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1. The Integumentary System Chapter 5
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. 20-30 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
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.