Chapter 5

Question 1

Integumentary system

Answer 1

System composed of the skin, hair, oil and sweat glands, nails, and sensory receptors.

Question 2

Skin

Answer 2

AKA cutaneous membrane; covers the external surface of the body and is the largest organ of the body in weight.

Question 3

What are the two main parts that skin consists of?

Answer 3

Epidermis and dermis

Question 4

Epidermis

Answer 4

The superficial, thinner portion, which is composed of epithelial tissue; is avascular (therefore, if you cut the epidermis, there is no bleeding); composed of keratinized stratified squamous epithelium.

Question 5

What are the four principle types of cells found in the epidermis?

Answer 5

Keratinocytes, melanocytes, intraepidermal macrophages, and tactile epithelium

Question 6

Keratinocytes

Answer 6

~90% of epidermal cells; arranged in four or five layers and produce the protein keratin and lamellar granules.

Question 7

Keratin

Answer 7

A tough fibrous protein that helps protect the skin and underlying tissues from abrasions, heat, microbes, and chemicals.

Question 8

Lamellar granules

Answer 8

Release a water-repellent sealant that decreases water entry and loss and inhibits the entry of foreign materials

Question 9

Melanocytes

Answer 9

~8% of epidermal cells; develop from the ectoderm of a developing embryo and produce the pigment melanin. Their long, slender projections extend between the keratinocytes and transfer melanin granules to them. Once inside the keratinocytes, the melanin granules cluster to form a protective veil over the nucleus, on the side towards the skin surface. They do this to shield the nuclear DNA from damage by UV light. Although their melanin granules effectively protect keratinocytes, melanocytes themselves are particularly susceptible to damage by UV light.

Question 10

Melanin

Answer 10

A yellow-red, or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet (UV) light.

Question 11

Intraepidermal macrophages

Answer 11

AKA Langerhans cells; arise from red bone marrow and migrate to the epidermis, where they constitute a small fraction of the epidermal cells; they participate in immune responses mounted against microbes that invade the skin and are easily damaged by UV light; their role in the immune response is to help other cells of the immune system recognize an invading microbe and destroy it.

Question 12

Tactile epithelium

Answer 12

AKA Merkel cells; are the least numerous of the epidermal cells; they are located in the deepest layer of the epidermal cells, where they contact the tactile discs (AKA Merkel’s disks); tactile epithelial cells and tactile disks detect touch sensations.

Question 13

Subcutaneous layer

Answer 13

AKA the hypodermis; deep to the dermis, but not part of the skin; this layer consists of areolar and adipose tissues. Fibers that extend from the dermis anchor the skin to the subcutaneous layer, which in turn attaches to underlying fascia, the connective tissue around muscles and bones; the subcutaneous layer serves as a storage depot for fat and contains large blood vessels that supply the skin.

Question 14

Lamellated corpuscles

Answer 14

AKA Pacinian corpuscles; nerve endings that are sensitive to pressure; the subcutaneous layer, and sometimes the dermis, contain these.

Question 15

What are the layers of the epidermis?

Answer 15

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

Question 16

Stratum basale

Answer 16

Deepest layer, composed of single row of cuboidal or columnar keratinocytes that contain scattered keratin intermediate filaments (tonofilaments); stem cells undergo cell division to produce new keratinocytes; melanocytes and tactile epithelial cells associated with tactile discs are scattered among keratinocytes.

Question 17

Stratum spinosum

Answer 17

Eight to ten rows of many-sided keratinocytes with bundles of keratin intermediate filaments; contains projections of melanocytes and intraepidermal macrophages.

Question 18

Stratum granulosum

Answer 18

Three to five rows of flattened keratinocytes, in
which organelles are beginning to degenerate; cells contain the protein keratohyalin (converts keratin intermediate filaments into keratin) and lamellar granules (release lipid-rich, water-repellent secretion).

Question 19

Stratum lucidum

Answer 19

Present only in skin of fingertips, palms, and soles; consists of four to six rows of clear, flat, dead keratinocytes with large amounts of keratin.

Question 20

Stratum corneum

Answer 20

Few to 50 or more rows of dead, flat keratinocytes that contain mostly keratin.

Question 21

Callus

Answer 21

An abnormal thickening of the stratum corneum.

