Chapter 5 Integumentary SystemRead the entire chapterLearning Outcomes:1. List and explain the functions of the integumentary system.2. List and describe the strata of the epidermis.3. Describe the changes that occur in keratinocytes as they move from the stratum basale to the stratum corneum.4. Compare the structure and location of thick skin and thin skin.5. How do melanin, carotene, and blood affect skin color?6. Name and compare the two layers of the dermis.7. Describe the tissue and functions of the subcutaneous tissue.8. Distinguish between vellus and terminal hair.9. List the common glands of the skin and the secretions of each.10. Explain how skin helps regulate body temperature.11. Describe the role of the skin in calcium ion level regulation.12. List and describe the 3 common types of skin cancer.

Integument:· covering the body· considered one organ or an organ system

Two components of the integument:· cutaneous membrane: skin · associated hairs, nails, glands

I. Cutaneous Membrane: skin· epidermis :

· most superficial layer of skin· consists of epithelial tissue· stratified squamous· avascualr · resists abrasion on the skin’s surface and reduces water loss through skin

· dermis : · underlying fibrous connective tissue· vascular · responsible for most of the structural strength of the skin

A. Functions of the skin· protection · excretion · maintain normal body temp · synthesis of vit D · sensory · storage

B. Epidermis : · composed of stratified squamous epithelia; therefore, affords mechanical protection

(abrasion)· basal cells are cuboidal and flatten toward the surface· contains no blood vessels· nourished by diffusion from capillaries of the dermis

types of cells in epidermis• keratinocytes :

· most abundant type of cell· give the epidermis its ability to resist abrasion and reduce water loss· epidermal cell that produces keratin

· keratin : a protein mixture which makes cells more durable

• melanocytes :

• contribute to skin color

• produce melanin

• found mainly in stratum basale

• langerhans cells :

• Dendritic cell found in skin

• part of the immune system

• merkel cells :

• specialized epidermal cells associated with nerve endings responsible for detecting light touch and superficial pressure

consists of 4-5 layers called strata: thin skin has 4 and thick skin (soles and palms) has 5Thick Skin:

• has all five epithelial strata

• stratum corneum has many layers of cells

• found in areas subject to friction such as soles and palms

Thin Skin:

• more flexible than thick skin

• each strata has fewer layers than thick skin

• stratum lucidum generally absent

• hair only found in thin skin

a. stratum basale (germinativum)· innermost layer, attached to the basement membrane · form epidermal ridges that interdigitate with dermis (increases SA) · dominant cell type is basal cells (stem cells): divide to produce cells that move into the

upper layers · divide and give rise to two daughter cells: 1 basal cell and 1 differentiated

· other cell types include sensory cells (Merkel cells) and melanocytes (produce melanin) b. Statum spinosum

· composed of keratinocytes held together by desmosomes · include special cells for defense (Langerhan cells)

c. Statum granulosum· cells no longer divide · lose nucleus and organelles · accumulate keratinohyaline granules and lamellated granules

· waterproofing material->provides durability· Lamellated granules :· Keratinohyline : nonmembrane bound protein granule in the cytoplasm of stratum granu-

losum cells of the epidermisd. Stratum lucidum

· clear layer · only found in thick skin (soles and palms)· composed mainly of dead keratinocytes

e. Stratum corneum· superficial layer of 20-30 cell layers · cells filled with keratin and surrounded by waterproofing material · dead cells still held together by desmosomes

C. Skin Color: result of the interaction between pigments and dermal blood supply1. Pigment:

a. carotene:· orange-yellow pigment · accumulate in epidermal cells and fatty tissue of the dermis · converted to vit A: important for maintenance of epithelia and synthesis of photorecep-

tors of the eye b. melanin:

· brown-black pigment responsible for hair, skin, and eye color· melanosome : vesicle of melanin transferred to keratinocytes · darkness of skin is dependent on the size of melanosomes and persistence into superficial

layers · sunblock; protects from UV exposure

2. Dermal Blood Supply· blood contains RBC with hemoglobin (red pigment) · increased blood flow to skin: flushed · decreased blood flow to skin: pale

· Cyanosis : blue tint of skin due to lack of oxygen· if O2 is associated with hemoglobin, turn bright red, if O2 is removed it appears purple

