Chapter Five Notes - Integumentary System PDF

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Bio 22 - Introductory Human Anatomy w/ Changaris
Notes on the integumentary system....

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Chapter Five: Integumentary System Study Questions Learning Objectives Describe the general structure of the integument. The integument, or skin, is the body’s largest organ, consisting of different tissue types that collectively perform specific activities. Consists of two distinct layers: Epidermis • cornified stratified squamous epithelium • avascular • acquires nutrients through diffusion from the underlying dermis Dermis – papillary layer • loose irregular connective tissue Dermis – reticular layer  dense irregular connective tissue

Identify the varied functions of the integument. The integument’s functions include providing mechanical protection and a physical barrier, protecting against water loss and microbial invasion, regulating temperature, aiding metabolism, contributing to immune defense, perceiving sensations, and excreting wastes through secretion

Describe the structure, composition and arrangement, and functions of the epidermal strata. Stratum Basale • deepest epidermal layer • single layer of cuboidal to low columnar cells • tightly attached to an underlying basement membrane that separates the epidermis from the connective tissue of the dermis

mitotic layer site of origin of tonofilaments occupied by three cells: • keratinocytes: stem cells that divide to provide both replacement stem cells and new keratinocytes that replace dead ones that shed from the surface; play a role in keratin synthesis; gives skin its strength and makes it waterproof; the most abundant cell in the epidermis • melanocytes: produce and store the pigment melanin; have long, branching cytoplasmic processes; • tactile cells: few in number and scattered, sensitive to touch; release chemicals that stimulate sensory nerve endings when compressed Stratum Spinosum • several layers of polygonal keratinocytes • keratinocytes that enter this layer from the stratum basale become non-dividing, highly specialized keratinocytes that attach to desmosomes • spiny appearance of cells due to shrinkage of cells from points of attachment • keratohyalin granule synthesis begins in this layer • contains the epidermal dendritic cells (immune cells that help fight epidermal function) Stratum Granulosum • consists of 3-5 layers of keratinocytes superficial to the stratum spinosum • flattened cells • two types of granules in the stratum granulosum: • keratohyalin granules: involved in the keratinization process • lamellar granules: fuse with the plasma membrane and extrude contents (lipids) into the extracellular (intercellular?) space • lipids serve as a water barrier to prevent water loss and protective functions of the skin • keratinization begins in this layer, by which the keratinocytes fill up with keratin • nuclei and organelles in this layer begin to degenerate and the cells start to die (part of keratinization process) Stratum Lucidum • thin, translucent region about 2-3 cell layers thick • only found in thick skin, such as the palms of the hand and soles of the feet • cells appear pale and featureless with indistinct boundaries (dead cells) • keratinocytes are flattened and filled with the protein eleidin (intermediate product in keratin maturation) • considered an artifact by dermatologists Stratum Corneum • most superficial layer of the epidermis • observable as the outermost layer of skin • consists of 20-30 layers of dead, scaly, interlocking keratinized cells called corneocytes, which are anucleate (lack a nucleus) and tightly packed together • contains large amounts of keratin, which are sloughed off from its external surface • normally dry and presents a thickened surface unsuitable for the growth of microorganisms • contains tonofilaments embedded in keratohyalin granules • • •

Identify the epidermal variations in thickness, color, and markings. Thick skin is found on the palms of the hands, the soles of the feet, and corresponding surfaces of the fingers and toes. • all five epidermal strata occur • contains sweat glands, but no hair follicles or sebaceous glands Thin skin covers most of the body. • lacks the stratum lucidum • contains hair follicles, sebaceous glands, and sweat glands Normal skin color is the result of a combination of hemoglobin in the blood of the dermis and variable quantities of pigments melanin and carotene.

Describe the organization and function of the layers of the dermis. Papillary Layer • superficial region of the dermis directly adjacent to the epidermis

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composed of loose (aerolar) irregular connective tissue forms dermal papillae which project toward the dermis, interlocking with deep projections called epidermal ridges • dermal papillae and epidermal ridges increase the area of contact between the epidermis and dermis and connect these areas contributes to reticular lamina layer of the basement membrane of the epidermis contains capillaries that supply nutrients to the cells of the epidermis houses sensory receptors (Meissner’s corpuscles) that continuously monitor touch on the surface of the epidermis

Reticular Layer • forms the deeper, major portion of the dermis • extends from the thin, overlying papillary layer to the underlying subcutaneous layer (adipose tissue) • consists primarily of dense irregular connective tissue through which large bundles of collagen fibers project in all directions • interwoven into a meshwork that surrounds structures within • contains hair follicles and arrector pili, sebaceous glands, sweat (eccrine and apocrine) glands, nerve, and blood vessels • Pacinian corpuscles • Krause (non-encapsulated nerve endings for temperature) • Ruffini (non-encapsulated nerve endings for vibration)

Identify nerve and blood supply to the dermis. Vasoconstriction of dermal blood vessels causes decreased circulation to the skin and a corresponding conservation of heat in the blood. Vasodilation of dermal blood vessels causes increased circulation to the skin and loss of excess heat.