Question 22

Keratinization

Answer 22

A process in which newly formed cells in the stratum basale are slowly pushed to the surface. As the cells move from one epidermal layer to the next, they accumulate more and more keratin. Then they undergo apoptosis. Eventually the keratinized cells slough off and are replaced by underlying cells that in turn become keratinized; process takes between four to six weeks.

Question 23

Epidermal growth factor (EGF)

Answer 23

Hormonelike proteins that play a role in regulating growth of the epidermis.

Question 24

Dermis

Answer 24

The deeper, thicker connective tissue portion; is vascular (therefore, if a cut penetrates to the dermis, there is bleeding); is composed of dense irregular connective tissue containing collagen and elastic fibers. This network of fibers has great tensile strength (resists pulling or stretching forces); the dermis also has the ability to stretch and recoil easily; it is much thicker than the epidermis.

Question 25

What are the two regions that the dermis can be divided into?

Answer 25

Papillary region and reticular region

Question 26

Papillary region

Answer 26

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.

Question 27

Dermal papillae

Answer 27

Small, nipple-shaped structures that project into the undersurface of the epidermis and increase the surface area of the papillary region.

Question 28

Capillary loops

Answer 28

Blood vessels; all dermal papillae contain them.

Question 29

Corpuscles of touch

Answer 29

AKA Meissner corpuscles; nerve endings that are sensitive to touch; some dermal papillae contain them.

Question 30

Free nerve endings

Answer 30

Dendrites that lack any apparent structural specialization; different free nerve endings initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching; some dermal papillae contain them.

Question 31

Reticular region

Answer 31

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.

Question 32

Extensibility

Answer 32

The ability to stretch; the combination of collagen and elastic fibers in the reticular region allows for this.

Question 33

Elasticity

Answer 33

The ability to return to original shape after stretching; the combination of collagen and elastic fibers in the reticular region allows for this. (Eg. Seen around joints and in pregnancy and obesity).

Question 34

Epidermal ridges

Answer 34

Found on the palms, fingers, soles, and toes, and appear either as either as straight lines or as a pattern of loops and whorls; epidermal ridges create a strong bond between the epidermis and dermis in a region of high mechanical stress; the epidermal ridges also increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction; finally, the epidermal ridges greatly increase surface area. Which increases the number of corpuscles of touch and thus increase tactile sensitivity; because the ducts of sweat glands open on the top of epidermal ridges as sweat pores, the sweat and ridges form fingerprints (or footprints) on touching a smooth object.

Question 35

Explain the basis for different skin colors

Answer 35

Melanin, hemoglobin, and carotene are three pigments that impact a wide variety of colors of skin. The amount of melanin causes the skin’s color to vary from pale yellow to reddish-brown to black. The number of melanocytes, the melanin-producing cells, is about the same in all people, so differences in skin color are due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes

Question 36

Hairs

Answer 36

Genetic and hormonal influences largely determine the thickness and the pattern of the hair distribution; hair on the head guards the scalp from injury in the sun’s rays. It also decreases heat loss from the scalp; eyebrows/eyelashes protect the eyes from foreign particles, similar to the way hair in the nostrils and in the external ear canal defends those structures; touch receptors (hair root plexuses) associated with hair follicles are activated whenever a hair is moved even slightly. Thus, hairs also function in sensing light touch.

Question 37

Hair shaft

Answer 37

Superficial portion of the hair, which projects above the surface of the skin.

Question 38

Hair root

Answer 38

Portion of the hair deep to the shaft the penetrates into the dermis, and sometimes into the subcutaneous layer.

Question 39

What three layers do the shaft and root of the hair consist of?

Answer 39

Medulla, cortex, and cuticle of the hair

Question 40

Medulla (of the shaft and root of the hair)

Answer 40

Inner layer; may be lacking in thinner hair; composed of two or three rows of irregular shaped cells that contain large amounts of pigment granules in dark hair, small amounts of pigment granules in gray hair, and lack pigment granules and the presence of air bubbles in white hair.

Question 41

Cortex (of the shaft and root of the hair)

Answer 41

Middle layer; forms the major part of the shaft and consists of elongated cells.

