Integumentary System

• _______________ membrane (skin) – our largest organ

• Accounts for _____ of body weight• Divided into two distinct layers

•__________•__________•Accessory structures

• Subcutaneous layer (_______________)

Functions Of The Integument

• _____________ and insulates deeper organs

• _____________ body from abrasion, trauma, chemicals, pathogens, temperature extremes and UV rays

• ___________ and ___________

• Contains ____________________associated with nerve endings

• Synthesis and storage of nutrients (______________)

Integumentary Structures

• Components of the Integumentary System

Figure 5-1

Skin Structures

The Epidermis- Four Main Cell Types • _____________ - found in

basal layer, manufacture and secrete pigment

• ______________ - basal layer, attached to sensory nerve endings

• _______________ – Arise from deepest layer of epidermis to stratum spinosum• Produce __________ – a tough

fibrous protein• Produce _____________ and

__________• Keratinocytes are dead at skin's

surface• __________________ - stratum

spinosum, part of immune system macrophage-like

The Epidermis• Stratified squamous epithelium

• Several distinct cell layers• ________________—five layers on palms and soles• ________________—four layers on rest of body

Layers of The Epidermis

• Stratum ____________• Most

_______________ layer

• Dead, flattened (squamous) cells

• Abundant keratin - __________ (cornified) tough, water-resistant protein

• Protects skin against abrasion and penetration

• Stratum ___________ (clear layer)• Occurs only in thick

skin – palms and soles

• Composed of a few rows of flat, dead keratinocytes

Layers of The Epidermis• Stratum ___________ (grainy

layer)• Consists of keratinocytes

• Tonofilaments• Keratohyaline granules

– help form keratin• Lamellated granules –

contain a waterproofing glycolipid

• Stratum ___________ (spiny layer)• “Spiny” appearance caused

by artifacts of histological preparation

• Contains thick bundles of intermediate filaments (tonofilaments)

• Resist ____________• Contain protein

_____________ • Contains _____________

Langerhans cells

Layers of the Epidermis

• Stratum ___________• __________ layer of

epidermis• Attached to underlying

dermis• _____________ actively

divide• __________– associated

with sensory nerve ending• __________ – secrete the

pigment melanin

Epidermal Cells and Layers of the Epidermis

Figure 5.3

Sources of Skin Color

• Melanocytes• Make ________from tyrosine• Melanin provides _____

protection• Gives ____________ to

brown-black color

• Carotene• Contributes

_________________• Provided from _____ (carrots

and tomatoes)

• Hemoglobin - blood pigment• Caucasian skin contains

little ___________• Allows __________ color

of blood to show through

Dermis• _____________ major layer of the skin• Provides mechanical strength, ___________, and

protection for underlying tissues• ___________________and contains a variety of

sensory receptors that provide information about the external environment

• Two layers• ________________– includes dermal papillae• ______________- deeper layer – 80% of thickness of

dermis

• _________________- creases on palms

Layers of the Dermis• Papillary layer

• Underlies epidermis• Named for dermal papillae• Aerolar __________________• Supports, nourishes epidermis• Provides sensory nerves,

lymphatics, and ____________

• Reticular layer• Tough, dense, fibrous layer• Dense __________________• Collagen fibers - limit ________• Elastic fibers - provide __________• Blends into papillary layer (above)• Blends into _______________ layer

(below)

Dermal Components• Epidermal accessory

organs

• Cells of connective ________________

• Communication with other organ systems• _______________• ______________• _____________

• Sensation• Control of blood flow

and secretion

Subcutaneous Layer - Hypodermis• Composed ____________________________________________

• ______________ skin position• Loosely attached to dermis• Loosely attached to muscle

• Contains _________________cells• Provides ________________• ______________ underlying organs

• Safely receives hypodermic needles

Hair

• ___________ strands of dead keratinized cells produced by hair follicles

• Contains hard ___________ which is tougher and more durable than soft keratin of the skin

• Chief parts of a hair• ___________ – imbedded

in the skin• ____________ – projects

above skin's surface

Hair

• Hair Shaft organized into three concentric layers• ___________ – central core • __________ – surrounds medulla• ___________ – outermost layer

