1. The Integumentary System
Chapter 5

2. The Integumentary System
Composed of the skin, sweat and oil glands, hair, and nails.
Accounts for 7% of the body’s weight.
Major role is protection from pathogens and dehydration.
Varies in thickness from 1.5 to 4.0 mm.
Composed of 3 distinct layers.
Epidermis, Dermis, and hypodermis or superficial fascia

4. Epidermis Outermost layer.
Composed mostly of keratinized stratified squamous epithelium.
Contains 4 distinct cell types and 4 to 5 distinct layers.

5. Cell Types of the Epidermis
Keratinocytes—produce keratin, a fibrous protein that give the epidermis its protective properties. These cells are tightly connected by desmosomes. Arise from the stratum basale. Undergo continuous mitosis. Are pushed upward and continuously become more keratinized.Those on the surface of the skin are dead. Millions rub off per day.
Friction may lead to a thickening of the cells known as a callus.

6. Cell Types of the Epidermis
Melanocytes—synthesize melanin.
Located at the deepest layer of the epidermis.
The melanin is transferred to the keratocytes.
Protects against UV damage.

7. Cell Types of the Epidermis
Langerhans’ cells—arise from the bone marrow.
Act as macrophages that activate the immune system.
Merkel cells—present at the junction of the epidermis and dermis. Associated with sensory receptors.

9. Layers of the Epidermis
Thick skin (on palms, fingertips, soles) has 5 strata.
Thin skin has only 4. The stratum lucidum is absent and the other layers are visibly thinner.
Stratum Basale—deepest layer. Attached to the dermis. Sometimes called the stratum germinativum because of the constant mitosis that occurs there. Made of a single row of keratinocytes.

10. Layers of the Epidermis
Stratum Spinosum—Several layers thick. Contain many intermediate filaments. Consist mainly of keratin like filaments. Resist tension. Melanin granules and Langerhan’s cells are abundant in this layer.
Stratum Granulosum—3-5 cell layers thick.Keratinocytes become more flattened and the cells contain more keratin and lamellated granules.
Stratum Lucidum—thin layer of dead keratinocytes. Present only in thick skin.

11. Layers of the Epidermis
Stratum Corneum—Outermost layer cell layers thick. Cells have thick cell membranes and a great deal of keratin.Cells are referred to as cornified.

12. The Dermis Made mostly of connective tissue.
The hide of the human body.
Richly innervated and vascularized.
Contains the hair follicles, sweat glands, oil glands, lymphatic vessels, and many sensory receptors.

14. The Dermis Consists of 2 layers.
Papillary layer—areolar connective tissue, heavily vascularized. Contains the dermal papillae, capillary loops, and Meissner’s corpuscles.
In some areas these lie on top of the dermal ridges. Cause the epidermal ridges that cause fingerprints.
Reticular layer—dense irregular connective tissue.
Importance of this structure.
Flexure lines.

15. The Dermis Skin color—determined by melanin, carotene, and hemoglobin.
Why do different people have different skin colors?
Freckles & moles
Role of melanin
Role and source of carotenes & hemoglobins.

16. The Dermis Photosensitivity Cyanosis Erythema Pallor—paleness Jaundice
Bronzing
Bruises & hematomas

17. Skin Appendages Sweat Glands—more than 2.5 million per person.
Eccrine sweat glands—coil in the dermis, a duct leads to a pore at the skin’s superficial surface.
Sweat contents
How does sweat work?
Apocrine sweat glands—in the axillary and anogenital areas. Empty into hair follicles. Contains fatty substances and proteins. May cause body odor. Begin to function at puberty. May contain pheromones.

18. Sin Appendages Ceruminous glands—secrete earwax.
Mammary glands—secrete milk.
Sebaceous Glands—oil glands. Found everywhere except the palms and soles.
Secrete sebum.Usually secreted into hair follicles.
Bactericidal + other functions.

19. Skin Appendages Whiteheads Blackheads Acne—staphylococcus
Hair—covers the entire body except for the palms, soles, lips, nipples, and parts of the genitalia.
Functions of hair.
Mostly dead keratinized cells.

20. Hair Parts of the hair Shaft Root Hair color Hair follicle Medulla
Cortex
Cuticle
Split ends
Root
Hair color
Hair follicle
Hair bulb
Root hair plexus
Arrector pili—How and why is this important?
Hair papilla

22. Hair Vellus Hairs Terminal Hairs—androgen sensitive Electrolysis
Hirsutism
Alopecia
Male-pattern baldness
Sex-influenced trait

23. Nails Modification of the epidermis Composed of keratin.
Composed of a free edge, body, and a root.
Nail bed—epidermis under the nail.
Nail matrix—growth occurs here.
Lunula
cuticle

26. Functions of the Integument
Chemical barriers—acid mantle, human defensin
Biological Barriers—Langerhan’s cells and macrophages.
Physical barrier
Some substances can cross the skin.
Lipid soluble substances.
Oleoresins—poison ivy.
Organic solvents.
Salts of heavy metals

27. Functions of the Integument
Temperature Regulation
Sweat glands
Vasodilation and vasoconstriction
Cutaneous Sensation
Meissner’s corpuscles
Pacinian corpuscles
Root hair plexuses
Pain and heat/cold receptors
Metabolic Functions
Vitamin D synthesis
Blood Reservoir
Shunts more blood into the circulation when needed.
Excretion

29. Skin disorders
Causes
Basal cell carcinoma—30% of caucasians get this type of skin cancer. Does not metastasize.
Squamous Cell carcinoma—arises from the keratinocytes in the stratum spinosum. May metastasize.
Melanoma—arises in the melanocytes. Rapidly metastasizes.
ABCD rule– Asymmetry, Border irregularity, Color, Diameter

30. Burns Denaturation of cell proteins.
Dehydration, protein loss, and infection.
First degree burns—only the epidermis.
Second degree burns—epidermis and upper dermis. May include blisters.
Third degree burns—full thickness. Not painful. Skin grafting is almost always necessary.
Grafting techniques
Autograft
Dangers of facial burns and burns near joints.

31. Aging Effects Lanugo Coat Vernix Caseosa Thinning of the skin
Slowing of epidermal cell replacment.