the integumentary system - edl• the integumentary system is made up of the skin and several...

The Integumentary SystemChapter 5

Goals- Integumentary system

• Function of integumentary system

• Structure of the Skin and its accessory structures

• Disorders of skin

Skin• Also called the cutaneous membrane or the

integument

• Covers the entire surface of the body

• Largest organ in the body; 1.8 m2

• Comprised of all 4 tissue types

• The integumentary system is made up of the skin and several accessory organs

• Two regions – epidermis and dermis

• Hypodermis or subcutaneous tissue attaches the skin to underlying tissue

4

Skin Anatomy

Largest organ in body

• Organ?

• What tissue types are in the integumentary system

– Epithelial- covers surface

– Connective tissue- tough/flexible protein fiber acts like organic glue

– Muscle tissue-interacts with hairs

– Nervous tissue- allows us to detect external stimulus

Layers of skin

• Two layers

– Epidermis (5 layers)- Outer layer

• External portion-layers of dead flattened skin containing keratin- protect and give elasticity

• Interior portion- living cells that are constantly dividing and pushing upwards to replace dead cells that are sloughed off

– Dermis- Inner layer

• Thicker layer that is the control center of the skin

• Hypodermis/ Subcutaneous

Function of Skin

• Protection/Physical Barrier

• Cutaneous Sensation

• Thermoregulation

• Vitamin D synthesis

• Blood Reservoir

Protection

• Micro-organisms

• Water loss

• The sun’s harmful rays/uv radiation• Burns

• Cancer

Sensory Organ

• Tactile receptors in skin

– Thermal

– Touch (light v. deep)

– Pressure (light v. deep)

– Pain

Thermoregulation/Heat Balance

• Sweating

– Sweat gland

• Evaporation of sweat cools our body

• Blood flow through cutaneous blood vessels

– Cutaneous Vasodilation-Flushing

– Cutaneous Vasoconstriction-Pallid

Synthesis of Vitamin D

• Skin as a gland- produces a hormone

• Cholesterol + UV light Vitamin D

• Vitamin D converted to Calcitriol in liver and kidney.

• Why is Vitamin D important?

– Regulates absorption of Calcium in digestive tract

– Important for bone growth

• Rickets

Largest organ in body

• Organ?

• What tissue types are in the integumentary system

– Epithelial- covers surface

– Connective tissue- tough/flexible protein fiber acts like organic glue

– Muscle tissue-interacts with hairs

– Nervous tissue- allows us to detect external stimulus

Layers of skin

• Two layers

– Epidermis (5 layers)- Outer layer

• External portion-layers of dead flattened skin containing keratin- protect and give elasticity

• Interior portion- living cells that are constantly dividing and pushing upwards to replace dead cells that are sloughed off

– Dermis- Inner layer

• Thicker layer that is the control center of the skin

• Hypodermis/ Subcutaneous

Epidermis

• Outer, thinner region

• Stratified Squamous Epithelium

• 5 layers (strata)

– Stratum Corneum -C- Come

– Stratum lucidum- -L- Let’s

– Stratum granulosum - G- Get

– Stratum spinosum - S- Sun

– Stratum Basale - B- Burned

Stratum Basale• Deepest layer/just superficial to dermis• Constantly dividing • New cells pushed upward to surface, die and

slough off• Cells:

– Keratinocytes-keratin-water proofing protein– Melanocytes- melanin- give skin color/uv protection– Langerhans cells- macrophages– Stem cells

• Sensory Nerve– Free nerve endings: pain and temperature sensation– Merkel cells/Tactile Cells- touch sensation

Stratum Spinosum

• Cells still dividing

• Take on spiny appearance due to keratin fibers

Stratum Granulosum

• Cell death starting to occur

• Cells die and condense- Flattened cells

• Contain keratin and dark staining pigment granules

• Keratin-glycolipid secreted (hydrophobic)forms a water barrier

Stratum Lucidum

• Only in thick skin –palms/soles

• Provides protection from constant friction

Stratum Corneum

• Tough uppermost layer of epidermis

• Keratinized cells- hardened and dead

• Protects body from

• Cells will slough off/exfoliate…dust

• Life cycle of cell in epidermis- 3 weeks

Cells in the Epidermis

• Keratinocytes- 90%– Keratin– Function: physical

barrier/prevent H2O loss

• Melanocytes– Melanin– Function: UV protection– Skin color

• Langerhan cells– Guardians of the skin

• Merkel cell/Tactile disk– Light touch/sensation

Dermis

Control Center of the Skin

Dermis• Thicker than epidermis (varies in thickness)