Identify and describe the structure and function of the subcutaneous layer. Also called the hypodermis layer, the subcutaneous layer is not considered part of the integument. This layer consists of both loose connective tissue and adipose connective tissue (fat layer). The connective fibers of the reticular layer of the dermis are extensively interwoven with those of the subcutaneous layer to stabilize the position of the skin and bind it to the underlying tissues. The subcutaneous layer pads and protects the body and its parts, acts as an energy reservoir, and provides thermal insulation.

Describe the structure and function of nails. Nails are scalelike modifications formed from stratum corneum and protect the exposed distal tips of the fingers and toes and prevent damage or distortion when the fingers or toes are subjected to mechanical stress.

Identify the components of a hair and a hair follicle. A single hair has the shape of a slender filament, and is composed of keratinized cells growing from hair follicles that extend deep in the dermis. Three zones can be recognized along the length of a hair: • Hair bulb • consists of living epithelial cells • a swelling at the base where the hair originates in the dermis • surrounds a small hair papilla (small amount of connective tissue containing tiny blood vessels and nerves) • Hair root • portion of the hair deep in the skin surface • consists of dead epithelial cells • Hair shaf • portion of the hair that extends beyond the skin surface • consists of dead epithelial cells Hair production involves a special type of keratinization that occurs in the hair matrix, where basal epithelial cells divide and produce daughter cells that are pushed toward the surface Medulla: is a remnant of the sof core of the matrix, composed of loosely arranged cells and air spaces, and contains flexible, sof keratin. Cortex: several layers of flattened cells closer to the outer surface of the developing hair Hair follicle: an oblique tube that surrounds the root hair; always extends into the dermis and sometimes into the subcutaneous layer Connective tissue root sheath: outer concentric layer of the follicle wall originating from the dermis Epithelial tissue root sheath: inner concentric layer of the follicle wall originating from the epidermis • internal root sheath: surrounds the hair and deep part of the shaf; produced by peripheral cells of the matrix; cells are quickly destroyed • external root sheath: extends between the skin surface and hair matix Arrector pili: thin ribbons of smooth muscles that extend from the dermal papillae to the mid-region of hair follicles; usually stimulated in response to an emotional state or exposure to cold temperatures to produce “goosebumps”

Identify and describe the characteristics of sweat glands, sebaceous glands, and other glands found in the skin. Sweat glands produce a watery solution that performs specific functions. • coiled, tubular secretory portion is the reticular dermis layer or the subcutaneous layer • sweat gland duct carries the secretion to the surface of the epidermis (eccrine) or hair follicle (apocrine) • the opening of the sweat gland duct is a sweat pore Merocrine (eccrine) sweat glands • simple, coiled, tubular glands that release secretions onto skin surface • most numerous in the palms of the hand, soles of the feet, forehead, and back • clear secretion produced is termed sweat, and is a mixture of water, sodium/chloride ions, urea, and uric acid • controlled by the nervous system • functions include thermoregulation of body temperature, secretion of excess water and electrolytes, and protection against environmental hazards

Apocrine sweat glands • simple, coiled, tubular glands that release secretions into hair follicles • located in axillary and anogenital regions (armpit, nipples, groin, and anus) • secretion is viscous, cloudy, and composed of lipids and proteins that are acted upon by bacteria (producing an odor) • secretion is influenced by hormones and may function in both signaling and communication • ceruminous (wax) glands are modified apocrine glands that secrete wax (in outer ear canal) • mammary glands are modified apocrine glands that secrete milk Sebaceous Glands (Oil glands) • holocrine glands that discharge and oily, waxy secretion callem sebum (mixture of fats, cholesterol, proteins, and salts) • secretions are usually released into a hair follicle • some secretions are released directly onto the skin (lips, glans of penis, labia minora, nipple, areola of breast) • sebum functions as a lubricant to keep the skin and hair from becoming dry, brittle, and cracked • distributed over most of the body except the palms and soles; most abundant on face and scalp • sebum has bactericidal properties

Challenge Yourself Matching Match each numbered items with the most closely related lettered item. 1. 2. 3. 4. 5. 6.

Integument: (g) composed of epidermis and dermis Fingernails: (e) formed from stratum corneum Keratin: (i) fibrous protein in epidermis Tactile cells: (f) receptors for touch Melanocytes: (j) pigment forming cells Keratinocytes: (b) most numerous epidermal cell

7. 8. 9. 10.

Epidermal dendritic cell: (c) a phagocytic cell (active in immune response) Subcutaneous layer: (d) layer deep to the dermis Reticular layer: (h) dense irregular connective tissue Arrector pili: (a) smooth muscle attached to hair follicle

Multiple Choice Select the best answer from the four choices provided. 1.

Strawberry-colored birthmarks are also called a. cavernous hemangiomas b. freckles c. capillary hemangiomas d. erythema

2.

The layer of the epidermis in which cells begin the process of keratinization is the a. stratum corneum b. stratum basale c. stratum lucidum d. stratum granulosum

3.

