1. The Integumentary System5
The Integumentary System

2. Consists of three major regions
Skin (Integument)
Consists of three major regions
Epidermis—superficial region
Dermis—middle region
Hypodermis (superficial fascia)—deepest region

3. Skin (Integument) More on the Hypodermis
Subcutaneous layer deep (beneath) to skin (not technically part of skin)
Mostly adipose tissue
Anchors the skin to underlying muscle
Allows skin to slide over muscle
Acts as shock absorber & insulator

4. • 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

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

6. Most superficial layer; 20–30 layers of dead
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
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
Figure 5.2a

7. Layers of the Epidermis: Stratum Basale (Basal Layer)
Deepest epidermal layer firmly attached to the dermis
Single row of stem cells
Also called stratum germinativum: cells undergo rapid division (site of mitosis)
Journey from basal layer to surface
Takes 25–45 days

8. Layers of the Epidermis: Stratum Spinosum (Prickly Layer)
Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes
Contains keratinocytes, melanin granules and highest concentration of epidermal dendritic cells
Several cell layers thick

9. Layers of the Epidermis: Stratum Granulosum (Granular Layer)
Thin; three to five cell layers in which the cells flatten
Keratohyaline and lamellated granules accumulate
Contains keratinocytes that are undergoing a great deal of physical changes (making them tough, outer cells of the epidermis)

10. Layers of the Epidermis: Stratum Lucidum (Clear Layer)
In thick skin
Thin, transparent band superficial to the stratum granulosum
A few rows of flat, dead keratinocytes

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

12. Most superficial layer; 20–30 layers of dead
Stratum corneum
Most superficial layer; 20–30 layers of dead
cells represented only by flat membranous
sacs filled with keratin. Glycolipids in
extracellular space.
Keratinocytes
Stratum granulosum
Three to five layers of flattened cells,
organelles deteriorating; cytoplasm full of
lamellated granules (release lipids) and
keratohyaline granules.
Stratum spinosum
Several layers of keratinocytes unified by
desmosomes. Cells contain thick bundles of
intermediate filaments made of pre-keratin.
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.
Dermis
Desmosomes
Sensory
nerve ending
Melanin granule
Epidermal
dendritic cell
Melanocyte
Tactile
(Merkel) cell
(b)
Figure 5.2b

13. Strong, flexible connective tissue
Dermis
Strong, flexible connective tissue
Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells
Two layers:
Papillary
Reticular

14. • 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

15. Layers of the Dermis: Papillary Layer
Papillary layer (thin, superficial)
Areolar connective tissue with collagen and elastic fibers and blood vessels (highly vascularized)
Dermal papillae contain:
Capillary loops
Meissner’s corpuscles
Free nerve endings

16. Layers of the Dermis: Reticular Layer
~80% of the thickness of dermis
Dense irregular connective tissue
Collagen fibers provide strength and resiliency
Elastic fibers provide stretch-recoil properties

17. Skin Markings: Friction Ridges
Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints

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

19. Skin Markings: Cleavage Lines
Collagen fibers arranged in bundles form cleavage (tension) lines
Incisions made parallel to cleavage lines heal more readily

20. (b)
Figure 5.4b

21. Three 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
Local accumulations of melanin

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

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

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

25. (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

26. Sweat Glands
Apocrine sweat glands—confined to axillary and anogenital areas
Produce sebum: true sweat + fatty substances and proteins
Ducts connect to hair follicles
Functional from puberty onward (as sexual scent glands?)
Specialized apocrine glands
3. Ceruminous glands—in external ear canal; secrete cerumen (earwax)
4. Mammary glands- secrete breast milk

27. Sebaceous (Oil) Glands
Widely distributed (all over the body except palms & soles)
Most develop from hair follicles
Become active at puberty
Simple alveolar glands
Holocrine glands that secretes products into hair follicles or skin pores
Secrete sebum (after hormone stimulation)
Oily holocrine secretion
Bactericidal
Softens hair and skin

