Anatomy Midterm; Chapter 5 Integumentary System

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Anatomy and Physiology

The Integument

- 1st line of defense
- largest system of the body

2 Main Parts of Integument

- cutaneous membrane (skin)
- accessory structures

Cutaneous Membrane

- epidermis: superficial; epithelial tissues
- dermis: middle; connective tissue; dense irregular


Plus: subcutaneous: deep; superficial fascia; connective tissues

Accessory Structures

-originate in dermis and extend through the epidermis to the skin surface

ie. hair, nails, multicellular exocrine glands; blood vessels, sensory receptors for pain/temp/pressure

Functions of the Skin

Protection: underlying tissues and organs
Excretion: salts, waters, and organic wastes
Regulation: insulation and evaporation
Storage: energy; lipids within adipose
Sensation: touch, pressure, pain, temperature
Synthesizes: vitamin D

Characteristics of Epidermis

- stratified squamous epithelium
- avascular
- protects underlying tissue

Keratinocytes

- most abundant cells in the epidermis
- produce and contain large amounts of keratin
- thick, wavy, fibrous protein

Thin Skin

covers most of body, has 4 layers of keratinocytes

Layers of Epidermis

Deep to Superficial:
Stratum Germanitivum
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum

Stratum Germinativum

- lot of basal cells
- attached to basal lamina by desmosomes
- forms a strong bond between epidermis and dermis
- epidermal ridges: form fingerpoints

Merkel Cells

- cells of stratum germinativum
- found in hairless skin
- respond to touch

Melanocytes

- cells of stratum germinativum
- contain the pigment melanin
- scattered throughout germinativum

Basal Cells

- stem cells
-cells of stratum germinativum

Stratum Spinosum

- "spiny layer"
- keratinocytes continue to divide, increasing thickness of epithelium
- 8-10 layers of keratinocytes
- cells shrink until their cytoskeletons stick out (spiny)

Langerhans Cells

- in stratum spinosum
- defend against microorganisms and cancer cells

Stratum Granulosum

- "grainy layer"
- keratinocytes stop dividing and start producing:
~ keratin: a tough, waxy, fibrous protein
~ cells fill with keratin, dehydrate, and begin to die

Stratum Lucidum

- "clear layer"
- found only in thick skin
- covers stratum granulosum
- keratinocytes are: dead, flat, densely packed with keratin, cells have become keratinized

Keratinization

- formation of a layer of dead, protective cells filled with keratin
- occurs on all exposed skin surfaces except the eyes

Stratum Corneum

- "horn layer"
- exposed surface of skin
- 15 to 30 layers of keratinized cells
- water resistant
- shed and replaced every 2 weeks

Skin Life Cycle

- it takes 15 to 30 days for a cell to move from
- stratum germinativum to stratum corneum

Skin Color

Depends on:
1. the pigments carotene and melanin
2. blood circulation (red cells)
3. illness

Carotene

- orange-yellow pigment
- found in orange vegetables (squash, carrots)
- accumulates in keratinocytes and adipocytes
- can be converted to vitamin A

Melanin

- yellow-brown pigment
- produced by melanocytes in stratum germinativum
- stored in transport vesicles: melanosomes
- then transferred to keratinocytes

Melanocytes

Functions:
1. protects skin from sun damage
- excessive UV radiation causes:
~ DNA mutations -> Cancer
~ Fibroblast impairment -> wrinkles
- UV radiation activates melanocytes

Blood Flow

- highly oxegenated blood i bright red
- a drop in blood flow creates pale skin

Cyanosis

- a severe reduction in blood flow of oxygenation
- bluish skin tint

Jaundice

- build up of bile
- produced by liver
- yellow color of skin and eyes

Vitiligo

- leukoderma
- loss of melanocytes
- loss of pigment

Melanoma

- cancer of the melanocytes in the germinativum
- least common type of cancer
- most dangerous type: aggressive metastasis (spreads rapidly)
- often starts out as a mole

Basel Cell Carcinoma

- cancer of the keratinocytes in the germinativum
- most common cancer type
- safe: non- metastasizing

Dermis

- deep to epidermis and superficial to the subcutaneous layer
- vascular and innervated
- anchors accessory structures of the epidermis: hair follicles and glands
- 2 layers: papillary layer (superficial) + reticular layer (deep)

