Chapter 5: The Integumentary System Flashcards

Question

What is **Stratum corneum**? ## Footnote Structure of the Skin

Answer 1

* Few-50 or more rows of dead, flat keratinocytes. * Contain mostly keratin. ## Footnote Structure of the Skin

Answer 2

* Process where cells move from one epidermal layer to the next. * They accumulate more and more keratin. * Newly formed cells in stratum basale slowly pushed to surface. * Eventually, keratinized cells slough off. * Replaced by underlying cells that in turn become keratinized.. ## Footnote Structure of the Skin

Answer 3

* Protein that stimulates cell growth and differentiation. ## Footnote Structure of the Skin

Answer 4

Is the second, deeper part of the skin. Is composed of dense irregular connective tissue containing collagen and elastic fibers. Woven network of ibers has great tensile strength. Has ability to stretch and recoil easily. Much thicker than epidermis. Few vells present in dermis include predominantly fibroblasts, with some macrophages, and a few adipocytes near its boundary with subcutaneous layer. Blood vessels, nerves, glands, hair follicles are embedded in dermal layer. Can be divided into a **thin superficial papillary region** and a **thick deeper reticular region**. ## Footnote Structure of the Skin

Answer 5

Makes up about one-fifth of the tickness of the total layer. Contains thin collagen and fine elastic fibers. Surface area is greatly increased by dermal papillae (small, nipple-shaped structures that project into the undersurface of the epidermis). All dermal papillae contain capillary loops (blood vessels). Some contain tactile receptors called corpuscles of touch (or Meissner corpuscles), nerve endings that are sensitive to touch. Other dermal papillae also contain free nerve endings, dendrites that lack any apparent structural specialization. ## Footnote Structure of the Skin

Answer 6

Reticular region which is attached to the subcutaneous layer, contains bundles of thick collagen fibers, scattered fibroblasts, and various wandering cells (such as macrophages). Some adipose cells can be present in deepest part of the layer, along with some coarse elastic fibers. Collagen fibers in reticular region are arranged in netlike manner and have a more regular arrangement. Hekps the skin resist stretching. Blood vessels, nerves, hair follicles, sebaceous (oil) glands, and sudoriferous (sweat) glands occupy the spaces between fibers. ## Footnote Structure of the Skin

Answer 7

Superficial portion of dermis (about one-fifth); consists of areolar connective tissue with thin collagen and fine elastic fibers; contains dermal ridges that house blood capillaries, corpuscles of touch, and free nerve endings. ## Footnote Structure of the Skin

Answer 8

Deeper portion of dermis (about four-fifths); consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers. Spaces between fibers contain some adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands. ## Footnote Structure of the Skin

Answer 9

Are produced during third month of fetal development as downward projections of the epidermis into the dermis between the dermal papillae of the papillary region. Epidermal ridges create a strong bond between the epidermis and dermis in a region of high mechanical stress. Also increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction. Increases tactile sensitivity. Because ducts of sweat glands open on the tops of epidermal ridges as sweat pores, the sweat and ridges form fingerprints (or footprints) on touching a smooth object. ## Footnote Structure of the Skin

Answer 10

1. Melanin 2. Hemoglobin 3. Carotene The amount of melanin causes skins color to vary from pale yellow to reddish-brown to black. Melanocytes, the melanin-producing cells, are most plentiful in epidermis of penis, nipples of breasts, area just around nipples (areolae), face and limbs. Differences in skin color are due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes. ## Footnote Structure of the Skin

Answer 11

Hair, skin glands and nails are accessory structures of the skin. Develop from the embryonic epidermis. ## Footnote Accessory Structures of the Skin

Answer 12

Are present on most skin surfaces except palms, palmar surfaces of fingers, the soles, and plantar surfaces of feet. In adults, hair most heavily distributed across scalp, in eyebrows, in axillae and around external genitalia. Hairs function in sensing light tough, protection from foreign particles. Hairs are growth of epidermis comprosed of dead, keratinized epidermal cells. ## Footnote Accessory Structures of the Skin

Answer 13

The superficial portion of the hair, which projects above the surface of the skin. ## Footnote Accessory Structures of the Skin

Answer 14

The portion of the hair deep to the shaft that penetrates into the dermis, and sometimes into sibcutaneous layer. The shaft and root of the hair both consist of three concenrtic layers of cells: 1. Medulla 2. Cortex 3. Cuticle ## Footnote Accessory Structures of the Skin

Answer 15

**Hair shaft** is the superficial portion of the hair. **Hair root** is portion of the hair deep to the shaft that penetrates into the dermis. Shaft and root of hair consist of 3 subcutaneous layers of cells: medulla, cortex, and cuticle of the hair. **Inner medulla** is composed of 2-3 rowas of irregularly shaped cells that contain large armount of pigment granules in dark hair, small amounts of pigment granules in gray hair, and a lack of pigment granules and present of air bubbles in white hair. **Middle cortex** forms major part of shaft and consists of elongated cells. **Cuticle of the hair**, the outermost layer, consists of a single layer of thin, flat cells that are most heavily keratinized. ## Footnote Accessory Structures of the Skin

