1. Chapter 2 The Integumentary System

2. Integumentary System The body’s covering
Includes: skin, nails, and hairs
Skin: cutaneous membrane
The skin (integument), is the largest organ of the body covering over 7600 cm2 (3000 in2)

3. Structure Two main parts
Epidermis - surface epithelial layer
Dermis - deeper connective tissue layer
Subcutaneous (subQ) layer or hypodermis lies deep to dermis; is not part of the skin

4. Integumentary System

5. Epidermis Keratinized stratified squamous epithelium Cell types (4):
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

6. Epidermal Cells Keratinocytes 90% of epidermal cells 4-5 layers
Produce keratin
Protects skin
Waterproofs skin

7. Epidermal Cells Melanocytes
Produce melanin that gives color to skin, hairs
Transfer pigment to keratinocytes
Make up 8% of epidermal cells

8. Epidermal Cells Langerhans cells Merkel cells Immune response
Sense of touch
Consist of tactile disc and neuron for touch sensation

9. Epidermal Layers Four Layers (strata) Stratum basale
Includes stem cells; new cells arise here
Stratum spinosum: 8-10 cell layer
Cells beginning to look flattened
Stratum granulosum makes keratin
Losing cell organelles and nuclei
Have waterproofing lipid
Stratum corneum: flattened dead cells
Cells here consist mostly of keratin.
Cells here are shed and replaced from below.

10. Layers of the Epidermis

11. Dermis The dermis has several important characteristics:
is composed of connective tissue containing collagen and elastic fibers
contains two layers
the outer papillary region consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (including capillary loops), corpuscles of touch and free nerve endings

12. Dermis
The deeper reticular region consists of dense irregular connective tissue containing collagen and elastic fibers adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands
Striae or stretch marks can appear if the skin is stretched too much

13. Dermis
Lines of cleavage - “tension lines” in the skin indicate the predominant direction of underlying collagen fibers
Epidermal ridges reflect contours of the underlying dermal papillae and form the basis for fingerprints (and footprints); their function is to increase firmness of grip by increasing friction.
Dermatoglyphics - the study of the pattern of epidermal ridges

14. Skin Color
Normal skin color is caused by the expression of a combination of i) melanin, ii) carotene & iii) hemoglobin.
Melanin – brown-black pigment produced in the melanocytes of the stratum basale
All races have virtually same # of melanocytes, but the amount of melanin produced + degree of granular aggregation of the melanin determine whether an individual’s skin color is black, brown, tan or white
Melanin – protective device against UV damage
Gradual exposure to sunlight promotes the increased production of melanin within the melanocytes – tanning
Albino – normal melanocytes but lacks the enzyme tyrosinase (tyrosine melanin)
Vitiligo – lacks of melanocytes in localized area – white spot

15. Albino
vitiligo

16. Coloration of the Skin
Carotene – yellowish pigment found in epidermal cells and fatty parts of the dermis
Carotene is abundant is the skin of Asians + melanin – yellow-tan skin
Hemoglobin – not a pigment, oxygen-binding pigment found in RBC
Oxygenated blood flowing through the dermis gives the skin its pinkish tones

17. Accessory Structures
Hair
Skin glands
Nails

18. Hair Found on most skin surfaces Made of fused keratinized cells
Not on palmar surfaces of hand and fingers or plantar surfaces of feet
Made of fused keratinized cells
Consists of shaft and root
Surrounded by hair follicle
Base is bulb which includes growing matrix producing cells
Nerves in hair root plexuses
Muscle that pulls on hair: arrector pili
Causes hair to stand on end

19. Hair

20. Humans have three distinct kinds of hair
Lanugo is a fine, silky fetal hair that appears during the last trimester of development. Not evident on a baby at birth unless it has been born prematurely.
Angora hair grows continuously in length, as on the scalp of males and females and on the face of males.
Definitive hair grows to a certain length and then ceases to grow. It is the most common type of hair. Eg. eyelashes, eyebrows, pubic & axillary hair.

21. Glands Sebaceous gland: secrete oily sebum Sudoriferous (sweat) gland
Connected to hair follicles; keeps hair from drying out
Sudoriferous (sweat) gland
Eccrine sweat gland
Wide distribution – thermoregulation
Apocrine sweat gland
Axilla, groin, areolae, beard
Contain other cell material
Ceruminous (wax) gland
Wax combines with sebum to produce earwax

22. Nails Plates of packed hard dead keratinized cells
Nail body: major visible portion
Free edge: part extending past finger or toe
Root: cells deep to here (in nail matrix) form new nail cells

23. Nails

24. Functions of Skin Temperature regulation Protection Sensory reception
Excretion and absorption: small amounts
Vitamin D synthesis

25. Thermoregulation
Body temperature tends to increase as a result of exercise, fever, or an increase in environmental temperature.
Homeostasis is maintained by the loss of excess heat.
The blood vessels (arterioles) in the dermis dilate and allow more blood to flow through the skin, thus transferring heat from deeper tissues to the skin.
To counteract environmental heat gain or to get rid of excess heat produced by the body, sweat is produced.
The sweat spreads over the surface of the skin, and as it evaporates, heat is lost from the body.

26. Thermoregulation
If body temperature drops below normal, heat can be conserved by a decrease in the diameter of dermal blood vessels, thus reducing blood flow to the skin.
With less warm blood flowing through the skin, however, the skin temperature decreases.
If the skin temperature drops below approximately 15 degrees Celsius, blood vessels constrict, which helps to prevent tissue damage from the cold.
Contraction of the arrector pili muscles causes hair to stand on end, but with the sparse amount of hair covering the body, this does not significantly reduce heat loss in humans.
Hair on the head, however, is an effective insulator.

27. Aging Adolescence: can develop acne
Most effects in dermis, with visible signs of aging by about age 40. These include:
Loss of collagen fibers
Loss of elasticity
Loss of immune responses
Decreased melanocyte functions:
gray hair, skin blotches
Thinning of skin and hairs
Anti-aging treatments

28. Conditions of the skin & associated structures indicating nutritional deficiencies or body dysfunctions
Condition
Deficiency
Comments
General dermatitis
Zinc
Redness & itching
Scrotal or vulva dermatitis
Riboflavin
Inflammation in genital region
Hyperpigmentation
B12, folic acid, or starvation
Dark pigmentation on backs of hands & feet
Dry, stiff, brittle hair
Protein, kcal, & other nutrients
Usually occurs in young children or infants
Follicular hyperkeratosis
Vit A, unsaturated fatty acids
Rough skin due to keratotic plugs from hair follicles
Pellagrous dermatitis
Niacin & tryptophan
Lesions on areas exposed to sun
Thickened skin at pressure point
Niacin
Noted at belt area at the hips
Spoon nails
Iron
Thin nails that are concave of spoon-shaped
Dry skin
H20 or thyroid hormone
Dehydration, hypothyroidism, rough skin
Oily skin (acne)
Hyperactivity of sebaceous glands

29. Spoon nail

30. Additional Info: Sun Safety Tips
Watch the clock
Avoid exposure from 10AM – 4PM
Sunblock SPF 15 or 30 if at high risk
UVA/UVB
Apply 30min before exposure
Reapply every 2hrs
Wear sunglasses & protective clothing
Do not prolong sun exposure just because you are wearing sunscreen!
Copyright 2010, John Wiley & Sons, Inc.