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I. Membranes
A. Classified by tissue types.
1. Epithelial Membranes (layer of epithelia and
connective tissue) = Simple organ
a. Cutaneous Membrane (skin) composed of
stratified squamous and dense connective
tissue. Unique because it is primarily a “dry”
membrane.
b. Mucous Membrane (mucosa) composed
of epithelia and loose connective tissue.
i. Membrane lines body cavities that open to the exterior
(digestive, respiratory, urinary and reproductive)
ii. A “wet” membrane continuously bathed in secretions
(mucus or urine).
iii. Cell types vary (squamous or columnar) typically
specialized for secretion (mucus) or absorption
(digestive tract).
c. Serous Membranes (serosa) composed of simple squamous and aerolar
connective tissue.
i. Line body cavities that are closed to the exterior (except dorsal
cavity and joints)
ii. Occurs in pairs:
1. Layer that lines the body cavity is known as the
parietal layer
2. Layer that lines the body organ is the visceral layer
3. Fluid between layers
iii. Function of membrane is to decrease friction between organs.
Ex. Heart and lungs, stomach and intestine.
iv. Location of membrane can dictate name.
Ex. Pleura around lungs; pericardium around heart, peritoneum in
abdominal cavity.
2. Connective Tissue Membranes/Synovial Membranes (composed of
soft aerolar tissue)
a. Lines:
i. fibrous capsules of your joints,
ii. bursa (sacs of connective tissue at some joints),
iii. tendon sheaths
b. Protects against friction between moving parts of the body.
II The Integument System Structure (skin and its derivatives)
A. Epidermis – top most superficial layer
1. Composed of stratified squamous epithelial
2. Avascular and not innervated (no nerves)
3. Different cell types:
a. Keratinocytes – produce keratin helps with
waterproofing of the skin; these cells are lost
through friction.
b. Melanocytes – produce melanin (primary skin
pigment), found in the lowest level of epidermis.
Function is to protect the DNA in the nucleus
from the UV radiation of the sun.
Amount and kind of melanin determine skin
color.
c. Immune system cells in lower layers for early
detection (called Langerhans cells)
4. Layers of epidermis
a. Stratum corneum – most superficial layer, numerous
cell layers (20 to 30); cells are dead (cornified) and flake
off easily. Major protective layer.
b. Stratum Lucidum – Only present on palms and soles of
your feet. Cells are clear and dead (too far to receive
nutrients and oxygen)
c. Stratum Granulosum
d. Stratum Spinosum
e. Stratum Basale/Germinativum – layer of rapid cell
division.
2. Dermis – Intermediate layer and the thickest “your hide”
1. Composed of dense fibrous connective tissue
2. Primary function is to hold the body together therefore it is
very
strong and stretchy
3. Composed of two layers
a. Papillary layer – upper/superficial layer
i. Contains dermal papillae (ridges that
extend up into the dermis) these are the
ridges of your fingerprints. Increase
friction.
ii. Capillaries extend into the ridges to
provide nutrients to stratum basal layer
by diffusion.
iii. Location of pain receptors
(Meissner’s corpuscles)
b. Reticular layer – thicker layer of the dermis
i. Contains blood vessels, sweat and oil glands,
pressure receptors (Pacinian corpuscles),
phagocytes (immune cells) and collagen and
elastic fibers.
a. Collagen – help keep skin hydrated
b. Elastic – help with skin “stretchyness”
c. Hypodermis – Deepest layer of skin
1. Composed of adipose tissue
2. Anchors the two other layers to underlying organs also
insulate and act as a shock absorber.
III Appendages of the Skin – Arise from the epidermis
(stratum basal)
A. Cutaneous Exocrine (have a duct) glands
1. Sebaceous Gland / Oil Glands
a. Found everywhere except palms of
hands and feet.
b. Duct empties into a hair follicle.
c. Sebum is the product excreted
composed of oils, chemicals that kill
bacteria and fragmented cells.
d. Function to lubricate the skin and
hair and protection against microbial
invasion.
2. Sudoriferous / Sweat Glands
a. 2.5 million per person
b. Two types:
i. Eccrine Glands – more numerous and found
everywhere; primary excretion is sweat (water, salts,
vitamin C, metabolic wastes, and lactic acid) Secretion
empties out onto the skin through a pore
ii. Apocrine Glands – Only found in axillary and
genital areas; empty into hair follicle; secretions contain
fatty acids and proteins (causes body odor when
microbes digest); function not yet clear.
B. Hair and Hair Follicle
1. Layers of hair – cuticle (outer most, looks like
shingles on a roof), cortex (area of color) and medulla
(core, different pattern in each species)
2. Types of hair:
a. Vellus hair – “peach fuzz” covers the entire
body.
b. Terminal hair – darker hair on head, eye lashes,
eye brows, pubic area, etc…
c. Function of the hair – protection (eye lashes, nose hairs,
etc..)
d. Hair follicle
IV Function of the integument (the best coat you’ll ever
wear)
A. Thermoregulation – maintaining proper body
temperature
1. Capillaries in the dermis can dilate (get bigger)
releasing heat from the skin (red and swollen)
causing a flushed appearance; or become
restricted and redirect blood flow
away from skin to more vital parts of the body (why
your skin feels cold)
2. Sweat glands -release of water from sweat
results in evaporative cooling.
