Integumentary System:Skin & Body Membranes

Unit 2: Integumentary System

1b. Investigate the interdependence of the various body systems to each other and to the body as a whole.

2a. Relate the structure of the integumentary system to its functional role in protecting the body and maintaining homeostasis.

4e. Describe the effects of aging on body systems.

Points of Interest

• Comp Book instructions for writing prompts

• Cancer—p. 102-103

• Tattoos—p. 113

Classification of Body MembranesThere are two major kinds of body membranes:

Epithelial Membranes &

Connective Tissue Membranes

Classification of Body MembranesA. Epithelial Membranes:

– covering & lining

– contain an epithelial sheet but always combined with an under-layer of connective tissue

1.Cutaneous Membranes: the skin

Classification of Body Membranes2. Mucous Membranes: the mucosa

– lines any body cavities that open to the

exterior

– always “moist” because continually

bathed in secretions (fluids or mucous)

– adapted for absorption or secretion

Classification of Body Membranes

3. Serous Membranes: the serosa

– one layer of simple sqaumous

epithelial on a layer of loose areolar

– Line all body cavities NOT open to the

exterior

– (except dorsal body/joint cavities)

– Named based on location (e.g.—the

pleura of the lungs, pericardium)

Classification of Body Membranes

3. Serous Membranes (continued)

– Made of two layers:

• Parietal layer– near wall of ventral

body cavity; fused to this wall

• Visceral layer—near internal organs

– Layers separated and/or filled with serous fluid

• allowing movement (due to function) of organs without friction

Classification of Body MembranesB. Connective Tissue Membranes:

•Synovial membranes—composed of areolar tissue with NO epithelial tissue at all

– These line the capsules surrounding the joints, the bursae, and tendon sheaths

The Integumentary System is thelargest organ system in the body

• it is made up of the skin and structures found within the skin (hair, nails, glands, and nerve endings)

Functions of the Skin:

1. Protection – covers the surface of the body

2. Regulation of body temperature

• Protection against bacterial invasion, dehydration (loss of

body fluids), and UV radiation

• Sweat produced from sweat glands helps to cool the body

Functions of the Skin

3. Sensation

• The skin is packed with nerve endings and sense receptors that detect heat, cold, touch, pressure, and pain

4. Synthesis of Vitamin D

• Skin has the ability to produce vitamin D if it is exposed to UV radiation

Structure of the Skin:

The skin is made up of 3 parts:

epidermis

dermis

hypodermis

1. Epidermis – the outermost layer of skin

• it is made up of 20 – 30 layers of epithelial cells

The epidermis can be further subdivided into the corneal layer and the basal layer

Corneal layer is the outermost layer of the epidermis

• it is made up of several layers of dead, flattened epithelial cells that are filled with keratin (these cells are constantly being worn away)

Corneal Layer

Keratin is a tough waterproofing protein that prevents the skin from drying out

Basal layer is the lowermost portion of the epidermis

• it is composed of 2 types of living cells: epithelial cells (replaces cells lost from the

corneal layer) and melanocytes (pigmented cells that produce melanin)

Basal Layer

Melanin is the brown pigment that colors the skin and protects from UV radiation

• the more they are exposed to UV light, the more melanin they produce

Skin colorAll of the following contribute to

overall skin color:

• Carotene

• Hemoglobin

• Melanin

Though part of the skin, keratin is colorless, and so it does not determine skin color

Corneal Layer

Basal Layer

Dermis

The outer surface of our skin on the hands and feet develop epidermal ridges in the 3rd and 4th month of fetal development

• these are commonly referred to as fingerprints and footprints

• the function of the epidermal ridges is to increase the grip of the hand or foot by increasing friction

The epidermis also produces hair, nails, sweat glands and oil glands

• hair is produced by special epidermal structures called hair follicles

• as new cells are added to the base of the hair, the hair is pushed upward

Why does it hurt when you pull a hair out, but not when you have a haircut?

