Skin Continued Region 1 Region 2 Region 3

Skin Continued Region 1 Region 2 Region 3

Dermis (Region 2) Structure – Collagen and elastic fibers located throughout the dermis • Collagen fibers give skin its toughness • Elastic fibers give skin elasticity – Blood vessels – Differs in thickness (ex. thick on feet and hands/thinner on eyelids)

2 Layers of the dermis 1. Papillary layer (upper) made of areolar connective tissue – Upper region (papillary) – Dermal papillae – projections that increase surface area. – Cause ridges in epidermis: make our fingerprints – Meissner’s corpuscles – touch receptors – Pain receptors – Capillaries (must nourish the epidermis) – Hold epidermis to the dermis

2. Reticular Layer (Deep tissue) Dense irregular connective tissue and Adipose CT – Contains: • Blood vessels • Hair • Pacinian corpuscles: pressure receptors • Oil glands (sebaceous) • Sweat glands and ducts (eccrine and apocrine) • Heat and cold receptors • Phagocytes (phago- eater) immune cells

Hypodermis or Subcutaneous layer (Region 3) • Function • Attaches dermis to underlying bone and muscle • Stores body fat (approx. ½ of the body’s fat) What type of tissue must this be?

Appendages of the Skin Exocrine Glands 1. Sebaceous glands – Located by hair root – Produce oil (sebum) • Lubricant for skin (keeps it soft) • Prevents brittle hair • Stops excess evaportion – Cause blackheads and pimples • Gland becomes enlarged because a build up of waste products from the bacteria on the surface of the skin

2. Sweat glands (AKA: Sudoriferous) – Produce sweat 1. Eccrine – Found everywhere but in margin of lips, nail beds, and eardums – Open via duct to pore on skin surface 2. Apocrine – found in armpit, pubic and areola – Ducts empty into hair follicles

Sweat Composition – Mostly water, Salts and Urea (nitrogen waste also found in urine) • Function – Helps dissipate excess heat (cools the body) – Excretes waste products – Acidic nature inhibits bacteria growth

3. Hair – – Produced by hair follicle: sheath surround hair root Consists of hard keratinized epithelial cells (dead) Melanocytes provide pigment for hair color Arrector pili muscle • Smooth muscle (involuntary) • Pulls hairs upright when cold or frightened

Accessory Organs - Wax • Wax (ceruminous) – located in outer ear canal – Produces cerumen – Secretions provide defense against foreign bodies

Accessory Organs - Nails • Nails – Scale-like modifications of the epidermis • Heavily keratinized – Stratum basale extends beneath the nail bed • Responsible for growth – Lack of pigment makes them colorless • Function – Grasp and manipulate objects