Topic 4 Flashcards
keratinocytes?
are the main cell types of the
epidermis.
Produce keratin filaments.
Keratin is tough fibrous
protein that gives strength
& helps with water-
proofing
melanocytes?
are the secondary cell type of the
epidermis.
Produce melanin pigment & then transfer it to nearby keratinocytes.
Stratum Basale
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
Langerhans cells?
Are specialized immune cells that phagocytize foreign invaders and help activate the immune
response
Merkel cells?
are mechanoreceptors
associated with fine
touch and pressure
Stratum Spinosum
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
Stratum Granulosum
(Granular Layer)
3-5 rows of keratinocytes
Cells begin to flatten
Organelles begin to deteriorate
Cells are becoming keratinized
ECM becomes filled with water-resistant glycolipids
Stratum Lucidum
Present only in thick skin
Thin & translucent
A few rows of flat/dead
keratinocytes
Stratum Corneum
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
Fingerprints
- These epidermal ridges form
in thick skin (palms, soles) - Epidermis conforms to the
contours of the underlying
dermis
Papillary Layer of the Dermis
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
Reticular Layer of the Dermis
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
Hypodermis (subcutaneous tissue)
- Layer of adipose tissue below the dermis
- Not technically part of the skin, but has some key supporting roles
melanin
- Produced by
melanocytes - Transferred to
keratinocytes - Protects DNA
from UV damage
(pigment shields
for nuclei)
carotene
- Yellow-orange pigment
- Dietary (from vegetables → like carrots)
- Accumulates in stratum corneum and hypodermis
- Most obvious in areas of thick skin (palms and soles)
blood/Hb
The pinkish hue of lighter skin is due to the crimson color of oxygenated Hb in the RBCs of dermal capillaries
Hair Structure (Hair Matrix)
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.
Hair Structure (Arrector pili)
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.
Hair Functions
- Protection
- Sensory input – insects!!!
- Thermoregulation
- Communication
Anagen phase
Active phase; follicle is producing new hair (weeks to years)
Catagen phase
end of the active phase
Telogen phase
resting period (2-4 months)
Hair loss
- 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
Nail Function
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
Sebaceous Gland
- 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)
Eccrine sweat glands
– 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
Apocrine sweat glands
– 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?)
Burns
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
