chapter 4 biosci
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CHAPTER 4: BODY MEMBRANES
Body Membranes
-Cover surfaces
-Line body surfaces
-Form protective, often lubricating sheets around organs
TWO MAJOR GROUPS:
1. Epithelial Membranes
-include cutaneous (skin), mucous, serous
membranes
2. Connective Tissue Membranes
- represented by synovial membranes
A. EPITHELIAL MEMBRANES
- Also called covering and lining membranes
- Calling these membranes epithelial is inaccurate:
although they all contain an epithelial sheet,
it’s always combined w/ an underlying layer
of connective tissue
- simple organs
I. Cutaneous Membranes
-skin
-superficial epidermis: keratinizing stratified
squamous epithelium
-underlying dermis: mostly dense (fibrous)
connective tissue
-dry membrane: only membrane exposed to air
II. Mucous membrane
-epithelium resting on a loose connective tissue
membrane called: lamina propria
-lines all body cavities
that open to the exteriorrespiratory, digestive, urinary, reproductive
tracts
-cellular makeup varies
Most contain either stratified squamous
or simple columnar epithelium
-wet, moist membranes bathed in secretions or
urine
-often for absorption or secretion
-not all mucous membranes secrete mucous
Respiratory & digestive: secrete mucous
Urinary tract: no secretion of mucous
III. Serous membranes
-layer of simple squamous resting on a thin of
layer of areolar connective tissue
-line body cavities closed to the exterior
Except for dorsal body cavity, joint
cavities
-occur in pairs:
1. Parietal layer
- lines a specific portion of the wall of the
ventral body cavity, folds itself to form:
2. Visceral layer
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-covers the outside of the organs in that
cavity
- Parietal-Visceral relationship may be viewed
as: pushing your fist (organ) into a limp
balloon partially filled with water
Part that clings closely to fist: visceralserosa lining organ’s external surface
Outer wall of balloon: parietal serosa
that lines walls of the cavity, fused to
cavity wall (never exposed)
- contains serous fluid
-thin, clear fluid secreted by parietal and
visceral membranes to separate them
-allows organs to slide easily across cavity
walls w/o friction (pumping heart, stomach
churning)
-specific names depend on locations:
1. Peritoneum
-lines abdominal cavity, covering its organs
2. Pleura
-surrounding lungs
3. Pericardium
-surrounding
B. CONNECTIVE TISSUE MEMBRANES
Synovial membranes
- composed of soft areolar connective tissue and
contain no epithelial cells at all
-line fibrous capsules surrounding joints:
1.provide smooth surface
2. secrete a lubricating fluid
- also line small sacs of connective tissue:
bursae and tendon sheaths = cushion organs moving
against each other during muscle activity
INTEGUMENTARY SYSTEM
-Skin, its derivatives (sweat and oil glands, hair, nails)
-Skin is also called the integument, meaning covering
Functions:
-NOT ALL PROTECTIVE
1. Keeps water and other precious molecules in the
body, keeps water out
-contains keratin that is cornified or hardened to
prevent water loss
2. Insulates and cushions deeper body organs and
protects entire body from:-Mechanical damage (bumps and cuts)
-Chemical damage (acids and bases)
-UV rays (sunlight)
-bacteria
3. Regulates heat loss from body surface
-capillary network and sweat glands
4. Acts as mini-excretory system
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-urea, salts and water are lost when we sweat
5. Manufactures proteins to synthesize Vitamin D
6. Contain cutaneous sensory receptors
-touch, pain, pressure, temperature
*study table 4.1 page 114
Structure of the Skin:
Two kinds of tissue:
1. Epidermis
-stratified squamous epithelium capable of
keratinizing, or becoming hard
2.
Dermis
- mostly dense connective tissue
*epidermis and dermis are firmly connected
*blister
-result of burn or friction causing epidermis and
dermis to separate, allowing interstitial fluid to
accumulate in the cavity
3. Subcutaneous tissue
- deep to the dermis or hypodermis
-adipose tissue
-
not considered part of the skin, only anchors skin
to underlying organs
-serves as:
1. shock absorber
2. insulates deeper tissues from extreme
temperature
3. responsible for woman’s curves
I. Epidermis
-composed of 5 layers: stratum basale,
spinosum, granulosum, lucidum and corneum
- avascular
-most cells are keratinocytes, a fibrous proteinthat makes epidermis a tough protective layer
Stratum basale/ germinativum
-connected to the dermis
-epidermal cells that receive the most adequate
nourishment via diffusion from the dermis
-epidermal cells here continuously undergo cell
division, and millions of cells are produced daily
(stratum germinativum)
Stratum spinosum and stratum granulosum
-where daughter cells are pushed further, away
from the source of nutrition
-
cells become flatter, and increasingly full of
keratin
Stratum lucidum
-when cells finally die, they form this
-not present in all skin regions, only in regions
where skin is hairless and extra thick: palms and
soles
-has accumulating keratin that secretes a water-
repellent glycolipid into the extracellular
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-point where di na talaga abot ng cells ang blood
supply and nutrients from dermis
Stratum corneum
-20 to 30 cell layers thick
-3/4 of the epidermal thickness
-contains cornified or horny cells Shinglelike dead cell remnants, completely
filled w/ keratin (tough protein, durable
overcoat for the body, protection from ext.
