Accessory Organs Integumentary System

Accessory Organs Located mostly in the dermis (reticular region) Originate in the epidermis A group of cells from the epidermis migrate into the dermis The process of forming these organs starts in the dermis Hair, nails, sweat glands, sebaceous glands These are called the epidermal derivatives

Hair Protects the skin from sunlight and foreign particles Hair follicle: downward extension of the epidermis into the dermis Hair Root: the part surrounded by the follicle Hair shaft: the part that extends away from the body Bulb: the base of the hair follicle, cluster of blood vessels here that supplies nutrition

Hair Arrector pilli: small band of smooth muscle, from the follicle to the papillary region The contraction of the muscle pulls the hair vertical Frightened of cold Small amount of heat is generated Goose bumps Another important structure is the sebaceous gland which will have its own slides...

Hair Growth Hair growth Similar to dividing cells of the epidermis New growth in the deeper region pushes the new cells toward the surface Cytoplasm of the dead cells is replaced by keratin The hair shaft is composed of keratin 1 mm every 3 days Shaving or cutting has no effect on the growth rate Example: androgens (a male hormone) inhibits follicle activity, breaking the cycle of growth, loss, and replacement Male pattern baldness

Hair Color Provided by melanin Various concentrations to produce different shades As age increases, the amount of melanin is reduced Gray or white hair

Pause and Process Why do we say that hair “originates” in the epidermis? It looks like it grows out of the dermis… From where does hair get blood supply to grow? Hair = hair follicle, hair root, hair shaft… Which of these do you expect to be made of living cells? Which do you expect to be made of dead cells? How do hair cells behave similarly to skin cells (pattern of cell growth and death)? Arrector pilli connect the follicle to the papillary region.... What layer is the papillary region in? What is a distinguishing characteristic of the papillary region? Use the pictures in previous slides to help with explanation of these answers

Sebaceous Glands Secrete sebum into a duct Water, fats, salts, cholesterol, protein Keeps hair and skin soft and pliable Water-resistant layer on the skin surface Oil glands Cluster of glandular epithelial cells Not in palms and soles Blackheads form when these ducts are clogged or swollen Blackheads = clogged pore that is open - air oxidizes the melanin and it changes color to black Whitehead = clogged pore that is closed - air does not oxidize the melanin

Sweat Glands AKA sudoriferous glands Numerous throughout skin Sweat Water, salts, small amount of urea Secretion helps maintain body temperature Evaporation off the body Originates as a single coiled tube In the dermis or hypodermis Passes through to the surface via a pore

Sweat Glands Two types Eccrine: throughout the skin, watery sweat in response to elevated body temperature Apocrine: begin during puberty in response to sex hormones Thickened sweat, microorganisms, may have strong odor Periods of emotional stress More numerous in armpits and groin

Pause and Process Both Sebaceous glands and Sweat Glands secrete their products into ducts… what type of gland does this make them? Endocrine or Exocrine? What is the function of sebum? How do sweat glands help us to maintain homeostasis? Contrast eccrine and apocrine glands.

Nails Compressed outer layer of epidermis (...made of keratin) Nail body = visible part Cuticle = flap of stratum corneum overlying the proximal end Nail root = deep to the cuticle, contains the nail matrix Nail matrix = stratum basale** Lunula = visible crescent; part of the nail matrix

Receptors Distal ends of nerves, wrapped in connective tissue Translate physical changes of environment into electrical impulses, brain interprets signals as sensations. (called “Transduction”) Types of receptors in the skin: Mechanoreceptors Nocioreceptors Thermoreceptors

Pause and Process How is the growth of your nails similar to the growth of your skin? What two layers are receptors located in? What do mechanoreceptors transduce? Thermoreceptors? Nocioreceptors?