The Integumentary System
Skin (Integument)
Overview of the Skin• Largest organ of the body (15% of body weight)• Skin thickness variable, normally 1-2 mm• Protection
– chemical barrier (waterproof)– physical barrier (tough)– immune system activator
• Body temperature regulation – blood flow through the skin– sweat glands– hairs
• Sensation– sense touch, temperature and pain
• provides information outside of the body
Functions of the Integumentary System
• Largest organ of the body • Protection – chemical, physical, and mechanical barrier:
Stratified layers of keratinized cells create a tough barrier impermeable to most foreign invaders.
• Body temperature regulation is accomplished by:– Regulation of blood flow to skin: dilation (cooling) and
constriction (warming) of dermal vessels– Increasing sweat gland secretions to cool the body
Functions of the Integumentary System
• Metabolic functions – synthesis of vitamin D in dermal blood vessels
• Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume
• Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat
Skin (Integument)
• Consists of three major regions– Epidermis – outermost superficial region– Dermis – middle region– Hypodermis (superficial fascia) – deepest
region• Deep Fascia: lies under the hypodermis.
– Lines the muscles arteries and nerves
Epidermis
• Outer portion of the skin is exposed to the external environment and functions in protection.
• Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers (strata).
• Cell types include keratinocytes, melanocytes, Merkel cells, and Langerhans cells.
Cell and Layers of the Epidermis
• Deepest epidermal layer firmly attached to the dermis.• Consists of a single row of the youngest keratinocytes
melanocytes and merkel cells.– Keratinocytes – produce the fibrous protein keratin which
makes the cells more resistant to punctures and abrasions.
– Melanocytes – produce the brown pigment melanin. The darker your skin the greater the concentration of these cells. Protects against UV radiation (sunlight) damage.
– Merkel cells – function as touch receptors in association with sensory nerve endings.
• Cells undergo rapid division, hence its alternate name, stratum germinativum.
Layers of the Epidermis: Stratum Basale (Basal Layer)
• Keratinocytes form desmosomes which hold the cells together. • The spiny appearance is the result of the forces that
pull these cells apart.
• Langerhans( dendritic) cells: macrophages from bone marrow that migrate to the epidermis.
– Capture foreign material and present it to the immune system are abundant in this layer.
Stratum Spinosum (Prickly Layer)
• 3-5 cell layers thick made of keratinocytes.• Keratinocytes undergo apoptosis
– (programmed cell death).– Keratinocytes produce keratin
• A tough protein that makes the skin resistant to abrasions.
– Exocytose glycolipids accumulate in between the cells of this layer.
• Providing the waterproofing property to skin– This will also cut off nutrients for the more
superficial layers of the epidermis
Stratum Granulosum (Granular Layer)
Stratum Lucidum
• Thin translucent zone seen only in thick skin( Lips, palms of hands and soles of feet.
• Keratinocytes have no nucleus or organelles – dead cells since they no longer have a blood
supply.– does not stain well which give a clear appearance.
• Outermost layer of keratinized cells
• Accounts for three quarters of the epidermal thickness– ( approximately 30 layers thick)
• Functions include:– Waterproofing and preventing water loss.– Protection from abrasion and penetration.
Stratum Corneum (Horny Layer)
Dermis
Papillary layer
Reticular layer
Layers of the Dermis
• Papillary layer– Its superior surface contains finger like projections called dermal
papillae which adhere to the basal layer of the epidermis.– Dermal papillae contain capillary loops, Meissner’s corpuscles
( light touch), and free nerve endings ( pain )• Reticular layer
– Accounts for approximately 80% of the thickness of the skin– Dense irregular Collagen fibers in this layer add strength and
resiliency to the skin– Has a rich blood supply – Location of several types of glands and sensory receptors– Contains hair follicles and associated nerve and arrector pili
muscle
Hair Function and Distribution
• Functions of hair include:– Thermoregulation
• When skin senses cold piloerector muscles are stimulated. Hair becomes erect and goose bumps form.
