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 dermis1. 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 SkinExocrine Glands1. 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