Answer 16

Surrounds the root of the hair, which is made up of an **external root sheath** and an **internal rooth sheath**. The external root sheath is a downward continuation of the epidermis. The internal root sheath is produced by the matrix and forms a cellular tubular sheath of epithelium between the external root sheath and the hair. Together, external and internal root sheaths are referred to as the **epithelial root sheath**. Dense dermis surrounding the hair follicle is called the **dermal root sheath**. Base of each hair follicle and its surrounding dermal root sheath is an onion-shaped structure, the **hair bulb**. This structure houses a nipple-shaped indentation, the **papilla of the hair**, which contains areolar connective tissue and many blood vessels that nourish the growing hair follicle. Bulb also contains a germinal layer of cells called **hair matrix**. Sebaceous (oil) glands and a bundle of smooth muscle cells are also assiated with hairs. The smooth muscle is the arrector pili. Surrounding each hair follicle are dendrites of neurins that form a **hair root plexus**, which is sensitive to touch. Hair root plexuses generate nerve impulses if their hair shafts are moved. ## Footnote Accessory Structures of the Skin

Answer 17

Also called oil glands, are simple, branched acinar (rounded) glands. WIth few exceptions, they are connected to hair follicles. Secreting portion of a sebaceous gland lies in the dermis and usually opens into the neck of hair follicle. Secrete oily substance called sebum, a mixture of triglycerides, cholesterol, proteins, and inorganic salts. ## Footnote Accessory Structures of the Skin

Answer 18

There are 3-4 million in the body. Also called sweat glands. Cells of these glands release sweat, or perspiration, into hair follicles or onto skin surface through pores. Sweat glands are divided into 2 main types, **eccrine** and **apocrine**, based on their structure and type of secretion. ## Footnote Accessory Structures of the Skin

Answer 19

Are simple, coiled tubular glands that are much more common than apocrine sweat glands. Distributed throughout the skin of most regions of the body, especially in the skin of forehead, palms, and soles. Secretory portion of eccrine sweat glands is located mostly in deep dermis. Excretory duct projects through dermis and epidermis and ends as a pore at surface of epidermis. ## Footnote Accessory Structures of the Skin

Answer 20

The homeostatic regulation of body temperature. ## Footnote Accessory Structures of the Skin

Answer 21

Simple, coiled tubular glands but have larger ducts and lumens than eccrine glands. Found mainly in skin of axilla, groin, areolae of the breasts, and bearded regions of the face in adult males. Their secretion is via exocytosis, which is chanracteristic of eccrine glands. Secretory portion of these sweat glands is located in the lower dermis or upper subcutaneous layer, and the excretory duct opens into hair follicles. Sweat appears milky or yellowish in color. ## Footnote Accessory Structures of the Skin

Answer 22

Are modified sweat glands in the external ear. Produce a waxy lubricating secretion. Secretory portions of ceruminous glands lie in the subcutaneous later, deep to sebaceous glands. Excretory ducts open either directly onto surface of the external auditory canal or into ducts of sebaceous glands. Combined secretion of ceruminous and sebaceous glands is a yellowish material called **cerumen** or earwax. ## Footnote Accessory Structures of the Skin

Answer 23

**Distribution**: Largely in lips, glans penis, labia minora, and tarsal glands; small in trunk and limbs; absent in palms and soles. **Location of secretory portion**: Dermis. **Termination of excretory duct**: Mostly connected to hair follicle. **Secretion**: Sebum (mixture of triglycerides, cholesterol, proteins, and inorganic salts). **Functions**: Prevent hairs from drying out, prevent water loss from skin, keep skin soft, inhibit growth of some bacteria. **Onset of function**: Relatively inactive during childhood; activated during puberty. ## Footnote Accessory Structures of the Skin

Answer 24

**Distribution**: Throughout skin of most regions of body, especially skin of forehead, palms, and soles. **Location of secretory portion**: Mostly in deep dermis (sometimes in upper subcutaneous layer). **Termination of excretory duct**: Surface of epidermis. **Secretion**: Perspiration, which consists of water, ions (Na+, Cl-), urea, uric acid, ammonia, amino acids, glucose, and lactic acid. **Function**: Regulation of body temperature, waste removal, stimulated during emotional stress. **Onset of function**: Soon after birth. ## Footnote Accessory Structures of the Skin

Answer 25

**Distribution**: Skin of axillae, groin, areolae, bearded region of face, clitoris, and labia minora. **Location of secretory portion**: Mostly in deep dermis and upper subcutaneous layer. **Termination of excretory duct**: Hair follicles. **Secretion**: Perspiration, which consists of same components as eccrine sweat glands plus lipids and proteins. **Functions**: Stimulated during emotional stress and sexual excitement. **Onset of function**: Puberty. ## Footnote Accessory Structures of the Skin