The sweat glands that communicate with skin surfaces only in the axillary, areolar, pubic, and anal regions are a. apocrine glands b. merocrine glands c. sebaceous glands d. all of these are correct

4.

Which of the following is not a function of the integument? a. acts as a physical barrier b. stores calcium in the dermis c. regulates temperature through vasoconstriction and vasodilation of dermal blood vessels d. participates in immune defense

5.

Which of the following layers contains areolar connective tissue and dermal papillae? a. reticular layer b. subcutaneous layer c. papillary layer d. epidermis

6.

Melanin is a. an orange-yellow pigment that strengthens the epidermis b. a pigment that accumulates inside keratinocytes c. a protein fiber found in the dermis d. a pigment that gives the characteristic color to hemoglobin

7.

The layer of squamous epithelium that forms by the seventh week of development to give rise to the integument is the a. mesenchyme b. periderm

c. d.

basal layer sebaceous layer

8.

The cells in a hair follicle that are responsible for forming hair are the a. papillary cells b. matrix cells c. medullary cells d. cortex cells

9.

Which epidermal cell type is responsible for detecting touch sensations? a. keratinocyte b. melanocyte c. tactile cell d. epidermal dendritic cell

10. Water loss due to evaporation of interstitial fluid through the surface of the skin is termed a. latent perspiration b. sensible perspiration c. active perspiration d. insensible perspiration

Content Review 1.

What effect does the protein keratin have on both the appearance and the function of the integument? Cells filled with keratin are strong, so they assist the protective and physical barrier functions of the integument.

2.

Describe two ways in which the skin helps regulate body temperature. Vasodilation of blood vessels in the dermis allows excess heat to dissipate through the skin and be lost. Merocrine sweat glands secrete a thin, watery fluid called perspiration that helps remove heat from the body as it evaporates.

3.

List the layers of the epidermis from deep to superficial and compare their structure. The presence of many blood vessels in the subcutaneous layer promotes rapid absorption of material absorbed into the extracellular fluid.

4.

Identify and distinguish among the three types of hair produced during a person’s lifetime. Lanugo is fine, unpigmented, downy hair that first appears on the fetus in the second trimester of development. Vellus is unpigmented or lightly pigmented human hair that has replaced most of the lanugo at birth. It is the primary human hair and found on most of the body. Terminal hair is coarser, pigmented, and longer than vellus. It grows on the scalp and is also the hair of eyebrows and eyelids. At puberty, vellus is replaced by terminal hair in the axillary and pubic regions.

5.

List and discuss the three zones along the length of a hair. Along the length of a hair there are three recognizable zones: (1) the hair bulb consists of epithelial cells and is a swelling at the base where the hair originates in the dermis; the epithelium at the base of the bulb surrounds a small hair papilla, which is composed of a small amount of connective tissue containing tiny blood vessels; (2) the root is within the follicle internal to the skin surface, and (3) the shaf is that portion of the hair that extends beyond the skin surface.

6.

How do apocrine and merocrine sweat glands differ in structure and function? Apocrine sweat glands are simple coiled, tubular glands that release their secretion into hair follicles at the armpit (axillae), around the nipples (areola), in the groin (pubis), and around the axons (anal region). They secrete a viscous, cloudy, protein- and lipid-containing product that is acted upon by bacterium, producing a distinct, noticeable odor solution that is probably used as a communicating material. Merocrine sweat glands are simple coiled, tubular glands that release their product onto the surface of the skin. Their secretory product is a thin, watery solution that functions in thermoregulation, secretion, and anti-bacterial protection.

7.

Describe how the skin is involved in vitamin D production. Vitamin D3 is a cholesterol derivative synthesized from cholecalciferol, which is produced by some epidermal cells when they are exposed to ultraviolet radiation. Calcitriol is synthesized from the cholecalciferol by some endocrine cells in the kidney. Calcitriol is the active form of vitamin D3.

8.

Briefly discuss the origin and function of sebum. Sebum is produced by sebaceous glands. It is an oily, waxy secretion that has some bactericidal properties.

9.

Describe the four steps in wound repair of the integument. (1) Bleeding into the wound; clotting proteins and platelets halt bleeding. White blood cells and antibodies clean the wound and fight infection that may have been introduced. (2) A blood clot forms; internal to the clot, macrophages and neutrophils clean the wound of cellular debris. (3) Damaged blood vessels regenerate and grow in the wound. A sof mass deep in the wound becomes granulation tissue that initially forms in a healing wound. Macrophages remove the clotted blood. Fibroblasts produce new collagen in the region. (4) Epithelial regeneration of the epidermis occurs. These new epithelial cells migrate over the wound, creeping internally to the now superficial remains of the clot (the scab). The connective tissue is replaced by fibrosis.

10. What are some effects of aging on the integument? Aging causes the following changes in the integument: increased time to repair damage, decreased elasticity, diminished immune response due to fewer epidermal dendritic cells, increased dryness, altered pigmentation, diminished sweat production, thinning or loss of hair, and diminished vitamin D production....