Integument

Question 1

Skin percentage body mass

Answer 1

15-20%

Question 2

Skin functions

Answer 2

. Protection against mechanical assaults
. Barrier to biological and chemical and physical agents including UV radiation
. Moisture control
. Thermoregulation
. Sensory reception
. Metabolism (synthesis of vit. D3, removal of excess of electrolytes in sweat)

Question 3

Epidermis

Answer 3

. Continuously proliferating stratified squamous keratinized epithelium
. Keratinocyte is principal cell
. Includes melanocytes, langerhans cells, Merkel cells
. Thick/thin skin based on thickness of epidermis only (thick on sole of foot and palm of hand, thin everywhere else)

Question 4

Dermis

Answer 4

. CT, blood vessels, nerves, sensory receptors, and skin appendages
. Epidermis and dermis bound by specialized basement membrane
. Rete ridges: epidermal down growths that extend into superficial dermis and result in formation of dermal upward projections (dermal papillae)

Question 5

Hypodermis

Answer 5

. SubQ

. Often not soldiered part of skin

Question 6

Where is the thickest skin?

Answer 6

Upper portion of back

Question 7

Keratinocytes

Answer 7

. Arise from deepest layer of epidermis
. Move toward free surface as they differentiate
. Contain keratin
. During differentiation they lose mitotic abilities but continue to produce keratin
. Keratin represents about half of total protein in superficial cell layer

Question 8

Basal layer of epidermis (stratum basale)

Answer 8

. Single layer cuboidal cells separated from dermis by basement membrane
. Hemidesmosomes bind cell to basal lamina
. Desmosomes bind cells to each other
. Keratinocytes frequently under mitosis

Question 9

Human epidermis renewed every ____

Answer 9

15-30 days

Question 10

Spinous layer of epidermis (stratum spinosum)

Answer 10

. Prickle cell layer
. Thickest layer
. Keratinocytes produce cytoplasmic intermediate filaments (cytokeratins)
. Cytokeratins form bundles (tonofilaments)
. Aggregates of tonofilaments (tonofibrils)
. Tonofibrils bind to desmosomes btw adjacent keratinocytes

Question 11

Granular layer of epidermis (stratum granulosum)

Answer 11

. 3-5 layers of flattened cells undergoing keratinization
. Cytoplasm contains basophilic keratohyalin granules and filaggrin protein w/in granules and lamellar granules (golgi-derived w/ lipids)

Question 12

Stratum lucidum

Answer 12

. Only in thick skin

. Thin layer flattened keratinocytes w/ lost nuclei and organelles and packed keratin filaments

Question 13

Stratum corneum layer in epidermis

Answer 13

. 15-20 layers of keratinized cells filled w/ keratin filaments

Question 14

Melanocytes

Answer 14

. Derived from neural crest
. Synthesize melanin that absorbs UV radiation
. Located in stratum basale w/ long processes into stratum spinosum
. Functionally related to 4-10 keratinocytes forming epidermal-melanin unit
. Sends melanosomes to keratinocyte cytoplasm

Question 15

Carotene

Answer 15

Yellow pigment in skin and adipose that affects skin color

Question 16

Langerhans cells

Answer 16

. Antigen-presenting cells derived from bone marrow

. 2-8% epidermal cells mostly in stratum spinosum

Question 17

Merkel cells

Answer 17

. Mechanoreceptor cell that detect light touch
. Located in stratum basale
. Joined by desmosomes to keratinocytes

Question 18

Papillary dermis

Answer 18

. Dermis immediately adjacent to epidermis

. Has fine collagen fibers and small blood vessels, sensory nerve endings and structures

Question 19

Reticular dermis

Answer 19

. Deeper, dense irregular CT rich in collagen and elastic fibers

Question 20

Dermis functions

Answer 20

. Responsible for tone and texture of skin

. When aging the collagen and elastin in upper dermis degenerate and skin loses texture and wrinkles

