1. The Integumentary System
The body’s largest organ is the skin ~ 9-11 pounds (7% total body wt)
An average adult male covers 20 square feet
An average adult female covers 17 square feet
Skin is constantly flaking away and replaced completely every 4 weeks
On average, every person sheds 40 pounds of skin in a lifetime
Everything you see when you look at someone is dead!

2. The Integumentary System
Would you be enticed by an advertisement for a coat that is waterproof, stretchable, washable, and permanent-press, that automatically repairs small cuts, rips and burns, and that is guaranteed to last a lifetime with reasonable care?

3. Integumentary System Integument means “covering” Structures
Skin (cutaneous membrane)
Cut- or cutis- = the true skin; -ous = possessing, full of
Covers 15 to 20 square feet
Average weight is 9 pounds (7% of body weight)
Composed of two layers
Epidermis (epithelial) and dermis (fibrous CT)
Skin derivatives
Sweat glands, oil glands, hairs and nails

4. Skin (Integument) Functions
Mechanical (physical) protection (barrier)
Hardness of keratinized cells (intact epidermis)
Chemical protection (barrier)
Melanin produced by melanocytes provides shield to prevent UV damage
“Acid mantle”
Acidic secretions that inhibits bacteria
Desiccation
Prevention of drying out (keratin waterproofs)

5. Skin (Integument) Functions
Biological protection (barrier)
Langerhans’ cells in epidermis and macrophages (phagocytes) in dermis ingest foreign substances and pathogens

6. Skin (Integument) Functions
Temperature Regulation
Normal conditions sweat glands produce ~ 500 mL of sweat a day
If body temperature rises, nervous system stimulates blood vessels to dilate and sweat glands to secrete sweat
Heat loss
Activate sweat glands produce sweat
which evaporate and cool the body
Allow blood to flush in skin capillary beds
and radiate from surface of the skin
Heat retention
Not allowing blood to flush into skin capillary beds

7. Skin Functions Cutaneous sensation
Cutaneous sensory receptors (nervous system)
Exteroceptors (respond to external stimuli)
Detect pain, light pressure, deep pressure, and temperature (hot and cold)
Meissner’s corpuscles (dermal papillae)
Light pressure and touch
Pacinian corpuscles (deep dermis)
Deep pressure
Free nerve endings
Painful stimuli like chemicals, temperature change, or pain

8. Skin (Integument) Functions
Metabolic functions (chemical reactions)
Modified cholesterol molecules in skin are converted to vitamin D by sunlight
Without vitamin D calcium cannot be absorbed in the intestines
Blood reservoir
Dermal vascular supply is extensive and can hold large volumes of blood (about 5% of entire blood volume)

9. Skin (Integument) Functions
Excretion
Nitrogen-containing wastes, water and salts are eliminated in sweat

10. Skin Structure

11. Skin Structure Epidermis (outer layer) (Epi - = upon, on)
Keratinized stratified squamous epithelium
Avascular (without blood vessels)
Oxygen and nutrients diffuse from dermis
Dermis (inner layer)
Dense fibrous CT with collagen and elastic fibers
Much thicker
Contains blood vessels, nerve fibers, etc.
Hypodermis (underlying layer or subcutaneous)
Adipose tissue
Anchors skin to the underlying structures
Shock absorber and insulator to reduce heat loss

13. Cells of the Epidermis Keratinocytes (most) Melanocytes
Langerhans’ (dendritic) cells
Tactile (Merkel) cells

14. Cells of the Epidermis Keratinocytes Primary cell type of epidermis
Produces keratin
Protein that gives epidermis its protective function
Arise in deepest layer (stratum basale)
New cells push old cells upward and by the time they reach the surface they are dead cells filled with keratin
Millions of cells rub off each day
Completely new epidermis every days
Persistent friction causes a thickening of the epidermis called a callus

15. Cells of the Epidermis Melanocytes Spider-shaped epithelial cells
Produce the pigment melanin
Found in the deepest layer of epidermis (stratum basale)
keratinization
In keratinocytes the melanin accumulate on ‘sunny side’ or superficial side of nucleus and forms a shield that protects it from UV radiation – natural sunscreen

16. Cells of the Epidermis Langerhans’ (dendritic) cells
White blood cells that arise from bone marrow and migrate to epidermis
Ingest foreign substances
Key activators of immune system
Tactile (Merkel) cells
Shaped like a spiky hemisphere
Rarely found and associated with sensory nerve ending
Sensory receptor for touch

17. Layers of Epidermis Variation of thickness depends on location in body
Four or five structurally different layers called strata
Thick skin – palms, fingertips, soles of feet consists of all five layers
Thin skin – rest of the body the stratum lucidum is not present
Deep to superficial
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum (thick skin only)
Stratum corneum

18. Layers of Epidermis Stratum basale
Deepest layer – closest to dermis
Cells rest on underlying dermis
Basal cells
90% are keratinocytes
10% are melanocytes and other types
Stratum spinosum (prickly cell layer)
Several cell layers thick of flattened cells with bundles of keratin
Langerhans’ (dendritic) cells are most abundant in this layer

19. Layers of Epidermis Stratum granulosum Stratum lucidum (clear layer)
Very thin region (3-5 layers)
Last layer that can obtain nutrients from diffusion
Process of keratinization begins here and cells die
Cells flatten and ‘toughen’ up
Stratum lucidum (clear layer)
2-3 rows of clear, flat, dead cells
Translucent layer that looks like a band
Visible only in thick skin

20. Layers of Epidermis Stratum corneum Outermost layer
20 to 30 cells thick of dead cells
High levels of keratin
Protection against abrasion and penetration, water repellant (prevents water loss)
Average person sheds 8 lb of dead skin cells in a year

21. Epidermis Check-up
While walking barefoot in the barn, Jeremy stepped on a rusty nail that penetrated the depth of the epidermis on the sole of his foot. Name the layers the nail pierced from the superficial skin surface to the junction with the dermis.
What is the stratum basale’s function?
Given that epithelia are avascular, what layer would be expected to have the best-nourished cells?
Stratum basale  stratum spinosum stratum granulosum 
stratum lucidum  stratum corneum
To produce new keratinocytes and keratin
Stratum basale

22. Dermis (Derm = skin) Second major skin region It is your “hide”
Strong, flexible connective tissue layer
Cells
Fibroblasts, macrophages, mast cells and white blood cells
Matrix
Embedded with collagen, elastic and reticular fibers
Rich in nerve fibers, blood vessels, and lymphatic vessels
Major portions of hair follicles, sweat and oil glands reside in dermis

23. Dermis (Derma = skin) Two major layers of dermis Papillary layer
Reticular layer

24. Dermis (Derma = skin) Papillary layer
Papilla = any nipple-like projection
Thin superficial layer
Areolar connective tissue
Superior surface is called the dermal papillae
Projections that protrude into epidermis
Some contain capillary loops, free nerve endings, and Meissner’s corpuscles
Where we get our fingerprint

25. Dermis – your ‘hide’ Reticular layer Deepest layer
Dense connective tissue
80% of the thickness of the dermis
Highly vascular - lots of blood vessels
Matrix contains thick bundles of collagen fibers (strength and resiliency) and elastic fibers (stretch-recoil)
Wrinkling of the skin is caused by loss of the elasticity of the skin
Many appendages are located here: sweat glands, oil glands and nerve receptors

26. Skin Structure
Figure 4.4

27. Dermis Check Up
What layer of the dermis is responsible for producing finger-print patterns?
What cell component of the hypodermis makes it a good shock absorber?
You have just gotten a paper cut. It is very painful, but it doesn’t bleed. Has the cut penetrated into the dermis or just the epidermis? What component of the layer was affected?
Papillary layer – dermal papillae
Adipocytes
Epidermis – tactile cells

