1. The Skin

2. Skin Color Three factors for skin color:
Amount and kind of melanin
Amount of carotene (orange-yellow pigment)
Amount of oxygen bound to hemoglobin
More melanin production, darker skin color
People with less melanin have a rosy color b/c oxygen rich blood flushes through membranes
Skin turns yellow-orange when large amount of carotene is ingested

3. Influence of emotional stimulus. Possible diseases:
Erythema:
Jaundice, or
Bruises or black-and-blue marks
Blood has escaped circulation and clotted in tissue space = hematomas
Unusual tendency to bruising CAN be caused by vitamin C deficiency or hemophilia (bleeder’s disease)

4. Erythema reddened skin (blushing)
From embarrassment OR fever, hypertension, inflammation, allergy

5. Jaundice yellow cast abnormal yellow skin tone
Liver disorder: excess bile absorbed into blood, circulated throughout, and deposited in body tissues

6. Pallor aka blanching pale skin tone
Emotional stress OR anemia, low bp, or impaired blood flow

7. Cyanosis Hemoglobin is poorly oxygenated Blood and skin appear blue
Common during heart failure
Better apparent in mucous membranes and nail beds

8. Appendages of the skin Cutaneous glands Hairs Hair follicles Nails
Each come out of the epidermis
Each play a role in maintaining homeostasis

9. Cutaneous Glands All the exocrine glands
Sebaceous glands
Sweat glands
Formed by cells of stratum basale
Push into deeper skin
Reside in dermis

10. Sebaceous (oil) glands
Found all over skin, except palm and soles
Ducts empty into hair follicles
Product of the gland is called sebum
Mix of oil and fragmented cells
Keeps skin soft and moist
Prevents hair from being brittle
Contains bacteria killing chemicals
Become active during adolescence

11. Blocking of sebaceous glands
Whitehead appears
Material accumulates, oxidizes, dries and darkens
blackhead
Acne
Active infection of sebaceous gland
Sebborhea
Overactivity of sebaceous glands
Begins on scalp as pink, raised lesions
Gradually forms yellow/brown crust that flakes off as dandruff
Can also occur in face and trunk

12. Sweat Glands More than 2.5 million per person Two types Eccrine
apocrine

13. Eccrine Sweat Glands Produce sweat Acidic Reaches skin via pore
Primarily water plus salts, vitamin C, metabolic wastes, lactic acid
Acidic
Inhibits bacterial growth
Reaches skin via pore
“pores” on face do not serve same purpose
These are outlets for hair follicles
Important in heat-regulation
Come with nerve endings that cause sweat secretion if body temp is too high

14. Apocrine Sweat Glands Found in axillary and genital areas
Secretions contain fatty acids, proteins, as well as things in eccrine secretions
May have milky or yellowish color
Odorless
Bacteria can use proteins and fats as source of nutrients
Leads to musky, unpleasant odor
Begin function during puberty due to androgens
Minimal role in thermoregulation
Activated by nerve fibers during pain and stress

15. Hair and Hair Follicles
Once upon a time…
Served as insulator
Today…
Guards head
Shields eyes
Keeps foreign particles out of respiratory tract

16. Hair and Hair Follicle Hair is produced by a hair follicle
Hair is formed by division of stratum basale epithelial cells in hair bulb matrix at the inferior end of the hair
Bulk of hair shaft is dead material
Each hair has central core (medulla) enclosed by cortex, which in turn is enclosed by cuticle
Cuticle
formed by overlapping layers
Prevents matting and keeps hairs apart
Heavily kreatinized for strength

18. Hair and Hair Follicles
Pigment from melanocytes (prod melanin)
Come in variety of size and shapes
Determines type of hair
i.e. oval shaft -> smooth & silky hair
i.e. flat, ribbonlike shaft -> curly or kinky hair
Arrector pili
Small bands of smooth muscles
Connect hair follicle to dermal tissue
Muscle contraction leads to “goose bumps”

19. Nails Scalelike modificaiton of epidermis
Three parts: free edge, body, root
Borders overlapped by skin folds, called nail folds
Thick proximal nail = cuticle
Nail matrix responsible for growth
Cells produce and become keratinized
Mostly nonliving material
Transparent and colorless
Red color due to blood supply in dermis
Lunula is white because thickened matrix