1. Accessory Organs
Integumentary System

2. Accessory Organs Located mostly in the dermis (reticular region)
Originate in the epidermis
A group of cells from the epidermis migrate into the dermis
The process of forming these organs starts in the dermis
Hair, nails, sweat glands, sebaceous glands
These are called the epidermal derivatives

3. Hair Protects the skin from sunlight and foreign particles
Hair follicle: downward extension of the epidermis into the dermis
Hair Root: the part surrounded by the follicle
Hair shaft: the part that extends away from the body
Bulb: the base of the hair follicle, cluster of blood vessels here that supplies nutrition

4. Hair
Arrector pilli: small band of smooth muscle, from the follicle to the papillary region
The contraction of the muscle pulls the hair vertical
Frightened of cold
Small amount of heat is generated
Goose bumps
Another important structure is the sebaceous gland which will have its own slides...

5. Hair Growth Hair growth
Similar to dividing cells of the epidermis
New growth in the deeper region pushes the new cells toward the surface
Cytoplasm of the dead cells is replaced by keratin
The hair shaft is composed of keratin
1 mm every 3 days
Shaving or cutting has no effect on the growth rate
Example: androgens (a male hormone) inhibits follicle activity, breaking the cycle of growth, loss, and replacement
Male pattern baldness

6. Hair Color Provided by melanin
Various concentrations to produce different shades
As age increases, the amount of melanin is reduced
Gray or white hair

7. Pause and Process
Why do we say that hair “originates” in the epidermis? It looks like it grows out of the dermis…
From where does hair get blood supply to grow?
Hair = hair follicle, hair root, hair shaft… Which of these do you expect to be made of living cells? Which do you expect to be made of dead cells?
How do hair cells behave similarly to skin cells (pattern of cell growth and death)?
Arrector pilli connect the follicle to the papillary region.... What layer is the papillary region in? What is a distinguishing characteristic of the papillary region?
Use the pictures in previous slides to help with explanation of these answers

8. Sebaceous Glands Secrete sebum into a duct
Water, fats, salts, cholesterol, protein
Keeps hair and skin soft and pliable
Water-resistant layer on the skin surface
Oil glands
Cluster of glandular epithelial cells
Not in palms and soles
Blackheads form when these ducts are clogged or swollen
Blackheads = clogged pore that is open - air oxidizes the melanin and it changes color to black
Whitehead = clogged pore that is closed - air does not oxidize the melanin

9. Sweat Glands AKA sudoriferous glands Numerous throughout skin Sweat
Water, salts, small amount of urea
Secretion helps maintain body temperature
Evaporation off the body
Originates as a single coiled tube
In the dermis or hypodermis
Passes through to the surface via a pore

10. Sweat Glands
Two types
Eccrine: throughout the skin, watery sweat in response to elevated body temperature
Apocrine: begin during puberty in response to sex hormones
Thickened sweat, microorganisms, may have strong odor
Periods of emotional stress
More numerous in armpits and groin

11. Pause and Process
Both Sebaceous glands and Sweat Glands secrete their products into ducts… what type of gland does this make them? Endocrine or Exocrine?
What is the function of sebum?
How do sweat glands help us to maintain homeostasis?
Contrast eccrine and apocrine glands.

12. Nails Compressed outer layer of epidermis (...made of keratin)
Nail body = visible part
Cuticle = flap of stratum corneum overlying the proximal end
Nail root = deep to the cuticle, contains the nail matrix
Nail matrix = stratum basale**
Lunula = visible crescent; part of the nail matrix

13. Receptors Distal ends of nerves, wrapped in connective tissue
Translate physical changes of environment into electrical impulses, brain interprets signals as sensations. (called “Transduction”)
Types of receptors in the skin:
Mechanoreceptors
Nocioreceptors
Thermoreceptors

14. Pause and Process
How is the growth of your nails similar to the growth of your skin?
What two layers are receptors located in?
What do mechanoreceptors transduce? Thermoreceptors? Nocioreceptors?