environment & water loss, resist biological,
chemical and physical assaults)
-rubs and flakes off slowly and steadily (18 kg/ 40 lb
in a lifetime)food source for dust mites
-replaced by cells produced by basale cells (new
epidermis every 25-45 days)
Melanin
-pigment that ranges from yellow-brown-black
-produced by special spider-shaped cells called
melanocytes (found in basale)
-when skin is exposed to sunlight, melanocytes are
stimulated to produce more melanin (tanning)
-As melanocytes produce melanin, membrane-
bound granules are accumulated within them
(melanosomes)these granules move to the ends
of the spidery arms of the melanocytestaken up
by keratinocytesInside keratinocytes, melanin
forms pigment umbrella over the superficial side of
the nuclei that shields DNA from damaging effects
of UV rays
-freckles and moles are seen where melanin is
concentrated in one spot
II. Dermis-“hide”
-strong, stretchy envelope that helps hold the body
together
-made up of dense fibrous connective tissue
-vary in thickness like epidermis
Two regions:
1. Papillary layer
- upper dermal region, uneven
-contains dermal papillae
peglike projections from superior surface
indent epidermis
has capillary loops that furnish nutrients to
epidermis
house pain receptors (free nerve endings)
and touch receptors (meissner’s)
increase friction and gripping ability (looped
and whorled ridges on palms and soles)
Papillary patterns are genetically
predetermined: fingerprints (identifying
films of sweat)
2. Reticular layer
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-deepest skin layer
-contains blood vessels, sweat, oil glands and pressure
receptors (pacinian)
-phagocytes are found here and throughout dermis
-collagen and elastic fibers:
Collagen: toughness of dermis; attract and bindwater to hydrate skin
Elastic: elasticity while young
-abundantly supplied with blood vessels: to maintain
body temperature homeostasis
When temp. is high, capillaries of dermis
become engorged w/ heated blood
When temp. is cool, blood bypasses the dermis
capillaries temporarily, to allow internal temp.
to stay high
SKIN COLOR
3 pigments:
1. Melanin- yellow, reddish, brown or black
2. Carotene- deposited in corneum and subcutaneous
tissue, yellow-orange
3. Oxygen-rich hemoglobin- in red blood cells
*Emotions also influence skin color
Disease states:
1. Redness or erythema: embarrassment (fever),
hypertension, inflammation or allergy
2. Pallor or blanching: pale (fear, anger), anemia, low
blood pressure or impaired blood flow
3. Jaundice: usually signifies a liver disorder in w/c
excess bile pigments are absorbed into the blood &
deposited in body tissues
4. Bruises or black and blue marks: sites where blood
has escaped from circulation and clotted in tissue
spaces (hematomas); may signify deficiency in Vit. Cor hemophilia (bleeder’s disease)
Appendages of the Skin
-arise from the epidermis, maintains unique role body
homeostasis
I. Cutaneous Glands
-all exocrine glands that release secretions to the
skin surface via ducts
-pushed into deeper skin regions from basale, and
resides in dermis
Two groups:
A. Sebaceous glands
-oil glands
-found all over skin except palm and sole
-ducts empty into a hair follicle, but some open
directly onto the skin surface
-sebum
-product of the sebaceous glands
-mixture of oily substances and
fragmented cells
-lubricant that keeps the skin soft and
moist
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-prevents hair from becoming brittle
-contains chemicals that kill bacteria
-become very active during adolescence because
hormones are produced
B. Sweat Glands
-also called sudoriferous glands
-widely distributed in the skin
-
2.5 million glands per person
Two types:
I. Eccrine
-more numerous
-produce sweat
clear secretion that is
1. primarily water
2. salts (sodium chloride)
3. vitamin C
4. traces of metabolic wastes
(ammonia, urea, uric acid)
5. lactic acid (chemical that accumulates
during vigorous muscle activity)
sweat is acidic (ph 4 to 6)
which inhibits the growth of
bacteria
sweat reaches the skin
surface via a duct the opens
externally as a funnel shaped pore
- important for heat regulation
supplied w/ nerve endlngs that
cause them to secrete sweat
when external temperature or
body temp. is high
- it is possible to lose up to 7 L of water on a hot day
- if internal temp. changes more than a few degrees 37C or 98.2 F, life threatening changes occur in the
body
II. Apocrine Glands
-largely confined to the axillary, genital areas of
the body
-larger than eccrine glands, ducts empty into
hair follicles
-secretion
fatty acids and proteins + other substances
milky or yellowish in color
odorless, but when bacteria that live on
skin use its proteins and fats as source of
nutrients, it takes on an unpleasant odor
produced continuously
- begin to function under the influence of
androgens (male sex hormones)
- play a minimal role in thermoregulation
- precise function: not known yet
- activated by nerve fibers during
pain/stress/sexual foreplay
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C. Hair and hair follicles
-serves minor protective functions
I. Hair
-produced by hair follicle (flexile epithelial
structure)-root
Part of hair enclosed in the follicle
- shaft
Part projecting from the surface of the
scalp or skin
Dead, almost entirely protein
-hair is formed by division of the well
nourished stratum basale epithelial cells in
the matrix (growth zone)
-medulla
Central core
-cortex
Surrounds medulla, bound by cuticle
-cuticle
Single layer of cells that overlap each
other like shingles on a roof
This arrangement allows to keep hairs
apart and keep them from matting
Most heavily keratinized region:
provides strength and helps inner hair
layers tightly compacted
Most subject to abrasion, “split ends”
-hair pigment
Made by melanocytes in the hair bulb
Varying types of melanin combine to produce hair
color
Hair types:
1. When hair shaft is oval-hair is smooth and silky, person has wavy hair
2. When hair shaft is flat and ribbonlike
-hair is curly or kinky
3. When hair shaft perfectly round
-hair is straight and tends to be course
-hair is found everywhere except:
1. palm and sole
2. nipples
3. lips
-hairs are among the fastest growing tissues of the
body
-hormones account for the development of hairy
regions: scalp, pubic, axillary areas
II. Hair follicles
- Compound structures
- Inner epidermal sheath
Composed of epithelial tissue and forms the
hair
- Outer dermal sheath
Dermal connective tissue
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Supplies blood vessels to the epidermal
portion and reinforces it
Nippelike papilla provides blood supply to
matrix in the hair bulb
- Arrector pili
-connect each side of the hair follicle to the dermaltissue
-when these muscles contract, hair is pulled upright
dimpling the skin surface w/ goose bumps
-hair raising phenomenon is not very useful to
humans
D. NAILS
Nail
-scale like modification of the epidermis that
corresponds to the hoof or claw of other
animals
-has a free edge, a body (visible portion), and
root (embedded in the skin)
-borders of the nail are overlapped by skin folds
called nail folds
-cuticle
Thick proximal nail fold
-nail bed
Stratum basale of the epidermis extends
beneath the nail
-nail matrix
Thickened proximal area of the nail bed
Responsible for nail growth
- As nail cells are produced by matrix, they become
heavily keratinized and die
- Nails are transparent and nearly colorless, but look
pink because of the blood supply in the underlying
dermis
Exception: lunula (white crescent)= lowblood supply due to thick underlying skin
Homeostatic Imbalances of Skin
- The skin can develop over 1000 different ailments
I. Infections and Allergies
A. Athelete’s foot
-itchy, red, peeling condition of the skin
between toes, resulting from fungus
infection
-tinea pedis
B. Boils and carbuncles
-inflammation of hair follicles and sebaceous
glands
-common in the dorsal neck
-Carbuncles: composite boils typically caused
by infection: staphylococcus aureus
C. Cold sores
-small fluid filled blisters that itch and sting
caused by herpes simplex infection
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-localizes in the cutaneous nerve until
activated by emotional upset, fever or UV
rays
-usually occur around the lips and oral
mucosa of mouth
D. Contact dermatitis
-itching, redness and swelling of the skin,
progressing to blistering
-caused by exposure of the skin to chemicals
E. Impetigo
-pink, water-filled raised lesions that develop
a yellow crust and rupture
-highly contagious staphylococcus infection
-common among elementary school-aged
children
F. Psoriasis
-chronic
-overproduction of skin cells that result in
reddened epidermal lesions covered w/ dry,
silvery scales that itch, burn, crack and bleed
-when sever, may be disfiguring
-also believed to be an autoimmune disorder
in w/c immune system attacks a person’s
own tissues
attacks are triggered by trauma, infection,
hormonal changes or stress
II. Burns
-skin is only as thick as a paper towel
Burn
-is tissue damage and cell death caused by
intense heat, electricity, UV rays or certain
chemicals
When skin is burned and its cells destroyed:
1. The body loses its precious supply of fluids
containing proteins and electrolytes as these
seep from the burned surfaces
2. Dehydration and electrolyte imbalance follow
and lead to shutdown of kidneys and circulatory
shock (inadequate circulation of blood caused by
low blood volume)
