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 carcinomab) Squamous cell carcinomac) 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.