Integumentary System Anatomy - Ch 12 Med Term

Integumentary System

Integumentary System

• Average adult has two square yards of skin, making it the largest body organ

• Consists of skin and its related structures

  • Sebaceous Glands

  • Sweat Glands

  • Hair

  • Nails

Functions of Skin

• Keeps the body waterproof

• When intact, blocks the entrance of pathogens

• Contains receptors for the sense of touch

• Synthesizes vitamin D from the sun

Sebaceous glands

Secretes sebum that lubricates skin and discourages growth of bacteria on skin

Sweat glands

• Assist with body water content and temperature regulation

• Excretion of small amounts of metabolic wastes

Hair

Helps control the loss of body heat

Nails

Protect dorsal surface of last bone of each toe and finger

Skin

• Specializes Tissues

• Three layers

  • Epidermis

  • Dermis

  • Subcutaneous

Epidermis

• Outermost layer of skin

• Made of specialized epithelial tissues

• Contains no blood vessels or connective tissue

• Depends on the lower layers for nourishment

Epithelial tissues

Form protective covering for internal and external surfaces of the body

Squamous epithelial tissues

• Forms upper layer of epidermis

• Flat, scaly cells continuously shed

Basal layer

• Lowest layer of epidermis

• Site of new cell production

• When cells reach surface, they die and become filled with keratin

Keratin

• Fibrous, water-repellent protein

  • Soft Keratin: Component of Epidermis

  • Hard Keratin: Found in hair and nails

Melanocytes

• Special cells in basal cell layer

• Produce and contain dark brown to black pigment known as melanin

Melanin

• Pigment that determines color of skin, produces freckles and age spots

• Protects skin from some of the harmful UV rays

Dermis

• Directly below epidermis

• Contains connective tissue, blood and lymph vessels, nerve fibers, hair follicles, sebaceous glands and sweat glands

• Sensory nerve endings

  • Sensory receptors for touch, temperature, pain and pressure

Collagen

Tough flexible fibrous protein found in skin, bones, cartilage, tendons and ligaments

Mast Cells

• Found in connective tissue of dermis

• Respond to injury, infection or allergy by producing and releasing heparin and histamine

Subcutaneous Layer

• Located below the layers of skin

• Connects skin to the surface muscles

• Made of loos connective tissue and adipose tissue

• Lipocytes manufacture and store large qualities of fat

Sebaceous Glands

• Located in dermis

• Closely associated with hair

• Sebum

  • Oily substance released through ducts opening into hair follicles

  • Lubricates skin

  • Acidic, discourages growth of bacteria

Mammary Glands

• Produce milk

• Also part of reproductive system

Sudoriferous glands

• Located on almost all body surfaces

• Apocrine

  • Found at hair follicles

• Eccrine

  • Open onto skin

Pores

• Opening on the surface of skin

• Act as ducts of the sweat glands

Perspiration

• Secreted by sweat glands

• 99% water plus salt and metabolic waste

• Evaporation of sweat cools the body

HIdrosis

Production and excretion of perspiration

Hair follicles

Sacs holding the root of hair fibers

Arrector pili

Muscle fibers attached to hair follicles that cause hair to stand erect and reduces heat loss

Unguis

Fingernail or toenail

Nail Body

• Translucent

• Molded to surface of underlying tissues

• Made of hard, keratinized plates of epidermal cells

Nail Bed

• Joins nail body to underlying connective tissue

• Nourishes the nail

• Blood vessels provide pink color

Free edge

• Portion of nail not attached to the nail bed

• Extends beyond tip of the finger or toe

Lunula

• Half-moon-shaped region at nail root

• Site of new keratin cell formation

Cuticle

Epidermis attached to the surface of nail

Nail root

Fastens mail to finger/toe

Closed comedo

whitehead

Open comedo

blackhead