Question 42

Cuticle of the hair

Answer 42

Outermost layer; consists of a single layer of thin, flat cells that are most heavily keratinized. Cuticle cells on the shaft are arranged like shingles on the side of a house, with their free edges pointing toward the end of the hair.

Question 43

Hair follicle

Answer 43

Made up of an external root sheath and an internal root sheath; external root sheath is a downward continuation of the epidermis; the internal root sheath is produced by a matrix and forms cellular tubular sheath of epithelium between the external root sheath and the hair.

Question 44

Together, the external and internal root sheath are referred to as the ______.

Answer 44

Epithelial root sheath

Question 45

Dermal root sheath

Answer 45

Dense dermis surrounding hair follicle.

Question 46

Hair bulb

Answer 46

Onion-shaped structure that are at the base of each hair follicle and its surrounding dermal root sheath.

Question 47

Papilla of the hair

Answer 47

Nipple-shaped indentation which contains areolar connective tissue and many blood vessels that nourish the growing hair follicle.

Question 48

Hair matrix

Answer 48

A germinal layer of cells in the hair bulb; the hair matrix cells arise from the stratum basale, the site of cell division; hence, hair matrix cells are responsible for the growth of existing hairs, and they produce new hairs when old hairs are shed; this replacement process occurs within the same follicle; hair matrix cells also give rise to the cells of the internal root sheath.

Question 49

Arrector pilli

Answer 49

Smooth muscle cells associated with hairs; extends from the superficial dermis in the skin to the dermal root sheath around the side of the hair follicle; in it’s normal position, hair emerges at a less than 90-degree angle to the surface of the skin. Under physiological or emotional stress, such as cold or fright, autonomic nerve endings stimulate the arrector pili muscles to contract, which pulls the hair shafts perpendicular to the skin surface. This action causes “goose bumps” or “gooseflesh” because the skin around the shaft forms slight elevations.

Question 50

Hair root plexus

Answer 50

Dendrites of neurons surrounding each hair follicle; are sensitive to touch. Generate nerve impulses if their hair shafts are moved.

Question 51

Sebaceous glands are also known as ______.

Answer 51

Oil glands

Question 52

Describe the distribution of sebaceous (oil) glands

Answer 52

Largely in lips, glans penis, labia minora, and tarsal glands; small in trunk and limbs; absent in palms and soles.

Question 53

Describe the location of the secretory portion of sebaceous (oil) glands

Answer 53

Dermis

Question 54

Where is the termination of excretory ducts of sebaceous (oil) glands?

Answer 54

Mostly connected to hair follicle.

Question 55

What do sebaceous (oil) glands secrete?

Answer 55

Sebum (mixture of triglycerides, cholesterol, proteins, and inorganic salts).

Question 56

Describe the functions of sebaceous (oil) glands

Answer 56

Prevent hairs from drying out, prevent water loss from skin, keep skin soft, inhibit growth of some bacteria.

Question 57

What is the onset of function for sebaceous (oil) glands?

Answer 57

Relatively inactive during childhood; activated during puberty.

Question 58

Sudoriferous glands are also known as ______.

Answer 58

Sweat glands

Question 59

Describe the distribution of eccrine sweat glands

Answer 59

Throughout skin of most regions of body, especially skin of forehead, palms, and soles.

Question 60

Describe the location of the secretory portion of eccrine sweat glands

Answer 60

Mostly in deep dermis (sometimes in upper subcutaneous layer).

Question 61

Where is the termination of excretory ducts of eccrine sweat glands?

Answer 61

Surface of epidermis.

Question 62

What do eccrine sweat glands secrete?

Answer 62

Perspiration, which consists of water, ions (Na+, Cl−), urea, uric acid, ammonia, amino acids, glucose, and lactic acid.

Question 63

Describe the functions of eccrine sweat glands

Answer 63

Regulation of body temperature, waste removal, stimulated during emotional stress.

Question 64

What is the onset of function for eccrine sweat glands?

Answer 64

Soon after birth.

Question 65

Thermoregulation

Answer 65

The homeostatic regulation of body temperature.

Question 66

Thermoregulatory sweating

Answer 66

Helping the body achieve thermoregulation; during thermoregulatory sweating, sweat first forms on the forehead and scalp and then extends to the rest of the body, forming last on the palms and soles.

