The Integumentary System

Question 1

What are the two major parts of the integumentary system?

Answer 1

▪ Cutaneous membrane (skin)
▪ Accessory structures

Question 2

What are the components of the cutaneous memebrane

Answer 2

– Outer epidermis
▪ Superficial epithelium
– Inner dermis
▪ Connective tissues

Question 3

What are the accessory structure

Answer 3

– Originate in the dermis
– Extend through the epidermis to skin surface
▪ Hair and hair follicles
▪ Exocrine glands
▪ Nails

Question 4

What is another name for the subcutaneous layer

Answer 4

hypodermis

Question 5

Describe the subcutaneous layer

Answer 5

– Loose connective tissue
– Below the dermis

Question 6

What are the functions of the integumentary system?

Answer 6

– Protection of underlying tissues and organs
– Excretion of salts, water, and organic wastes
– Maintenance of normal body temperature
– Production of melanin
– Production of keratin
– Synthesis of vitamin3D
– Storage of lipids
– Detection of touch, pressure, pain, etc.
– Coordination of the immune response

Question 7

Describe the main structural features
of the epidermis, and explain the functional significance of each.

Answer 7

• Epidermis
  – Stratified squamous epithelium
  – Avascular, like all epithelia
  – Nutrients and oxygen diffuse from capillaries in the dermis

Question 8

What are the cells of the epidermis?

Answer 8

– Keratinocytes
▪ The body’s most abundant epithelial cells
▪ Contain large amounts of keratin

Question 9

What are the two types of skin

Answer 9

Thin skin
▪ Covers most of the body
▪ Has four layers of keratinocytes
– Thick skin
▪ Covers the palms of the hands and soles of the feet
▪ Has five layers of keratinocytes

Question 10

What are the five strata of keratinocytes in thick skin

Answer 10

– From basement membrane to free surface
▪ Stratum basale
▪ Stratum spinosum
▪ Stratum granulosum
▪ Stratum lucidum
▪ Stratum corneum

Question 11

Describe the Stratum Basale

Answer 11

– Attached to basement membrane by hemidesmosomes
– Forms a strong bond between epidermis and dermis
– Contains epidermal ridges
▪ Lie next to dermal papillae in dermis
– Has many basal cells, or germinative cells
▪ Stem cells that replace superficial keratinocytes

Question 12

Describe the specialized structures of stratum basale

Answer 12

– Tactile discs
▪ Tactile (Merkel) cells with sensory nerve endings
▪ Found in hairless skin
▪ Respond to touch
– Melanocytes
▪ Contain the pigment melanin

Question 13

Describe the Stratum spinosum

Answer 13

The “spiny layer”
– Eight to ten layers of keratinocytes bound by
desmosomes
– Cells appear spiny in histological sections
– Produced by division of cells in stratum basale, some of which continue dividing
– Contains dendritic (Langerhans) cells, which are active in immune response

Question 14

Describe the stratum granulosum layer

Answer 14

the “granular layer”
– Three to five layers of keratinocytes
– Produced from cells of stratum spinosum
– Most cells stop dividing and produce
▪ Keratin
▪ Keratohyalin
– Forms dense granules
– Promotes cellular dehydration and cross-linking of keratin fibers
– After production of proteins, cells die

Question 15

Describe the stratum lucidum

Answer 15

The “clear layer”
– Found only in thick skin
– Covers stratum granulosum

Question 16

Describe the Stratum corneum

Answer 16

—the “horny layer”
– Exposed surface of skin
– Water resistant
– 15 to 30 layers of keratinized cells
▪ Keratinization is the formation of protective layers of cells filled with keratin
– New cells move from stratum basale to stratum corneum in 7 to 10 days
– Exposed cells are shed after two weeks

Question 17

What are the two ways water is lost from the skin?

Answer 17

– Insensible perspiration
▪ Water diffuses across stratum corneum and
evaporates from skin
▪ 500 mL per day
▪ Rate increases if stratum corneum is damaged (e.g., from burns)
– Sensible perspiration
▪ Water excreted by sweat glands

Question 18

What is the function of the Epidermal growth factor?

