The Integumentary System Chapter 6 Anatomy and Physiology

The Integumentary System Chapter 6 Anatomy and Physiology

Structure of Skin • Cutaneous Membrane: membrane that is the skin (organ) • Two layers 1. Epidermis: composed of epithelial tissue 2. Dermis: composed of connective tissue; vascular – Dermal-epidermal junction separates them • Hypodermis: subcutaneous layer of fat and areolar tissue beneath the dermis

Thick and Thin Skin • Of the epidermis • Thick Skin: – Found covering palms of hands, soles of feet, and other areas subject to friction – Contains all 5 layers of the epidermis – Dermal papillae are raised to form hand or foot prints – No hair

• Thin Skin – Number of cell layers in strata and number of strata is less – No ridges present – May contain hair

The Epidermis • Composed of Epithelial Cells – Keratinocytes: filled with keratin (a tough, fibrous protein); compose 90% of the epidermis – Melanocytes: give skin color and absorb UV radiation; may be absent in some areas – Langerhans Cells: play a limited role in immunological reactions

Cell Layers • 5 Layers or Strata in the Epidermis 1. Stratum corneum: superficial layer of epidermis • • • acts as a barrier for harmful agents that may enter the skin Made up of squamous cells containing keratin, which acts as a water repellant Keratinization: the process by which cells in this layer are formed from cells in deeper layers of the epidermis 2. Stratum lucidum: packed with keratinocytes; nuclei absent, and cells are filled with eleidin, which acts to block water loss or penetration and will eventually form keratin – Absent in thin skin

3. Stratum granulosum: keratinization starts here • • Cells in this region have started to degenerate, so nuclei are absent and a high number of lysosomes May also be absent in thin skin 4. Statum spinosum: 8 -10 layers of irregularly shaped cells • Rich in RNA for protein synthesis of keratin

5. Stratum basale: single layer of columnar cells – Cells undergo mitosis here and then migrate to the skins surface where they are shed

Epidermal Growth and Repair • Turnover and regeneration time: the time period required for a population of cells to mature and reproduce – About every 35 days a new layer of skin makes if from the stratum basale to the skin surface – Abrasions speed the process – Prolonged abrasions may cause calluses, or an increased thickness in the stratum corneum

Dermal-Epidermal Junction • Composed of basement membrane • Also includes fibrous elements and a polysaccharide gel that “glues” the epidermis to the dermis • Provides support to the epidermis and acts as a barrier against other cells and large molecules

Dermal-Epidermal Junction

Dermis • Composed of a thin papillary and thick reticular layer • Functions: – Provides protection against mechanical injury and compression – Reservoir for water and electrolytes – Nerves found in the dermis provide sensory – Vascular: contain blood vessels, which help to regulate body temp. – May also contain muscle fibers, hair follicles, and sweat and sebaceous glands

The Dermis

Papillary Layer of the Dermis • Composed of dermal papillae, which are bumps that project into the epidermis causing ridges that in some places are very well defined (fingerprints)

Reticular Layer of the Dermis • Composed of collagenous and elastic fibers, making the skin tough, yet stretchable • Serves as a point of attachment for skeletal and smooth muscles – Arrector pili muscles in the dermis are attached to your hair follicles that cause it to stand on end (goose bumps) – Skeletal muscles in the skin on the face • Sensory receptors for sensations such as pain, pressure, touch, and temperature can also be found here

Dermal Growth and Repair • The dermal layer does not continually repair itself like the epidermis • More common in wounds – Langer’s Lines: show the patterns of reticular fibers as they appear in different parts of the body • The directionality of a wound or incision determines how quickly it will heal • Stretch marks appear when the elastic fibers of the dermis are stretched too much or too rapidly

Skin Color • Determined by the quantity of melanin deposited in the cells of the epidermis

Melanin • Produced by the melanocytes of the stratum basale • The amount of melanin produced is determined by genetics, sun exposure, and secretion of hormones • Tyrosinase is the enzyme that regulates the process of melanin production • What condition do you think results from the congenital birth defect of no tyrosinase being manufactured in the cells?

