Integumentary System Integumentary system is the skin and the organs derived from it (hair, glands, nails) One of the largest organs 2 square meters; 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 keratin (process starts)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 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 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 1mm 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 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

Nails Compressed outer layer of the epidermis Composed of keratin Protect ends of fingers and toes, help pick up small objects, and grip the floor 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, shock- absorbing 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