Dermis And Accessory Structures

 Majority of cells are keratinocytes  “Ashiness” is caused by this layer of dead skin cells being very rough and raggedy.  DUST you see around is made up of dead skin cells!

* Lucidum only found in often used areas. * Basale has cells that are continuously dividing

Epidermis is avascular (no blood vessels) Epithelial tissue Dermis is highly vascular (has blood vessels) Connective tissue

 Thick layer under the epidermis  Strong, flexible connective tissue  Fiber types Collagen Elastic Reticular

 Rich supply of nerves and vessels  Critical role in Temperature Regulation

 Two layers Papillary – areolar connective tissue; includes dermal papillae Reticular – “ reticulum ” (network) of collagen and reticular fibers

 Derived from epidermis but extend into dermis  Include Hair and hair follicles Sebaceous (oil) glands Sweat (sudoiferous) glands Nails

 Of hard keratin  Corresponds to hooves and claws  Grows from nail matrix

Nail body Free edge Nail root Matrix Lunula (moon)

 Derived from epidermis  Made of hard keratin  Everywhere but palms, soles, nipples, parts of genitalia  Hair develops in follicles

 Parts Root imbedded in skin Shaft projecting above skin surface Hair bulb where hair is produced Hair follicle wall is extension of epidermis

Dermal Papilla Cuticle Cortex Medulla Hair Bulb Sebaceous Gland Arrector Pili Muscle Hair Shaft Hair Root Hair Follicle Wall Three layers Medulla core Cortex surrounds medulla Cuticle single layers, overlapping

Dermal Papilla Cuticle Cortex Medulla Hair Bulb Sebaceous Gland Arrector Pili Muscle Hair Shaft Hair Root Hair Follicle Wall

Smooth muscle attaches to follicle Raises hairs Response to fright or cold Function?

 Thermoregulation– less in man than other mammals  Sense light touch of the skin  Protection – scalp  Three concentric layers Medulla (core) Cortex (surrounds medulla) Cuticle (single layers, overlapping)  Functions of hair

 Hair growth: averages 2 mm/week Active stage: hair is growing Resting phase: no hair growth, then shed  At the base of the follicle, hair papilla Contains blood vessels and nerves Nourishes hair  Bulb  Contains matrix – epithelial cells responsible for growth  Contains melanocytes

 Hair loss Thinning – age related Male pattern baldness  Hair color Amount of melanin for black or brown; distinct form of melanin for red White: decreased melanin and air bubbles in the medulla Genetically determined though influenced by hormones and environment

 Entire body except palms and soles  Connect to hair follicle 

 Produce sebum – oily waxy substance  Oils and lubricates  Can cause blackheads, lead to acne if follicle ruptures from buildup.

 All over body  Function: Prevent overheating  500 cc to 12 l/day! (is mostly water)  Produced in response to stress as well as heat

 Merocrine Most numerous True sweat: 99% water, some salts, traces of waste Open through pores  Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with time - odor

 When you sweat, heat leaves the body through your pores.  When the sweat hits the outer surface of the skin, it is cooled by the air.  This lowers your body temperature.

The dermis is attached to underlying organs by the hypodermis (subcutaneous layer) Loose connective tissue Packed with adipose cells Stabilizes position of skin

 “ Hypodermis ” (Gk) = below the skin  “ Subcutaneous ” (Latin) = below the skin  Also called “ superficial fascia ” “ fascia ” (Latin) =band; in anatomy: sheet of connective tissue  Fatty tissue which stores fat and anchors skin (areolar tissue and adipose cells)  Different patterns of accumulation (male/female)