1. The Integumentary System

2. Skin (Integument)

3. 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

4. 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

5. 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

6. 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

7. 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.

8. Cell and Layers of the Epidermis

9. Layers of the Epidermis: Stratum Basale (Basal Layer)
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.

10. Stratum Spinosum (Prickly 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.

11. Stratum Granulosum (Granular 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

12. 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.

13. Stratum Corneum (Horny Layer)
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.

15. Dermis
Papillary layer
Reticular layer

16. 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

17. 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.

18. Hair

19. Sweat Glands Ceruminous glands Mammary 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.

20. Sebaceous Glands Sebaceous Glands
Simple alveolar glands found all over the body.
Secrete an oily secretion called sebum.
Soften skin when stimulated by hormones.

21. Glands

22. 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.

23. Deep Fascia Dense fibrous connective tissue
surrounds the muscles, bones, nerves and blood vessels.

24. 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.

25. 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.

26. Skin Cancer
Most skin tumors are benign and do not metastasize however:
The three major types of skin cancer are:
Basal cell carcinoma
Squamous cell carcinoma
Melanoma

28. 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.

29. 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.

30. 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.

31. 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?

32. 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.

33. Second-degree – epidermis and upper regions of dermis are damaged.
Symptoms mimic first degree burns, but blisters also appear.

34. 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.)

35. 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.