• the base of the hair is well nourished with blood vessels and has a good nerve supply

• as hair grows, the cells are pushed further away from the blood supply and die

• hair, like the outermost layer of the epidermis, is composed of dead cells filled with keratin

• fingernails and toenails are also made up of dead cells filled with keratin

• fingernails and toenails function to protect the ends of the fingers and toes

Function of the oil glands (sebaceous glands) is to lubricate the hair and skin

• keep them from drying out and becoming brittle

Function of the sweat glands is to regulate body temperature

• the evaporation of sweat from the skin’s surface removes heat and causes you

to feel cooler

Most sweat is 99% water and 1% dissolved salts and acids

• beginning at puberty, the sweat glands located in your armpits secrete sweat

that contains proteins and fatty acids

• bacteria love to feed on these proteins and fatty acids. It is the waste products of these bacteria that causes the foul odor we smell when a person does not use deodorants

• antiperspirants work because they contain Aluminum. Aluminum kills bacteria, therefore sweat does not have a foul odor

• Note: deodorants do not kill bacteria, they function only to mask the odor

2. Dermis – thickest portion of the skin

• 15 – 40 times thicker than epidermis

• it lies just beneath the epidermis

• abundant blood supply (blood vessels are not found in the epidermis). When you are cold, you body constricts these blood vessels. When you are hot, your body dilates the blood vessels

• free nerve endings (detect pain)

• several types of sensory receptors (touch, pressure, heat, and cold)

• hair follicles – structures that produce hair (it hurts when hair is pulled out because the nerve at the base of the follicle is stimulated)

• arrector pili muscles are attached to hair follicles. When you are cold, these

muscles contract causing goose bumps

3. Hypodermis – the lower most layer of the skin

• it lies just beneath the dermis and contains a large amount of fat

hypodermis

Functions of the hypodermis:

• acts as shock absorber

• provides insulation to conserve body heat

• stores fat-soluble vitamins (A, D, E, and K• serves as an energy reserve

Disorders of the Skin:1. Conditions related to Allergies

a. Contact dermatitis: allergic reaction to chemicals (poison ivy or other person-specific allergen)

b. Eczema

• A group of skin conditions characterized by irritation and/or inflammation

• Related to hay fever and asthma

Disorders of the Skin:2. Infections of the skin

a. Athlete’s foot: fungal infection

b. Boils and carbuncles: bacterial infection in the hair follicles and sebaceous glands

c. Cold sores: viral infection

d. Impetigo: highly contagious bacterial infection (Staphylococcus)

Lesions on mouth and nose

e. Wart – mass produced by uncontrolled growth of epithelial cells caused by a virus

• most warts are noncancerous

f. ringworm – fungal infection

a. Basal cell carcinoma –

The least serious and most common type of skin cancer

it affects the non-pigment producing epithelial cells of the epidermis

3. Cancers of the skin

Cure rate 99% if lesion is removed

Sun induced, slow growing

b. Squamous Cell Carcinoma

• Occurs in the epidermal layer of the skin

• Sun induced

• Chance of complete cure is good if detected early

c. Malignant melanoma –

•accounts for about 5% of cancers

•the most deadly type of skin cancer because it can spread quickly

• affects the pigment producing cells (melanocytes) of the basal layer of the epidermis

• survival rate is 50%

• the person usually dies within months of diagnosis

• American Cancer Society (ACS) recommends that sunbathers and tanning-bed users should check for new moles & pigmented spots frequently using the ABCD rule

A-B-C-D Rule for recognizing melanoma

4. Other notable homeostatic imbalances

a. Acne – inflammation of the oil glands, which typically begins around puberty

b. Psoriasis• believed to be autoimmune • overproduction of skin cells leads

to itchy, scaly lesions• can be disfiguring

http://randycourtneytripproth.blogspot.com/

c. Junctional Epidermolysis Bullosa (EB)

- rare, recessive genetic disorder

- epidermis and dermis are not tightly bound together

d. Albinism – an inherited condition in which a person’s melanocytes cannot produce melanin

• their skin is pink and their eyes are ice blue, while their hair is whitish-blonde

• they have no protection against UV rays

e. Burns

i. First degree- damage to the epidermis

• Red, swollen

e. Burns

ii. Second degree- damage to epidermis & upper region of the dermis

• Red, painful, blisters

e. Burnsiii. Third degree- entire thickness of skin is

damaged• Burned area is white or black• Nerve endings dead• Regeneration not possible (skin graft)

Third degree chemical burn, Ghana

Click image for internet case study

f. Decubitus ulcer

•occurs in bedridden patients who are not turned regularly

•weight and pressure restricts blood supply to skin

•lack of blood supply leads to cell death

•breaks/cracks in skin appear at pressure sites

Click here for images showing the progressive stages of decubitus ulceration