28. Normal Skin Color
Skin Color Variations
Skin Appendages

29. Normal Skin Color Three pigments contribute to skin color
Melanin (only one made in skin)
Carotene
Hemoglobin

30. Normal Skin Color Melanin (Melan - = black)
Pigment found in eyes, skin and hair
Function is to protect cells from UV radiation – a natural sunscreen
Range in color from yellow to tan to reddish-brown to black
Produced by melanocytes and phagocytized by keratinocytes

31. Normal Skin Color Melanin
Exposure to sun = increase in melanin production
Darker-skinned people tend to live near the equator and those with lighter skin live near the poles
Freckles and moles are local accumulation of melanin
Albinism (albin- = white)
No melanin produced; eyes, skin and hair are white

32. Normal Skin Color Carotene
Yellow-orange pigment found in certain plant products such as carrots
Found predominantly in the stratum corneum
Can be changed by altering diet and it is not dangerous to health
Carotene can be converted to Vitamin A in the liver
Essential for normal vision and protection of epithelial tissues

33. Normal Skin Color Hemoglobin
Oxygen carrying pigment found in red blood cells and gives them their red color
Produces a pinkish hue of fair skin
Caucasian skin contains small amounts of melanin, so the color can show through easier
Oxygen content determines the extent of red coloring
When capillaries are open the blood is rushed to the surface causing redness

34. Skin Color Variations Cyanosis (Blue color disorder)
Hemoglobin is poorly oxygenated
The skin and blood appear blue
Occurs during heart failure and respiratory disorders
In darker skinned individuals, the skin does not appear cyanotic because of so much melanin
Apparent in mucous membranes and nail beds
Redness (Erythema)
Capillaries dilate and open up to bring blood to the surface
Caused by irritation or injury
Other causes are embarrassment, fever, hypertension or allergy

35. Skin Color Variations Pallor or blanching (Paleness or white)
Blood is either shunted or directed away from surface
Fear, anger, anemia or low blood pressure.
Jaundice (yellow cast)
Caused by the buildup of yellow bile pigments from the liver called bilirubin
They accumulate in the blood and are deposited in body tissues like the skin or whites of eyes

36. Skin Color Variations Hematomas (Bruises)
Collection of blood, usually clotted, in a tissue or organ, usually caused by a break in a blood vessel
Black and blue bruises
Hema- = blood and -oma = tumor

38. Appendages of the Skin
Derivatives of the epidermis called skin appendages
Nails, sweat glands, sebaceous (oil) glands and hair
Each appendage plays a unique role in maintaining homeostasis

39. Sudoriferous (sweat) glands
Distributed over the entire skin except nipples, lips, and some genitalia
Most numerous gland ~2.5 million/person
Two types
Eccrine and apocrine
Simple, coiled tubular glands
Sweat is secreted into and through the gland’s duct system to the surface of the skin
Sudor = sweat

40. Eccrine glands Found almost everywhere and most numerous
Abundant on palms, soles and forehead
Secretory part lies coiled in dermis
Duct extends to open in a pore
Eccrine gland secretion (sweat)
Sweat
99% water with some salts, vitamin C, antibodies and traces of wastes
Composition of sweat depends on genetics and diet
Acidic with pH between 4-6

41. Apocrine Glands
Found in axillary and genital areas (about 2000 of them)
Found deeper in dermis and larger than eccrine glands
Ducts empty into hair follicles
Apocrine gland sweat composition
Same as eccrine sweat plus fatty substances and proteins
Odorless and appears milky or white
Bacteria eats organic molecules in the sweat and causes body odor
Begin functioning at puberty

42. Functions of Sweat Controlled by the nervous system
Can be heat-induced or emotionally induced (cold sweat)
Heat-induced begins on forehead and spreads inferiorly
Emotionally induced begins on the palms, soles and then spreads
Excretes waste products
Acidic nature inhibits bacteria growth

43. Sudoriferous glands Ceruminous glands Modified apocrine glands
Found in lining of external ear canal
Produce cerumen (ear wax)
Functions to deter insects and block entry of foreign materials.
Mammary glands
Specialized sweat glands
Secretes milk