Answer 26

**Distribution**: External auditory canal. **Location of secretory portion**: Subcutaneous layer. **Termination of excretory duct**: Surface of external auditory canal or into ducts of sebaceous glands. **Secretion**: Cerumen, a waxy material. **Functions**: Impede entrance of foreign bodies and insects into external ear canal, waterproof canal, prevent microbes from entering cells. **Onset of function**: Soon after birth. ## Footnote Accessory Structures of the Skin

Answer 27

Are plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of the distal portions of the digits. Each nail consists of nail body, a free edge and a nail root. ## Footnote Accessory Structures of the Skin

Answer 28

The visable portion of the nail. Is comparable to the stratum corneum of the epidermis of the skin with exception that its flattened, keratinized cells fill with a harder type of keratin and the cells are not shed. Below nail body is a region of epithelium and a deeper layer of dermis. Nail body appears pink because blood flowing through capillaries in the underlying dermis. ## Footnote Accessory Structures of the Skin

Answer 29

The part of the nail body that may extend past the distal end of the digit. Free edge is white because there are no underlying capillaries. ## Footnote Accessory Structures of the Skin

Answer 30

The portion of the nail that is buried in a fold of skin. The whitish, crescent-shaped area of the proximal end of the nail body is called the lunula. Appears whitish beacause the vascular tissue underneath does not show through due to a thickened region of epithelium in the area. Beneath the free edge is a thickened region of stratum corneum called hyponychium. ## Footnote Accessory Structures of the Skin

Answer 31

Is the skin below the nail plate that extends from the lunula to the hyponychium. Epidermis of the nail bed lacks a stratum granulosum. The eponychium or cuticle is a narrow band of epidermis that extends from and adheres to margin of the nail wall. ## Footnote Accessory Structures of the Skin

Answer 32

It is a small torn piece of skin at the side or base of a fingernail or toenail, usually caused by dryness of the eponychium. ## Footnote Accessory Structures of the Skin

Answer 33

Is the portion of the epithelium proximal to the nail root. The superficial nail matrix cells divide mitotically to produce new nail cells. Growth rate of nails is determined by the rate of mitosis in matrix cells, which is influenced by factors such as a person's age, health and nutritional status. ## Footnote Accessory Structures of the Skin

Answer 34

1. Protect the distal end of the digits. 2. Provide support and counterpressure to the palmar surface of the fingers to enhance touch perception and manipulation. 3. Allow us to grasp and manipulate small objects, and they can be used to scratch and groom the body in various ways. ## Footnote Accessory Structures of the Skin

Answer 35

Include thermoregulation, storage of blood, protection, cutaneous sensations, excretion and absorption, and synthesis of vitamin D. ## Footnote Functions of the skin

Answer 36

The homestatic regulation of body temperature. Skin contributes in 2 ways: by liberating sweat at its surface and by adjusting the flow of blood in the dermis. In response to low environmental temperature, production of sweat from eccrine sweat glands is decreased, which helps conserve heat. Blood vessels in the dermis of skin constrict, which decreases blood low through the skin and reduces heat loss from body. Skeletal muscle contractions generate body heat. ## Footnote Functions of the Skin

Answer 37

Extensive network of blood vessels that carry 8-10% of the total blood flow in a resting adult, is located in the dermis. For this reason, the skin acts as a blood reservoir. ## Footnote Functions of the Skin

Answer 38

Skin provides protection in various ways. Keratin protects underlying tissues from microbes, abrasions, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes. Lipids released by lamellar granules inhibit evaporation of water from skin surface, thus guarding against dehydration. Oily sebum from sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals. Acidic pH of perspiration retards the growth of some microbes. Pigment melanin helps shield against effects of UV light. ## Footnote Functions of the Skin

Answer 39

There is a wide variety of nerve endings and receptors distributed throughout the skin, including tactile discs of the epidermis, the corpuscles of touch in the dermis, and hair root plexuses around each hair follicle. Sensation of pain, is usually an indication of impending or actual tissue damage. ## Footnote Functions of the Skin

Answer 40

Skin normally has small role in exretion and absorption. About 400mL of water evaporates through skin daily. Sweat removes water and heat from the body, also is the vehicle for excretion of small amounts of salt, carbon dioxide, and two organic molecules that result from breakdown of proteins-ammonia and urea. Certain lipid-soluble materials do penetrate the skin. These include fat-soluble vitamines (A, D, E, and K), certain drugs, and gases oxygen and carbon dioxide. ## Footnote Functions of the Skin

Answer 41

Synthesis of Vitamin D requires activation of a precursor molecule in the skin by UV rays in sunlight. Enzymes in liver and kidneys then modify the activated molecule, finally producing calcitriol, the most active form of vitamin D. Calcitriol is a hormone that aids in absorption of calcium from foods in GI tract into blood. Vitamin D is believed to enhance phagocytic activity, increase production of antimicrobial substances in phagocytes, regulate immune functions, and help reduce inflammation. ## Footnote Functions of the Skin