D. Dermis: connective tissue layer beneath the epidermis1. Papillar layer

· most superficial· loose connective tissue · contains capillaries and sensory neurons · dermal papillae : extend between the epidermal ridges· supply the overlying epidermis with nutrients, remove waste products, and aid in regulat-

ing body temp. 2. Reticular layer

· dense irregular connective tissue · main layer of the dermis· gives strength to skin· collagen fibers extend into papillary layer and the subcutaneous tissue (layer of tissue un-

derlying the dermis) · continuous with subcutaneous layer· forms a mat of irregularly arranged fibers that are resistant to stretching in many direc-

tions · cleavage lines are the result of the elastic and collagen fibers being arranged more in

some directions than others

E. Condition of the skin:· collagen and elastin fibers in the dermis allow for stretching of dermis without damage · aging, hormones and UV exposure diminish the amount of elastin in the skin, leading to

wrinkles · stretchmarks are the result of when the elastic capabilities of the elastin fibers are ex-

ceeded · when the skin is overstretched, the dermis ruptures and leaves lines visible

through the epidermisF. Lines of Cleavage

· result of the parallel bundles of collagen and elastin fibers · surgeons study these lines of cleavage to determine where to make incisions

G. Subcutaneous Tissue· also called the hypodermis· stabilizes the position of the skin · loose connective tissue with lots of fat cells · reduces heat loss, shock absorber, energy reserve

H. Accessory Structure:1. Hair

· found over most of the body· not found on palms, soles, lips, nipples, parts of external genitalia, and distal seg-

ments of fingers and toes· originate in organs called hair follicles · functions of hair include:

· protection from UV· cushioning· insulating· sensation· preventing entry into the body

· types of hair include the peach fuzz (vellus) and terminal hair · vellus : short, fine, usually unpigmented hair that covers the body except for the

scalp, eyebrows, and eyelids. much of vellus is replaced at puberty by terminal hairs.

· terminal hair : long, course, usually pigmented hair found in the scalp, eyebrows, and eyelids, replacing vellus hair

2. Glands: exocrine· sebaceous glands :

· oil glands· located in dermis· produce sebum: an oily white substance rich in lipids· classified as holocrine glands· connected by a duct to the upper part of the hair follicle · sebum oils the hair and skin surface which prevents drying and protects agains

some bacteria· sebaceous follicles lack hair

· sweat gland s: apocrine sweat glands in the armpits, groin area release thick fluid; mero-crine sweat glands are distributed all over the body and produce the sensible perspiration

· Apocrine :· gland whose cells contribute cytoplasm to its secretions· simple, coiled, tubular glands that usually open into hair follicles superfi-

cial to the opening of the sebaceous glands· DO NOT REGULATE TEMP!· become active at puberty as a result of sex hormones· secretions contain organic substances that are odorless when first released

but quickly metabolize by bacteria to cause what is known as body odor· Merocrine :

· secrete products with no loss of cellular material· most common type of sweat gland· simple, coiled, tubular glands that open directly onto the surface of the

skin through sweat pores· mammary glands :

· modified apocrine sweat glands located in breasts· produce milk· only fully developed in pregnant mothers

· ceruminous glands : · modified eccrine sweat gland· located in ear canal· produces ear wax (cerumen) which prevents the entry of dirt and small insects

3. Nails :

• found on the tips of fingers and toes

• provide protection

I. Role of skin in calcium uptake· exposure to sunlight triggers cells in the stratum spinosum and stratum germinativum to

convert a steroid to Vitamin D (cholecalciferol) · functions as a hormone to stimulate the uptake of calcium and phosphate from the

intestines, to promote their release from bones, and to reduce calcium loss from the kidneys, resulting in increased blood calcium phosphate levels

· Cholecalciferol is converted to an intermediate by the liver · The intermediate is used by the kidney to synthesize the hormone calcitriol

· calcitriol regulates the absorption of calcium and phosphorus at the small intestines

· Inadequate supplies of calcium and phosphorus decreases bone growth and maintenance

 J. Perspiration• conduction : the transfer of heat between two parts of a stationary system, caused by a

temperature difference between the parts.

• convection : the transfer of heat by the circulation or movement of the heated parts of a liquid or gas.

• evaporation : to convert or change into vapor

• Insensible perspiration : water from interstitial fluid slowly rises to skin surface and will evaporate

• Sensible perspiration : involves secretions from eccrine sweat glands-controlled by ner-vous system

***Blisters are the result of pooling of fluid in areas of tissue damage: where layers have sepa-rated

K. Skin CancerMost tumors are benign and do not metastasizeSome are malignantbenign:malignant:metastasize:Risk factors for skin cancer: UV exposure, genetic predisposition, chemical or infection exposureTypes of Skin Cancers:1. Basal cell carcinoma

· most common type of skin cancer· affects cells in the stratum basale

· least malignant · effects stratum geminativum · sun exposed areas of face · removal or destruction of the tumor cures most cases

2. Squamous cell carcinoma· effect statum spinosum · scalp, ears, lower lip and hands · grows rapidly · removal or destruction of tumor cures most cases

3. Malignant melanoma· cancer of melanocytes · most dangerous · usually develops in pigmented moles, but can appear spontaneously