•
Body membranes
– Cover body surfaces
– Line body cavities
– Form protective sheets around
organs
• Two types of body membranes:
• Epithelial membranes
• Connective tissue membranes
Classification of Body Membranes
• Epithelial membranes:
– cover and lines the internal
or external cavities
– Composed of epithelial
cells attaching to
• underling tissue with
the help of connective
tissue layer
– E.g.
• Cutaneous membrane
• Mucous membrane
• Serous membrane
Epithelial membrane
• Cutaneous membrane : skin
• Dry membrane
• Outermost protective boundary
• Superficial epidermis is
composed of
– Keratinized stratified
squamous epithelium
• Underlying dermis is build from
– dense connective tissue
Epithelial membrane
• Mucous Membranes:
• Surface epithelium attached to
the underlying tissue with
loose connective tissue
• Lines all body cavities
that open to the
exterior body surface such as
digestive, respiratory, urinary,
reproductive tracts
• absorption and secretion
Epithelial membrane
• Serous Membranes:
• Surface is a layer of simple
squamous epithelium
• Underlying layer is a thin layer of
areolar connective tissue
• Lines open body cavities that are
closed to the exterior of the body
• Serous membranes occur in pairs
separated by serous fluid
– Visceral layer covers the outside
of the organ
– Parietal layer lines a portion of
the wall of ventral body cavity
• Specific serous membranes
– Peritoneum
• Abdominal cavity
– Pleura
• Around the lungs
– Pericardium
• Around the heart
Classification of Body Membranes
• Connective tissue
membranes:
•
Synovial Membranes
– composed of areolar
connective tissue layer
– contains no epithelial
cells
– Lines fibrous capsules
surrounding joints
– Secretes a lubricating
fluid to prevent friction
• Consists of skin and accessory structures
• Such as hair, nails, and glands
• Covers the outside of the body
• Forms the boundary between body and external
environment
• Protects the body from the outside world
• Protection : Skin protects against abrasion, UV light,
reduce water loss, prevent microorganism entry
• Sensation: Has sensory receptors, detect heat,
cold, touch, pressure, pain
• Temperature regulation: By control of blood flow
through skin, sweat glands
• Vitamin D production: Skin produce Vitamin D – UV
light
• Excretion: Excrete through skin
•
•
•
•
•
Covers the entire outer surface of the body
Consists of two layers:
Epidermis
Dermis
Epidermis: Superficial layer of
epithelial tissue
– Resists abrasion
– Reduces water loss
• Dermis: Deep layer of
connective tissue
– Structural strength
• Hypodermis:
– Loose connective tissue that connects
skin to underlying structures (muscle or bone)
– Not part of skin
Skin Structure
• Epidermis – outer layer
– Stratified squamous
epithelium
– Often keratinized
(hardened by keratin)
– Prevents loss of water
– Avascular
• Epidermis – 5 layers
• stratum basale: bottom most
single layer attached to the
dermis
– Undergoes mitotic cell division
and replaces top layers as they
move up
– Receive nourishment from the
underlying dermis that contains
capillaries
•
•
Stratum Spinosum
Stratum granulosum
• Epidermis – 5 layers
• Stratum lucidum
– Formed from dead cells of the
deeper strata
– Occurs only in thick, hairless
skin of the palms of hands and
soles of feet
•
• stratum corneum
– Top layer exposed to sun is Rich
in keratin protein
– Constantly replaced as they get
damaged
– Several layers that are Dead
cells
• Keratinocytes: Secrete protein
called
– keratin that gives toughness to
skin
• Melanocytes : produce melanin
– Found in stratum basale
– gives skin different shades of color
• Amount of melanin produced
depends upon
– genetics and exposure to sunlight
• Melanin is produced in response
to
– UV light to protect the DNA
– Prevent skin cancer
Skin Structure
Skin Color
• Three pigments contribute to skin color:
• Melanin
– Amount and kind of melanin in epidermis
– Yellow, brown or black pigments
• Carotene
– Orange-yellow pigment from some vegetables
• Hemoglobin
– Red coloring from blood cells in dermis capillaries
– Oxygen content determines the extent of red coloring
• Dermis
– Dense connective tissue made of
collagen and elastin fibers
– Decreases with aging leading to
wrinkles
– Collagen fibers give skin its
toughness
– Elastic fibers give skin elasticity
– Maintains body temperature,
– response to stimuli
– Consists of two layers
• Papillary layer
• Reticular layer
• Dermis
• upper papillary layer : contact with
epidermis
– Contains fingerlike projections,
called dermal papillae, extend
towards epidermis
– In the palms, fingers, soles, and
toes papillae forms friction
ridges which improves the grip
of hand and feet
– Supplied with receptors for
various senses
– Unique to each individual
• Dermis
• Lower reticular layer in contact with underlying
hypodermis
– Carries the blood vessels, glands, nerves,
pressure receptors, phagocytes
• Deep to skin
• Not part of skin
• Consists of loose connective tissue
with collagen and elastic fibers
• Main types of cells in hypodermis
are:
– Fibroblasts
– Adipose cells
– Macrophages
• Hypodermis is also called
– Subcutaneous tissue
• Contains about one-half of body’s
fat. Functions as
– Energy source
– Insulation
– Padding
Appendages of the Skin
• Skin appendages consists of:
• Cutaneous glands : Are exocrine glands
– Sebaceous glands
– Sweat glands
• Hair and Hair follicles
• Nails
• Sebaceous glands
– Found all over the body except palms
and soles of the feet
– They produce oily substance also
known as sebum
• It contains oil and fragmented cells
• Lubricant for skin and
protects the skin from dryness
• Kills bacteria
– Most have ducts that empty into
hair follicles
– Glands are activated at puberty
• Skin during puberty is oily
– Acne : overactive sebaceous
glands leading to pimples
• Sweat glands : Widely
distributed in skin. Two types
– Eccrine: Open via duct to
pore on skin surface
• Found all over the body
• Produce salty sweat that
prevents bacterial growth
• Regulate body temperature
– Apocrine: Ducts empty into
hair follicles
• Found in axillary and genital
areas
• Secretion has fatty acids and
proteins in addition to sweat
• Begins working after puberty
• Gives unpleasant odor
Sweat and Its Function
• Composition
– Mostly water
– Some metabolic waste
– Fatty acids and proteins (apocrine only)
• Function
– Helps dissipate excess heat
– Excretes waste products
– Acidic nature inhibits bacteria growth
• Odor is from associated bacteria
Hair
–
–
–
–
–
Consists of hard keratinized epithelial cells
Melanocytes provide pigment for hair color
Present all over the skin except: soles, palms, lips, nipples
Size and thickness varies depending on their location
Texture( soft or rough) varies depending on the amount of
keratin protein
• Hair is produced by hair
follicle
• Hair is divided into
• Shaft
• Root
• Shaft- protrudes above skin
surface
• Root- located below skin
surface
• Root & shaft of hair are
composed of dead keratinized
epithelial cells
• Each hair consists of 3 concentric
layers:
– Central medulla
– Cortex surrounds medulla
– Cuticle on outside of cortex
• Most heavily keratinized
• Hair follicle: Consists of
– Epithelial root sheath
– Dermal root sheath
– Epithelial root sheath:
– Composed of epithelial tissue
– Forms the hair
– Dermal root sheath:
– Composed of dermal connective
tissue
– Dermal region supplies blood
vessels to epidermal portion
Associated Hair Structures
• Arrector pilli
– Smooth muscle cells
– connect each side of the
hair follicle
– When this muscle is pulled,
makes the hair stand erect
and gives raise to goose
bumps
– Protects from loose of heat
from the body
 Nail is protecting covering of distal part
