1. INTEGUMENTARY SYSTEM

2. Introduction to the SKIN!
Integumentary System
Skin (aka- cutaneous membrane)
Nails
Hair Follicles
Skin Glands
The skin is the largest organ by weight
Functions:
Protective covering
Slows water loss
Regulates body temperature
Houses sensory receptors
Excretes small amounts of waste
Helps in vitamin D formation

3. Tissues of the Skin- Into to Layers
2 distinct layers
Epidermis
Outer layer
Stratified squamous epithelium
Dermis
Inner layer
Connective tissue
Smooth muscle tissue
Nervous tissue
Blood
Layers are separated by a basement membrane

4. Tissues of the Skin- Hypodermis
Subcutaneous layer
Aka- hypodermis
Not part of the skin
Areolar and adipose tissues
Binds skin to underlying organs
Helps insulate
Contains blood vessels that supply the skin
The dermis and hypodermis lack a sharp boundary

6. Tissues of the Skin- Injections
Intradermal injections
Injected into the skin
Subcutaneous injections
Injected into the hypodermis
Administered through a hollow needle
Also called hypodermic injections
Transdermal patches
Drug passes into the epidermis through a permeable membrane
Motion sickness, chest pain, blood pressure, smoking cessation

7. The Epidermis- Characteristics and Functions
Lacks blood vessels
Thickest on palms and soles ( mm)
Other body regions average mm
Production of new epidermal cells balances loss of dead cells in healthy skin
Skin does not completely wear away
Cell division increases where skin is rubbed/pressed regularly
Leads to calluses and corns
Protective Functions
Shields against water loss
Prevents injury
Protects against harmful chemicals
Keeps out pathogens

8. The Epidermis-Layers 4 main layers: Stratum corneum Stratum granulosum
Outermost layer
Keratinized, dead epithelial cells
Keratinization- hardening of cells, waterproof keratin proteins made and stored in the cells
Stratum granulosum
Strantum spinosum
Stratum basale
Deepest layer
Able to divide and grown
Receive nutrients from dermis
Contains melanocytes

9. The Epidermis- Pigmentation
The epidermis contains melanocytes
Produce the pigment melanin
Found in the stratum basale
Melanin
Provides skin color
Absorbs UV radiation

10. Effect of Environmental Factors
Sunlight, UV light, X rays
Rapidly darken melanin
Stimulate melanocytes to produce more pigment
Pigment is transferred to nearby cells
Effect of Blood
Well oxygenated blood is bright red
Light-complexioned people may appear pink
Dilated vessels redden the skin
Overheated, embarrassed, under the influence of alcohol
Constriction of vesssel cause loss of color
Low body temperature, frightened/anxious person

11. Human Skin Color
Determined by heredity and environmental & physiological factors
All people have ~same number of melanocytes
Differences in skin color result from different amounts of melanin produced
Controlled by several genes
More melanin = darker skin

12. The Dermis- General Characteristics
The boundary between the epidermis and dermis is uneven
Dermal papillae extend from dermis into ridges of the epidermis
Increases surface area
Most abundant in hands and feet
Form fingerprints
Genes determine general patterns
Fetal movement forms distinct characteristics
The dermis binds epidermis to underlying tissues
Thickness ranges from 0.5 mm to 3.0 mm

13. The Dermis- Layers Papillary Layer Reticular Layer Upper layer
Areolar connective tissue
Reticular Layer
Lower layer
Dense irregular connective tissue
Give skin toughness and elasticity

14. The Dermis- Additional Components
Smooth muscle fibers
Can wrinkle the skin (testes)
Associated with hair follicles and glands
Skeletal muscle fibers
Voluntary movements (facial expressions)

15. Accessory Structures (blood, hair follicles, glands)
Nerve cells
Carry impulses to dermal muscles and glands
Carry sensory impulses away from sensory receptors
Lamellated corpuscles
In deep dermis
Respond to heavy pressure
Tactile corpuscles
In upper dermis
Sense light touch and texture
Accessory Structures (blood, hair follicles, glands)

16. Accessory Structures of the Skin- Nails
Protective coverings
Components:
Nail plate
Nail bed
Skin surface
Lunula
Most actively growing region
Produces keratinized, dead cells
Wears away with normal use
Analogous to hoofs and claws of other animals

17. Accessory Structures of the Skin- Hair Follicles
Hair is present on all surfaces except: palms, soles, lips, nipples and parts of external reproductive organs
Not well developed on other surfaces (forehead)
Originates in epidermis
Nourished by dermis
Grow, divide and push older cells toward surface
Cells become keratinized and die
Create the hair shaft

18. Average hair loss is 20-100 hairs a day
A single hair grows 2-6 years and is then replaced by a completely new hair
Genes determine hair color
direct the type and amount of pigment produced by melanocytes
Arrector pili muscles attaches to each hair follicle
Contraction causes hair to stand up
Causes goose bumps

19. Accessory Structures of the Skin- Glands
Sebaceous glands
Associated with hair follicles
Oil glands
Produce sebum (oil and cell fragments)
Ducts usually empty into hair follicles
Activated by hormones
Keep hairs and skin soft, pliable and waterproof
Not on palms or soles

20. Specialized sweat glands
~2 million per person
Widespread
Originates in deep dermis
Eccrine glands
Most numerous
Abundant on forehead, neck, back
Palms and soles
Respond to elevated body temperature
Also respond to emotional stress
Apocrine glands
Develop a scent as they mix with skin bacteria
Activated at puberty
React to emotional upset, fright, pain, sexual arousal
Most unmberous in axillary regions and groin
Specialized sweat glands
Ceruminous glands- ear wax
Female mammary glands- milk