Functions of the Skin • • Protection Sensation Movement without Injury Endocrine Excretion Immunity Temperature Regulation

Protection • Of underlying tissues from invasion of microorganisms • From dehydration • Melanin protects us from harmful effects of UV radiation • Surface Film helps in these processes: – Composed of a mixture of substances secreted by the sweat and sebaceous glands

Sensation • Of pressure, touch, temperature, pain, and vibration • Due to widespread placement of millions of different somatic sensory receptors in the skin • Allow for response to changes in the external and internal environment

Movement without Injury • Elasticity and growth of skin allows movement and growth without tearing or lacerating

Excretion • Plays a minor role in excretion of body wastes such as uric acid, urea, and ammonia

Endocrine Functions • Vitamin D Production – Begins in the skin when exposure to UV light – Causes a chemical to be converted and then transported to the liver and kidneys where it is converted to Vitamin D – Hormone: any substance that is produced in one body area and then is transported through the blood to another body area where it has an effect

Immunity • Langerhan cells, with the help of T-cells can trigger an immune reaction in certain diseases

Homeostasis • Constant temperature is needed in order for biochemical reactions to occur at certain rates • Heat Production: produced by the metabolism of foods by muscles and glands (liver) • Heat Loss: 80% occurs through the skin – Regulated by the vasoconstriction and vasodialation of blood vessels – Heat can then be lost through evaporation, radiation, conduction, and convection

• Evaporation: of fluid from the skin surface causes heat loss • Radiation: the transfer of heat from the body surface to nearby cooler objects (does not require contact between the two) • Conduction: the transfer of heat to any substance actually in contact with the body • Convection: transfer of air away from a surface by movement of heated air or fluid particles

Regulation of Heat Loss • Negative Feedback Loop – Detected by temperature receptors (sensor) – Message sent to the hypothalamus in the brain (integrator) – Hypothalamus sends a signal to the effector, which may be sweat glands or blood vessels

Skin Disease/Disorder Research • Define: – Dermatosis – Dermatitis • Research with a partner the skin disorder assigned to you and find the following information: – Symptoms: how it affects the skin or any skin appendages – What causes the disease or disorder – Any treatments – Pictures • Present your research in the form of a powerpoint presentation

Skin Disorders • Vitiligo • Basal and squamous cell carcinoma • Malignant melanoma • Acne • Eczema • Psoriasis • Scleroderma • warts • • Urticaria Decubitus Impetigo Tinea Hair loss/baldness Scabies Leprosy Seborrheic dermatitis

Burns • A thermal injury or lesion caused by contact of the skin with some hot object or fire, overexposure to UV light, electric current, or corrosive chemicals

Estimating Surface Area of Burns • Rule of Palms: the size of your palm represents approx. 1% of the surface area of your body • Rule of Nines: body is divided into 11 areas, each composing approx. 9% of the surface area of the body

Degree of Burn Injury • 1 st degree burns: causes minor discomfort and some redness of skin (sunburn); no blistering, minimal if any tissue destruction

• 2 nd Degree Burns: involves deep epidermal layers and upper layer of dermis – damage to skin appendages – Severe pain, swelling, blisters, scarring common

• 3 rd Degree Burns: destruction of epidermis and dermis, maybe even muscle or bone damage – Insensitive to pain due to nerve damage

Appendages on the Skin • Includes: – Hair – Nails – Glands

Hair • Types of Hair – Lanugo: covers a fetus; soft and fine hair – Vellus: replaces lanugo hair after birth; stonger, fine, with little pigment – Terminal: pubic and axillary hair appears at puberty (more on men than women)

Structures in the Hair • Follicle has two layers – Outer dermal root sheath – Epithelial root sheath • Germinal matrix: cap of cells at the base of the follicle • Papilla: small mound of dermis; contains capillaries that supply the germinating matrix

• Shaft: visible part of the hair • Medulla: inner core of the hair • Cortex: surrounds medulla; made of layers of keratinized cells that contain melanin

Hair Color and Texture • Melanin is responsible for hair color – Dark hair: more melanin – Red hair: unique melanin that contains iron – White or gray: no melanin • Texture of hair depends on the shape of the shaft – Straight hair: round, cylindrical shaft – Wavy hair: flat shaft; not as strong

Hair Trivia • Hair alternates between periods of growth and rest and grows on average about ½ inch a month • Head hair lives between 2 -6 years • Cutting or shaving your hair does NOT make it grow faster • Hair does NOT continue growing after death

Nails • Made of keratinized epidermal cells • Nail Root lies under the fold of skin known as the cuticle • Lunula: crescentwhite shaped area on nail • Nails grow about 0. 5 mm a week

Skin Glands • Three kinds of skin glands – Sweat – Sebaceous – ceruminous

Sweat Glands • Most numerous • Two groups – Eccrine: throughout the body produce sweat rich in salts, ammonia, uric acid, urea, and other wastes • Sweat aids in the rid of wastes and temperature control – Apocrine: located in the armpit, areola of the breast, and around the anus; begin to function at puberty to release a more viscous and colored secretion than eccrine glands

Sebaceous Glands • Secrete oil (sebum) for the hair and skin • Two glands for each hair • Aids in preventing water loss, contains anti-fungal properties

Ceruminous Glands • Special variety or modification of apocrine glands found in the ear canal • Secrete cerumen, which is a brown waxy substance that protects the skin in the ear canal from dehydration, but can harden and cause blockage