Integumentary System Integumentary system is the skin and

Integumentary System Integumentary system is the skin and the organs derived from it (hair, glands, nails) One of the largest organs 2 square meters; 10 -11 lbs. Largest sense organ in the body The study of the skin is Dermatology

Functions of the Integumentary system 1. Regulation of body temperature – Cellular metabolism produces heat as a waste product. – High temperature • Dilate surface blood vessels • Sweating – Low temperature • Surface vessels constrict • shivering

Additional Functions 2. Protection physical abrasion dehydration ultraviolet radiation 3. Sensation touch vibration pain temperature

Additional Functions 4. Excretion 5. Immunity/ Resistance 6. Blood Reservoir 8 -10 % in a resting adult 7. Synthesis of vitamin D UV light aids absorption of calcium

Structure

Epidermis Structure

Stratum Basale • Deepest layer • Columnar cells capable of continued cell division. • Newly made cells get pushed to surface where there is less blood supply and they begin to die.

Stratum spinosum • Multiple layered arrangement of cuboidal cells • Are spiny or prickly in appearance, due to molecular bridges that connect them to other cells

Stratum granulosum • 3 -5 rows of flattened cells • Cytoplasm of cells contain granules • The granules are protein that transforming into waterproofing protein keratin (process starts) • Cells begin to die

Stratum lucidum • Present in only the thick skin of palms of hands and soles of feet • 3 -4 rows of flattened dead cells (Transparent) • Process of keratin formation continues here

Stratum corneum • • Most superficial 20 -50 rows flattened dead cells Cells are “sloughed off” by normal wear Each cell contain keratin, protects skin from water loss • When skin is exposed to water for long periods of time the water in skin moves outward by osmosis and causes wrinkles in the skin

Skin Color- Melanocytes • Determined by cells in between the dividing cells of the Stratum basale. • Secrete a dark colored pigment called melanin • Greater amount melanin the darker the skin • Regulated by DNA but can be altered by UV light, prolonged exposure can increase the melanin secretion and darken the skin (Tanning) • Function of Melanocytes- protection from UV light.

Skin Color - Carotene • Pigment • Present in the Stratum corneum and dermis • Most present in people with Asian origin, gives a yellow hue • Pinkish color of Caucasian people is attributed to small amounts of melanin and carotene, influenced by blood in blood vessels

Dermis- Overview • Region of connective tissue, located deep to the epidermis. • Scattered apart unlike the epidermis • Contains a large amount of collagen • Blood vessels extend through to the stratum basale

Dermis - Structure • 2 areas • Superficial area adjacent to epidermis called papillary region • Deep thicker area reticular region

Dermis- reticular region • Deep to the papillary region and is much thicker • Composed of dense irregular connective tissue • Named for the collagenous, elastic and reticular fibers • These fibers give the dermis, strength, extensibility, and elasticity • Wrinkles occur because of a change in these fibers • The accessory organs are located here.

Dermis- papillary region • Composed of loose (areolar) connective tissue. • Named for finger like projections called papillae, that extend into the epidermis. • Papillae provide the dermis with a bumpy surface that strengths the connection between the dermis and the epidermis. • In the palms, fingers, soles and toes they form contours in the skin called friction ridges. • Friction ridges occur in patters that are genetically determined. (Fingerprints)

Accessory Organs- Hair • Protects the skin from injury from sunlight and other particles • Supported by the epithelial cells- Hair follicle • 2 portions – root-part surrounded by the follicle, shaft-extends away from the body surface • Bulb- the place where the hair gets nutrients

Hair Growth • Similar to skin growth, old cells get pushed up to the surface. • Developing cells located in the bulb • The shaft is made up of dead cells • Normal rate of growth 1 mm every 3 days

Associated with hair follicles: • Arrector pili- small narrow band of smooth muscle that extends at an angle from the follicle to the papillary region. • The contraction of this muscle causes the hair to stand up, like when cold of scared • The contraction of this muscle causes a small amount of heat, and the contraction of many of those muscles causes “goose bumps”

Sebaceous Glands • Oil glands • Consists of cluster of glandular epithelial cells, connected to a hair follicle by a duct • Not located on the palms and soles • Secrete sebum- used to keep hair and skin soft and pliable, a water resistant layer

Sweat Glands • Sudoriferous glands – secrete watery substance called sweat. • Helps maintain body temperature • Pore- opening to the skin surface • 2 types of glands- eccrine-function throughout life and distributed throughout the body, apocrine- function during puberty and respond to production of sex hormone

• Compressed outer layer of the epidermis • Composed of keratin • Protect ends of fingers and toes, help pick up small objects, and grip the floor Nails Nail root Nail body

Receptors • Consists of the distal ends of nerve cells wrapped in a capsule of connective tissue • Carry impulses to the brain • Interpretation of sensation takes place, hot cold, pressure, pain and fine touch • Two types of receptors -Pacinian corpuscles- sense pressure changes -Meissner’s corpuscles- sense slight pressure change- light touch Others respond to pain and temperature changes

Hypodermis • Not usually considered a component of skin organ • Deep region of the dermis, connects to underlying body structures, by way of collagen • Composed of adipose tissue and loose connective tissue • Varies in thickness over the body • Insulates deep tissue from temp changes, shockabsorbing cushion and reserved for energy storage

Homeostasis • Skin plays a key role in regulating temperature – Cellular metabolism produces heat as a waste product. – High temperature • Dilate surface blood vessels • Sweating – Low temperature • Surface vessels constrict • shivering

Skin Repair • Steps in wound healing: 1. Bleeding as a result of damage to blood vessels in dermis. Inflammation of tissue surrounding , brings phagocytic cells (White blood cells) to site. 2. Establishment of clot (Scab)- epithelial cells migrate around the scab and reproduce. 3. Continued epithelial reproduction and production of new intercellular material in the dermis. 4. Replacement of scab with scar tissue