Papillary Layer

- areolar tissues
- small capillaries: supply the germinativum
- sensory receptors
- lymph vessels

Dermal Papillae

- increase surface area between the epidermis and dermis
- strengthens attachment
- increases diffusion of germinativum

Reticular Layer

- deep layer of dermis
- dense irregular connective tissue
- supports: hair, glands, nerves, vessels, and muscle

Dermis

strong- due to collagen fibers
elastic- due to elastic fibers
flexible

Lines of Cleavage

- collagen and elastic fibers in the dermis
- are arranged in parallel bundles
- resist force in a specific direction

Dermatitis

- inflammation of the papillary layer
- causes:
~ chemical irritation: poison ivy, lotions
~ mechanical irritation: clothing, jewerly
~ infection: virus, bacteria
- itching or pain

Subcutaneous Layer

- located deep to the dermis and superficial to muscle and bone
- also called: hypodermis or superficial fascia
- composed of areolar and adipose connective tissues
- stabilizes the skin to deeper tissues
- allows skeletal muscle to move independently from the skin
- arteries and veins: supply dermal papillary layer
- nerves control: blood flow, gland secretion, sensory receptors

Glands of Accessory Structures

Sebaceous Gland (oil)- sebum
Sudorifirous Gland- sweat

Hair

- body is covered with except: palms, soles, lips, and portions of external genitalia
- functions: protects and insulates, guards openings against insects and dust
- sensitive to very light touch

Hair Follicle

- located deep in dermis
- produces nonliving hairs
- wrapped in a sheath of dense irregular CT
- base is surrounded by sensory nerves: root hair plexus

Hair Root

- lower part of the hair
- attached to the dermis

Hair Shaft

- protects upper part of hair
- NOT attached to dermis

Arrector Pili

- involuntary smooth muscle
- causes hair to stand up
- produces "goose bumps"
- contracts sebaceous gland

Sebaceous Gland

- lubricates and conditions hair and corneum
- prevents against bacterial infection

Hair Color

- produced by melanocytes
- determined by genes

Nail Body

- visible portion of the nail
- covers the nail bed: epithelium
- dead, tightly compressed keratin filled cells

Lunula

Pale crescent at the base of the nail

Free Edge

extends over the hyponychium (corneum)
Epithelial Cells

Nail Root

germinative portion

Eponychium

the cuticle

Functions of Nail

- protects fingertips from injury
- used as tools

Sebaceous Gland

(oil glands)
- holocrine glands
- secrete sebum:
~ oily substance composed of lipids
~ lubricates epidermis and hair
~ inhibits bacterial growth

2 Types of Sebaceous Glands

1. sebaceous glands: associated with hair follicles
2. sebaceous follicles: discharge directly onto skin surface (epithelial surface)
ie. face, back, chest, nipples, male genitalia

Sudorifirous Gland

(sweat glands)
2 Types:
1. merocrine glands: (also eccrine glands) widely distributed over body surface, more on palms and plantar surfaces, secrete directly onto cutaneous surface
2. apocrine glands: (merocrine secretions) associated with hair follicles, found in axillary and pubic regions, produce sticky, cloudy secretions, odoriferous

Merocrine Sweat

Functions:
1. cools skin: skin plays a major role in thermoregulation: the removal of heat from dermal circulation b the evaporation of warmed sweat (perspiration)
2. excretes excess water and electrolytes
3. flushes microorganisms and harmful chemicals from skin surface
4. contains antibacterial proteins

Mammary Glands

- produce milk
- apocrine secretions

Ceruminous Glands

- modified sudorifirous glands
- produce cerumen- earwax
- protect the eardrum from debris and infection

Step 1

- bleeding occurs
- mast cells trigger an inflammatory response

Step 2

- "the inflammatory response"
- germinative cells migrate around the wound
- macrophages clean the area
- fibroblasts and endothelial cells move in producing granulation tissue
- a scab (blood clot) stabilizes and protects the area
- fibrin: protein fibers

Step 3

- fibroblasts produce scar tissue
- inflammation increases, clot disintegrates

Step 4

- fibroblasts strengthen scar tissue
- a raised keloid may form

Thick Skin

covers palms of hands and soles of feet, has 5 layers of keratinocytes

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