1. Integumentary System

2. SKIN LAYERS (Epidermis and Dermis) EPIDERMIS (outside to inside)
EPIDERMIS (outside to inside)
Stratum Corneum
Thin and flat cells
Dead
Continually shed (35 days to new skin)
Cytoplasm – full of protein keratin
Water repellent
Cells are very dry
If soak in water, cells act as sponge and absorb water
Skin puckers, bulges when in water a long time
Allowed to dry out wrinkles disappear
Barrier to water loss, outside chemicals, and outside bacteria

3. Stratum Lucidum Stratum Granulosum Clear layer Dead - No nuclei
Prevents water loss
Apparent in “thick layers” of skin – soles of feet
and palms of hand
Stratum Granulosum
Keratinization begins in this layer
Intense staining granules

4. Stratum spinosum Irregular-shaped cells
Desmosomes – joining adjacent cells
Spot welds
Heat, friction, or irritants break bonds
and results in blisters
Gives a spiny appearance
Heavy production of keratin (heavy RNA
and protein synthesis)

6. Stratum basale Single layer of columnar cells
Deepest cells undergo mitosis
Migrate from this layer to surface of skin
Regeneration of cells about 3-4 weeks
Abrasions or constant pressure increases
mitotic activity
Leads to a thickened corneum (calluses)

10. DERMIS – Corium (much thicker than the epidermis)
Thicker than Epidermis
Skin strength in the dermis
Storage area for water

11. Dermis Papillary layer
Thin layer that projects into the epidermis – dermal papillae
Responsible for fingerprinting

12. Dermis Reticular layer Collagen fibers give strength to the skin
Commercial processing of animal skin – leather
Elastic fibers give skin its give
Point of attachment for muscle
Results in facial expressions and scalp movement
Hair follicles have arrector pili muscle attached
Hair stands on end in extreme fright (skin crawl)
Raises the skin around it – “goose bumps”
Doesn’t shed and regenerate
Contains sensory receptors (pain, pressure, touch,
and temperature)

13. SUBCUTANEOUS LAYER OR HYPODERMIS
Not really part of the skin itself
Lies between dermis and underlying tissues
Rich in fat or adipose tissue
Choice for subcutaneous injections and absorption of materials

14. SKIN COLOR Determined by 3 factors Amount of melanin
Carotene – yellow pigment
Hemoglobin at the surface

15. Melanin – production occurs in Melanocytes
Located in the Stratum basale
Melanin – dark brown pigment
Tyrosine (aa) → Melanin
Requires enzyme tyrosinase
Absence of enzyme – results in albinism
Decreased enzyme – results in graying of hair and white skin of elderly
Controlled by genes
Environmental control – exposure to sun (increases melanin production)
Meant as protection to UV damaging rays (mutations)

19. Carotene – yellowish color
Hemoglobin – reddish color
Depends on volume of blood in skin capillaries

20. FUNCTIONS OF THE SKIN Protection –
Microorganisms – mechanical and lysozymes
From water loss – keratin
Chemicals – keratin
Physical damage – Collagen strength
UV radiation - Melanin

21. Sensation – sensory receptors puts us in contact with our external environment
Pressure, touch, pain, and temperature

22. Excretion – salts and wastes (ammonia and urea)
Vitamin D production (hormone or endocrine function)– UV light causes a chemical reaction that allows vitamin D formation
Important in calcium absorption for strong bones

23. Immunity Macrophages are in the tissue to repel foreign invaders
Langerhans cells work with Helper T cells – trigger immune reaction to disease

26. Body Temperature Homeostasis (balance)
Heat Loss
Increases the flow of blood to the skin dermis – Vasodilation
Sweating and evaporation allow heat to be removed
Heat Conservation
Decreases the flow of blood to the skin dermis – Vasoconstriction

27. SKIN APPENDAGES
HAIR
Present all over body EXCEPT – lips, nipples, palms of hands and soles of feet
Parts of the hair
Shaft – hair seen above the surface of the skin
Root part of shaft below the surface
Follicle – tube that surrounds the hair below the surface of the skin
Epidermal layers spread down into the dermis
Contain mitotic layer for hair shaft formation
Melanocytes are present that give color to the hair
Papilla - Supplies blood capillaries for nourishment

30. Hair color
Amount of melanin deposited in the middle of the hair determines color
Special melanin containing iron results in red hair
Gray and White hair decrease or absence of melanin
Straight or curly hair
Straight hair – round shaft
Curly hair – flat shaft

31. NAILS Nail body - visible part of nail (keratinized epithelial cells)
Root of nail – hidden by the cuticle
Lunula - crescent-shaped white area
Stratum germinativum below lunula – site of nail growth
Rich blood vessels below nail give a pink color to nail

32. SKIN GLANDS (Cutaneous glands)
All are exocrine glands (they release their secretions to the skin surface via ducts)
Sebaceous (Oil) Glands- found all over the skin, except on palms of the hands and soles of the feet.
Sebum- secreted by sebaceous glands
Made up of an oily substance and
fragmented cells
A lubricant that keeps the skin
soft and moist and prevents the hair
from becoming brittle.
Contains chemicals to kill bacteria

33. Sweat glands- “sudoriferous glands”- more than 2.5 million per person
Eccrine glands- found all over the skin
Produce sweat (water plus some salts, vitamin C, traces of metabolic wastes (ammonia, urea, uric acid), and lactic acid.
The sweat glands are supplied with nerve endings

34. Apocrine sweat glands- axillary and genital areas
Larger than eccrine glands
Secretions contain fatty acids and proteins as well as all substances present in eccrine secretions.
May be milky or yellow in color.
Odorless, but when bacteria begin to grow on the nutrients in the secretions, it takes on a musky smell.
Apocrine glands begin to function during puberty under the influence of androgen