Question 21

Nerve endings found in dermis

Answer 21

. meissner’s corpuscles: touch receptors found in papillary dermis
. Pacinian corpuscles: deep pressure receptors in deep dermis and hypodermis
. Ruffini corpuscles: stretch and tension receptors in deep dermis
. Krause end bulbs: mechanoreceptors found in lining of oropharynx and conjunctiva of the eye

Question 22

Hypodermis

Answer 22

. Loose CT and adipose
. Binds skin loosely to subadjacent organs
. Compartmentilized by fibrous septa running from deep reticular dermis to fascial tissue that underlies hypodermis
. Larger vessels that supply and drain dermal blood vasculature

Question 23

Sebaceous glands

Answer 23

. Produce sebum (skin lubricant w/ slight antibiotic effect)
. Assoc. w/ hair follicles usually, but can be unrelated (eye like, oral cavity)
. Cluster of 3-5 alveoli
. Secretory cells get larger as they accumulate lipid droplets
. Entire secretory cell is released as product (holocrine)

Question 24

Sweat glands

Answer 24

. Found everywhere but lip margins and parts of genitalia

. Most abundant on palm of hand and sole of foot

Question 25

. Eccrine sweat glands

Answer 25

. Simple coiled tubular glands formed by secretory portion (w/in deep reticular dermis) and excretory eccrine duct . Becomes straight as it ascends vertically through dermis towards skin surface . Secretory cells are clear, larger cells that secrete bulk of watery sweat and smaller cells that secrete glycoprotein . Attenuated outer layer of myoepithelial cells that form discontinuous layer btw secretory cells and basement membrane

Question 26

Apocrine sweat glands

Answer 26

. Limited distribution . Found in axilla and groin . Secretory portion in deep reticular dermis or hypodermis . Secretory portion located in deep reticular dermis or hypodermis and is coiled tubule w/ diliated lumen . Secretory product discharged via ducts into upper parts of the hair follicle above sebaceous gland . Not functional until puberty

Question 27

Where is hair not present?

Answer 27

. Skin of palms and soles . Lip . Parts of genitalia

Question 28

Components of hair

Answer 28

. Shaft: protrudes above the surface of the epidermis | . Root: embedded in skin

Question 29

Where does hair form?

Answer 29

. W/in epidermal invaginations in hair follicles | . In assoc. w/ sebaceous glands and smooth muscle bundle (arrector pili)

Question 30

Hair bulb

Answer 30

. Terminal dilation in hair follicle

Question 31

Dermal papilla

Answer 31

. Contains blood capillaries | . Inserts into base of hair bulb

Question 32

Keratinocytes continuous w/ ___ layer of epidermis to cover dermal papilla

Answer 32

.basal layer

Question 33

What occurs during active hair growth?

Answer 33

. Epithelial cells proliferate to form layers of hair follicle . Undergo keratinization, melanin accumulation and maturation

Question 34

Medulla in regards to hair

Answer 34

. Center of hair root

Question 35

Cortex in regards to hair

Answer 35

. Heavily keratinized cels around medulla

Question 36

Hair cuticle

Answer 36

. Thin layer of keratinized cells covering cortex

Question 37

Root sheath

Answer 37

. Continuous w/ outermost cells of hair bulb . Internal root sheath: surrounds initial part of hair root but degenerates over sebaceous gland level . External root sheath: covers internal sheath and extends to epidermis and is continous w/ strata basale and spinosum

Question 38

Nails

Answer 38

. Hard players of keratin on dorsal surface of each distal phalanx . Nail root covered by fold of skin and has cuticle/eponychium (extension of stratum corneum) . Bound to nail bed (bed of epidermis w/ stratum basale and spinosum)

Question 39

How is nail root formed?

Answer 39

From nail matrix | . Cells divide, move distally and become keratinized

Question 40

Hyponychium

Answer 40

. Epidermal fold where distal end of nail plate becomes free of nail bed