Topic 4

Question 1

keratinocytes?

Answer 1

are the main cell types of the
epidermis.

Produce keratin filaments.

Keratin is tough fibrous
protein that gives strength
& helps with water-
proofing

Question 2

melanocytes?

Answer 2

are the secondary cell type of the
epidermis.

Produce melanin pigment & then transfer it to nearby keratinocytes.

Question 3

Stratum Basale

Answer 3

Deepest layer –
attached to dermis

A single row of stem
cells – keratinocytes
here undergo rapid cell
division to replace
those lost from the
surface

Aka stratum germinativum

Melanocytes found
here

Question 3

Langerhans cells?

Answer 3

Are specialized immune cells that phagocytize foreign invaders and help activate the immune
response

Question 3

Merkel cells?

Answer 3

are mechanoreceptors
associated with fine
touch and pressure

Question 4

Stratum Spinosum

Answer 4

8-10 rows of keratinocytes

Cells held together by
desmosomes

Cells contain web-like system of intermediate keratin filaments
attached to desmosomes

Abundant melanin granules &
Langerhans cells

Question 5

Stratum Granulosum
(Granular Layer)

Answer 5

3-5 rows of keratinocytes

Cells begin to flatten

Organelles begin to deteriorate

Cells are becoming keratinized

ECM becomes filled with water-resistant glycolipids

Question 6

Stratum Lucidum

Answer 6

Present only in thick skin

Thin & translucent

A few rows of flat/dead
keratinocytes

Question 7

Stratum Corneum

Answer 7

15-30 layers of dead
keratinocytes that are
full of keratin

Up to 75% of
epidermal thickness

Functions:
* Waterproofs
* Protects against biological, chemical, & mechanical assault

Question 8

Fingerprints

Answer 8

• These epidermal ridges form
  in thick skin (palms, soles)
• Epidermis conforms to the
  contours of the underlying
  dermis

Question 9

Papillary Layer of the Dermis

Answer 9

Consists of finger-like projections of connective tissue called dermal papillae

Areolar connective tissue with
collagen & elastic fibers

Loose connective tissue allows
the papillary layer to contain
capillaries, small lymphatic
vessels, touch receptors, free
nerve ending, & immune cells

Question 10

Reticular Layer of the Dermis

Answer 10

About 80% of dermal thickness

Dense irregular connective tissue

Collagen fibers provide strength
& resiliency

Elastic fibers allow for stretch &
recoil

Larger blood & lymphatic
vessels, neurons, touch
receptors, and accessory
structures found here

Question 11

Hypodermis (subcutaneous tissue)

Answer 11

• Layer of adipose tissue below the dermis
• Not technically part of the skin, but has some key supporting roles

Question 12

melanin

Answer 12

• Produced by
  melanocytes
• Transferred to
  keratinocytes
• Protects DNA
  from UV damage
  (pigment shields
  for nuclei)

Question 13

carotene

Answer 13

• Yellow-orange pigment
• Dietary (from vegetables → like carrots)
• Accumulates in stratum corneum and hypodermis
• Most obvious in areas of thick skin (palms and soles)

Question 14

blood/Hb

Answer 14

The pinkish hue of lighter skin is due to the crimson color of oxygenated Hb in the RBCs of dermal capillaries

Question 15

Hair Structure (Hair Matrix)

Answer 15

The hair matrix is responsible for
producing the hair.

Cell division here creates the
cells of the cuticle, cortex, and
medulla.

Produce “hard” keratin proteins;
account for the more rigid
structure associated with the
hair and nails.

Question 16

Hair Structure (Arrector pili)

Answer 16

Arrector pili are smooth muscle
cells attached to the hair follicle.
Contraction pulls hair follicles
upright, causes “goose bumps,”
and forces sebum out of the
follicle onto the skin surface.

Question 17

Hair Functions

Answer 17

• Protection
• Sensory input – insects!!!
• Thermoregulation
• Communication

Question 18

Anagen phase

Answer 18

Active phase; follicle is producing new hair (weeks to years)

Question 19

Catagen phase

Answer 19

end of the active phase

Question 19

Telogen phase

Answer 19

resting period (2-4 months)

Question 20

Hair loss

Answer 20

• Alopecia (baldness): follicles have a
  limited # of growth cycles; hairs shed
  faster than they are replaced
• Male pattern baldness
  – Altered response to a testosterone derivative
  – Growth cycle becomes so short that most
  hairs never emerge from follicles

Question 21

Nail Function

Answer 21

Protect tips of fingers and toes
Tools that help us pick up small objects
Contain large amounts of hard keratin
Nail matrix is what actually produces the nail

Question 22

Sebaceous Gland

Answer 22

• Widely distributed – except palms and soles
• Most develop from hair follicles
• Oily holocrine secretion called sebum
• Functions of sebum
  1. Softens and lubricates skin &
  hair
  2. Limits water loss
  3. Antibacterial
• Become more active at puberty (↑ sex hormones)

Question 22

Eccrine sweat glands

Answer 22

– Widely distributed
– Particularly abundant on palms, soles, forehead
– Ducts connect to pores that open at skin’s surface
– Secretion = sweat
- 99% water
- NaCl, vitamin C, antibodies, dermcidin (microbe killer), metabolic wastes
– FUNCTION: Thermoregulation– cooling
– Controlled by sympathetic division of ANS – emotional stress can trigger sweating

Question 23

Apocrine sweat glands

Answer 23

– They are merocrine glands!
– Found in axillary and
anogenital regions
– Ducts connect to hair follicles
– Secretion is similar to eccrine
sweat glands but also contain
fatty substances and
proteins
– Functional from puberty
onward (as sexual scent
glands?)

Question 24

Burns

Answer 24

First-degree burn
* Superficial; only epidermis damaged
* Symptoms: redness, swelling, pain

Second-degree burn
* Damage the epidermis and some of the dermis
* Symptoms: redness, swelling, pain, blistering

Third-degree burn
* Damage full thickness of skin and tissues below
* Symptoms: color can be gray-white, cherry red, or
even black; little to no swelling; no pain