Download Integumentary System

Integumentary System
Our Body’s Armor
Function
The skin (integument) has many key functions:
• Protection from
1. mechanical damage
2. chemical damage
3. bacterial damage
4. UV radiation
5. Thermal (heat/cold) damage
6. Desiccation (drying out)
• Aids in body heat loss or heat retention
• Aids in excretion of urea and uric acid
(perspiration)
• synthesizes vitamin D
The skin is composed of two kinds of tissue: the
outer epidermis and the underlying dermis.
Epidermis
• Stratified squamous epithelium that can keratinize
(become hard/tough)
• Avascular
• Has 5 layers:
• Stratum basale
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum
• Stratum corneum
Stratum basale
• Location: Deepest layer of epidermis (closest to
the dermis)
• Description: Only layer that receives adequate
nourishment; constantly undergoes cell division
(mitosis)
• Specialized structures: melanocytes that produce
melanin
• Function: to produce new cells, which replace
those of the upper layers
Stratum spinosum
• Location: above stratum germinativum
• Description: Cells become flatter and more
keratinized
Stratum granulosum
• Location: above stratum spinosum
• Description: Cells become even flatter and more
keratinized
Stratum lucidum
• Location: above stratum granulosum
• Description: Clear layer with flatter and
more keratinized cells
Stratum corneum
• Location: Outermost layer of the epidermis
• Description: 20-30 cells thick; accounts for ¾ of
the epidermal thickness
• Specialized structures: Horny (cornified) cells,
which are dead, keratin-filled cells
• Function: water-proofing, protection from the
environment
Dermis
• Strong, stretchy envelope that holds the body
together (“hide”)
• Has collagen (toughness and hydration) and
elastic fibers (elasticity)—as we age, elasticity
decreases
• Vascular (blood vessels help maintain body
temp.)
• Consists of two major regions or layers:
• Papillary region
• Reticular layer
Papillary region
• Location: Upper dermal region
• Description: Uneven layer with finger-like
projections that indent the epidermis (dermal
papillae); leads to fingerprints
• Specialized structures: capillary loops, pain
receptors, touch receptors, dermal papillae
Reticular layer
• Location: deepest skin layer
• Description: deepest layer of the skin
• Specialized structures: blood vessels, sweat/oil
glands, deep pressure receptors, phagocytes
Subcutaneous Tissue
• Below the dermis
• Adipose tissue that anchors the skin to underlying
organs
• Shock absorber and insulator
Skin Color
• Skin color is determined by 3 pigments:
• amount of melanin in epidermis (red,
yellow, or black)
• amount of carotene in stratum corneum
and subcutaneous tissue (orange-yellow)
• amount of O2 bound to hemoglobin in
red blood cells of the dermal blood vessels
Homeostatic Imbalances
• Redness (erythema)—reddened skin due to blushing,
fever, allergy, or inflammation
• Pallor—paleness due to emotional stress, anemia, or
low blood pressure
• Jaundice—yellowed skin due to a liver disorder in
which bile is deposited in body tissue
• Bruises—caused by escaped blood that has clotted in
tissue spaces (hematomas)
Cutaneous glands
Sebaceous glands (oil glands)
• Description: empty into a hair follicle or directly onto the skin; produce sebum, a
mixture of oils and fragmented cells
• Location: all over the skin, except on the palms of hands and soles of feet
• Structure: exocrine gland that releases sebum to the surface or to a hair follicle
• Function: kills bacteria, keeps skin soft and moist, prevents hair from becoming brittle
Sudoriferous glands (sweat glands ):
• Description: produce sweat (eccrine glands), which is a mixture of H2O, salts, urea,
and Vitamin C; produce fatty acids, proteins and sweat (apocrine glands); empty into
pores
• Location: throughout the skin; 2.5 million per person
• Structure: coiled gland that releases sweat or other materials to the surface
• Function: inhibits bacterial growth; controls temperature (when evaporation occurs,
a lot of heat leaves too!)
Hair:
• Description: flexible epithelial structure produced by a hair follicle
• Location: outer surface of skin
• Structure:
• Root: part of the hair enclosed in the follicle
• Shaft: part of the hair projecting from the surface of the scalp or skin
• Hair bulb: the inferior end of the follicle that has epithelial cells that are wellnourished and divide to form the hair
• Hair follicles: compound structures consisting of an inner (epidermal) and
outer (dermal) sheath; produces a hair
• Arrector pili: small bands of smooth muscle cells that connect each side of the
hair follicle to the dermal tissue; cause “goose bumps”
• Function: protection (head, eyes, nose); some insulation
Nails:
• Description: scale-like modifications of the epidermis; transparent, nearly
colorless; mostly non-living
• Location: fingers and toes
• Structure: free edge, body, root, nail folds
• Function: tools to help pick up small objects or to scratch an itch
Homeostatic Imbalances
• Athlete’s foot—fungal infection between the toes
• Boils/carbuncles—inflammation of hair follicles and
sebaceous glands due to bacteria
• Cold sores—fluid-filled blisters that itch and sting;
caused by the herpes virus
• Contact dermatitis—itching, swelling skin; caused by
exposure to chemicals that provoke reactions
• Impetigo—pink, water-filled lesions that develop a
crust and rupture; bacterial
• Psoriasis—red lesions covered with dry, silvery scales
Burns
• 1st degree: only epidermis is damaged
• 2nd degree: epidermis and upper dermis are
damaged
• 3rd degree: destruction of the entire thickness of
the skin (epidermis and dermis)
Skin Cancer
• Most common type of cancer in humans
• basal cell carcinoma: cells of the stratum basale can no
longer form keratin
• squamous cell carcinoma: cancer cells in the stratum
spinosum
• malignant melanoma: cancer of melanocytes
• ABCD rule—look for asymmetry, border irregularity,
color (change in), and diameter of spots