The Integumentary System Chapter 6 Pp 112-124

Objectives 6.1 Skin and Its Tissues 6.2 Accessory Organs Describe the structure functions of layers of the skin Summarize factors that determine skin color 6.2 Accessory Organs Describe the accessory organs associated with skin 6.3 Regulation of Body Temperature Explain how skin helps regulate body temperature 6.4 Healing of Wounds Describe the events that are part of wound healing

MRSA http://www.5min.com/Video/Early-Signs-of-MRSA-4192096 http://www.5min.com/Video/Grant-Hill-on-Preventing-MRSA-450668411

6.1 Skin and its Tissues Cutaneous 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): deepest layer; attached to dermis; youngest skin cells; reproductive layer Stratum Spinosum:Several layers thick; contains melanin (pigment that provides skin color) Stratum Granulosum: thin, waterproofing layer

Stratum Lucidum: clear layer; present in the soles of feet and palms of hands 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 Factors Melanin: 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 tissue Rich in nerve fibers, blood vessels, and lymphatic vessels; hair follicles, oil and sweat glands Blood vessels here help regulate body temperature Stretch marks: stretching of the skin leading to tearing of the dermis

Two dermal layers Papillary layer Reticular layer Vascular Touch receptors called Meissner’s corpuscles Dermal ridges help increase friction and help create fingerprints Reticular layer 80% of dermal thickness

Hair and fingernails of deceased continue to grow. 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 vessels 300 eccrine glands 30 hairs 600 pain receptors 4 sebaceous glands 9000 nerve endings 6 cold sensors, 36 heat sensors, 75 pressure sensors And almost 12 meters of nerves!

6.2 Accessory Organs Nails Sebacceous glands Hair Follicles Protective covers on the ends of fingers and toes Specialized keratinized cells Hair Follicles Hair develops from epidermal cells originating at the base of a follicle Newly formed cells push older cells outward to be keratinized Hair color is determined by genes that control amount of melanin produced Grows an average of 9 inches/yr Sebacceous glands Usually associated with hair follicles Secrete sebum, a waterproofing oil Sweat Glands A 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 wounds Inflammation 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                                                                

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