Answer 18

– Promotes division of basal cells
– Accelerates keratin production
– Stimulates epidermal repair
– Stimulates glandular secretion

Question 19

Describe the structures and functions
of the dermis.

Answer 19

–Located between epidermis and subcutaneous layer
–Anchors epidermal accessory structures (e.g., hair follicles and sweat glands)
–Two components
▪Outer papillary layer
▪Deeper reticular layer

Question 20

Describe the papillary layer

Answer 20

– Consists of areolar tissue
– Contains capillaries, lymphatic vessels, and sensory neurons
– Named for dermal papillae that project between epidermal ridges
– Becomes inflamed in dermatitis
▪ Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
▪ May produce itching or pain

Question 21

Describe the reticular layer

Answer 21

– Consists of dense irregular connective tissue
– Contains collagen and elastic fibers
– The dermis contains all cells of connective tissue proper

Question 22

Explain the dermal strength and elasticity

Answer 22

– Collagen fibers
▪ Very strong, resist stretching
▪ Easily bent or twisted
▪ Limit flexibility to prevent tissue damage
– Elastic fibers
▪ Permit stretching and then recoil to original length
▪ Provide flexibility
– Fibers and water provide flexibility and resilience
▪ Known as skin turgor

Question 23

Explain tension lines

Answer 23

– Produced by parallel bundles of collagen and elastic fibers in the dermis
– Resist forces applied to skin
– A cut made parallel to a tension line remains shut, heals well
▪ A cut at a right angle pulls open and scars

Question 24

Describe the dermal blood supply

Answer 24

– Cutaneous plexus
▪ Deep network of arteries along the reticular layer
– Subpapillary plexus
▪ Network of small arteries in papillary layer
▪ Capillaries drain into small veins that lead to larger veins in subcutaneous layer
– Contusion (bruise)
▪ Caused by damage to blood vessels in dermis

Question 25

Describe the innervation of skin

Answer 25

– Nerve fibers in skin ▪ Control blood flow ▪ Adjust gland secretion rates ▪ Monitor sensory receptors

Question 26

Sensory receptors respond to

Answer 26

– Light touch—tactile (Meissner) corpuscles, in dermal papillae – Deep pressure and vibration—lamellar (Pacinian) corpuscles, in the reticular layer

Question 27

Skin color is influenced by two pigments in the epidermis

Answer 27

– Melanin – Carotene

Question 28

What is the color of melanin

Answer 28

red-yellow or brown-black pigment

Question 29

Which cell produce melanin

Answer 29

mealanocytes

Question 30

Where is melanin stored?

Answer 30

Stored in intracellular vesicles (melanosomes) ▪ Transferred to keratinocytes ▪ Dark-skinned people have large, numerous melanosomes

Question 31

What is the color of carotene?

Answer 31

orange-yellow pigment

Question 32

Where is the carotene found

Answer 32

in orange vegetables – Accumulates in epidermal cells, deep dermis, and subcutaneous layer – Can be converted to vitamin A, required for ▪ Maintenance of epithelia ▪ Synthesis of photoreceptor pigments in eye

Question 33

Describe the illness and skin color

Answer 33

– Jaundice ▪ Buildup of bile produced by liver ▪ Skin and whites of eyes may turn yellow – Pituitary tumor ▪ Excess MSH increases production of melanin – Addison’s disease ▪ Causes pituitary gland to release excess ACTH, which has an effect similar to MSH – Vitiligo ▪ Loss of melanocytes causing loss of color

Question 34

Describe the interaction between sunlight and vitamin D3 production

Answer 34

* Vitamin3D (cholecalciferol) – Produced by epidermal cells in presence of UV radiation – Liver and kidneys together convert vitamin3D into calcitriol ▪ Essential for absorption of calcium and phosphate ions by small intestine – Insufficient vitamin3D can cause rickets

Question 35

Hairs cover almost all of the body, except

Answer 35

– Palms of hands, sides of fingers – Sides and soles of feet, sides of toes – Lips – Portions of external genitalia

Question 36

What is the function of hair

Answer 36

– Protect and insulate – Guard openings from particles and insects – Serve as sensory receptors

Question 37

Describe the hair follicles

Answer 37

– Extend deep into dermis – Produce nonliving hairs – Wrapped in a dense connective tissue sheath – Base is surrounded by sensory nerves (root hair plexus) – Arrector pili muscle ▪ Involuntary smooth muscle ▪ Contraction causes hairs to stand up ▪ Produces “goose bumps”

Question 38

What are the regions of the hair?

