The Integumentary System

Chapter 11

pg 204-205

The Integumentary System• Composed of the skin, sweat and oil glands, hair, and nails

• Accounts for 7% of the body’s weight.

• Major role is protection from disease causing critters and dehydration.

• Plays large role in homeostatsis = maintaining constant internal environment in the body

• Creates vitamins (D), has lots of sensory receptors

3 distinct layers• Epidermis, Dermis, and hypodermis

Regions of SkinEpidermis

• Outermost layer

• Composed mostly of stratified squamous epithelium

• Base cells get squashed as push to surface, where they produce keratin protein and harden (armor)

• Dandruff = accelerated keratinization (3-4X too fast)

• Fingerprints = patterns in the epidermis

• Contains 4 distinct cell types and 4 to 5 distinct layers.

Cell Types of the Epidermis

• Melanocytes—synthesize melanin.

• Located at the deepest layer of the epidermis.

• The melanin is transferred to the keratocytes.

• Protects against UV damage.

The Dermis

• Made mostly of connective tissue.

• The hide of the human body.

• Richly innervated and vascularized.

• Contains the hair follicles, sweat glands, oil glands, lymphatic vessels, and many sensory receptors.

The Dermis

• Consists of 2 layers.– Papillary layer—areolar connective tissue, heavily

vascularized. Contains the dermal papillae, capillary loops, and Meissner’s corpuscles.

– In some areas these lie on top of the dermal ridges. Cause the epidermal ridges that cause fingerprints.

– Reticular layer—dense irregular connective tissue. • Importance of this structure.

• Flexure lines.

The Dermis

• Skin color—determined by melanin, carotene, and hemoglobin.

• Why do different people have different skin colors?

• Freckles & moles• Role of melanin• Role and source of carotenes &

hemoglobins.

The Dermis

• Photosensitivity

• Erythema

• Pallor—paleness

• Jaundice

• Bronzing

• Bruises & hematomas

Skin Appendages

• Whiteheads• Blackheads• Acne—staphylococcus• Hair—covers the entire body except for the

palms, soles, lips, nipples, and parts of the genitalia.

• Functions of hair.• Mostly dead keratinized cells.

Nails

• Modification of the epidermis• Composed of keratin protein (like hair).• Composed of a free edge, body, and a root.

• Nail root — epidermis gives rise to cells• Lunula – dense collection of cells (a white

moon)• Nail Body – cells of the nail

Functions of the Integument

• Chemical barriers• Biological Barriers• Physical barrier

Functions of the Integument• Temperature Regulation

– Sweat glands

• Sensation– Many nerves present

• Metabolic Functions– Vitamin D synthesis

• Blood Reservoir– Shunts more blood into the circulation when needed.

• Excretion

Hair Follicles

• Located in the dermis

• Shaft extends out of epidermis

• Papilli muscles hold shaft erect giving goose bumps

• Root of hair = epithelial cells

• Epidermal cells die and keratinize, becoming hair

Oil Glands = Sebaceous Glands

- meant to lubricate growing hair with “sebum”

- designed to keep skin supple

- white heads and blackheads form when glands do not discharge to skin's surface

- Acne = inflammaton of sebaceous glands influenced by hormones

Sweat Glands

- Some open to hair follicles

- Most open to epidermis

- Cooling system --> homeostasis