Ch. 5 The Integumentary System

Question 1

Functions of the Skin

Answer 1

• thermoregulation (sweat glands, vasodilation (loss heat), vasoconstriction)
• blood reservoir (mainly dermis)
• protection from external environment
• cutaneous sensations
• excretion and absorption
• synthesis of vitamin D

Question 2

Epidermis

Answer 2

outer, thinner layer that consists of keratinized stratified squamous Epithelium; consists of four principle cells:

1. keratinocytes: (90% of cells) produce keratin which provides protection against microbes, chemicals, heat and abrasion
2. Melanocytes: (8%) produce the pigment, melanin that protects against damage by ultraviolet radiation
3. Langerhans cells: (intraepidermal macrophage cells) arise from red bone marrow and involved in immune responses, damaged by UV light
4. Merkel cells: (tactile cells) deepest layer of the epidermis, function in the sensation of touch along with the adjacent tactile (merkel) discs

Question 3

Stratum Basale

Answer 3

deepest layer of epidermis, continuous cell division to produce keratinocytes
nuclei are large with abundant ribosomes, small Golgi complex and few mitochondria
intermediate filaments keratin protect deeper layers from injury
melanocytes and Merkel cells are found in this layer

Question 4

Facts about the skin

Answer 4

• covers the body and is the largest organ of the body by surface area and weight
• 2 square meters and weighs 4.5-5kg and form about 7% of body weight
• .5-4mm thick, thinnest on the eyelids, thickest on the heels; average thickness is 1-2mm
• skin is organ because it performs a specific function, blood vessels, nerves

Question 5

Stratum Spinosum

Answer 5

• 8-10 layers of thorn-like keratinocytes with bundles of tonofilaments
• cells in superficial layers are flat
• intermediate keratin filaments are present, provides strength and stability
• melanocytes and Langerhans cells are present and include arm-like processes

Question 6

Stratum Granulosum

Answer 6

• 3-5 rows of flattened keratinocytes undergoing apoptosis
• keratohyalin converts keratin intermediate filaments into keratin
• lamellar granules fuse with the plasma membrane and release a lipid-rich water repellent secretion
• granules prevent water loss and microbe entry

Question 7

Stratum Lucidum

Answer 7

• present in only thick skin areas (fingertips, palms, soles)
• 4-6 layers of clear, flat, dead keratinocytes containing large amount of keratin and thickened plasma membrane
• parallel arrangement of keratin provides an additional level of toughness in thick skin

Question 8

Stratum Corneum

Answer 8

• 25-30 layers of flattened dead keratinocytes
• cells are extremely thin, flat, plasma-membrane-enclosed packages of keratin called corneocytes or squames that are shed and replaced by cells from the deeper strata
• protect deeper layers
• constant friction stimulates increased cell production and keratin developing a callus (thickening of skin)

Question 9

Dermis

Answer 9

• composed of dense irregular connective tissue
• collagen and elastic fibers provides tensile strength
• divided into two layers

Question 10

Papillary Region

Answer 10

• 1/5 of the thickness of the dermis, superficial layer
• consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (undersurface, taller and numerous in sensative regions), capillary loops, corpuscles of touch (Meissner’s corpuscles), and free nerve endings detect cool, warm, tickle, pain and itching

Question 11

Reticular Region

Answer 11

• attached to subcutaneous layer, contains bundles of thick collagen and elastic fibers (dense irregular tissue), adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands, blood vessels
• tension lines in the skin indicate predominant direction of underlying collagen fibers
• provides extensibility and elasticity, striae appear when stretched too much

Question 12

Striae

Answer 12

extensive stretching of the collagenous fibers (internal damage) within dermis causes stretch marks
- obesity, pregnancy, and weight lifting

Question 13

Wrinkles

Answer 13

loosening of both layers of dermis causes wrinkles and increases with the age of a person

Question 14

Lines of Cleavage

Answer 14

• underlying collagen fibers tend to orient more in one direction than another in reticular region
• predominant in palmar surface of fingers and are arranged in parallel to long axis of the digits
• important to plastic surgeons

Question 15

Melanin

Answer 15

• yellow-red or brown-black pigment produced by melanocytes (located mostly in the epidermis where it absorbs UV radition)
• amount of melanin causes the skin’s color to vary from pale yellow to red to tan to black
• melanocytes are more concentrated in the skin of penis, nipple, areolae, face and limbs
• melanocytes are about same in number in all people, skin color is due to the amount of melanocytes produced
• freckles are accumulation of melanin

