Transcript Integumentary Anatomy Updated for Test

The Integumentary System
A high quality saran wrap
Functions
• PROTECTION from:
– Mechanical damage (damage from the external environment/damage
caused by movement and physical stress)
– Chemical damage (damage from chemicals harmful to the skin)
– Bacterial damage (damage from harmful bacteria trying to enter the
body)
– UV radiation (melanin protects us from the harmful rays of the sun)
– Thermal damage (damage from heat/cold)
– Desiccation (drying out – the skin helps us maintain our aqueous
internal environment)
Functions
• Aids in heat loss or heat retention. (helps us
maintain our body’s temperature within its
homeostatic range)
• Aids in excretion of urea and uric acid (waste
that is excreted in sweat)
• Synthesizes Vitamin D (modified cholesterol
molecules in the skin are converted into
Vitamin D when exposed to sunlight)
Two Layers
• Epidermis (this is what you see when you look at
someone!)
-Outer covering. Composed of epithelial tissue.
(epithelial tissue is avascular – it does not have its
own blood supply)
• Dermis
-Lies deep to the epidermis.
-Composed mostly of dense connective tissue.
(dense connective tissue is highly vascularized – it
provides the oxygen and nutrients carried in the
blood to the epidermis)
The Epidermis
• Composed solely of epithelial cells
-Stratified Squamous Epithelial cells
Why can a man shave and not bleed despite ripping off several layers of
cells? This is because epithelial tissue is avascular – a person will not bleed
when shaving until they have cut all the way through the epidermis and
struck the dermis!
How do epidermal cells receive nourishment? They receive
nourishment provided by the blood that flows to the dermis.
The Epidermis
• Most of the epidermal cells are KERATINOCYTES.
-Produce keratin, a tough fibrous protein (insoluble);
the more keratin in a cell, the “tougher” the cell is!
Epidermis
• Composed of five layers:
– Stratum basale
– Stratum spinosum
– Stratum granulosum
– Stratum lucidum
– Stratum corneum
Beagles Should Grow Less Corn
Stratum Basale
• Closest to dermis. This is the
deepest layer of the epidermis
• Constantly dividing. Division of
cells in the basale layer make it
possible for our skin to “recycle”
itself, as new cells push up to
become more superficial layers.
• Contains Melanocytes
– Melanocytes are cells that
produce melanin, a pigment that
gives skin its color. Phagocytosis
of melanin by basale cells allows
melanin to form a superficial
shield for the DNA in our cells to
protect it from the sun’s harmful
rays.
Stratum Spinosum
• Lies superficial to
stratum basale.
• Cells become flatter.
• Increasingly filled with
keratin.
Stratum Granulosum
• Extremely flat.
• Full of keratin.
• Last layer of living cells.
Stratum Lucidum
• Clear layer of dead cells.
• Found only in hairless,
extra-thick skin.
Examples? Skin of the
palms and soles of the
feet
• The cells in the stratum lucidum
are dead because of an extremely
high keratin content and the
distance between them and the
vascular dermis.
Stratum Corneum
•
•
•
•
Most superficial layer.
20-30 cell layers thick.
Dead cells.
Most keratinized layer
of cells
• Replaced every 25-45
days.
The Dermis
• The hide.
• Composed of dense fibrous connective tissue.
• Two major regions:
– Papillary layer
– Reticular layer
• What happens when the Dermis separates from the Epidermis? Typically
the dermis will separate from the epidermis when the skin experiences
friction (an example of this would be changing directions quickly during
basketball) A pocket of air will form, exposing our touch receptors in the
papillary layer. This is a blister.
Papillary Layer
• Dermal papillae form
finger-like projections.
• Indent the overlying
epidermis…this is why
we have fingerprints.
• Contain capillary loops
(these are blood vessels
that provide nutrients to
epidermis
• Contain pain and touch receptors
as well (these are called
meissner’s corpuscles)
Reticular Layer
• Deepest layer of cutaneous membrane (the
cutaneous membrane refers to the dermis and the
epidermis combined).
• Contains skin appendages (hair, nails, glands).
• Composed of collagen and elastin (it is the loss of
collagen and elastin in the reticular layer later in life
as well as the loss of adipose tissue beneath the skin
that results in “wrinkles”)
Reticular Layer Cont’d
• Contains blood vessels, sweat and oil glands, and
deep pressure receptors (pacinian corpuscles)
• Phagocytes protect against harmful bacteria (this is
the last layer of protection against harmful bacteria
before it can enter the body)
• Capillaries maintain body temperature
– Swell with blood to release heat at surface (this lowers
core body temperature, even though it makes our skin feel
“flushed”)
– Constrict for bypass to retain heat (this keeps core body
temperatures high, even though it makes our extremities
feel cold)
Hypodermis
•
•
•
•
•
Hypo = below
“Below dermis”
NOT PART OF SKIN
Composed of adipose tissue
Functions:
– Anchor skin
– Shock absorber
– Insulation
Summary
Cutaneous Membrane
Epidermis
Dermis
Stratum Basale
Papillary Layer
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
Reticular Layer
Accessory organs of the skin
Types of Appendages
• Nails
• Hair
• Cutaneous Glands
-Sebaceous glands
-Sweat glands
-Eccrine glands
-Apocrine glands
Nails: Protection for ends of
fingers/toes
• Heavily keratinized (these cells are dead).
• nail plate- the nail itself; this is the hard, shiny
surface that we see
• nail bed- overlies skin surface. If you pull back
the tip of your finger and see where the nail
connects to the skin, you are looking at the
nail bed
• Lunula (white, half moon circle at the base of
the nail)- cells under lunula divide quickly,
keratinize, and become the nail plate
Hair: insulate, protect, conceal
Hair
• Grows from epidermal
cells at base of hair
follicle (tubelike
depression)
• These cells are
nourished from dermal
blood vessels
• Epidermal cells divide
 push cells toward
surface  cells
die/Keratinize form
shaft of hair
Arrector Pili
• Smooth muscle
• Cause hair to “stand on
end”  goosebumps
Sebaceous Glands: keeps hair &
skin soft, pliable, waterproof
• Everywhere except palms of
hands and soles of feet.
• Secrete sebum: oily mixture of
fatty material & cellular debris
• Associated w/ hair follicles
• Acne: bacteria will accumulate in
a pore, irritating the pore and
causing it to swell shut. The
newly formed cavity will fill with
sebum, and result in a “pimple”
that needs to be popped.
Eccrine Sweat Glands: Respond to
body temperature
• Forehead, neck, back, etc.
• Sweat leaves through pores
• Sweat = water + some salts (electrolytes) +
metabolic wastes (urea)
• Sweat is one of the skin’s methods of lowering
body temperature
Apocrine Glands
• Found in the axillary and genital areas
• Activate during puberty
– Tend to excrete when emotionally
upset/frightened/in pain
In the following picture, label:
•
•
•
•
•
•
•
Epidermis
Dermis
Hypodermis
Hair follicle
Arrector pili
Sebaceous gland
Eccrine sweat gland