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Unit 3: Integumentary System

Dr
...
Protection = skin protects against abrasion, UV light,
microorganisms, dehydration
2
...
Vitamin D production = skin produces a molecule
that can be transformed into vitamin D when
exposed to UV light
4
...
Excretion = small amounts of waste lost through
skin/gland secretions

2

Skin = Dermis + epidermis
•

Dermis = layer of dense connective tissue

•

Epidermis = (upon the dermis) layer of
keratinized stratified squamous epithelium
a
...
Dermis = house
c
...
Attaches skin to underlying bone and muscle
2
...
Not part of the skin
4
...
Padding & insulation
b
...
Site of subcutaneous injections

3

Hypodermis

Epidermis
2
...
Prevents water loss, injury, entrance of harmful
chemicals
b
...
Mitosis in deepest layers, pushing older cells to
surface where they slough off
ii
...
Deeper replicating cells replace cells lost from
the surface
c
...

• These cells are tightly connected by desmosomes
...

• Undergo continuous mitosis
...

• Those on the surface of the skin are dead
...

• Friction may lead to a thickening of the cells known
as a callus
...

Located at the deepest layer of the epidermis
...

Protects against UV damage
...

• Act as macrophages that activate the immune
system
...
Associated with
sensory receptors
...

• Thin skin has only 4
...


8

Stratum Basale
• Epidermis is stratified (strata = layer)
• Single layer cells on basement membrane
• Cuboidal or columnar cells – mitosis every 19 days

• Cell types in this layer
– Keratinocytes
• undergo mitosis to replace epidermis

– Melanocytes
• distribute melanin through cell processes
• melanin picked up by keratinocytes

– Merkel cells are touch receptors
• form Merkel disc
6-17

Stratum Spinosum
• Several layers of keratinocytes
– appear spiny due to shrinkage
during histological preparation

• Contains dendritic (Langerhans) cells
– macrophages from bone marrow
that migrate to the epidermis
– 800 cells/millimeter2
– help protect body against pathogens by “presenting”
them to the immune system

6-18

9

Stratum Granulosum
• 3 to 5 layers Flat keratinocytes
• Contain keratinohyalin granules
– combine with filaments of cytoskeleton
to form keratin

• Produces lipid-filled vesicles that release a
glycolipid by exocytosis to waterproof the skin
– forms a barrier between surface cells
and deeper layers of the epidermis
– cuts off surface strata from nutrient supply

6-19

Stratum Lucidum
• Thin translucent zone seen only in thick skin
• Keratinocytes are packed with eleidin, a
precursor to keratin
– does not stain well

• Cells have no nucleus or organelles

6-20

10

Stratum Corneum
• Up to 30 layers of dead, scaly,
keratinized cells
– surface cells flake off (exfoliate)

• 25+ layers of dead cells joined by desmosomes
• Calluses (hard skin) = increase in number of
layers in stratum corneum due to friction
• Corn = similar reaction as callus, just over a
bony prominence
6-21

Dermis
• Thickness = 0
...
Supply epidermis with nutrients
ii
...
Regulate body temperature
iv
...
Melanin (black) = group of pigments determining
color of skin, hair, and eyes
i
...
Melanocytes (black cell)
• Golgi bodies in melanocytes package
melanin into melanosomes, then
phagocytized by epithelial cells (Fig
...
4)

13

Melanin Transfer from Melanocyte to keratinocytes

Melanin
•
•
•
•
•

Large amounts of melanin in freckles, moles, genitalia,
nipples, areolas
Less melanin in lips, palms, soles
Racial variations – due to amount, kind, and
distribution of melanin
All races have ~same number of melanocytes
Melanin production determined by genetic factors, light
exposure, hormones

14

Melanocyte

Abnormal Skin Colors
• Cyanosis = blueness from deficiency of oxygen in
the circulating blood (cold weather)
• Erythema = redness due to dilated cutaneous
vessels (anger, sunburn, embarrassment)
• Jaundice = yellowing of skin and sclera due to
excess of bilirubin in blood (liver disease)

6-30

15

Abnormal Skin Colors
• Bronzing = golden-brown color of Addison disease
(deficiency of glucocorticoid hormone)
• Pallor = pale color from lack of blood flow
• Albinism = a genetic lack of melanin
• Hematoma = a bruise (visible clotted blood)

Pregnancy – darker nipples and areolas, genitalia,
cheekbones, forehead, chest, midline
Tattooing is a permanent coloration of the skin in which
a foreign pigment is injected into the dermis
...
Hemangiomas (birthmarks)
discolored skin caused by benign tumors of dermal
blood capillaries (strawberry birthmarks disappear in
childhood -- port wine birthmarks last for life)

2
...
Hair shaft = portion of hair above skin surface
b
...
Hair bulb = base of hair root
d
...
Cortex (bark) = surrounds the medulla
f
...
Hair follicle = extension of epidermis deep into dermis
i
...

6-40

20

Hair Color and Texture, Blond

Blond hair contain pheomelanin pigment, but little
6-41
eumelanin
...


21

Hair Color and Texture, Gray and White

White hair = air in medulla and lack of pigment in
cortex
...

6-43

Arrector Pili: Muscle
Arrector pili (that which
raises, hair) = contraction of
these muscles cause hair to
“stand on end”…
goosebumps 
a
...
Evolutionary advantage in
mammals – traps air (heat)
for insulation, also look
larger - intimidation

22

Hair Growth and Loss
Thinning or baldness = alopecia
Pattern baldness = genetic and hormonal
sex-influenced trait(dominant in males, recessive
in females); expressed only with high
testosterone levels
Hirsutism = excessive hair growth
hormone imbalance (ovary or adrenal cortex
problem)

Nails
• Derivative of stratum corneum
– densely packed cells filled with hard keratin

• Flat nails allow for fleshy, sensitive fingertips
• Growth rate is 1 mm per week
– new cells added by mitosis in the nail matrix
– nail plate is visible part of nail
• medical diagnosis of iron deficiency = concave nails

6-46

23

Fingernail Structure

6-47

Cutaneous Glands

6-48

24

Sebaceous Glands
a
...
Produce sebum – oily
substance lubricating
hair & skin surface,
preventing drying out
& bacterial infection

Sudoriferous (Sweat) Glands – 2 types
a
...
Simple, coiled tubular w/ ducts opening to skin
surface
ii
...
Produce sweat: slightly salty water-based
secretion
• Evaporative cooling
• Emotional stress produces sweat in palms,
soles, axillae (used in lie detector tests!)

25

Sudoriferous (Sweat) Glands – 2 types

Sudoriferous (Sweat) Glands – 2 types
b
...
Simple, coiled tubular with ducts opening into
hair follicles of axillae & genitalia
• Become active at puberty due to sex
hormone influence
ii
...
Protection
1
...
Prevents entry of microorganisms/foreign
substances (secretions & skin)
3
...
Protects against UV light damage (melanin)
5
...
Damage protection/defense (nails)

Physiology of the Integumentary System
B
...
Nervous receptors in dermis & epidermis (pain, heat, cold,
pressure)
C
...
Vitamin D precursor made in skin, modified by liver, sent
to kidney were becomes vitamin D
2
...
Temperature Regulation
1
...
Blood vessels (arterioles) in dermis dilate to lose heat,
constrict to keep it in
E
...
Removal of waste products from the body – small role
2
...


Most common type of cancer (UV radiation,
chemicals, radiation)
2
...
Treatment: surgery or radiation
3
...
Produce tumors – continue dividing, can be
fatal
4
...
Can be fatal (will metastasize)

Skin Cancer

Sqaumous cell carcinoma

Basal cell carcinoma

Melanoma

30



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