Answer 38

– Hair root ▪ Portion that anchors it into skin – Hair shaft ▪ Upper part of the hair

Question 39

Describe the hair structure

Answer 39

– Medulla ▪ Central core – Cortex ▪ Intermediate layer – Cuticle ▪ Surface layer

Question 40

What are the layers of the follicle?

Answer 40

– Internal root sheath ▪ Surrounds hair root – External root sheath ▪ Extends from skin surface to hair matrix – Glassy membrane ▪ Clear layer wrapped in connective tissue sheath

Question 41

Explain hair production

Answer 41

– Begins at the hair bulb, at base of hair follicle ▪ Surrounds hair papilla—connective tissue containing capillaries and nerves ▪ At base of hair bulb, epithelial cells form a layer known as hair matrix – Produces hair – As cells divide, hair is pushed up and out of skin

Question 42

Explain Hair production

Answer 42

– Begins at the hair bulb, at base of hair follicle ▪ Surrounds hair papilla—connective tissue containing capillaries and nerves ▪ At base of hair bulb, epithelial cells form a layer known as hair matrix – Produces hair – As cells divide, hair is pushed up and out of skin

Question 43

What are the types of hair

Answer 43

– Vellus hairs ▪ Soft, fine hairs that cover most of body surface – Terminal hairs ▪ Heavy, pigmented hairs ▪ On head, eyebrows, and eyelashes ▪ Other parts of body after puberty

Question 44

What are the types of exocrine glands in the skin?

Answer 44

– Sebaceous glands (oil glands) ▪ Holocrine glands ▪ Discharge lipid secretion (sebum) into hair follicles – Lubricates and protects hair shaft – Inhibits growth of bacteria – Sweat glands ▪ Apocrine sweat glands ▪ Eccrine sweat glands

Question 45

What are the types of sebaceous glands

Answer 45

– Simple branched alveolar glands ▪ Associated with hair follicles – Sebaceous follicles ▪ Large sebaceous glands not associated with hair ▪ Discharge sebum directly onto skin surface ▪ Located on face, back, chest, nipples, external genitalia

Question 46

Where are apocrine sweat glands found

Answer 46

in armpits, around nipples and in pubic region

Question 47

Describe the function of the apocrine sweat glands

Answer 47

– Secrete products into hair follicles via merocrine secretion – Produce sticky, cloudy secretions ▪ Nutrient source for bacteria, which cause odors – Surrounded by myoepithelial cells ▪ Squeeze secretions out of glands in response to hormonal or nervous signals

Question 48

Describe the eccrine sweat glands

Answer 48

– Coiled, tubular glands that discharge directly onto skin surface (sensible perspiration) – Widely distributed on body surface ▪ Especially on palms and soles

Question 49

What is the function of the eccrine sweat glands?

Answer 49

▪ Cooling surface of skin to reduce body temperature ▪ Excreting water and electrolytes ▪ Providing protection from environmental hazards

Question 50

What are the other integumentary glands?

Answer 50

– Mammary glands ▪ Produce milk – Ceruminous glands ▪ Produce cerumen (earwax) – Prevents foreign particles from reaching the eardrum

Question 51

Describe the nail

Answer 51

– Protect tips of fingers and toes – Made of dead cells packed with keratin – Metabolic disorders can change nail structure ▪ Example: pitted nails may result from psoriasis

Question 52

Describe the stricture of a nail

Answer 52

– Nail body ▪ Visible portion of the nail ▪ Covers the nail bed – Sides of nails ▪ Lie in lateral nail grooves ▪ Surrounded by lateral nail folds – Skin beneath the distal free edge of the nail is the hyponychium (onyx, nail)