28. (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

29. Hair (pili) Functions Distribution
Alerting the body to presence of insects on the skin
Guarding the scalp against physical trauma, heat loss, and sunlight
Distribution
Entire surface except palms, soles, lips, nipples, and portions of external genitalia

30. The main regions of a hair:
Hair (pili)
The main regions of a hair:
shaft
root
Three layers of keratinized cells:
inner core: medulla
middle layer: cortex
outer layer: cuticle

31. Consists of dead keratinized cells Produced by hair follicles
Contains hard keratin; more durable than soft keratin of skin
Hair pigments: melanins (yellow, rust brown, black)
made by melanocytes at the base of the hair follicle.
Gray/white hair: decreased melanin production, increased air bubbles in shaft

32. (a) Diagram of a cross section of a hair within its follicle Sebaceous
Follicle wall
• Connective tissue
root sheath
• Glassy membrane
• External epithelial
• Internal epithelial
Hair shaft
Hair
• Cuticle
• Cortex
• Medulla
Arrector
pili
(a) Diagram of a cross section of
a hair within its follicle
Sebaceous
gland
Hair root
Hair bulb
Figure 5.6a

33. (b) Photomicrograph of a cross section of a hair and hair
Follicle wall
• Connective tissue
root sheath
• Glassy membrane
• External epithelial
root sheath
• Internal epithelial
root sheath
Hair
• Cuticle
• Cortex
Hair shaft
• Medulla
Arrector
pili
(b) Photomicrograph of a cross
section of a hair and hair
follicle (250x)
Sebaceous
gland
Hair root
Hair bulb
Figure 5.6b

34. Hair Follicle
Extends/folds down from the epidermal surface into dermis (occasionally into hypodermis)
Two-layered wall:
outer connective tissue root sheath
glossy membrane: thickened basement membrane
inner epithelial root sheath

35. Hair bulb: expanded deep end that’s surrounded by root hair plexus.
Hair Follicle
Hair bulb: expanded deep end that’s surrounded by root hair plexus.
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
Responsible for “goose bumps”

36. • Connective tissue root sheath Hair bulb • Glassy membrane
Hair shaft
Arrector
pili
Sebaceous
gland
Hair root
Follicle wall
• Connective tissue root sheath
Hair bulb
• Glassy membrane
• External epithelial root sheath
• Internal epithelial root sheath
Hair root
• Cuticle
• Cortex
• Medulla
Hair matrix
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

37. (d) Photomicrograph of longitudinal view
Follicle wall
• Connective
tissue root sheath
Hair shaft
• Glassy membrane
• External epithelial
root sheath
• Internal epithelial
root sheath
Arrector
pili
Hair root
• Cuticle
Sebaceous
gland
• Cortex
• Medulla
Hair root
Hair matrix
Hair bulb
Hair papilla
Subcutaneous
adipose tissue
(d) Photomicrograph of longitudinal view
of the hair bulb in the follicle (160x)
Figure 5.6d

38. Types of Hair Classifications:
Vellus—pale, fine body hair of children and adult females
Terminal—coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)

39. Types of Hair Hair Growth
Growth phase (weeks to years) followed by regressive stage and resting phase (1–3 months)
Growth phase varies (6–10 years in scalp, 3–4 months in eyebrows)
Influenced by many factors (nutrition & hormones)
Rate varies based on area of body, gender, and age.