44. Sebaceous (Oil) Glands
Found all over the body except on palms and soles of feet
Secrete an oily substance called sebum
Softens and lubricates hair and skin
Bactericidal (bacteria-killing) action
Develop and secrete into hair follicles
Stimulated by hormones and activated at puberty

45. Sebaceous (Oil) Glands
Blackheads
Appears on surface of skin when a sebaceous gland duct is blocked and the sebum accumulates
Acne
An active inflammation of the sebaceous glands accompanied by ‘pimples’ (pustules)
Usually caused by bacterial infection

46. Plotting of Sweat Glands

47. Hair
Millions of hairs are distributed all over the body except on the palms, soles, lips, nipples, and parts of external genitalia
Flexible strands produced by hair follicles
Consist largely of dead, keratinized cells
Melanocytes provide pigment for hair color
Hair Functions
Not really used for warmth anymore
Sense insects on the skin before they bite us
Hair on scalp guards the head from physical trauma, heat loss and sunlight
Eyelashes shield the eyes
Nose hairs filter large particles from the air

48. Hair Regions of a hair Hair Shaft Projects from the skin
Extends halfway down the embedded portion
Hair Root
Remainder of hair deep in the follicle

49. Hair Anatomy Hair has 3 concentric layers of keratinized cells
Medulla - central core
Consists of large cells and open spaces
Cortex – surrounds medulla
Several layers of flattened cells
Cuticle - outside of cortex
Single layer of cells that overlap each other
Looks like shingles on a roof
Most heavily keratinized and provides strength
“Split ends” occurs when the cuticle wears away

50. Hair Follicle
Epithelial tissue folds down from the epidermis into the dermis
Deep end of the follicle forms a hair bulb
Hair follicle is the wall around the hair
Two sheaths
Outer connective tissue root sheath derived from the dermis
Inner epithelial root sheath derived from the epidermis
Figure 4.7a

51. Hair Follicle Hair papilla Hair matrix (growth zone)
Dermal connective tissue protrudes into the hair bulb
Contains capillaries that supplies the nutrients to the hair
Hair matrix (growth zone)
Actively dividing area of the hair bulb
Produces the hair
Figure 4.7a

52. Hair Follicle Arrector pili
Each hair follicle has a smooth muscle attached to it
Hair follicles approach surface of the skin at a slight angle
Muscle contraction pulls the hair follicle to an upright position
Causes a dimple in the skin – goosebumps
Response to fear or cold temperatures

53. Hair Growth Hair growth is influenced by many factors
Nutrition and hormones
Hirsutism (excessive hairiness)
Results from an adrenal gland or ovarian tumor that secretes an abnormally high amount of androgens
Androgens control the growth of hair and are produced by ovaries and adrenal glands
These tumors are usually removed as soon as possible

54. Hirsuitism

55. Hair Thinning and Baldness
A hair follicle only has a limited number of cycles in it
Hair grows fastest from the teen years to the 40s and then it slows
Alopecia (scientific term for baldness)
When the hairs are not replaced as they are shed leads to hair thinning or baldness due to age
True Baldness
Male pattern baldness that is genetically determined, sex-influenced condition
Hair thinning can occur because of high fever, surgery, emotional trauma, certain drugs, and protein-deficient diets
If the cause is removed or corrected, the hair will grow back
Hair loss due to severe burns or follicular damage is permanent

57. Skin Homeostatic Imbalances
A disease or condition as a result of a disturbance in homeostasis
Skin Homeostatic Imbalances
Cancer
Burns
Bacterial, viral or yeast infections

58. Skin Cancer Cancer Two types of tumors
When cells fail to follow normal controls of cell division and multiply excessively it results in a tumor
Two types of tumors
Benign (most tumors like warts)
Does not spread and grows slowly
Malignant (mal = ‘bad’)
Grow relentlessly and may become killers
Metastasis
Cells tend to break away from the mass and travel via blood or lymph to other body organs where they can grow into new masses

