BIOL 319 EXAM 3 COHN QUESTIONS
AND ANSWERS GRADED A+ 2025/2026
What organ is part of the integumentary system
skin (the only organ)
the skin
- largest organ of the body (~11 lbs)
- composed of 2 layers
skin also known as the
cutaneous membrane
what are the two layers of the skin
1. epidermis
2. dermis
"thick skin" meaning
thick epidermis
where is epidermis the thickest?
palms of hands and soles of feet
epidermis is always _____ than the dermis
thinner
where is the SKIN the thinnest?
eyelids
where is the SKIN the thickest?
between the shoulder blades
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,epidermis contains though skin cells impenetrable by water at mature level that
- the outermost layer of protection
- help you stay hydrated
are there blood vessels that penetrate the epidermis
no
where is the dividing line of the epidermis
basement membrane
does the dermis contain blood vessels
yes
how many layers of the epidermis are there?
4- thin epidermis
5- thick epidermis
what are the 5 layers of the epidermis (from deepest to most superficial)
1. stratum basale
2. stratum spinosum
3. stratum granulosum
4. stratum lucidum
5. stratum corneum
what is the layer only in thick skin?
stratum lucidum
as cells age they are pushed up
superficially
stratum basale
- deepest layer/basement layer
- stem cell layer
- 1/2 cells thick
- not epithelial cells yet
- always undergoing rapid division
-- mitotic layer
- desmosomes connect these cells to each other
hemidesmosomes
attaches the deepest layer (basal layer) to the basement membrane
stratum spinosum
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, - "spiny surface"
-- attachment points look like spines when shrinking away from each other
- cells thrive
- begin to form squamous shape
- functional skin cells
-- produce higher level of desmosomes
- begin producing keratin
-- makes cells tougher
-- internal water repellent (1st step)
- about 6-8 cells thick
- begin manufacturing lamellar bodies
-- hydrophobic
- cells get ready for apoptosis while getting more superficial
lamellar bodies
fill up with glycolipids (sugary fat)
stratum granulosum
- about 6 cells thick
- cells about to die
- before death:
-- accelerate keratin production
--- keratin cells make a grainy appearance
-- lamellar bodies release glycolipid into interstitial space
--- water cannot move into cells
stratum lucidum
- lucid/clear layer
- only in thick epidermis
stratum corneum
- thickest layer
- about 30-50 cells thick
- "cornified layer"
-- dead cells
- desmosomes and glycolipids
- keratinocytes take up melanin & help protect from UV light
cell types in the epidermis
keratinocytes, melanocytes, merkel cells, langerhans cells
melanocytes
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
AND ANSWERS GRADED A+ 2025/2026
What organ is part of the integumentary system
skin (the only organ)
the skin
- largest organ of the body (~11 lbs)
- composed of 2 layers
skin also known as the
cutaneous membrane
what are the two layers of the skin
1. epidermis
2. dermis
"thick skin" meaning
thick epidermis
where is epidermis the thickest?
palms of hands and soles of feet
epidermis is always _____ than the dermis
thinner
where is the SKIN the thinnest?
eyelids
where is the SKIN the thickest?
between the shoulder blades
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,epidermis contains though skin cells impenetrable by water at mature level that
- the outermost layer of protection
- help you stay hydrated
are there blood vessels that penetrate the epidermis
no
where is the dividing line of the epidermis
basement membrane
does the dermis contain blood vessels
yes
how many layers of the epidermis are there?
4- thin epidermis
5- thick epidermis
what are the 5 layers of the epidermis (from deepest to most superficial)
1. stratum basale
2. stratum spinosum
3. stratum granulosum
4. stratum lucidum
5. stratum corneum
what is the layer only in thick skin?
stratum lucidum
as cells age they are pushed up
superficially
stratum basale
- deepest layer/basement layer
- stem cell layer
- 1/2 cells thick
- not epithelial cells yet
- always undergoing rapid division
-- mitotic layer
- desmosomes connect these cells to each other
hemidesmosomes
attaches the deepest layer (basal layer) to the basement membrane
stratum spinosum
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, - "spiny surface"
-- attachment points look like spines when shrinking away from each other
- cells thrive
- begin to form squamous shape
- functional skin cells
-- produce higher level of desmosomes
- begin producing keratin
-- makes cells tougher
-- internal water repellent (1st step)
- about 6-8 cells thick
- begin manufacturing lamellar bodies
-- hydrophobic
- cells get ready for apoptosis while getting more superficial
lamellar bodies
fill up with glycolipids (sugary fat)
stratum granulosum
- about 6 cells thick
- cells about to die
- before death:
-- accelerate keratin production
--- keratin cells make a grainy appearance
-- lamellar bodies release glycolipid into interstitial space
--- water cannot move into cells
stratum lucidum
- lucid/clear layer
- only in thick epidermis
stratum corneum
- thickest layer
- about 30-50 cells thick
- "cornified layer"
-- dead cells
- desmosomes and glycolipids
- keratinocytes take up melanin & help protect from UV light
cell types in the epidermis
keratinocytes, melanocytes, merkel cells, langerhans cells
melanocytes
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