40. Hair Thinning and Baldness
Alopecia—hair thinning (possibly some balding) 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

41. Structure of a Nail
Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes
Forms a clear, protective covering
Made of hard keratin
Have a free edge, a body, and a proximal root

42. Phalanx (bone of fingertip)
Lateral
nail fold
Lunule
(a)
Free edge
of nail
Body
of nail
Eponychium
(cuticle)
Proximal
nail fold
Nail bed
Root of nail
Nail
matrix
(b)
Hyponychium
Phalanx (bone of fingertip)
Figure 5.7

43. Functions of the Integumentary System
Protection—three types of barriers
1. Chemical
Low pH secretions (acid mantle) and defensins retard bacterial activity
Skin secretions & melanin
2. Biological barriers
Epidermal dendritic cells, macrophages of dermis, and DNA

44. Functions of the Integumentary System
3. Physical/mechanical barriers
Provided by the continuity of skin & hardness of keratinized cells
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

45. 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 (capillaries) and increased sweat gland activity (sensible perspirations) cool the body
Cutaneous sensations
Cutaneous sensory receptors present in layers of the skin
Temperature, touch, and pain

46. Functions of the Integumentary System
Metabolic functions
Synthesis of vitamin D precursor and collagenase when exposed to sunlight
Chemical conversion of carcinogens and some hormones
Blood reservoir—up to 5% of body’s blood volume; can be diverted if needed
Excretion—nitrogenous wastes and salt in sweat

47. Most skin tumors are benign (do not metastasize)
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

48. Skin Cancer Three major types: Basal cell carcinoma Most common
Squamous cell carcinoma
Second most common
Melanoma
Most dangerous

49. Cured by surgical excision in 99% of cases
Basal Cell Carcinoma
Least malignant
Stratum basale cells proliferate and slowly invade dermis and hypodermis
Cured by surgical excision in 99% of cases

50. Figure 5.8a

51. Squamous Cell Carcinoma
Involves keratinocytes of stratum spinosum
Most common on scalp, ears, lower lip, and hands
Good prognosis if treated by radiation therapy or removed surgically
Will metastasize if not removed
Grows rapidly

52. Figure 5.8b

53. Melanoma
Involves melanocytes
Highly metastatic and resistant to chemotherapy
Treated by wide surgical excision accompanied by immunotherapy

54. Characteristics (ABCD rule)
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)

55. Figure 5.8c

56. (tissue damage, denatured protein, cell death)
Burns
Heat, electricity, radiation, certain chemicals 
Burn
(tissue damage, denatured protein, cell death)
Immediate threat:
Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock
After first 24 hours, infection is greatest threat

57. Rule of Nines
Used to estimate the volume of fluid loss from burns

58. Anterior and posterior head and neck, 9%
Totals 4 1 / % 2
Anterior and posterior
head and neck, 9%
Anterior and posterior
upper limbs, 18%
Anterior
trunk,
18% 1 4 / % 4 1 / %
Anterior and posterior
trunk, 36% 2 2 9% 9%
(Perineum, 1%)
Anterior and posterior
lower limbs, 36%
100%
Figure 5.9

59. Partial-Thickness Burns
First degree
Epidermal damage only
Localized redness, edema (swelling), and pain
Second degree
Epidermal and upper dermal damage
Blisters appear

60. 1st degree burn 2nd degree burn (a) Skin bearing partial
thickness burn (1st and
2nd degree burns)
Figure 5.10a

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

62. 3rd degree burn (b) Skin bearing full thickness burn (3rd degree burn)
Figure 5.10b

63. 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

64. Developmental Aspects: Fetal
Ectoderm  epidermis
Mesoderm  dermis and hypodermis
By end of fourth month skin is fairly well formed
Lanugo coat: covering of delicate hairs in 5th and 6th month
Vernix caseosa: sebaceous gland secretion; protects skin of fetus

65. Developmental Aspects: Adolescent to Adult
During infancy and childhood, the skin thickens and more subcutaneous fat is deposited
Adolescence: Sebaceous gland activity increases (skin & hair become oilier)
Optimal appearance in 20s and 30s
Effects of cumulative environmental assaults show after age 30
Scaling and dermatitis become more common

66. Developmental Aspects: Old Age
Epidermal replacement slows, skin becomes thin, dry, and itchy
More prone to bruising and other injuries
Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles
Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells