The Integumentary System

Question 1

Classes of body membranes

Answer 1

• Lines or covers portions of internal or external body surface
• Consists of:
– Epithelium
– Connective tissue support
• Specific classes:
– Mucous membrane: mucus cells, moist
– Serous membrane: visceral and parietal layer
• Pleura, pericardium and peritoneum
– Synovial membrane: no true epithelial layer
– Cutaneous membrane

Question 2

Cutaneous membrane: skin

Answer 2

• Covers body surface, thick and waterproof
• Epithelium (epidermis) and connective tissue support (dermis)

Question 3

Skin functions

Answer 3

• Protection: 1st line of defense!
– Attack, water gain, water
loss (dehydration),
environment, UV radiation
• Elimination (release) of
substance via glands
• Thermoregulation
• Melanin production
• Keratin production
• Makes vitamin D3
• Lipid and blood storage
• Sensory perception, relay to NS
• Communication

Question 4

The Integumentary System

Answer 4

• Contains largest organ - the skin!
– “the integument”
• Skin: Cutaneous membrane
– Epidermis: epithelial tissue
– Dermis: connective tissue
• Skin accessories: glands, nails, hair
– Originates from epithelium
– In dermis, penetrates epidermis
• Subcutaneous layer: hypodermis
– Not part of integument
– Superficial fascia: anchors to muscle
(mostly), bone
– Areolar, adipose (1/2 body
fat!…liposuction)
– Rich blood supply: subcutaneous/
hypodermal injections

Question 5

The Epidermis

Answer 5

• Avascular stratified squamous epithelium- no bleeding when damaged!
– Layered, 4 cell types
– Basement membrane separates from dermis
– Not as thick as dermis, nutrition and O2 via diffusion
– Basal surface (dividing cells) - more metabolic demands
– Apical surface- exposed surface, dead cells fall off and are replaced

Question 6

The 4 cells
of the
epidermis

Answer 6

Keratinocytes: majority, Melanocytes, Merkel (tactile) cells, Dendritic (Langerhans) cells: immune response

Question 7

Keratinocytes: majority

Answer 7

– Make keratin protein
– Desmosomes
between cells – very
strong connections!!
– Protection: resists
mechanical stress
and H20 loss
– Mitotically active
cells at basal surface
– Replacement of dead
cells at apical surface
• New epidermis
monthly!

Question 8

Melanocytes

Answer 8

– Produce melanin: brown/black – orange/red pigment
– Skin color, UV absorption, DNA protection

Question 9

Merkel (tactile) cells

Answer 9

– Sensitive to touch, communicate with nerve ending (disc) about touch, shape,
patterns

Question 10

Dendritic (Langerhans) cells: immune response

Answer 10

– Phagocytes, starts immune response (vs. invaders, epidermal cancer cells)

Question 11

The epidermis structure

Answer 11

• Keratinocytes in layers of skin at
various life cycle development
• Basal surface
– Mitosis - birth of keratinocytes
– Hemidesmosomes connect to
extracellular matrix of dermis
• Move towards apical surface
– Connected by desmosomes
– Keratinization – make keratin
– Resistance/protection vs.
mechanical stress and
waterproofing
– Cells die – due to keratin and
distance from nutrients, O2
• Apical surface – groups of dead
keratinocytes are shed and replaced

Question 12

Melanin and UV
protection

Answer 12

• Melanin produced
by melanocytes
transferred to
keratinocytes
– Concentrated
peri-nuclear
• Protect DNA
– Melanin
synthesis ↑
with UV
exposure

Question 13

Epidermal variation: Skin color
Pigments:

Answer 13

• Melanin: two forms
– Melanocytes synthesize
– Transferred to keratinocytes
– All have melanocytes, melanin
type/amount, stability varies
– Freckles, moles, vitiligo,
albinism
• RBC Hemoglobin in dermis blood
– Red tint visible through skin
• Carotene accumulation from diet
– Can be converted to vitamin A
– Excess collects in superficial
epithelium and fat of
dermis/subcutaneous layer

Question 14

Skin cancer

Answer 14

• Basal cell carcinoma: 80%, most common
– Sun exposure increases risk
– Slow-growing, surgical removal
treatment
• Squamous cell carcinoma: 2nd most
common
– Sun exposure increases risk
– Grows faster, can metastasize
– But early detection surgical removal
treats
• Melanoma: 2-3%, most dangerous!
– ↑ division of melanocytes
– Sun exposure increases risk
– Very metastatic, most difficult to treat
– Early detection key!

Question 15

Epidermal function: Vitamin D3

Answer 15

• UV radiation (10-15 mins/ 2x week):
– Epidermal cells produce cholecalciferol (vitamin D3)
– Kidneys eventually make calcitriol (active form
vitamin D3)
• Aids calcium /phosphorus absorption in GI tract
• Insufficient vitamin D3: Rickets

Question 16

The dermis

Answer 16

• Your “hide” under
epithelium
• Connective tissue with
collagen (strong) and
elastic (stretchy) protein
fibers
• Little cell division…Tattoos?
• Good blood/nerve supply
• Epidermal accessory
structures rooted
• “Dermatitis”
• Two tissue components
– Superficial papillary
layer
– Deeper reticular layer

Question 17

The dermis: the papillary layer

Answer 17

• Thin, superficial, monitored by phagocytes
• Dermal papilla: projections of dermis ↑ surface area
– Interlock tight with epidermis
– Support epidermis with blood supply
– Sensory (nerve) receptors

Question 18

The dermis: the reticular layer

Answer 18

• Major part of dermis, epithelial accessory structures anchored
• Large collagen fiber bundles and elastic fibers: strength and stress
resistance in many directions
– Striae (stretch marks): dermal tearing, fibers overstretched
• Sensory (nerve) receptors

Question 19

Dermal
features

Answer 19

• Cleavage or tension lines
– Indicate overall direction of collagen fiber bundles in reticular layer
– Knowledge of lines important for surgeons when making incisions to
enhance healing

Question 20

The dermis: innervation

Answer 20

• Nerve supply (innervation)
controls:
– Blood flow: can redirect as
necessary
– Gland secretions
review
• Different sensory receptors:
– Sense light touch, deep
pressure, vibration, pain,
other

Question 21

Burns

Answer 21

• Most immediate threat: infection!, loss of body fluids and dehydration
• Degrees of burns based on severity and ability to heal
– First degree: epidermis, no blisters, no scars
– Second degree: epidermis and part dermis, blisters, possible scarring
– Third degree: all epidermis, dermis and deeper tissues; not usually
painful at first, fluids and skin grafts often needed, significant scarring

Question 22

Epithelial wound healing

Answer 22

• Epithelial wound healing: expect bleeding??
– Epithelial cells migrate, contact inhibition, cell division

Question 23

Deep
wound
healing

Answer 23

• Bleeding!
• Blood clotting
• Cleaning of
wound:
inflammation
• Migration of
epithelial cells
• Scar tissue
forms
• Blood vessels
regrow
• Epithelium
regenerates

Question 24

Integumentary accessory structures

Answer 24

• Hair, nails: harder keratin than epidermis
• Sebaceous and sweat glands
• Forms from embryonic epidermis that folds into dermis
• Located in dermis: penetrate through epidermal skin surface

Question 25

Glandular Epithelia

Answer 25

• Make/secrete particular
substance into ducts, onto
surface, into blood
– Exocrine glands: have ducts
• Produce secretions
• Onto epithelial surfaces
(lumen, skin)
– Endocrine glands: ductless
• Release hormones
• Into interstitial fluid,
blood
• Not all epithelial

Question 26

Exocrine skin glands

Answer 26

Sebaceous (oil) glands, Sudoriferous/sweat glands, Apocrine sweat glands, Merocrine sweat glands

Question 27

Sebaceous (oil) glands

Answer 27

– Cells release sebum into hair follicle or through skin surface
pore, absent on palms and soles of feet
• Inhibits bacteria, lubricates, softens, prevents dehydration
– Mostly inactive in childhood, with hormones of puberty-
stimulate them to secrete
– Keeps skin moist, hydrophobic barrier
– Acne- sebum, dead cells in gland, infection

Question 28

Sudoriferous/sweat glands

Answer 28

sweat into hair follicles or on
surface of skin
1. Apocrine
2. Merocrine

Question 29

Apocrine sweat glands

Answer 29

– Released into hair follicles in armpit, pubic, nipple area
– Begins secretion around puberty due to hormones
– Bacteria feeds on it and causes odor (body odor)
– Activated by hormones, stress, emotional sweating
– Function uncertain …pheromones?

Question 30

Merocrine sweat glands

Answer 30

– Most numerous
– Palms, soles of feet,
forehead, many others
– Releases directly onto
skin surface through
sweat pores: SWEATING
– Functions:
• Thermoregulation! Reduce body temp through evaporation of
water from skin
• Water, electrolyte, drug elimination
• Protection: environmental chemicals diluted, prevent growth
of microbes