Question 67

Insensible perspiration

Answer 67

Sweat the evaporates from the skin before it is perceived as moisture.

Question 68

Sensible perspiration

Answer 68

Sweat that is excreted in large amounts and is seen as moisture on the skin.

Question 69

Emotional sweating

Answer 69

AKA cold sweating; sweat in response to an emotional stress such as fear or embarrassment; in contrast to thermoregulatory sweating, emotional sweating first occurs on the palms, soles, and axillae, and then spreads to other areas of the body.

Question 70

Describe the distribution of apocrine sweat glands

Answer 70

Skin of axillae, groin, areolae, bearded regions of face, clitoris, and labia minora.

Question 71

Describe the location of the secretory portion of apocrine sweat glands

Answer 71

Mostly in deep dermis and upper subcutaneous layer.

Question 72

Where is the termination of excretory ducts of apocrine sweat glands?

Answer 72

Hair follicles.

Question 73

What do apocrine sweat glands secrete?

Answer 73

Perspiration, which consists of same components as eccrine sweat glands plus lipids and proteins.

Question 74

Describe the functions of apocrine sweat glands

Answer 74

Stimulated during emotional stress and sexual excitement.

Question 75

What is the onset of function for apocrine sweat glands?

Answer 75

Puberty.

Question 76

Describe the distribution of ceruminous glands

Answer 76

External auditory canal.

Question 77

Describe the location of the secretory portion of ceruminous glands

Answer 77

Subcutaneous layer.

Question 78

Where is the termination of excretory ducts of ceruminous glands?

Answer 78

Surface of external auditory canal or into ducts of sebaceous glands.

Question 79

What do ceruminous glands secrete?

Answer 79

Cerumen, a waxy material. AKA earwax

Question 80

Describe the functions of ceruminous glands

Answer 80

Impede entrance of foreign bodies and insects into external ear canal, waterproof canal, prevent microbes from entering cells.

Question 81

What is the onset of function for ceruminous glands?

Answer 81

Soon after birth

Question 82

What three things do nails consist of?

Answer 82

Nail body, free edge, and nail root

Question 83

Nail body

Answer 83

AKA plate; is the visible portion of the nail; comparable to the stratum corneum of the epidermis of the skin, with the exception that its flattened, keratinized cells fill with a harder type of keratin and the cells are not shed; below the nail body is a region of epithelium and a deeper layer of dermis; most of the nail body appears pink because of blood flowing through the capillaries in the underlying dermis.

Question 84

Free edge

Answer 84

Part of the nail body that may extend past the distal end of the digit; the free edge is white because there are no underlying capillaries.

Question 85

Nail root

Answer 85

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. It appears whitish because the vascular tissue underneath does not show through due to a thickened region of epithelium in the area.

Question 86

Hyponychium

Answer 86

Thickened region of the stratum corneum that is just beneath the free edge; junction between the free edge and skin of the fingertip and secures the nail to the fingertip.

Question 87

Nail bed

Answer 87

Skin below the nail plate that extends from the lunula to the hyponychium; the epidermis of the nail bed lacks a stratum granulosum.

Question 88

Eponychium

Answer 88

AKA cuticle; narrow band of epidermis that extends from and adheres to the margin (lateral border) of the nail wall; it occupies the proximal border of the nail and consists of stratum corneum. A hangnail has nothing to do with the nail itself, it is a small torn piece if skin at the side or base of a fingernail or toenail, usually caused by the dryness of the eponychium.

Question 89

Nail matrix

Answer 89

The portion of the epithelium proximal to the nail root. The superficial nail matrix cells divide mitotically to produce new nail cells. The growth 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. Nail growth also varies according to the season, the time of day, and environmental temperature. The growth rate is somewhat slower in toenails. The longer the digit the faster the nail grows.

Question 90

What are the three functions of nails?

Answer 90

1. They protect the distal end of the digits. 2. They provide support and counterpressure to the palmar surface of the fingers to enhance touch perception and manipulation. 3. They allow us to grasp and manipulate small objects, and they can be used to scratch and groom the body in various ways.

Question 91

Describe the distribution of thin skin

Answer 91

All parts of body except areas such as palms, palmar surface of digits, and soles.

Question 92

Describe the epidermal thickness for thin skin?

