1. Dermis Hair shaft Pore Dermal papillae (papillary layer of dermis)
Epidermis
Meissner's corpuscle
Free nerve ending
Reticular layer of dermis
Sebaceous (oil) gland
Dermis
Arrector pili muscle
Sensory nerve fiber
Eccrine sweat gland
Pacinian corpuscle
Hypodermis
(superficial
fascia)
Artery
Vein
Hair root
Adipose tissue
Hair follicle
Eccrine sweat
gland
Hair follicle receptor
(root hair plexus)
Figure 5.1

2. Dermis
Second major skin region containing strong, flexible connective tissue
Cell types include fibroblasts, macrophages, and occasionally mast cells and white blood cells
Composed of two layers – papillary (bumpy) and reticular (netlike)
Contains a wide variety of accessory organs, including hair follicles, glands, sensory receptors, smooth muscles, and blood vessels

3. Layers of the Dermis: Papillary Layer
Papillary layer = Stratum Papillarosum
Areolar connective tissue with collagen and elastic fibers
Its superficial surface contains peglike projections called dermal papillae
Dermal papillae contain capillary loops, Meissner’s corpuscles (light touch receptors), and free nerve endings (pain receptors)
Patterns of these bumps found on dermal ridges form fingerprints, which increase friction needed to grip objects. Sweat gland pores along the dermal ridges leave fingerprint patterns on objects we touch.

4. Layers of the Dermis: Reticular Layer
Reticular layer = Stratum Reticulosum
Accounts for approximately 80% of the thickness of the skin
Named for network of protein fibers criss-crossing throughout the tissue
Collagen fibers in this layer add strength and resiliency to the skin
Elastin fibers provide stretch-recoil properties

5. Hypodermis
Subcutaneous layer deep to the skin
Composed of adipose and areolar connective tissue

6. Skin Color Three pigments contribute to skin color
Melanin – yellow to reddish-brown to black pigment, responsible for dark skin colors. Melanin is formed by melanocytes and secreted; then absorbed by nearby keratinocytes
Different races have different amounts of melanin.
Freckles and pigmented moles – result from local accumulations of melanin
Albinos lack the gene for making melanin.
Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet
Hemoglobin – reddish pigment responsible for the pinkish hue of the skin. The skin color depends on the amount of oxygen carried by the hemoglobin.

7. Integumentary Functions
Hair shaft
Pore
Dermal papillae
(papillary layer
of dermis)
Epidermis
Meissner's corpuscle
Free nerve ending
Reticular layer of dermis
Sebaceous (oil) gland
Dermis
Arrector pili muscle
Sensory nerve fiber
Eccrine sweat gland
Pacinian corpuscle
Hypodermis
(superficial
fascia)
Artery
Vein
Hair root
Adipose tissue
Hair follicle
Eccrine sweat
gland
Hair follicle receptor
(root hair plexus)
Figure 5.1

8. List the Functions Represented by Dermo!!!!!!!!!

9. Functions of the Integumentary System
Protection
Body temperature regulation
Cutaneous sensation (Touch)
Metabolic functions (Synthesis of molecules)
Water retention
Excretion
(Extras: Homeostasis, Blood Reservoir)

10. Integumentary Functions: Protection
Skin acts as a chemical, physical, biological, and mechanical barrier
Stratum corneum prevents molecules (including water) to enter or exit
Entire dermis makes physical layer around body
Langerhans cells attack bacteria and viruses

11. Integumentary Functions: Thermoregulation
Thermoregulation is accomplished by negative feedback interactions between the skin, muscles, and the brain.
Dilation (release heat to environment) and constriction (conserves heat in body) of dermal vessels
Increasing sweat gland secretions to cool the body by evaporation
Activating arrector pili muscles lifts hairs to trap heat and warm the body (more effective in furred mammals than humans)
Hypothalamus of brain is control center (part of midbrain)
Muscles shiver to produce heat when body temperature drops – but this is deeper than the skin

12. Integumentary Functions: Sense of Touch
Several types of touch receptors embedded in skin
Light touch is sensed by Merkel’s discs (found in epidermis), Meissner’s corpuscles (found in dermal papillae), and root hair plexuses (wrapped around hair follicles).
Deep pressure is sensed by Pacinian corpuscles (found deep in the dermis).
Pain is sensed by free nerve endings throughout the epidermis and dermis.
Cold is sensed by Krause’s corpuscles, found in the dermis.
Heat is sensed by Rufinni’s corpuscles, found in the superficial dermis.

