The Integumentary System

Chapter 6

Pp 112-124

Objectives6.1 Skin and Its Tissues

Describe the structure functions of layers of the skinSummarize factors that determine skin color

6.2 Accessory OrgansDescribe the accessory organs associated with skin

6.3 Regulation of Body TemperatureExplain how skin helps regulate body temperature

6.4 Healing of WoundsDescribe the events that are part of wound healing

6.1 Skin and its TissuesCutaneous membrane ( the largest organ of the body)

Surface area of 1.2 –2.2 square meters Weighs 9-11 pounds (7% of total body weight)Composed of two distinct regions

• Epidermis: superficial layer• Dermis: deeper, thicker layer

• Beneath the dermis are masses of loose connective tissue and adipose tissue that collectively form the subcutaneous layer or the hypodermis.

6.1 Skin and its Tissues

Functions:First line of defense against outside invaders

Prevents heat and water loss to maintain homeostasis

Houses sensory receptors

Excretes waste

Produces biochemicals (oil and sweat)

Beauty is skin deep; ironic.

Composed of keratinized stratified squamous epithelium cells

Outer layer of cells are older cells that have hardened and filled with keratin (a protein)

We lose about 35,000 skin cells every minute

What happens to those lost cells?

The Epidermis

Replaced every 27 days

Some areas of the skin have five layers (soles and palms) and some have only four.

Stratum Germinativum (Basale)Stratum Germinativum (Basale): deepest layer; attached to dermis; youngest skin cells; reproductive layer

Stratum Spinosum:Stratum Spinosum:Several layers thick; contains melanin (pigment that provides skin color)

Stratum Granulosum:Stratum Granulosum: thin, waterproofing layer

Stratum Lucidum:Stratum Lucidum: clear layer; present in the soles of feet and palms of hands

StratumCorneum: StratumCorneum: outermost layer; cell fragments; contains keratin to protect skin;glycolipids waterproof this layer

Nutrients for the epidermis come from the underlying dermis.

Skin Color

Biological FactorsMelanin: dark pigment that absorbs UV rays, preventing mutations in the DNA of skin cells; produces yellow to reddish to black coloring

• Melanin is produced by melanocytes.

• All people have the same amount of melanocytes. It’s the amount of melanin they produce, that determines color.

Environmental and Physiological Factors of skin color

Sunlight, UV light from tanning beds, or X-rays increase production of melanin.

The amount of oxygen in blood affects the color of hemoglobin. Excess oxygen leads to pink tone; low amounts lead to cyanosis (bluish tint)

Beta-carotene: yellow to orange tone due to diets high in yellow veggies.

The Dermis: the hide

Strong, flexible connective tissueRich in nerve fibers, blood vessels, and lymphatic vessels; hair follicles, oil and sweat glandsBlood vessels here help regulate body temperatureStretch marks: stretching of the skin leading to tearing of the dermis

Two dermal layers

Papillary layerVascular

Touch receptors called Meissner’s corpuscles

Dermal ridges help increase friction and help create fingerprints

Reticular layer80% of dermal thickness

Fact or Myth?

Hair and fingernails of deceased continue to grow.

A patch of skin approximately 2cm square and 1.5 mm thick has:

2.75 meters of blood vessels300 eccrine glands30 hairs600 pain receptors4 sebaceous glands9000 nerve endings6 cold sensors, 36 heat sensors, 75 pressure sensorsAnd almost 12 meters of nerves!

6.2 Accessory OrgansNails

Protective covers on the ends of fingers and toesSpecialized keratinized cells

Hair FolliclesHair develops from epidermal cells originating at the base of a follicleNewly formed cells push older cells outward to be keratinizedHair color is determined by genes that control amount of melanin producedGrows an average of 9 inches/yr

Sebacceous glandsUsually associated with hair follicles

Secrete sebum, sebum, a waterproofing oil

Sweat GlandsA coiled tube

Sweat is primarily water but also contains waste and salt

• Two types: apocrine and eccrine

Try this at home!

Clean one palm of your hand with a cotton ball soaked in rubbing alcohol. Use the other palm

as your control. Run water over both your palms, shake off access water, and observe. You will probably notice that the water soaks

in more on the palm that you cleaned with alcohol. What is the purpose of the rubbing

alcohol in the experiment?

Sudoriferous Glands (Sweat glands): Apocrine gland: become active at puberty; respond to emotions and are located in the axillary and groin regions

Eccrine gland: respond throughout life in response to temperature; associated with forehead, neck, and back

6.3 Regulation of Body Temperature

The skin plays a key role in the homeostatic mechanism that regulates body temperature. Normal body temperature is 98.6F.

Body temp. increases: • dermal blood vessels relax and swell,

• sweat glands produce sweat

Body temp. decreases: • Dermal blood vessels contract pushing blood toward vital

organs

• Muscles in skin contract to produce friction

6.4 Healing of woundsInflammation

Redness, heat, swelling, pain

Scabs are formed when injury extends into the dermis and escaping blood forms a clot.Granulations are small, rounded masses in exposed tissues of large wounds. These lead to scar formation.

                                                                                      

Venous breakdown

Pressure Sore

                                                               

Burns

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