• Dense fibrous Connective Tissue (irregularly arranged)

• Collagenous fibers prevent skin from being torn

• Elastic fibers stretch to allow movement of muscles and joints

• Vascularization of dermis supplies oxygen and nutrients to cells of dermis and epidermis and causes temporary changes to skin color

• Numerous nerve fibers- sensory and motor

In the Dermis

• Hair follicles

• Glands

– Sebaceous

– Sudiferous

• Blood vessels

• Nerves

• Nerve endings

Papillary Folds

• Junction between epidermis and dermis

• Inter-digitates

• Function?

Hypodermis/Subcutaneous layer

• Composed of loose connective tissue and fascia that connects skin to underlying tissues

• Subdermal fat

• Superficial muscles

• Mostly adipose tissue and fascia

Accessory Structures of the Skin

Hair

• All over body except palms, soles, lips, nipples and part of external reproductive organs

• Types:

– Lanugo- fetal hair

– Vellus hair- thin, child’s hair

– Terminal hair- thicker, darker hair: puberty

Hair Follicle

• Formed from epidermal cells

• Located in dermis

• Cells become keratinized as they are pushed out

• Hair root-portion within follicle

• Hair shaft- portion that continues beyond skin

b: © The McGraw Hill Companies, Inc./Dr. Alvin Tesler, photographer

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Fig. 5.2

hair shaft

(beyond epidermis)

Epidermis

hair

root

sebaceous

(oil) gland

Dermisarrector

pili muscle

dermal blood

vessels

a.

region of

cell division

b.

LM 70x

Hair Follicle-Associated with:

• Sebaceous Gland (oil)

– Secrete sebum

• Arrector Pili muscle

– Smooth muscle attached to hair follicle

– Causes “pilo-erection”• Cold

• emotion

Hair Function

• Warmth

• Sensation

• Aid in cooling of skin

• Some protection

Glands of the skin

• Gland: groups of specialized cells that produce/secrete substances into ducts

– Sebaceous (oil) gland*

– Sudoriferous (sweat)*

– Mammary glands

Sebaceous Glands

• Opens into neck of hair follicle

• Secretes sebum

• Secretion is stimulated by sex hormones

• Comedones– Sebum plugging duct

• Acne vulgaris– Inflammation of

sebaceous gland

Acne Vulgaris

• At pilosebaceous unit

• Occurs at puberty (80%)

• Cause– Genetic

– Increase sebum

– bacteria

• Worse on face, back and chest– Densest population of

sebaceous follicles

Sudoriferous (sweat) glands

• Present in all areas of skin:

• Some more active under stress

• Types:

– Eccrine

– Apocrine glands

– Ceruminous glands

Eccrine Sweat Gland

• Open onto surface of skin secretes sweat

• Contains

– Water

– NaCl

– Urea- waste product

• Functions in Thermoregulation

– Evaporation of sweat cools body temperature

Apocrine glands

• Opens into hair follicle

• Location: genital, perianal, inguinal, axillary

• Function: ?

• Begins to secrete during puberty

• More with stress

• Smelly (fatty sweat + bacteria)

Blood and Lymphatic Vessels of skin

• None located in epidermis

• Cutaneous Blood Vessels in Dermis

– Flushing v. pallor

– Bruising

• Lymphatic vessels

– Conduct excess tissue fluid away from the region to be returned to blood stream

• edema

Nerve Fibers of Skin

• Majority in dermis (nerve endings in the epidermis)

• Sensory Nerve Fibers:– Thermoreceptors– Mechanoreceptors– Nociceptors/Pain receptors

• Motor Nerve Fibers:– Autonomic motor nerve fibers supply:

• Glands• Arector pili muscle• Cutaneous blood vessels

Nails

• Formed by specialized epithelial cells-

• Nail root- base of nail

• Nail body- visible portion of the nail

• Cuticles- folds of skin that hides the root

• Lunula- area of rapidly dividing cells

• Epithelial cells become keratinized as move away from the root

• Pink color due to vascular dermis under the nail body

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

body of nail

dermis

epidermis

finger bone

cuticle

nail root

nail bed

Fig. 5.1


stratum corneum

stratum lucidum

stratum granulosum

stratum spinosum

stratum basale

free nerve endings

dermal papilla

arrector pili muscle

sebaceous (oil) gland

capillariessweat gland

vein

artery

nerve

adipose connective tissue

Epidermis

hair shaft

Dermis

Hypodermis

hair follicle areolar

connective tissue

sensory

receptors

sensory

nerve fiber

Skin Cancer

• Begins with mutation of the skin cell DNA

• Non-melanoma cancers- less likely to metastasize

– Basal Cell carcinoma

– Squamous cell carcinoma

• Melanoma

Basal Cell Carcinoma

• Most common• UV radiation causes

epidermal basal cells to form a tumor

• Signs (varied):– Open sore that will not

heal– Recurring reddish patch– Smooth, circular growth

with raised edges– Shiny bump– Pale mark

• 95% curable

Squamous Cell Carcinoma

• 5x less common than basal cell carcinoma

• More likely to spread than BCC

• 1% die• Triggered by excessive UV

exposure• Similar presentation to

BCC but may present as wart-like lesion or scaly growth that bleeds and scabs

Melanoma

• More likely to be malignant

• Starts in melanocyte

• Triggered by excessive UV exposure

• Has the appearance of unusual mole

• More common in fair skinned people

Table 5.1

Fig. 5.5


a. Basal cell carcinoma c. Melanomab. Squamous cell carcinomaa: © Ken Greer/Visuals Unlimited; b: © Dr. P. Marazzi/SPL/Photo Researchers; c: © James Stevenson/SPL/Photo Researchers

Prevention

• Use broad-spectrum sunscreens of at least SPF 15

• Wear protective clothing to cover skin

• Wear UV sunglasses

• Stay out of sun between 10-3pm

• Avoid tanning beds

Wound healing

• Cut causes inflammatory response

• Steps of wound healing– Clot formation– Cells move to the area

(WBC and fibroblasts)– Fibroblasts pull margings

together and promote tissue regeneration

– Basal layer produces new cells

– Proliferatin fibroblasts form a scar

Fig. 5.6-1


wound

subcutaneous fat

White

blood cells

Dermis

of skin

blood

vessel

Epidermis

of skin

a.

Fig. 5.6-2


wound

subcutaneous fat

White

blood cells

Dermis

of skin

blood

vessel

Epidermis

of skin

a.

scab

fibroblast

white

blood cells

b.

Fig. 5.6-3


wound

subcutaneous fat

White

blood cells

Dermis

of skin

blood

vessel

Epidermis

of skin

a.

scab

fibroblast

white

blood cells

b.

fibroblast

regrowth of

blood vessel

regenerating

tissue

(epidermis)

scab

c.

Fig. 5.6


wound

subcutaneous fat

White

blood cells

Dermis

of skin

blood

vessel

Epidermis

of skin

a.

scab

fibroblast

white

blood cells

b.

fibroblast

regrowth of

blood vessel

regenerating

tissue

(epidermis)

scab

c.

regenerated

tissue

(epidermis)

scar tissue

(fibrosis)

fibroblast

freshly healed

epidermis

d.

Burns

• Cause: heat, radioactive, chemical, electrical

• Severity determined by:

– Depth• 1st, 2nd, 3rd

– Width• Rule of nines –estimates

burn severity

Fig. 5B


9%

9%

36%

9%

perineum

1%

18% 18%

First Degree Burns

• Epidermis only

• Red and painful

• No blisters or swelling

Second Degree burns

• Entire epidermis and part of dermis

• Erythema (red)

• Pain

• Blistering occurs

Third degree burns/ Full thickness

• Entire thickness of the skin

• Surface is leathery

• May be brown, black, tan, white or red

• Not painful

Fourth degree burn

• Burn that goes through entire thickness all the way to muscle or bone

Burns are critical if:

• Second degree burn >25% of body

• Third degree burn

– >10%

– On face, hands or feet

• Any 4th degree burn

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