Download Chapter 4 Skin and Body Membranes

Chapter 4 Skin and Body Membranes
I. Body membranes
 Classification of body
membranes
A. Epithelial membranes
1. cutaneous membranes – skin
– composed of stratified
squamous epithelium. –
exposed to air, dry membrane
2. mucous membrane - lines
all body cavities open to the
exterior (ex: respiratory,
digestive, urinary etc.) – wet
or moist membranes continuously bathed in
secretions. -–function –
absorption, secretion, some
produce mucus.
3. Serous membrane – lined
body cavities that are closed
to exterior (except dorsal
body cavity and joint
cavities). –occur in pairs
a. parietal layer – lines a
specific portion of the wall
of ventral body cavity.
b. Visceral layer – covers
outside of organ in that
cavity. *serous fluid –
between serous layers. –
allows organs to slide easily
across cavity walls.
c. Specific serous
membranes
1. peritoneum – surrounds
organs in abdominal
cavity.
2. Pleura – around lungs
3. Pericardium – around
heart
B. connective tissue membrane
1. synovial membranes –
connective tissue – no epithelial
tissue. –lines fibrous capsules
surrounding joints. – function
– provide a smooth surface and
secrete a lubrication fluid.
II. Integumentary system (skin)
A. functions of skin – protective
(see table 4.1)
1. Structure – composed of two
kinds of tissue
2. Epidermis – composed of
stratified squamous epithelium
– can keritanize the skin
becoming hard and tough.
3. Dermis – dense connective
tissue. *They fit firmly
together but may be separated
to form a blister. Under
epidermis and dermis is the
subcutaneous tissue – mostly
adipose. –not part of skin but
anchors skin.
B. Epidermis – avascular – does
not have a blood supply of its
own.
1. layers of epidermis
a. Stratum Germinativum
(Basale)– constantly
undergoing cell division.
Closest to dermis. – new
cells pushed upward,
become flatter, full of
keritan and die. – die
because they are unable to
get adequate nutrients and
oxygen because of lack of
blood supply.
b. 3 superficial layers –
stratum granulosum, stratum
spinosum, stratum lucidum.
c. Stratum corneum –
outermost layer 20 to 30
cells thick. – dead cells
filled w/keritan. – function –
protects deeper cells from
outer environment.
* new epidermis every 35 to
45 days.
2. Melanin – a pigment found
in melanocytes. (yellow to
brown to black.) - found in
stratum germinativum. –
tanning occurs when sunlight
stimulates melanocytes to
produce more melanin. –
Freckles and moles form
when melanin is accumulated
in one spot.
C. Dermis – 2nd main section of
skin.
- dense fibrous connective tissue
in two major divisions:
1. papillary layer – upper
dermal region. (uneven w/
finger-like projections on
superior surface.) - called
dermal papillae.
a. blood supply and nerves
reach into dermal papillae.
b. Pattern of dermal
papillae determine
fingerprints of each
person.
c. Sweat glands in fingers
cause you to leave
fingerprints on everything
touched.
2. reticular layer – deepest skin
layer.
a. contains blood vessels,
sweat glands, oil glands.
b. Many phagocytes (cells
that engulf foreign bodies)
to eat bacteria that
penetrate the epidermis.
c. Contains collagen and
elastic fibers (gives skin
moisture and elasticity) –
w/ age less fibers and
collagen; skin sags and
wrinkles.
d. Dermis has a good
supply of blood vessels.
Helps regulate body
temperature.
e. Decubitus ulcers bedsores – blood supply is
restricted to skin. Cells
die, skin breaks, cracks,
permanent damage may
result.
D. Skin color –
Three pigments contribute to
skin color:
1. amount and kind of melanin
(yellow, reddish brown, black)
2. amount of carotene
deposited in stratum corneum
and subcutaneous tissue.
3. Amount of oxygen bound to
hemoglobin (pigment in RBC)
in dermal blood vessels.
- cyanosis – skin appears blue –
when hemoglobin is poorly
oxygenated. (in dark skinned
people cyanosis is visible in
mucous membranes and nail
beds.)
4. skin color signaling disease
–
a. redness – fever, allergy etc.
b. pallor or blanching – pale ,
fever, anger, anemia, low
blood pressure, impaired
blood flow.
c. Jaundice (yellow cast) –
liver disorder.
d. Black and blue marks –
bruises – blood has collected
in tissue and out of
circulation.
