1. The Integumentary System
Chapter 5
Introduction to the Human Body

2. Skin Facts about skin Skin, AKA the cutaneous membrane
Largest organ in the body
Surface Area ≈ 2 m2
Weight ≈ 10 lbs
Very thin: only 0.5 – 4 mm thick
Dermatology

3. Layers
Skin layers
Epidermis
Dermis
Subcutaneous Layer

4. Epidermis Epidermis Keratinized stratified squamous epithelium
4 cell types:
Keratinocytes – 90% of epidermal cells; 4-5 layers
Keratin
Lamellar granules
Melanocytes – 8% of epidermal cells
Melanin
Transfers melanin to keratinocytes
Langerhans cells
Merkel cells (disk)

5. Epidermis Structure of epidermis
Most epidermis has four strata (layers) – Thin skin
Stratum basale –cuboidal or columnar keratinocytes
Stratum spinosum – layers of keratinocytes with desmosomes
Stratum granulosum – layers of flat keratinocytes
Thin stratum corneum – layers

6. SEM of Keratinocytes

7. Epidermis Where friction is greatest the skin has five layers
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum – 3-5 layers of clear, dead keratinocytes
Thick stratum corneum
Keratinization

8. Layers of Skin Cells

10. Review of the Epidermis
How is thick skin different from thin skin?
How is keratinization related to the structure of the epidermis?
Why are basal cells so important to the skin?
Why is the epidermis waterproof?

11. Warm Up #1 More non-biological analogies: Keratin Lamellar granules
Stratum basale
Stratum granulosum
Keratinization
Merkel cells
Langerhans cells

12. Skin Structure: Dermis
Mainly CT w/ collagen and elastin fibers
2 layers:
Stratum papillerosum (papillary layer)
Corpuscles of touch (Meissner corpuscles)
Free nerve endings

13. Skin Structure: Dermis, cont.
Stratum reticulosum (reticular layer)
Adipocytes, hair follicles, nerves, oil and sweat glands
Striae

15. Subcutaneous Layer Subcutaneous layer
Also called the hypodermis or SubQ layer
Composed of areolar CT and adipose
Contains lamellated corpuscles (Pacinian corpuscles)

17. Review of the Dermis / Hypodermis
Which tissues make up the dermis?
What are the 2 layers of the dermis?
What is the function of each layer?
Which tissues make up the hypodermis?
What is the function of the hypodermis?

18. Skin Color Skin Color: controlled by 3 pigments Melanin Carotene
Hemoglobin

19. Skin Color
Skin color differences
Freckles
Age Spots
Albanism

20. Accessory Organs: Hair
Hair (pili)
Threads of fused, dead, keratinized cells
3 main parts:
Shaft
Root
Follicle

21. Accessory Organs: Hair
Arrector pili
Color controlled by melanin
Present in most skin surfaces
Androgenic alopecia

23. Accessory Organs: Glands
Sebaceous
Sudoriferous
Eccrine
Apocrine
Ceruminous

24. Gland Review Which gland… Is responsible for body odor (B.O.)?
Protects your ears from infection?
Keeps you cool?
Keeps your hair from becoming dry and brittle?
Is found on the palms of your hands?
Is very active on your face during puberty?
Is not active until puberty?

25. Accessory Organs: Nails
Plates of tightly packed, hard, keratinized cells of the epidermis
Parts:
Nail body
Lunula
Cuticle
Free edge
Nail root
Nail matrix

27. Functions of the Skin Functions Protection underlying tissue
Regulation & excretion of fluid
Regulation of temperature
Synthesis of vitamin D
Cutaneous sensation reception
Communication
Immunity

28. Skin Conditions Skin Conditions Skin Cancer Acne Nevus Warts
Skin & Aging