• Pigmented by melanocytes at the base of the hair

Cross Section of a Hair

Figure 5.7a, b

Hair Follicle• ____________extending

from the epidermal surface into the dermis

• Deep end is expanded forming _____________

• __________ - nipple-shaped indentation with blood vessels and nerves   

• _________ - germinal layer of cells (actively dividing cells) right above the papilla

• A knot of _____________ (a root hair plexus) wraps around each hair bulb

• _______________stimulates these endings, hence our hairs act as sensitive touch receptors

• ____________muscle - bundle of smooth muscle contracts to make hair stand erect

Longitudinal Section of Follicle

Figure 5.7c, d

Hair Follicles

Hair Function and Distribution• Functions of hair include:

• Helping to maintain _____________

• Alerting the body _________________on the skin

• Guarding the scalp against ____________, heat loss, and sunlight

• Hair is distributed over the entire skin surface except• __________,__________,________

• Nipples and portions of the external genitalia

Sebaceous Glands (oil glands)• Occur over entire body - Except palms and soles• Simple ____________________

• _______________ secretion – entire cell breaks up to form secretion• Secretes an oily substance called _________• Most are associated with a _____________

• Functions of sebum• Softens and lubricates hair and skin• ___________________• ___________________

Sweat (Sudoriferous) Glands

• Two types:• __________________

• Most abundant sweat gland• “True sweat”

• 99% water with some salts• Contains traces of

metabolic wastes ~ 2% urea

• Role in _________________

• Widely present in skin (up to 500/cm2)

• ______________• Odorous secretion • Absent before ___________• Present in axillary, areolar,

anal and genital areas

Eccrine (Merocrine) Gland

Figure 5.10b

Nails• _____________ modification of epidermis made of hard

keratin• Parts of the nail

• Free edge• Body - dense mass of _______________• Root• Nail folds• _____________– cuticle

Skin Injury and Repair

Four Stages in Skin Healing• ______________

• Blood flow increases• Phagocytes attracted

• ______________• Cell division and

migration• ___________ formation

Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response.

Epidermis

Dermis

After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulationin the area. Clotting around the edgesof the affected area partially isolatesthe region.

Sweat gland

Scab

Macrophagesand

fibroblasts

Migratoryepithelialcells

Granulationtissue

Skin Injury and Repair

One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating.

Fibroblasts

After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis.

Scartissue

Skin Injury and Repair

Skin Injury and Repair

Table 5-1

Aging of the Skin

• Major Age-Related Changes•_____ and infection increase• Immune cells ___________•Sun protection diminishes•Skin becomes dry, ________•Hair thins, ________•Sagging, _________ occur•Heat loss ___________•Repair ________

Effects of UV Radiation• Beneficial effect - activates synthesis of

vitamin D3

• Harmful effects• ___________• Wrinkles, ___________• ___________________• ___________________

Types and Growth of Hair

_________ hairs•Body hairs of women and children

_________ hairs•Hair of scalp•Axillary and pubic area (at puberty)

_______________________•Due to aging•Male pattern baldness

Burns

Classified by severity•_______________– only upper epidermis

is damaged•_______________– upper part of dermis is

also damaged• _____________ appear• Skin heals with little scarring

•___________________• Consume ______________ of skin• Burned area appears white, red, or

_______________

Estimating Burns Using the Rule of Nines

Figure 5.11a

Skin Cancer

_______________________•Least malignant and ________________

_______________________•Arises from ________________ of stratum

spinosum

________________•A cancer of _________________ •The most dangerous type of skin cancer

Skin Cancer

Squamous cell carcinoma

Figure 5.12Melanoma

Squamous cell carcinoma

Basal cell carcinoma

The Skin Throughout Life

______________•Develops from embryonic ectoderm

________________•Develop from mesoderm

_________________•Develop from neural crest cells

The Skin Throughout Life

Fetal skin•Well formed after the ________________•At 5-6 months

• The fetus is covered with __________ (downy hairs)

•Fetal sebaceous glands produce ___________________

The Skin Throughout Life

Middle to old age•Skin thins and becomes _____________•Shows ____________ effects of

environmental damage•Skin ______________ become more

common