B. Physical and Chemical Damage - bumps, cuts,
scrapes, burns.
a. Keratinized cells in upper epidermis
b. Nerve receptors that alert central nervous
system to a problem
C. Microbe damage – bacteria
1. “acid mantle” secretions of epidermis slow/prevent
bacterial growth
2. Phagocytes in dermis that engulf pathogen (disease
causing microbes)
D. Desiccation – drying out
1. Keratinized epidermal cells
E. Excretion
1. Sweat – uric acid, heat, other toxins and chemicals.
2. Pheromones – through apocrine sweat glands
3. Oil – through sebaceous glands
F. Synthesis
1. Vitamin D (modified cholesterol and sunlight) helps
with calcium absorption in the digestive tract.
2. Proteins necessary for immunity.
G. UV radiation
1. Melanin protecting DNA in nucleus from mutations.
V Development of the Integument System
A. Fetal Development and Birth
1. Lanugo – downy hair that covers the fetus’s
body and is typically shed by birth.
2. Vernix caseosa – white secretion by the
sebaceous glands which protects the baby’s skin
in the uterus.
3. Milia – accumulation of sebaceous glands on
nose and forehead, typically disappear by 3rd
week.
4. Seborrhea – “cradle cap” formed from
overactive sebaceous glands forming raised
lesions that crust over and slough off.
5. As baby developed skin becomes thicker and
moist and more subcutaneous fat is deposited.
B. Adolescence
1. Sebaceous glands increase their activity and acne
(infection of sebaceous gland) can appear.
a. White head – sebaceous gland blocked by
sebum
b. Black head – when accumulated material
oxidizes and dries
c. 20’s and 30’s your skin is the best it will ever
look!
C. Old Age
1. Subcutaneous fat deposits decrease (intolerance of
cold due to l ack of insulation and thinness of skin can
lead to increase in bruising)
2. Decrease oil production and fewer collagen fibers
contribute to overall decrease in moisture level of skin.
3. Sagging is caused by the loss of elasticity of the
elastic fibers in the skin.
4. Overexposure to sun can lead to increase incidence
of skin cancer (accumulation of mutations over the
years)
5. Hair follicle numbers decrease by 1/3 by the age of
50 resulting in hair loss (alopecia) and melanocytes can
stop producing melanin in the follicle and the hair
appears “gray” (due to a delayed action gene)
D. How can we reverse this aging trend?
1. Stay out of the sun /use sunscreen
2. Good balanced diet (antiaging foods- blueberries,
nuts, brocolli, green leafy veggies, garlic, tomatoes, soy
beans, prunes, etc.)
3. Plenty of water
4. Cleanliness / good hygiene
VI Homeostatic Imbalances of the Skin (there are over
1000)
A. Changes in color
1. Redness /Erythema – dilation of capillaries in
the skin
2. Blanching/Pallor – pale skin can be indicative of
anemia, emotional stress, low blood pressure.
3. Jaundice – yellowing of skin from a liver
disorder (not breaking down bile properly and the
pigments are circulated through the blood)
4. Bruises – blood has escaped the vessels and
clotted in the tissues (hematoma)
B. Blockage in circulation results in cell death and therefore
tissue death. Ex. Bed sores result when patients are
bedridden, weight of the body puts pressure on the skin
and circulation is impaired in that area.
C. Blisters - skin is exposed to constant friction causing the
dermis and epidermis to separate
D. Attack by bacteria, virus and/or fungus or allergy.
Symptoms and effects to skin vary with cause. (read
over pg. 107 for specific types) Ringworm, caused by a
fungus in middle picture and impetigo caused by
bacteria in third picture.
E. Burns – tissue damage and cell death caused by
radiation, electricity, chemicals or heat
1. Dangerous because:
a. Loss of fluids (dehydration and electrolyte
imbalance)
b. Exposure to pathogens and risk of infection
(exposed area and depressed immune system)
2. Three types (classified by severity):
a. Partial Thickness Burns
1)First Degree Burn – Only epidermis is
damaged; symptoms are redness and
swelling in the area. Heals usually within
2 to 3 days.
2) Second Degree Burn – Epidermis and
upper layer of dermis affected; blisters
will appear; regeneration can occur (little
scarring)
2. Full Thickness Burns
Third Degree Burn – entire thickness of skin is burned; area
is charred (black) or blanched; nerve endings destroyed
(not initially painful); regeneration not possible, skin
must be grafted.
Burns are considered critical if the following criteria are met:
25% of body has 2nd degree burn
10% of body has 3rd degree burn
3rd degree burns on face and hands (loss of mobility due to
lack of regeneration and proximity to respiratory
system)
Look over the Rule of 9’s on page 108.
F. Skin Cancer
1.Cells divide uncontrollably and the cancer can
metastasize (move to other areas of the body); growth
can also be benign such as warts.
2. Factors that can predispose a person to skin cancer:
exposure to UV radiation (sun), frequent irritations,
genetics.
3.Types:
Basal Cell Carcinoma – least malignant; most common;
cells stop producing keratin and invade the dermis.
Relatively slow growing and 99% full cure if lesions
removed surgically. Sun induced!
Squamous Cell Carcinoma – Arise from stratum
spinosum layer; lesion is scaly in appearance; appears
on scalp, ears, tops of hands and lower lips; grows
more rapidly and can metastize.
Malignant melanoma – Cancer of melanocytes; often
deadly metastases quickly; survival 50% with early
detection.
Rule for detection – ABCD
Asymmetry of the lesion
Border irregularity (not smooth)
Color changes and different colors in same area
Diameter is larger than 6mm