I Body Membranes A B C D Serous

I. Body Membranes A. B. C. D. Serous Membranes- (serosae) membranes that do not open to the outside in the ventral cavity, secrete serous fluid Mucous Membranes(mucosae)-membranes that do open to the outside, secrete mucus Synovial Membranes- membranes that secrete synovial fluid into synovial (freely moveable) joint spaces Cutaneous Membranes- dry membranes that make up the integument

II. Functions of the Integumentary System A. Protection – chemical and mechanical barrier § Mechanical Barrierkeratinized stratified squamous epithelium melanocytes basement membrane dermal-epidermal junction • Chemical barrier acid mantle, melanocytes, keratin, basement membrane

B. Body temperature regulation is accomplished by negative feedback: § § Dilation (cooling) and constriction (warming) of dermal vessels Increasing sweat gland secretions to cool the body C. Cutaneous sensation –Tactile receptors sense touch, pressure and pain

Functions of the Integumentary System D. Metabolic functions – synthesis of vitamin D in dermal blood vessels E. Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume F. Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat G. Absorption- fat soluble materials can be absorbed , ex. Vitamin E

III. Skin (Integument) A. Consists of two major regions and one associated region § Epidermis – outermost superficial region § Dermis – middle region § Hypodermis (subcutaneous layer) – deepest region, associated with the skin- NOT A TRUE LAYER

Hair shaft Pore Dermal papillae (papillary layer of dermis) Epidermis Meissner's corpuscle Free nerve ending Reticular layer of dermis Sebaceous (oil) gland Arrector pili muscle Dermis Sensory nerve fiber Eccrine sweat gland Pacinian corpuscle Artery Hypodermis (superficial fascia) Hair root Hair follicle Eccrine sweat gland Vein Adipose tissue Hair follicle receptor (root hair plexus) Figure 5. 1

Skin structures § 1. epidermis 9. blood vessels § 2. papillary layer of dermis 10. hair root § 3. reticular layer of dermis 11. hair follicle § 4. hypodermis 12. § 5. sweat gland 13. sebaceous gland § 6. adipose tissue 14. dermal papillae § 7. root hair plexus 15. hair shaft § 8. Pacinian corpuscle 16. Meissner’s corpuscle 17. Sweat pore arrector pili muscle

B. Epidermis 1. Overview § § § Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers Cell types include keratinocytes, melanocytes, Merkel cells, and Langerhans’ cells Outer portion of the skin is a dry membrane exposed to the external environment and functions in protection

2. Cells of the Epidermis § § Keratinocytes – produce the fibrous protein keratin Melanocytes – produce the yellow, brown, red, or black pigment melanin Langerhans’ cells – epidermal macrophages that help activate the immune system Merkel cells – function as touch receptors in association with sensory nerve endings, when densely packed together they are called Merkel discs

Layers of the Epidermis Figure 5. 2 b

3. 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 Cells undergo rapid division, hence its alternate name, stratum germinativum

Stratum Spinosum (Prickly Layer) § § Cells contain a weblike system of intermediate filaments attached to desmosomes Melanin granules and Langerhans’ cells are abundant in this layer

Stratum Granulosum (Granular Layer) § § Thin; three to five cell layers in which drastic changes in keratinocyte appearance occurs Keratohyaline and lamellated granules accumulate in the cells of this layer

Stratum Lucidum (Clear Layer) § § § Thin, transparent band superficial to the stratum granulosum, appears clear when stained Consists of a few rows of flat, dead keratinocytes Present only in thick skin, absent in thin skin around the eyelids

Stratum Corneum (Horny Layer) § § § Outermost layer of keratinized cells Accounts for three quarters of the epidermal thickness Functions include: § Waterproofing § Protection from abrasion and penetration § Rendering the body relatively insensitive to biological, chemical, and physical assaults

Layers of the Epidermis Figure 5. 2 b

C. Dermis § § § Second major skin region containing strong, flexible connective tissue Cell types include fibroblasts, macrophages, and occasionally mast cells and white blood cells Composed of two layers – papillary and reticular

1. Layers of the Dermis: Papillary Layer § Papillary layer- very vascular § § Makes up 20% of dermis Areolar connective tissue with collagen and elastic fibers Its superior surface contains peglike projections called dermal papillae (causes fingerprints) Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings

2. Layers of the Dermis: Reticular Layer § Reticular layer- dense irregular CT § § Accounts for approximately 80% of the thickness of the skin Collagen fibers in this layer add strength and resiliency to the skin Elastin fibers provide stretch-recoil properties Contains hair root/bulb, glands, Pacinian corpuscles, blood vessels, nerve endings

D. Hypodermis- NOT A TRUE LAYER § Subcutaneous layer deep to the skin § Composed of adipose and areolar connective tissue § § Associated with the skin because it is used as an anchor, adheres skin to underlying fascia Useful in temperature regulation, vascularity, common injection site, protection and shock absorber

IV. Skin Color A. 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

B. Skin Coloration Changes § § § Cyanosis- lack of hemoglobin, “bluish” Erythema- “redness” of the skin due to blushing, fever, high bp, inflammation, allery Pallor- “blanching” of skin due to stress, fear, anemia, or low bp Jaundice- abnormal yellowish skin color due to excessive bilirubin pigment from liver Addison’s Disease- metallic bronzing of skin due to hypofunctioning adrenal gland Albinism- lack of melanin pigment, genetic disorder

V. Accessory Structures of the Skin A. Sweat Glands and Modified Glands § Different types prevent overheating of the body; secrete cerumen and milk § § Eccrine sweat glands – found in palms, soles of the feet, and forehead, for body temperature and acid mantle Apocrine sweat glands – found in axillary and genital areas, body odor (scent) Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen Lactiferous glands – specialized sweat glands that secrete milk

B. Sebaceous Glands § § Simple glands found all over the body except sides and soles of feet and palms of hands Soften skin when stimulated by hormones Secrete an oily secretion called sebum into hair shaft Used as a bactericide

C. Hair § § § Filamentous strands of dead keratinized cells produced by hair follicles found everywhere except palms, soles, and lips and portions of the external genitalia Contains hard keratin which is tougher and more durable than soft keratin of the skin Made up of the shaft projecting from the skin, and the root embedded in the skin Consists of a core called the medulla, a cortex, and an outermost cuticle Pigmented by melanocytes at the base of the hair

Hair Function and Distribution § Functions of hair include: § Helping to maintain warmth § Alerting the body to presence of insects on the skin § § Guarding the scalp against physical trauma, heat loss, and sunlight Types of Hair Vellus – pale, fine body hair found in children and the adult female Terminal – coarse, long hair of eyebrows, scalp, axillary, and pubic regions

Hair Follicle Figure 5. 5 a

Hair Follicle Figure 5. 5 c

D. Structure of a Nail § Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Figure 5. 6

§ § § Nails are made of hardened keratin Humans have flat nail surfaces versus curved nails, used as a tool for greater dexterity 3 main nail structures § Free edge § Nail body § Nail root

VI. Homeostatic Imbalances of the Skin A. Skin Cancer § § § Most skin tumors are benign and do not metastasize A crucial risk factor for nonmelanoma skin cancers is the disabling of the p 53 gene Newly developed skin lotions can fix damaged DNA

Skin Cancer § The three major types of skin cancer are: § Basal cell carcinoma § Squamous cell carcinoma § Melanoma

Basal Cell Carcinoma§ § Least malignant and most common skin cancer Stratum basale cells divide uncontrollably 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 § § Arises from keratinocytes of stratum spinosum Arise most often on scalp, ears, and lower lip, usually appears as red patch Grows rapidly and metastasizes if not removed Prognosis is good if treated by radiation therapy or removed surgically

Melanoma- 3 -5% of skin cancer types § Cancer of melanocytes is the most dangerous type of skin cancer because it is: § Highly metastatic § Resistant to chemotherapy

Skin Cancers Figure 5. 7 a–c

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: Elevation is useful in detection

Melanoma § § Treated by wide surgical excision accompanied by immunotherapy Chance of survival is poor if the lesion is over 4 mm thick

B. Burns § First-degree – only the epidermis is damaged § Symptoms include localized redness, swelling, and pain

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

Burns § 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- method divides body into derivatives or multiples of 9% Other methods used: Rule of Palms- palm width equals 1% Lund Browder Chart- used for infants and toddlers (head is larger for surface area)

Rule of Nines Figure 5. 8 a