The Integumentary System

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 • 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.