3. Later, infection becomes the most impt.
Threat and the leading cause of death (burned
skin is only sterile up to 24 hours; and the
patient’s immune system becomes depressed
w/in 1-2 days after severe burns)
RULE OF NINES
-volume of fluid lost can be estimated directly by
determining how much of the body surface is
burned
-divides the body in 11 areas, each accounting for
9% of total body surface area+ 1% in genitals
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Classification of Burns:
1. First degree burns
-only the epidermis is damaged
-temporary discomfort
-not usually serious and generally heal in 2-3 dayswithout attention
-sunburn
2. Second-degree burn
-injury to epidermis and upper region of dermis
-skin is red and painful, blisters appear
-regeneration can occur
-no permanent scar result if care is taken to prevent
infection
*first and second degree burns- partial-thickness
burns
3. Third degree burns
-destroy the entire thickness of the skin, so these
burns are also called full thickness burns
-burned area appears blanched or blackened
-not painful (destroyed nerve endings)
-regeneration is not possible, skin grafting must be
done
BURNS ARE CRITICAL WHEN:
1. Over 25% of the body has second degree burns
2. Over 10% of the body has third degree burns
3. Third degree burns on face, hands or feet
*Facial burns dangerous because: burns in
respiratory passage can cause suffocation & joint injuries
because scar tissue can severely limit joint mobility
Skin Cancer
-Most skin neoplasms are benign and do not spread
(metastasize) to other body areas
-single most common type of cancer
-causes: infections, chemicals, physical trauma
A. Basal Cell Carcinoma
-least malignant and most common type of skin
cancer
-cells of stratum basale are altered that they cannot
form keratin
-cancer cells proliferate, invading dermis and
subcutaneous tissue
-cancer lesions: occur most often on sun-exposed
areas and appear as shiny dome shaped
noduleslater develop into an ulcer w/ a pearly
beaded edge
- slow growing, metastasis seldom occurs before its
noticed
-cure: lesion is removed surgically
B. Squamous Cell Carcinoma
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-arises from cells of stratum spinosum
-lesion appears scaly, reddened papule (small round
elevation) forms an ulcer w/ a firm raised border
-appears mostly on scalp, ears, dorsum of hands,
lower lip
-grows rapidly and metastasizes to adjacent lymphnodes if not removed
-sun-induced
-when caught early and removed surgically/ by
radiation therapy, chance of full cure is good
C. Malignant Melanoma
-cancer of melanocytes
-5% of skin cancers
-often deadly
-can begin wherever there is a pigment, some
develop from pigmented moles
-arises from accumulated DNA damage in a skin cell,
appears like a spreading brown-black patch
-metastasizes fast to surrounding lymph and blood
vessels
-chance for survival 50%, early detection helps
-sunbathing, tanning
ABCD RULE:
1) Asymmetry- 2 sides of pigmented mole don’t
match
2) Border irregularity- borders of the lesion are not
smooth, exhibit indentations
3) Color-areas of different colors (blacks, browns,
tans, blues, reds)
4) Diameter- spot is larger than 6 mm in diameter
5) Elevation-above skin surface
Therapy: wide surgical excision w/ immunotherapy
DEVELOPMENTAL ASPECTS:
Lanugo
-during 5th
and 6th
months of fetal development, a
soon to be born infant is covered w/ this
-downy type of hair
-shed by birth
Vernix caseosa
-white, cheesy looking substance
-produced by sebaceous glands
-protects baby’s skin while floating in water-filled
sac inside mother
Newborn’s skin is very thin, and blood vessels are
easily seen through it
Milia
-accumulations in the sebaceous glands
-small white spots on nose and forehead
-disappear by 3rd
week of birth
As baby grows, skin becomes thicker and moist,
more subcutaneous fat is deposited
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During adolescence, hair and skin become more oily
as sebaceous glands are activated= acne may appear
Acne subsides in early adulthood, and skin reaches
its optimal appearance during 20s or 30s
Dermatitis or skin inflammations become more
common as visible changes are seen in our skin
During old age, amount of subcutaneous tissue
decreasesintolerance to cold
Skin also becomes drier, may become itchy andbothersome
Thinning of skin, makes it more susceptible to
bruising and other types of injuries
Decreased elasticity of skin + loss of subcutaneous
fat= allows bags to form under eyes and our jowls
begin to sag
Loss of elasticity: speeded up by smoking and
sunlight
By 50, number of hair follicles has dropped by 1/3
and continues to decline hair thinning and alopecia
(degree of baldness)
Male pattern baldness- maraming lalaki ang
nakakalbo
A bald man is not really hairless, the hairs are
colorless and tiny (vellus hairs) since the follicleshave begun to degenerate
Graying hair- genetically controlled by a “delayed
action gene” (once gene takes effect, the production
of melanin deposited decreases or is entirely absent)