Answer 92

0.10–0.15 mm (0.004–0.006 in.).

Question 93

Are epidermal strata present in thin skin?

Answer 93

Stratum lucidum essentially lacking; thinner strata spinosum and corneum.

Question 94

Are epidermal ridges present in thin skin?

Answer 94

Lacking due to poorly developed, fewer, and less well-organized dermal papillae.

Question 95

Are hair follicles and arrector pili muscles present in thin skin?

Answer 95

Present

Question 96

Are sebaceous glands present in thin skin?

Answer 96

Present

Question 97

Are sudoriferous glands present in thin skin?

Answer 97

Fewer.

Question 98

Are sensory receptors present in thin skin?

Answer 98

Sparser.

Question 99

Describe the distribution of thick skin

Answer 99

Areas such as palms, palmar surface of digits, and soles.

Question 100

Describe the epidermal thickness for thick skin?

Answer 100

0.6–4.5 mm (0.024–0.18 in.), due mostly to a thicker stratum corneum.

Question 101

Are epidermal strata present in thick skin?

Answer 101

Stratum lucidum present; thicker stratum spinosum and corneum.

Question 102

Are epidermal ridges present in thick skin?

Answer 102

Present due to well-developed and more numerous dermal papillae organized in parallel rows.

Question 103

Are hair follicles and arrector pili muscles present in thick skin?

Answer 103

Absent.

Question 104

Are sebaceous glands present in thick skin?

Answer 104

Absent.

Question 105

Are sudoriferous glands present in thick skin?

Answer 105

More numerous.

Question 106

Are sensory receptors present in thick skin?

Answer 106

Denser.

Question 107

How does the skin contribute to regulation of body temperature?

Answer 107

Contributes to thermoregulation in two ways: 1.) by liberating sweat at its surface and 2.) by adjusting the flow of blood in the dermis.

Question 108

How does the skin contribute to the storage of blood?

Answer 108

Skin acts as a blood reservoir as the dermis houses an extensive network of blood vessels that carry 8-10% of the totally blood flow in a resting adult.

Question 109

How does the skin contribute to protection?

Answer 109

The skin provides protection to the body in various ways; keratin protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes; lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus guarding against dehydration. They also retard entry of water across the skin surface during showers and swims; the oily sebum from the sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals (substances that kill bacteria); the acidic pH of perspiration retards the growth of some microbes; the pigment melanin helps shield against the damaging effects of ultraviolet light.

Question 110

Cutaneous sensations

Answer 110

Sensations that arise in the skin, including tactile sensations – touch, pressure, vibration, and tickling – as well as thermal sensations such as warmth and coolness. Another cutaneous sensation, pain, usually is an indication of impending or actual tissue damage. There is a wide variety of nerve endings and receptors distributed throughout the skin, including the tactile discs of the epidermis, the corpuscles of touch in the dermis, and hair root plexuses around each hair follicle.

Question 111

How does the skin contribute to excretion and absorption?

Answer 111

The skin normally has a small role in excretion, the elimination of substances from the body, and absorption, the passage of materials from the external environment into body cells. Despite the almost waterproof nature of the stratum corneum, about 400 mL of water evaporates through it daily. Besides removing water and heat from the body, sweat also is the vehicle for excretion of small amounts of salts, carbon dioxide, and two organic molecules that result from the breakdown of proteins – ammonia and urea. The absorption of water-soluble substances through the skin is negligible, but certain lipid-soluble materials do penetrate the skin. These include fat-soluble vitamins (A, D, E, and K), certain drugs, and the gases oxygen and carbon dioxide. Toxic materials that can be absorbed through the skin; certain drugs that are absorbed by the skin may be administered by applying adhesive patches to the skin.

Question 112

How does the skin contribute to synthesis of vitamin D?

Answer 112

Requires activation of a precursor molecule in the skin by ultraviolet (UV) rays in sunlight. Enzymes in the 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 the absorption of calcium from foods in the gastrointestinal tract into the blood. Most cells of the immune system have vitamin D receptors, and the cells activate vitamin D in response to an infection, especially a respiratory infection, such as influenza. Vitamin D is believed to enhance phagocytic activity, increase the production of antimicrobial substances in phagocytes, regulate immune functions, and help reduce inflammation.