These cover surfaces, line body
cavities, and form protective sheets
around organs
 Two main types:
◦ Epithelial membranes (cutaneous,
mucous, and serous membranes) and
are considered to be simple organs
◦ Connective tissue membranes
(synovial membranes)

Otherwise known as the skin
 Superficial epidermis is composed of a
keratinizing (hardening) stratified
squamous epithelium
 Underlying dermis is mostly dense
connective tissue
 Since it is exposed to the air, it is
considered to be a dry membrane
 (More to come later)

Also known as mucosa
 Used for absorption and secretion
 Epithelium resting on loose connective
tissue called lamina propria
 Lines all body cavities that open to the
exterior, such as the hollow organs of
the respiratory, digestive, urinary, and
reproductive tracts
 They are considered to be wet (moist)
membranes

Also known as serosa
 Simple squamous epithelium resting
on a thin layer of areolar connective
tissue
 Line body cavities that are closed to
the exterior
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Different areas have different names:
◦ Around the abdominal cavity organs –
peritoneum
◦ Around the lungs – pleura
◦ Around the heart - pericardium

Occur in pairs as it folds in on itself
◦ Parietal layer – outer wall (fused to cavity
wall)
◦ Visceral layer – inner wall (touches organ)
◦ Space between contains a little bit of a thin,
clear liquid called serous fluid (lubricant).

(Remember the balloon and fist model)
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Composed of just areolar connective tissue.
Line the fibrous capsules surrounding the
joints, small sacs called bursae, and tubelike
tendon sheaths
Provide a smooth surface and secrete a
lubricating fluid to cushion organs during
physical activities
And the Integumentary system (the skin and its
appendages
Some of the basic functions are…


Mechanical Damage
◦ How? It makes a physical barrier. Outer
layers has cells that contain keratin,
which toughens the cells and has
pressure receptors, which alert the body
of potential damage
Chemical Damage
◦ How? Once again the keratinized cells
block chemicals and pain receptors alert
the body
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Bacterial Damage
◦ How? Block the bacteria, but also the skin’s
secretion are acidic (inhibit growth) and skin
cells have phagocytes (eat the bacteria)
Ultraviolet Radiation
◦ How? Contains melanin that offers protection
from UV damage
Thermal Damage
◦ How? Contains hot, cold, and pain receptors
that alert the body
Desiccation (Drying Out)
◦ How? Contains waterproofing glycolipid and
keratin
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Aids in heat loss (activates sweat glands and
allows blood to flow closer to surface) and
heat retention (stops blood from rushing to
surface)
Aids in excretion of urea and uric acid (makes
up some of your sweat)
Synthesizes vitamin D (uses sunlight to
convert some cholesterol molecules to
vitamin D)
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Epidermis – “top layer” of skin, made up of
stratified squamous epithelium that is
capable of keratinizing
Dermis – “bottom layer” of skin, made of
dense connective tissue
Hypodermis or Subcutaneous tissue – not a
layer of skin, but connects skin to organs,
mostly adipose tissue and acts as a shock
absorber
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Stratum Basale – lies closest to the dermis and
therefore the blood supply, they are constantly
dividing and pushing cells up to the surface
Stratum Spinosum – become flatter and fuller of
keratin
Stratum Granulosum – keep getting flatter and
fuller
Stratum Lucidum – cells die and form this clear
layer
Stratum Corneum – cells are completely dead and
full of karetin. About the top 20-30 cell layers
thick. Layer closest to surface

Papillary Layer
◦ upper dermal region
◦ Contain fingerlike projections called
dermal papillae, which may contain
capillary loops to help nourish the
epidermis, pain receptors (nerve endings)
and touch receptors (Meissner’s
corpuscles)
◦ On hands and feet they are arranged in a
specific pattern. The result? Fingerprints.

Reticular Layer
◦ Deepest Layer of the skin
◦ Contains blood vessels, sweat and oil
glands, phagocytes, and deep pain
receptors called Pacinian corpuscles
◦ Contains both collagen (for toughness and
water retention) and elastic fibers (for
stretchiness)
◦ Contains blood vessels for heat control
◦ Contains nerves for responsiveness