ch 6 pt 1

Question 1

what is dermatology

Answer 1

scientific study and medical treatment of the integumentary system

receives more medical care/treatment than any other organ system

inspection of skin, hair, and nails= significant part of physical exam

Question 2

what is the most vulnuerable organ

Answer 2

skin

- exposed to radiation, trauma, infection, injurious chemicals

Question 3

what is the largest/heaviest organ

Answer 3

skin

-covers 1.5-2.0m^2 and composes 15% of body weight

Question 4

what falls under the integumentary system

Answer 4

hair, skin, nail, and cutaneous glands

Question 5

what are the layers of the skin

Answer 5

epidermis
dermis
hypodermis

Question 6

what are the tissues that make up the three layers of the skin

Answer 6

epidermis- stratified squamous epithelium

dermis- deeper connective tissue layer

hypodermis- connective tissue layer below dermis (not part of the skin but associated)

Question 7

what is thick skin

Answer 7

thick skin-
-covers front of hands, bottoms of feet

• 5 cellular layers ( stratum lucidum present = extra protection)
• has sweat glands, no hair follicles or sebaceous glands (oil)
• thicker than thin skin (0.5mm)

Question 8

what is thin skin

Answer 8

Thin skin
-covers rest of the body

• four cellular layers (no stratum lucdum)
• Possesses hair follicles, sebaceous glands, and sweat glands
• Epidermis about 0.1 mm thick

Question 9

what are the functions of the skin

Answer 9

• protection (resist trauma/infection w/ help of keratin)
• protect against UV rad, harmful chems h2o
• vitamin D synthesis (helps with first step)
• sensation (temp, pain, touch)
• thermoregulation (sweating, thermoreceptors)
• nonverbal communication (facial experessions/social acceptance/self image)

Question 10

what is the epidermis

Answer 10

• consists of keratinized stratified squamous epithelium
• includes dead cells at surface that are packed with keratin
• avascular
• sparse nerve endings for touch and pain

Question 11

what is keratin

Answer 11

protein produced by keratinocytes

tough and most numerous protein

Question 12

what are the five epidermal cell types

Answer 12

stem cells
keratinocytes
melanocytes 
tactile cells
dendritic cells

Question 13

what are stem cells

Answer 13

• Undifferentiated cells that give rise to keratinocytes (produce keratinocytes or melanocytes)
• aka must have centrioles
• In deepest layer of epidermis (stratum basale)
• skin replaced every 30-40 days

Question 14

what are keratinocytes

Answer 14

• Great majority of epidermal cells (most numerous)
• Synthesize keratin
• 3 parts to life cycle???

Question 15

melanocytes

Answer 15

-Synthesize pigment MELANIN that shields DNA from ultraviolet radiation

-Occur only in stratum basale but have branched processes that spread among keratinocytes and distribute melanin
(can protrude into dermis)

Question 16

what is melanin

Answer 16

dark protein protects from uv radiation and gives rise to skin color

Question 17

tactile cells

Answer 17

• Touch receptor cells associated with dermal nerve fibers
• free nerve endings present?
• In basal layer of epidermis
• detect fine touch and pressure

Question 18

dendritic cells

Answer 18

• Macrophages originating in BONE MARROW that guard against pathogens
• stimulate immune system against pathogens
• Found in stratum spinosum and granulosum

Question 19

what are the layers of the epidermis deepest to superficial

Answer 19

stratum basale

stratum spinosum

stratum granulosum

stratum lucidum (thick skin only

stratum corneum

Question 20

what is the stratum basale

Answer 20

• deepest epidermal layer
• A single layer of stem cells and keratinocytes resting on the basement membrane
• Stem cells divide and = keratinocytes that migrate toward skin surface to replace lost cells = very mitotic
• Also contains melanocytes and tactile cells

Question 21

stratum spinosum

Answer 21

• Several layers of keratinocytes joined together by desmosomes and tight junctions (the daughter keratinocytes joined together)
• Also contains some dendritic cells
• some stem cells present= mitotic

Question 22

stratum granulosum

Answer 22

• Three to five layers of flat keratinocytes
• everywhere in body
• granular cells

–produce lots keratin via keratinocytes

• keratin stored w/in cells = free ribosomes= stored in inclusions or cytoplasm

Question 23

stratum lucidum

Answer 23

• Thin, pale layer found ONLY in thick skin (palms/soles)
• Keratinocytes packed with clear protein (appears glossy= so much keratin)
• extra protection
• most organized

Question 24

stratum corneum

Answer 24

• surface layer
• Several layers (up to 30) of dead, scaly, keratinized cells (so full keratin that die and flake off)
• Resists abrasion, penetration, water loss
• stratified squamous (super strong)
• maintain desmosome (flexibility) when dead
• cuticle= 50-60 dead corneum

Question 25

keratinocytes history

Answer 25

- produced by stem cells in deepest layer via mitosis (has to be vascular area) - aka only mitotic until stratum granulosum - new ones push older ones up - as older=flatter=increase keratin production - 30-40 day until flake off - slower in old ppl - faster in injured/stressed -80 lbs lost yearly

Question 26

calluses or corns

Answer 26

thick accumulations of dead keratinocytes on hands or feet due to high stress area

Question 27

what is the dermis

Answer 27

- connective tissue layer beneath epidermis - mainly collagen - lots blood v's, sweat glands, sebaceous glands, and nerve endings - hair follicles and nail roots housed - cause facial expressions of emotion - wavy conspicuous boundary with epidermis

Question 28

dermal papillae

Answer 28

upward-finglerlike extensions of dermis

Question 29

epidermal ridges

Answer 29

downward waves of epidermis (prominent waves on ringers = friction ridges of fingerprint

Question 30

what are the layers of the dermis

Answer 30

papillary layer reticular layer

Question 31

what is the papillary layer

Answer 31

- superficial zone of dermis (apical layer) - Thin zone of areolar tissue in and near the dermal papilla - Allows for mobility of leukocytes and other defense cells - Rich in small blood vessels - c section if cut wrong =scare

Question 32

what is the reticular layer

Answer 32

- deeper and thicker layer of dermis - Consists of dense, irregular connective tissue - Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity - where dermal papillae interlock with epidermal ridges - some aerolar and collagen tissue - unorganized - blister arises here= insensible perperation

Question 33

Hypodermis

Answer 33

- Subcutaneous tissue - Has more areolar and adipose than dermis has = subqutaneous fate - Pads body and binds skin to underlying tissues - Common site of drug injection since it has many blood vessels also called sub Q, SCT, superficial fossa

Question 34

what is the function of the Subcutaneous fat in the hypodermis

Answer 34

energy resivoir thermal insulation thicker in women thinner in infants/elderly padding/protection

Question 35

melanin

Answer 35

- most significant factor in skin color - Produced by melanocytes, accumulates in keratinocytes - protects from uv rad, - color fades as melanin fades

Question 36

darker skinned people vs lighter skinned people

Answer 36

-same number of melanocytes In both Dark skin - produce greater quantity of melanin - break down melanin slower - melanin more spread out - melanized cells throughout epidermis light skin - melanin clump near keratinocyte nucleus - little melain seen beyond stratum basale

Question 37

albinos

Answer 37

no cells to produce melanin (most common in humans)

Question 38

what happens when there is exposure to uv light

Answer 38

stimulates melanin secretion =darkens skin | -fades as melanin degrades

Question 39

what other pigments influence skin color

Answer 39

Hemoglobin —pigment in red blood cells -Adds reddish to pinkish hue to skin Carotene —yellow pigment acquired from egg yolks and yellow/orange vegetables -Concentrates in stratum corneum and subcutaneous fat