hair follicles
Become active at puberty
Sebum
Oily
Bactericidal
Softens hair and skin
Slows water loss

23. (a) Photomicrograph of a sectioned sebaceous gland (220x)
Sweat
pore
Sebaceous
gland
Dermal
connective
tissue
Sebaceous
gland duct
Eccrine
gland
Hair in
hair follicle
Secretory cells
(a) Photomicrograph of a sectioned
sebaceous gland (220x)
Figure 5.5a

24. Hair Functions Distribution
Alert the body to presence of insects on the skin
Guard the scalp against physical trauma, heat loss, and sunlight
Distribution
Entire surface except palms, soles, lips, nipples, and portions of external genitalia

25. Hair Consists of dead keratinized cells
Contains hard keratin; more durable than soft keratin of skin
Hair pigments: made by melanocytes at the base of hair follicles
Various proportions of melanins of different colors (yellow, rust brown, black) combine to produce hair color
Gray/white hair: decreased melanin production, increased air bubbles in hair shaft

26. Hair Hair Follicle Hair follicle receptor (root hair plexus)
* Sensory nerve endings around each hair bulb (stimulated by bending a hair)
Arrector pili
*Smooth muscle attached to follicle
*Contraction pulls hair into upright position
*Responsible for “goose bumps”

27. Subcutaneous adipose tissue (c)
Hair shaft
Arrector pili
Sebaceous gland
Hair root
Hair bulb
Hair root
• Cuticle
• Cortex
Hair papilla
Melanocyte
Subcutaneous adipose tissue
(c)
Diagram of a longitudinal view of the expanded hair
bulb of the follicle, which encloses the matrix
Figure 5.6c

28. Hair Thinning and Baldness
Alopecia—hair thinning in both sexes after age 40
True (frank) baldness
Genetically determined and sex-influenced condition
Male pattern baldness is caused by follicular response to DHT (dihydrotestosterone)

29. Functions of the Integumentary System
Protection— 3 types of barriers
Chemical
> Low pH secretions (acid mantle) and defensins slow bacterial activity
Physical/mechanical barriers
> Keratin and glycolipids block most water and water- soluble substances
> Limited penetration of skin by lipid-soluble substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs
Biological barriers
> Dendritic cells, macrophages, and DNA

30. Functions of the Integumentary System
Body temperature regulation
~500 ml/day of routine insensible perspiration (at normal body temperature)
At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body
Cutaneous sensations
Temperature, touch, and pain

31. Functions of the Integumentary System
Metabolic functions:
>Synthesis of vitamin D
Blood reservoir:
>up to 5% of body’s blood volume in the skin
Excretion:
>nitrogenous wastes and salt in sweat

32. Skin Cancer Most skin tumors are benign (do not metastasize)
Risk factors
Overexposure to UV radiation
Frequent irritation of the skin
Some skin lotions contain enzymes in liposomes that can fix damaged DNA

33. Skin Cancer Three major types of Skin Cancer: 1. Basal Cell Carcinoma
*Least malignant, most common
*stratum basale cells grow & slowly invade dermis & hypodermis
*cured by surgical excision in 99% of cases
*cancer lesions occur on sun-exposed areas of the face & appear as shiny, dome-shaped nodules

34. Figure 5.8a

35. Skin Cancer 2. Squamous Cell Carcinoma *2nd most common skin cancer
*Involves keratinocytes of stratum spinosum
*Most common on scalp, ears, lower lip, and hands
*Good prognosis if treated by radiation therapy or removed surgically

36. Figure 5.8b

37. Skin Cancer 3. Melanoma *Involves melanocytes *Most dangerous
*Highly metastatic and resistant to chemotherapy
*Treated by wide surgical excision accompanied by immunotherapy

38. Figure 5.8c

39. Skin Cancer Melanoma Characteristics (ABCD rule):
A: Asymmetry; the two sides of the pigmented area do not match
B: Border exhibits indentations
C: Color is black, brown, tan, and sometimes red or blue
D: Diameter is larger than 6 mm (size of a pencil eraser)

40. (tissue damage, denatured protein, cell death)
Burns
Heat, electricity, radiation, certain chemicals 
Burn
(tissue damage, denatured protein, cell death)
Immediate threat of a burn:
Dehydration and electrolyte imbalance:
>leading to renal (kidney) shutdown and circulatory shock

41. Used to estimate the volume of fluid loss from burns
Burns Rule of Nines
Used to estimate the volume of fluid loss from burns
4.5%
Totals
Anterior and posterior head and neck, 9%
Anterior
trunk,
18%
4.5%
4.5%
Anterior and posterior upper limbs, 18%
Anterior and posterior trunk, 36%
(Perineum, 1%) 9% 9%
Anterior and posterior lower limbs, 36%
100%
Figure 5.9

42. Partial-Thickness Burns
1st degree
Epidermal damage only
Localized redness, edema (swelling), and pain
Sunburn
Usually heals in 2-3 days
2nd degree
Epidermal and upper dermal damage
Blisters appear
Usually heals in 3-4 weeks

43. 1st degree burn 2nd degree burn (a) Skin bearing partial
thickness burn (1st and
2nd degree burns)
Figure 5.10a

44. Full-Thickness Burns 3rd degree Entire thickness of skin damaged
Gray-white, cherry red, or black
No initial edema or pain (nerve endings destroyed)
Skin grafting usually necessary

45. 3rd degree burn (b) Skin bearing full thickness burn (3rd degree burn)
Figure 5.10b

46. The Skin Gun New Technology in Skin Grafting for Burn Victims

47. Severity of Burns Critical if:
>25% of the body has second-degree burns
>10% of the body has third-degree burns
Face, hands, or feet bear third-degree burns

48. Developmental Aspects of Skin: Adolescent to Adult
Sebaceous gland activity increases
Effects of cumulative environmental assaults show after age 30
Scaling and dermatitis become more common

49. Developmental Aspects of Skin : Old Age
Epidermal replacement slows
*skin becomes thin, dry, and itchy
Subcutaneous fat and elasticity decrease, *leading to cold intolerance and wrinkles
Increased risk of cancer *due to decreased numbers of melanocytes and dendritic cells