of finger or toe
 Tool for pick up small objects, scratching
 Nail contains a hard keratin
 Each nail has a
– free edge
– a body (visible portion)
– proximal root (embedded in the
skin)
Nail Structures
– Free edge: sharp
– Body: visible and attached to
underlying skin
– Root of nail: hidden beneath
the skin and rich in stratum
basale epithelial cells
– Responsible for nail growth
– Eponychium – proximal nail
fold that projects onto the
nail body
Skin Homeostatic Imbalances
• Infections
– Athletes foot:
• Caused by fungal infection
– Boils and carbuncles
• Inflammation of hair follicle
and sebaceous gland
• Effects neck and back
• Carbuncles result from
multiple boils
• Caused by Staphylococcus
aureus bacterial infection
Skin Homeostatic Imbalances
• Infections
– Cold sores
• Fluid filled blisters
• Around lips and oral cavity
• Caused by herpes simplex
virus
• Contact dermatitis
• Itching, redness and
swelling leading to blisters
• Exposures of chemicals
cause allergic reaction
– Impetigo
• Water filled lesion
• Caused by contagious
staphylococcus bacterial
infection
– Psoriasis
• Cause is unknown
• Chronic condition due to
overproduction of skin
cells leading to epidermal
lesions and scaling
• Triggered by trauma,
infection, stress
• Burns
– Damage to the skin
– Tissue damage and cell death
caused by heat, electricity, UV
radiation, or chemicals
– Resulting in Dehydration: due to
loss of fluids from the surface of
the burned skin leading to
• Electrolyte imbalance : due to kidney
function shut down
• Circulatory shock : due to low blood
volume
Rule of Nines: used to determine extent
of burns
• Body is divided into 11
areas for quick
estimation
– Each area represents
about 9%
– In addition to 1% of
genital area
• Burned tissue easily
get
– bacterial and fungal
infections
– Due to impaired
immune system
• First-degree burns
– Only epidermis is
damaged
– Skin is red and swollen
– Heal with in few days with
no scars
– E.g sun burn
• Second degree burns
– Epidermis and upper
dermis are damaged
– Skin is red with blisters
– Regenerate with in few
weeks and scars are not
present
Severity of
Burns
• Third-degree burns
– Destroys entire skin
layer ( epidermis
and dermis)
– Burn is gray-white
or black
– Nerve ending are
also destroyed
– Regeneration is not
possible
– Skin grafting is
essential
Severity of
Burns
Critical Burns
• Burns are considered critical if:
– Over 25% of body has second
degree burns
– Over 10% of the body has third
degree burns
– third degree burns of the face,
hands, or feet
• Face: restricts movement
of air through respiratory
tract
• Hands and feet: joint tissue
repair limits joint mobility
Skin Cancer
• Cancer ( neoplasm or
tumors)– abnormal cell
mass
• Two types
– Benign
• Does not spread
(encapsulated)
– Malignant
• Metastasized (moves)
to other parts of the
body
• Skin cancer is the most
common type of cancer
• Basal cell carcinoma
– Least malignant
– Most common type
– Arises from stratum basale
– Spread into dermis
– Slow growing and does not
undergo metastasis
– surgery
Skin Cancer
Types
Skin Cancer
Types
• Squamous cell carcinoma
– Arises from stratum
spinosum
– Sun induced commonly
seen in areas such as
hands, lips, scalp, ears
– Develops into ulcers
– Metastasizes to lymph
nodes
– Early removal allows a
good chance of cure
– Surgery or radiation
Skin Cancer Types
• Malignant melanoma
– Most deadly of skin
cancers
– Cancer of melanocytes
– Appears as a black patch
that seems to be growing
– Metastasizes rapidly to
lymph and blood vessels
– Detection uses ABCD rule
– Early detection helps in
increasing the chances of
survival
ABCD Rule
• A = Asymmetry
– Two sides of pigmented
mole do not match
• B = Border irregularity
– Borders of mole are not
smooth
• C = Color
– Different colors in
pigmented area
• D = Diameter
– Spot is larger then 6
mm in diameter