1. Chapter 5: The Integumentary System

2. Size of the Integument
The integument is the largest system of the body:
16% of body weight
1.5 to 2 m2 in area

3. Connections to other systems
Circulatory system:
blood vessels in the dermis
Nervous system:
sensory receptors for pain, touch, and temperature

4. Functions of Skin Protects underlying tissues and organs
Excretes salts, water, and organic wastes (glands)
Maintains body temperature (insulation and evaporation)

5. Functions of Skin Synthesizes vitamin D3 Stores lipids
Detects touch, pressure, pain, and temperature

6. Parts of the Integument
The integument is made up of
2 parts:
cutaneous membrane (skin)
accessory structures
hair, nails and glands

7. Parts of the Cutaneous Membrane
Outer epidermis:
superficial epithelium (epithelial tissues)
Inner dermis:
connective tissues

8. Skin Structure Epidermis—outer layer Stratified squamous epithelium
Outer layers keratinized (hardened by keratin)
Dermis
Dense connective tissue (beneath thin layer of loose CT)

9. Layers of the Epidermis
Stratum corneum – outer layers of dead, heavily keratinized cells
Stratum lucidum - thick, hairless, “clear layer” skin of palms and feet only
Stratum granulosum – “grainy layer” produces keratin
Stratum spinosum – “spiny layer” has an immune response
Stratum basale – a.k.a. stratum germinativum; stem cells here give rise to all other epidermal cells. Melanocytes located here.

10. Thin Skin
Covers most of the body
Has 4 layers of keratinocytes

11. Thick Skin Covers the palms of the hands and soles of the feet
Has 5 layers of keratinocytes

12. Keratin, Melanin, and an Amazing Factoid!
Keratin – tough, pliable protein; water resistant; gives skin, hair, and nails protective properties
Stratum corneum is ‘cornified’ = filled with keratin
Cells are shed everyday; stratum basale totally replaces epidermis every 25 – 45 days!!

13. Melanin – pigment of skin color
Produced by melanocytes (usually in stratum basale)
Color is yellow to brown to black
Amount depends upon genetics and exposure to sunlight
Protects skin from sun damage

14. Dermis – deep to epidermis: 2 layers (has capillaries and sensory neurons)
Papillary layer (upper dermal region)
Projections called dermal papillae
Capillary loops, pressure and pain receptors, fingerprints, made of areolar tissue
Reticular layer (deepest skin layer). Made of collagen & elastic fibers.
Blood vessels
Sweat and oil glands
Hair follicles
Deep pressure receptors

15. Damage to the Dermis: Skin Damage
Sagging and wrinkles (reduced skin elasticity) are caused by:
dehydration
age
hormonal changes
UV exposure

16. Stretch Marks Thickened tissue resulting from:
excessive stretching of skin due to:
pregnancy
weight gain

17. Lines of Cleavage
Clinically significant:
A cut parallel to a cleavage line will usually remain closed and heals with little scarring.
A cut at a right angle to a cleavage line will be pulled open as severed elastic fibers recoil and will result in greater scarring.

18. The skin contains two types of exocrine glands:
Sebaceous glands (oil glands):
secrete sebum -- inhibits bacteria growth, lubricates and protects hair and skin.
Sweat glands: (2 types)
apocrine – located in armpits and pubic region, produce a sticky, cloudy, and potentially odorous secretion. Begin secreting at puberty.
Mammary glands of the breast are modified apocrine sweat glands, a complex interaction between sex and pituitary hormones controls their development and secretion.
merocrine – secrete “sweat” onto the skin, composed of 99% H2O. Found all over the skin, the palms and soles have the highest number per cm2. Cools the skin surface, flushes the surface of the skin.

19. Hair Produced by hair follicles
Consists of keratinized epithelial cells
Melanocytes provide pigment

20. Arrector pili – smooth muscle attached to follicle and papillary layer cause ‘goosebumps’

21. Nails – heavily keratinized modifications of epidermis
Stratum basale in nail matrix responsible for growth, nail itself is mostly dead cells (like hair)

22. The Subcutaneous Layer
Subcutaneous layer (hypodermis):
Not part of the skin
Composed of loose connective tissue: areolar & adipose tissue.
½ of your fat is stored here
Lots of blood vessels, location of hypodermic injections.

23. Review

24. Burns – damage from heat, electricity, UV, chemicals

25. Severity of Burns Burns – damage from heat, electricity, UV, chemicals
First-degree burns
Epidermis only
Red and swollen (typical sunburn)
Second-degree burns
Epidermis and upper dermis damaged
Red with blisters
Third-degree burns
Entire skin layer destroyed
Burn is gray-white or black

27. Rule of 9’s to estimate burn area.

28. Skin Cancer
Figure 5–6

29. Skin Cancer – uncontrolled cell division in skin
Skin cancer = #1 cancer
Basal cell carcinoma – least malignant, most common, (stratum basale)
Squamous cell carcinoma – easy cure early, but does metastasize to lymph nodes, (stratum spinosum)
Malignant melanoma – most deadly, rapid metastasis to lymph and blood, (melanocytes)

30. ABCD Rule: detecting malignant melanoma
A = Asymmetry – opposite sides don’t match
B = Border irregularity – borders not smooth
C = Color – one mole, several colors
D = Diameter - >6mm (pencil eraser)

33. Hair and Hair Follicles
Figure 4.7c