13. Functions of the Integumentary System
Metabolic functions – synthesis of vitamin D in dermal blood vessels – requires exposure to sunlight
Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume
Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat

14. Accessory Organs of the Skin
Hair shaft
Pore
Dermal papillae
(papillary layer
of dermis)
Epidermis
Meissner's corpuscle
Free nerve ending
Reticular layer of dermis
Sebaceous (oil) gland
Dermis
Arrector pili muscle
Sensory nerve fiber
Eccrine sweat gland
Pacinian corpuscle
Hypodermis
(superficial
fascia)
Artery
Vein
Hair root
Adipose tissue
Hair follicle
Eccrine sweat
gland
Hair follicle receptor
(root hair plexus)
Figure 5.1

15. Sweat Glands (Sudoriferous glands)
Different types that either 1. prevent overheating of the body 2. secrete cerumen 3. secrete milk 4. secrete pheromones
Eccrine (merocrine) sweat glands – found all over body, especially in palms, soles of the feet, and forehead
Apocrine sweat glands – found in axillary and anogenital areas – may also release pheromones (molecules that influence the behavior of another organism)
Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen (“earwax”)
Mammary glands – specialized sweat glands that secrete milk

16. Sebaceous Glands
Simple alveolar (holocrine) glands found all over the body
Soften skin when stimulated by hormones
Secrete an oily secretion called sebum
Found along hair shafts where the sebum makes its way to the surface by following the hair pore
Blockage of pores causes acne
Sebum also has antibacterial activity

17. Hair
Filamentous strands of dead keratinized cells produced by hair follicles
Contains hard keratin which is tougher and more durable than soft keratin of the skin
Made up of the shaft projecting from the skin, and the root embedded in the skin
Consists of a core called the medulla, a cortex, and an outermost cuticle

18. Hair Color
Pigmented by melanocytes at the base of the hair
Color depends on type of pigment released as well as the amount
Dark hair: large amounts of melanin
Blonde hair: intermediate amounts of melanin
Red hair: melanin replaced by trichosiderin
White hair: no melanin or trichosiderin
Gray hair: mix of pigmented & unpigmented hair

19. Functions of hair include:
Hair Functions
Functions of hair include:
Helping to maintain warmth
Alerting the body to presence of insects on the skin
Guarding the scalp against physical trauma, heat loss, and sunlight
Attracting the opposite sex
Gathering tactile information

20. Hair is distributed over the entire skin surface except:
Hair Distribution
Hair is distributed over the entire skin surface except:
Palms, soles, and lips
Nipples and portions of the external genitalia

21. Hair Follicle
Root sheath extending from the epidermal surface into the dermis – includes both epithelial tissue (inner) and connective tissue (outer) regions – boundary between the epi. and conn. tissues is called the glassy membrane (thick basement memb.)
Deep end is expanded forming a hair bulb
A knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb
Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors

22. Hair Follicle Longitudinal Section
Figure 5.5c

23. Hair Follicle Cross Section
Figure 5.5a

24. Types of Hair
Vellus – pale, fine body hair found in children and the adult female
Terminal – coarse, long hair of eyebrows, scalp, axillary, and pubic regions

25. Hair Thinning and Baldness
Alopecia – hair thinning in both sexes
True, or frank, baldness
Genetically determined and sex-influenced condition
Male pattern baldness – caused by follicular response to DHT (dihydro testosterone)

26. Structure of a Nail
Scalelike modification of the epidermis made of keratin found on the distal, dorsal surface of fingers and toes
Figure 5.6