Question 16

Hemoglobin

Answer 16

oxygen-carrying pigment in red blood cells; located in erythrocytes flowing through dermal capillaries

Question 17

Carotene

Answer 17

yellow-orange pigment found in the stratum corneum, dermis, and subcutaneous layer

Question 18

Subcutaneous Layer

Answer 18

• not part of the skin but among its functions
• attaches the skin to the underlying tissues and organs
• areolar tissue or fiberous collagen fibers with adipose tissue
• contain lamellated (pacinian) corpuscles which detect external pressure applied to skin
• storage depot for fat and contains large blood vessels

Question 19

Nervus

Answer 19

local, harmless overgrown of melanin-forming cells

can become malignant upon exposure to excessive UV light

Question 20

Freckles

Answer 20

• yellowish or brown spot that represent localized areas of excessive melanocyte activity
• degree of pigmentation varies and depends on both sun exposure and heredity

Question 21

Hemangioma

Answer 21

• congenial anomaly that results in skin discolouration due to blood vessels that proliferate and form a benign tumour
• capillary hemangiomas (strawberry-colored birth marks)
• cavernous hemangiomas (port-wine stains)

Question 22

Hair Characteristics

Answer 22

• protection, reduction of heat loss, sensing light touch
• composed of dead, keratinized epidermal cells
• shaft: superficial portion of the hair, projects from the surface of the skin
• root: penetrates into the dermis
• hair follicle: surrounds the root; consists of an epithelial root sheath which in turn is surrounded by a dermal root sheath

Question 23

Papilla of the Hair

Answer 23

located at the base of a hair follicle is the bulb; it has an indentation called the papilla of the hair where blood vessels provide nourishment to the growing hair

Question 24

Hair Matrix

Answer 24

• part of bulb
• arise from stratum basale, the cite of cell division
• gives rise to the cells of the internal root sheath (forms cellular tubular sheath of epithelium between external root sheath and the hair), hair colour (melanocytes)

Question 25

Arrector Pili

Answer 25

• extends from the superficial dermis of the skin to the connective tissue sheath around the hair follicle
• nerve endings stimulate the arrector pili muscles to contract, pulling hair shafts perpendicular to surface (goosebumps)
• insulate or look intimidating

Question 26

Hair Root Plexus

Answer 26

• sensitive to touch, initiates nerve impulse if hair shaft is moved
• dendrites of neurons surrounding each hair follicle

Question 27

Sebaceous Glands

Answer 27

• oil glands, simple branched acinar glands connected to hair folicle
• lining of cuboidal cells, secrete an oily substance called sebum, which prevents dehydration of hair and skin
• inhibits growth of certain bacteria

Question 28

Sudoriferous Glands

Answer 28

• produce sweat by exocytosis through pores of into hair follicles
• eccrine or apocrine sweat glands

Question 29

Eccrine (merocrine) sweat glands

Answer 29

• simple, soiled tubular glands, located deep dermis
• an excretory duct that opens at a pore at the surface of the epidermis
• more common than apocrine glands
• sweat helps to cool body by evaporating, insensible perspiration (evaporates before perceived) sensible perspiration (larger amounts and is seen as moisture)
• eliminates small amounts of wastes
• not on margin of lips, nail bed, glans penis, clitoris, labia minora, and eardrum

Question 30

Apocrine Sweat Glands

Answer 30

• emotional sweating or cold sweat and sexual excitement
• larger ducts and lumens
• found mainly in skin of the axilla, groin, areolae, and bearded facial regions of adult males
• decompose proteins which causes body odor
• enlarge during ovulation and shrink during menstruation, become active only after puberty

Question 31

Ceruminous Glands

Answer 31

• modified sweat glands located in the ear canal; and nearby sebaceous glands
• produce waxy substance called cerumen (ear wax) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal

Question 32

Nails

Answer 32

• composed of hard, keratinized epidermal cells located over the dorsal surfaces of the ends of fingers and toes
• nail body: visible portion of the nail, does not shed
• free edge: extend past the distal end of the digit
• nail root: buried in a fold of skin
• lunula: whitish, crecent-shaped area of the proximal end of nail body
• hyponychium: secures nail to fingertip
• eponychium: cuticle is a narrow band of epidermis that adheres to the margin of nail wall
• nail matrix: cell division occurs resulting in growth of nail

Question 33

Functions of Nails

Answer 33

• help grasp and manipulate things
• protect against trauma to the ends of the digits
• scratching
• provide support and counter pressure to the palmar surface of the finger to enhance touch perception and manipulation