E. Appendages of Skin –
cutaneous glands, hair, hair
follicles and nails.
1. cutaneous glands- exocrine
glands – release their
secretions on the surface of the
skin.
a. sebaceous glands (oil) –
found all over skin except
palms and under feet. –
usually empty into hair
follicle, some directly on
surface.
- sebum – mixture of oily
substances and cell fragments.
- Blackheads – dried sebum,
darkens.
- Whiteheads – sebum clogging
up sebaceous gland’s duct.
b. sweat glands – (sudoriferous
glands) (over 2.5 million per
person.)
1. eccrine glands – produce
sweat all over body.
- efficient in heat regulating in
body.
- Sweat mostly salt, water, some
metabolic wastes.
2. apocrine sweat glands –
axillary and genital areas of
body. – ducts empty into
hair follicles. – secretions
contain fatty acids and
proteins, salt, water, etc. –
odorless until bacteria on
skin surface use protein
secreted as nutrients for
growth, takes on musky
smell. – play a minimum
role in thermoregulation. –
function unknown.
2.Hair and hair follicles
a. function – shielding eyes,
remove foreign bodies from
respiratory tract, insulation.
b. Hair – produced by hair follicle
1. flexible epithelial structure
2. root – enclosed in follicle.
3. Scalp – projecting from
skin.
4. Hairbulb – area where hair
is formed by division of
germinal epithelial cells.
5. Cells kertanize and die.
6. Mostly protein, mostly dead.
7. Layers of hair –
a. cuticle – outer layer
b. cortex – middle layer
c. medulla – center of hair
8. Melanocytes in hair bulb
determine hair color.
9. Shape of hair shaft
determines type of hair Ex:
wavy, straight, or curly.
10. Arrector pilli muscle –
muscle connecting hair to
dermis. – when cold or
frightened muscle contracts
forming “goosebumps”.
3. Nails – figure 4.7 pg 104 – nails
are dead cells.
F.Homeostatic Imbalances of skin
1. Infections and Allergies
a. athlete’s foot – resulting
from fungus infection.
b. Boils, carbuncles –
inflammation of hair follicles.
c. cold sores – fever blister –
caused by herpes virus.
d. Contact dermatitis – itching
redness swelling (exposed to
chemicals, allergic response).
e. Impetigo – caused by
staphlococcus infection.
f. Psoriasis – red skin covered
by dry, silvery scales.
2. Burns – tissue damage and
cell death caused by heat,
electricity, UV, chemicals.
a. body loses fluids
1. rule of nine – divides
body into 11 sections, 9 %
each to determine % of
body burned.
b. infection occurs
c. type of burns
1. 1st degree burns –only
epidermis is damage.
(sunburn usually).
2. 2nd degree burns –
epidermis and upper dermis
damage. – regrowth may
occur
3. 3rd degree – destroy
entire thickness of skin –
full thickness burns.
Regeneration not possible –
skin grafting must occur.
d. considered critical if :
1. over 25% of body 2nd
degree
2. over 10% of body 3rd
degree
3. 3rd degree on face, hands,
or feet.
3. Skin Cancer a. basal cell carcinoma – the
least malignant and most
common skin cancer. Cells in
the stratum germinativum no
longer honor the boundary
between epidermis and
dermis. They invade the
dermis and subcutaneous
tissue. Appear mostly on
sun-exposed areas of the face
and appear as shiny, dome
shaped nodules. – Full cure is
the rule of 99% of the cases
when surgically removed.
b. Squamous cell carcinoma –
arises from the cells of the
stratum spinosum. Appears
as a scaly reddened elevated
area. Appears most often on
the scalp, ears, hands and
lower lip. It will spread to the
lymph nodes in untreated.
Complete cure is possible if it
is surgically removed in time.
c. Malignant melanoma - a
cancer of melanocytes. –
Only about 5% of the skin
cancers. Often deadly.
Pigmented areas appear
spontaneously. It usually
appears as a spreading brown
to black patch that
metastasized rapidly to
surrounding lymph and blood
vessels. Chance for survival
is helped by early detection.
d. ABCD rule –
A. asymmetry
B. border irregularity
C. color
D. diameter