Clin Phys 7 - Hair and Skin

Question 1

what are the functions of the skin?

Answer 1

• protective barrier
• key for regulating body temp
• provides sensory information

Question 2

what is the largest and heaviest organ?

Answer 2

skin

Question 3

what are the layers of the skin?

Answer 3

• epidermis
• dermis
• subcutaneous

Question 4

what are the layers in the epidermis?

Answer 4

• stratum corneum
• stratum lucidum
  –only in thick skin
• stratum granulosum
• stratum spinosum
• stratum basale

Question 5

what is the most superficial layer of the epidermis?

Answer 5

stratum corneum

Question 6

what is the function of the stratum corneum

Answer 6

• prevents penetration of microbes
• prevents dehydration
• mechanical protection

Question 7

what is only found in thick skin of the palms, soles, and digits

Answer 7

stratum lucidum

Question 8

where are the dead cells?

Answer 8

stratum corneum and stratum lucidum

Question 9

where is the stratum granulosum?

Answer 9

between the stratum corneum and stratum spinosum

Question 10

what is the function of stratum granulosum?

Answer 10

○ Living cells that are re-organizing keratin and associating it with filaggrin and other proteins
○ Lamellar granules - lipid-rich, layered granules that help reduce water loss

Question 11

what is the function of stratum spinosum?

Answer 11

○ Very busy synthesizing keratin, proto-filaggrin, and other proteins
○ Eventually keratin becomes 50% of the cell mass of keratinocytes
○ Thick bundles of keratin called tonofibrils are linked to desmosomes

Question 12

what is the deepest epidermal layer?

Answer 12

stratum basale

Question 13

what is the function of stratum basale?

Answer 13

○ Stem cells divide and give rise to all of the layers
○ Melanocytes: synthesize and distribute melanin to keratinocytes
○ Wide range of sensory receptors
○ Resident immune cells
§ Langerhans cells

Question 14

what are fibrous proteins

Answer 14

strong, often flexible long proteins that have a relatively simple, repeating secondary structure

Question 15

what is alpha-keratin?

Answer 15

alpha-helical protein with many levels of structure:
○ Single “strand” protein arranged in an alpha helix
○ Two strands coiled around each other - “coiled coil”

Question 16

what is a protofilament of keratin

Answer 16

long chains of 2 coiled coils

Question 17

what is a protofibril

Answer 17

two long chains of protofilaments

Question 18

how are keratin held together?

Answer 18

hydrogen bonds and varying numbers of disulphide bonds

Question 19

what is the structure of keratin?

Answer 19

the alpha-helix is a right-handed coil, coiled-coil left handed

Question 20

what are the layers of dermal layers?

Answer 20

papillary and reticular layer

Question 21

explain the papillary layer of the dermis

Answer 21

superficial 1/5
- loose CT
interlocks dermis and epidermis
- papilla “finger”
- dermal papillae are vascularized
- also contains sensory receptors

Question 22

explain the reticular layer

Answer 22

dense irregular CT - type I collagen and elastic fibers
houses:
- hair follicles
- nerves, arteries, veins, and lymphatics
- sebaceous and sudorigerous glands
- some adipose tissue
- smooth muscle cells
- some sensory receptors

Question 23

what structure is collagen?

Answer 23

coil-coil structure but is not an alpha helix

Question 24

what is a tropocollagen?

Answer 24

3 collagen alpha chains are coiled around each other

Question 25

what is crucial to collagen formation and cross-linking of hydroxylated amino acids?

Answer 25

vitamin C

Question 26

what is a hair follicle?

Answer 26

an epidermal in-growth into the dermis that builds a long structure formed from hard keratin (a hair)

Question 27

what are some areas of the body without hair?

Answer 27

palms, soles, lips, genital structures

Question 28

what is a hair bulb

Answer 28

the bulbous part at the base of the follicle

Question 29

what are the 3 layes of the hair shaft?

Answer 29

• medulla: lightly keratinized
• cortex: filled with hard keratin
• cuticle: the structure of the keratinocytes is more easily seen - looks like “tiles” or “chingles”

Question 30

what causes the hair to erect or stand up

Answer 30

arrector pili

Question 31

what are the 3 phases of hair growth?

Answer 31

anagen, catagen, telogen

Question 32

what is anagen

Answer 32

longer period of mitotic activity and growth of the hair

Question 33

what is catagen?

Answer 33

arrested growth and regression of the hair bulb

Question 34

what is telogen?

Answer 34

cellular inactivity, often -> hair shredding

Question 35

what is hemoglobin?

Answer 35

red blood cells in vasculature below epidermis

Question 36

what is carotene?

Answer 36

yellow pigment from plants in the diet

Question 37

what is melanin?

Answer 37

pale yellow to black pigment produced by melanocytes

Question 38

what is a cyst?

Answer 38

any pocket of fluid lined by epithelium

Question 39

what is abscess?

Answer 39

a pocket of purulent fluid (bigger than a pustule) - not lined by epithelium

Question 40

what is Ulcer?

Answer 40

a defect in the epidermis, down at least to dermis level, usually due to impairment of healing/re-epithelialization

Question 41

what is Vascular lesions?

Answer 41

include telangiectasias (dilated arterioles, venules that one can see with the naked eye) and hemangiomas (many different types of vessel-rich, red or violet growths)

Question 42

what is scale?

Answer 42

accumulation or excess shedding of the stratum corneum - can be dry or waxy feeling

Question 43

what is psoriasis

Answer 43

• Extremely common
• Pathogenesis is not well understood: Chronic inflammatory condition that appears to have an autoimmune basis
  ○ Epidermal hyperproliferation - they divide really quickly
  ○ Abnormal differentiation of epidermal keratinocytes

Question 44

what is Vitiligo

Answer 44

• Pathogenesis is not well understood:
  ○ Disorder of skin pigmentation
  ○ Immune system attacks the cells that produce melanin