59. Skin Cancer Types
1 in 5 Americans will develop skin cancer at some point
Huge risk factor is too much UV radiation which damages DNA bases
Three types of skin cancer
Basal cell carcinoma
Squamous cell carcinoma
Melanoma

60. Skin Cancer Types Basal cell carcinoma
Least malignant but most common skin cancer (80%)
Stratum basal cells proliferate and invade the dermis and hypodermis
Occur most often on sun-exposed areas of face
Appear as shiny, dome-shaped nodules that develop a central ulcer with a pearly, beaded edge – sore that doesn’t heal

61. Skin Cancer Types
Basal cell carcinoma

62. Skin Cancer Types Squamous cell carcinoma
Second most common skin cancer
Affects men more than women
Arises from keratinocytes of the stratum spinosum
Lesion appears as a scaly reddened papule that arises usually on head and hands
Grows and metastasizes to lymph nodes quickly
Early removal allows a good chance of cure

63. Skin Cancer Types Basal Cell Carcinoma Squamous Cell Carcinoma
Cell type
Stratum basale (basal layer) keratinocytes
Stratum spinosum keratinocytes
Rank them by how common they are to get
1st
2nd
Seriousness and metastasis
Least malignant
Grows and metastasizes quickly
Appearance
Shiny, dome-shaped nodules with a central ulcer and a pearly edge
Scaly, reddened papule

64. Skin Cancer Types

65. Skin Cancer Types Malignant melanoma Most deadly of skin cancers
Highly metastatic and resistant to chemotherapy
Rare (2-3% of all skin cancers)
Cancer of melanocytes and can begin wherever there is pigment
Appears as a spreading brown to black patch
Early detection is key to survival
Detection uses ABCD rule

66. ABCD Rule A = Asymmetry Two sides of pigmented mole do not match
B = Border irregularity
Borders of mole are not smooth
C = Color
Different colors in pigmented area
D = Diameter
Spot is larger then 6 mm in diameter (pencil eraser)
Skin Cancer Video

67. Skin Homeostatic Imbalances
Burns
Tissue damage inflicted by intense heat (fire or materials), electricity, radiation (sunlight), or certain chemicals
Denature cell proteins and cause cell death
Immediate threat to life is loss of body fluids containing proteins and electrolytes
Results in dehydration and electrolyte imbalance
After initial crises, infection and sepsis becomes the main threat

68. Extent of Burn - Rules of Nines
Volume of fluid lost can be estimated by computing the percentage of body surface burned
Tool to approximate the extent of burns using the rule of nines
Body is divided into 11 areas
Each area represents about 9% of total body area
Head and neck = 9 %
Upper limbs = 18%
Trunk = 36%
Lower limbs = 36%
Genitals =1%

69. Severity of Burns
Burns are classified according to their severity (depth)
First-degree burns (epidermis)
Skin is red and swollen
Second degree burns (epidermis and upper dermis)
Skin is red with blisters
Third-degree burns (entire skin layer)
High risk for fluid loss
Burn is gray-white, cherry red or black
Nerve endings are destroyed so it is not painful at first
Skin regeneration may occur but will take too long
Usually skin grafting is required

70. Critical Burns Burns are considered critical if:
Over 25% of body has second degree burns
Over 10% of the body has third degree burns
There are third degree burns of the face, hands, or feet
Most third degree burns will never heal and may require a skin graft
Skin Grafting
Removal and transplanting of healthy skin from one area to another

71. Infections & Allergies
Psoriasis
A chronic condition characterized by reddened epidermal lesions covered with dry, silvery scales.
Athlete’s Foot
An itchy, red, peeling condition of the skin between the toes resulting from a fungal infection.
Cold Sores
Small fluid filled blistered that itch and sting, caused by a herpes simplex infection.

72. Infections & Allergies
Contact Dermatitis
Itching, redness, and swelling of the skin, progressing to blistering. Caused by the exposure of skin to chemicals that provoke allergic responses. (it is = swelling)
Impetigo
Pink, water-filled, raised lesions that develop (mouth and nose) a yellow crust and eventually rupture . Caused by staphylococcus infection.