Pair up & answer:
What is the largest organ in
the body?
(Hint: It’s also the most
superficial organ…)
The SKIN
What is the name of the
organ system that
contains the skin?
The INTEGUMENTARY
SYSTEM
The Integumentary
System
And Body Membranes
Skin
• Integument - another name for skin
• Principal organ of integumentary
system
• Sheetlike structure called membrane
• Great system to study to understand
how structure is related to function!
Pair up and answer:
Discuss one biological
example of how
structure is related to
function.
Classification of Body
Membranes
• Membranes cover
and protect the
body surface, line
body cavities, &
cover inner surfaces
of hollow organs
• Two major categories
– Epithelial - composed of
epithelial tissue and an
underlying layer of
specialized connective
tissue
– Connective - various
types of connective
tissue , no epithelial cells
Epithelial Membranes
• Cutaneous - skin, one
of largest organs,
composes 16% of body
weight
• Serous - found in
closed cavities
• Mucous - lines body
surfaces opening
directly to exterior
lumen
Connective Tissue
Membranes
• Unlike other types
of membranes, do
not contain
epithelial
components.
• Ex: Synovial
membranes lining
spaces b/t joints
(knee)
Structure of the Skin
• Composed of following
layers:
– Epidermis - outermost,
thin sheet of stratified
squamous epithelium
– Dermis - deeper, thicker
layer made up largely of
connective tissue.
– Connective tissue layer subcutaneous or
hypodermis.
Parts of Skin (click)
Epidermis
• Epithelial cells are
tightly packed into
many layers.
• Innermost - stratum
germinativum undergoes mitosis and
moves toward surface.
• This allows skin to
repair itself!
• As cells are made and
move up to the surface
the cytoplasm is
replaced by protein
keratin.
• Keratin is tough and
waterproof.
• Millions of cells with
keratin flake off all day.
Pair and answer:
When you wash your
hands, what happens to
your most superficial
skin cells?
They wash off and go down
the drain.
After years and years of
washing, how come you
don’t eventually wash
down to your muscles
and bones?
because skin cells are quickly and
constantly dividing
(though at a lower rate when you get
elderly-- that’s why they heal more
slowly)
Epidermis continued…
• Deepest cell layer
produces pigment,
melanin, by
melanocytes.
• Heredity (genes)
determines how dark or
light your skin is, to an
extent.
• What else determines
degree of color?
• Prolonged exposure to
sun increases melanin
deposits.
Dermis
• Dermis is the deeper
layer
• Thicker than epidermis
• Composed largely of
connective tissue.
• Cells are scattered
apart vs. close together.
• Have tough or
stretchable fibers in
between
• Upward projections,
dermal papillae,
form ridges and
grooves that make
fingerprints and bind
two layers together.
Fingerprints
• Dermal papillae patterns are unique to each person
and determine fingerprints, palm patterns, and
toeprints.
• Compare your palm patterns to your neighbor
Appendages of the Skin
• Hair
• Nails
• Glands
Because your nail bed (just deep to the nail body)
contains lots of blood vessels, it appears red
(or blue when blood oxygen levels drop).
Sebaceous Glands
• Secrete oil for the
hair and skin
• But why???
• “nature’s skin
cream”
• What type of gland
is this?
• Multicellular
exocrine
Skin Receptors:
http://www.sumanasinc.com/webcontent/anisamples/neurobiology/skinreceptors.swf
SKIN FUNCTIONS
• Before we proceed to skin disorders,
let’s clarify…
• What are three main functions of the
skin?
• Protection
• Temperature Regulation
• Sensation (detection of pain, etc.)
Blisters of the epidermis
• Cells of epidermis are
tightly packed together.
If weakened, blisters
can form.
• Epidermis and dermis
layers are “glued”
together. If damaged or
destroyed blisters will
also form.