– Hair protects against physical trauma, heat loss, and sunlight.
– Provide sensory perception.– Hair is distributed over the entire skin surface
except palms, soles, and lips, nipples and portions of the external genitalia.
Hair
Sweat Glands
• Different types prevent overheating of the body; secrete cerumen and milk– Eccrine (Merocrine) sweat glands – found in palms,
soles of the feet, and forehead. • Are found all over the body. Cool body off.
– Apocrine sweat glands – found in axillary and anogenital areas.
• Ceruminous glands – modified apocrine glands in external ear canal that
secrete cerumen. ( ear wax) • Mammary glands
– specialized sweat glands that secrete milk.
Sebaceous Glands
• Sebaceous Glands – Simple alveolar glands found all over the
body.– Secrete an oily secretion called sebum.– Soften skin when stimulated by hormones.
Glands
Hypodermis
• Subcutaneous layer deep to the skin.
• Composed of adipose and areolar connective tissue.
• Functions to insulate and cushion the body the body.
• Adipose provides a source of energy for ATP production.
Deep Fascia
• Dense fibrous connective tissue– surrounds the muscles, bones, nerves and blood vessels.
Skin Color
• Three pigments contribute to skin color– Melanin – yellow to reddish-brown to black
pigment, responsible for dark skin colors• Freckles and pigmented moles – result from local
accumulations of melanin.
– Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet.
– Hemoglobin – reddish pigment responsible for the pinkish hue of the skin.
Assessment of Skin color
• Cyanosis is a bluish discoloration of the skin or mucous membranes • caused by lack of oxygen in the blood.
• Yellowish color • may indicate cirrhosis of the liver due to accumulating bile
pigments in body tissue.• Pallor or Blanching:
• can be sign of anemia or emotional or physical stress ( Heart Attack)
• Black and Blues: • Bruises caused by blood escapes circulation and clots
underneath the skin. • Red color( erythema)
• indicate fever, allergy, infection inflammation and embarrassment.
Skin Cancer
• Most skin tumors are benign and do not metastasize however:
• The three major types of skin cancer are:a) Basal cell carcinoma
b) Squamous cell carcinoma
c) Melanoma
Basal Cell Carcinoma (a)
• Least malignant and most common skin cancer.
• Stratum basale cells proliferate and invade the dermis and hypodermis.
• Slow growing and do not often metastasize.
• Can be cured by surgical excision in 99% of the cases.
Squamous Cell Carcinoma (b)
• Arises from keratinocytes of stratum spinosum.
• Arise most often on scalp, ears, and lower lip.
• Grows rapidly and metastasizes if not removed.
• Prognosis is good if treated by radiation therapy or removed surgically.
Melanoma (c)
• Cancer of melanocytes is the most dangerous type of skin cancer because it is:– Highly metastatic– Resistant to chemotherapy
• Treated by wide surgical excision accompanied by immunotherapy.
• Chance of survival is poor if the lesion is over 4 mm thick.
Melanoma
• Melanomas have the following characteristics (ABCDE rule)– A: Asymmetry; the two sides of the pigmented
area do not match. – B: Border is irregular and exhibits indentations.– C: Color (pigmented area) is black, brown, tan,
and sometimes red or blue.– D: Diameter is larger than 6 mm. (size of a
pencil eraser)– E: Evolution : Is the mole changing?
Burns• Hot water, sunlight,
radiation, electric shock or acids and bases.– Death from fluid loss and
infection.
First-degree – only the epidermis is damaged– Symptoms include
localized redness, swelling, and pain.
Second-degree – epidermis and upper regions of dermis are damaged.– Symptoms mimic first
degree burns, but blisters also appear.
• Third-degree – entire thickness of the skin is damaged.– Burned area appears
gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed.)
Rule of Nines
• Estimates the severity of burns
• Burns considered critical if:– Over 25% of the body
has second-degree burns
– Over 10% of the body has third-degree burns
• third-degree burns on face, hands, or feet.