OVERVIEW/REVIEW: Levels OF Organization
Levels of organization:
1) Atoms
2) Molecules
3) Macromolecules
4) Organelle
5) Cell
6) Tissue
7) Organ
8) Organ system
9) Organism
INTEGUMENTARY SYSTEM
Mammalian tissue types
I.
II.
Types of tissues
A. Epithelial (covers body surfaces or other tissues, lines cavities & forms glands)
B. Connective (protects and supports the body & binds organs together)
C. Muscular (movement)
D. Nervous (initiates & transmits the nervous impulses that coordinates body activities)
Epithelial Tissue
A. Main functions
1. Protection
2. Absorption (intake of substances by cells of skin or mucus membranes)
3. Secretion (production & release of substances, i.e., perspiration, oil)
B. Epithelial subtypes
1. Covering and lining epithelium (external surfaces, some organs)
a. Lines body cavities, respiratory tract, digestive tract, blood vessels, ducts
b. w/ nervous system, makes up sense organs
2. Glandular epithelium (secreting portion of glands)
C. Morphology/arrangement of epithelium
1. Closely packed cells
2. Little or no intercellular material (matrix) between adjacent cells
3. Contiguous sheets; single or multilayered
4. May contain nerves, but are avascular
a. Vessels for nutrient supply/waste removal are in connective tissue below
b. Attached to epithelium by a basement membrane (collgen, glycoproteins)
5. Regularly spaced
D. Covering & lining epithelium
1. Arrangement of layers
a. Simple epithelium—specialized for absorption/filtration
i. in single layer
ii. tolerant of minimal wear & tear
b. stratified—layered
i. tolerant of a high degree of wear & tear
c. pseudostratified—least common
i. one cell layer thick
ii. some cells don’t reach the surface (those that do either secrete
mucus or have cilia)
III.
IV.
E. Cell shapes
1. May be used to categorize epithelium
a. Squamous—flat—attached to each other in a mosaic
b. Cuboidal—cube-shaped in scross-section (sometimes hexagonal)
c. Columnar—tall and cylindrical
Connective tissue
A.
Most abundant tissue
1.
binding and supporting
2.
highly vascular (except cartilage)
3.
cells widely scattered
4.
considerable amount of matrix
B.
Classification
1.
embryonic connective tissue
a.
present in embryo (first 2 months) & fetus (3 months >)
i.
mesenchyme—gives rise to all other connective tissue
ii.
mucous connective tissue—(Wharton’s jelly)—umbilical cord
2.
Adult connective tissue (does not change after birth)—see color sheets for types
and locations
Integumentary system
A.
Skin (cutis)—an organ structurally joined to perform specific activities
1.
about 7620 cm2 (3000 square inches) in the average adult
2.
generally thicker on dorsal surface; reversed on hands and feet (.02-.12 “)
B.
Functions
1.
first line of defense (immune system)
5.
Stimuli (response)
2.
hydration
6.
UV ray protection
3.
temperature regulation
7.
Vitamin D synthesis
4.
retention of inorganic & organic materials
C.
D.
Structure
1.
Epidermis—outer layers of stratified squamous epithelium (4-5 layers)
a.
basal layer cells reproduce & push upward
b.
cells die during the process & become keratinized
c.
are shed regularly from top layer & replaced from below
Skin color
1.
due to melanin (pigment) in epidermis
a.
amount of melanin produces colors from yellow to black
b.
number of melanocytes constant in all races; pigment production and
dispersal differs
i.
albinism = lack of melanin
ii.
freckles = concentrated patches of melanin
2.
melanocytes—melanin-prodcuing cells
a.
located in basal layer of epidermis
b.
makes melanin from tyrosine
i.
increased activity from UV radiation is for protection
c.
responds to MSH (melanocyte-stimulating hormone) from anterior
pituitary gland
3.
E.
F.
G.
carotene—pigment found in the skin of Oriental people
a.
some located in epidermis, but is mostly in dermis
4.
Caucasians
a.
“pink” color due to capillaries in the dermis not masked by pigment
nd
Dermis (2 principle layer)
1.
contains collagen and elastin fibers
2.
rich in blood vessels, nerves, glands, hair follicles
3.
papillary (upper) layer—loose connective tissue, fine elastic fibers
a.
rich in capillaries for thermoregulation
b.
responsible for fingerprints (aka, dermatoglyphics)
4.
reticular layer—dense, irregular connective tissue, bundles of collagen, coarse
elastic fibers for strength & elasticity
Subcutaneous layer—(aka, superficial fascia)
1.
areolar & adipose tissue
2.
fibers from dermis anchor them together
3.
is attached to underlying organs
Epidermal derivatives
1.
Hair
a.
primarily for protection (limited in humans)
i.
scalp hair protects from sun’s rays
ii.
brow/lashes—eyes from foreign particles
iii.
nostrils/external ear canal—insects & dust
b.
development & distribution
i.
follicles (downgrowths of epidermis) develops in 3rd & 4th fetal
months
a).
produce lanugo by 5th & 6th month, then shed prior to
birth (except brows, etc)
ii.
vellus—“fleecy” hair which covers the body several months
after birth (becomes terminal hairs @ puberty)
c.
structure
i.
hair = root + shaft
a)
shaft = superficial portion w/ 3 parts
a1)
medulla (inner)
a2)
cortex (middle)
a3)
cuticle
b)
root—penetrates demis & subQ layers (also has 3 parts)
& is attached to arrector pili muscles and nerves
2.
growth/replacement
a.
cycle of growing and resting
i.
grows about 0.04”/3 days
ii.
lose 70-100/day (subject to other factors)
b.
length is genetically determined
i.
growing phase lengthens hair
ii.
resting phase: hair root detaches & moves up the follicle
iii.
she or replaced by new hair
iv.
cutting/shaving has NO effect on growth!!
3.
V.
Glands
a.
sebaceous (oil) glands
i.
connected to hair follicles
ii.
secreting portion of dermis; opens into follicle or surface of skin
a)
missing in soles & palms; varies everywhere else
b.
sudoriferous glands (sweat)
i.
distributed throughout body (except nailbeds, fingers, etc)
ii.
produce sweat (water, salts, urea, uric acid, amino acids,
ammonia, sugar, lactic & ascorbic acids (*Good bacteria
food…pew!!)
iii.
primary function = thermoregulation, but also assists in
waste removal
iv.
may be modified ceruminous glands (external auditory meatus);
secretes waxy cerumen
4.
Nails—hands, feet; keratinized epidermal cells
a.
nail body—portion of nail that is visible
b.
free edge—projects beyond distal end of digit
c.
nail root—hidden in nail groove
d.
lunula—whitish, semilunar area @ proximal end of digit
e.
nail fold—surrounds proximal & lateral borders
f.
nail bed—epidermal layer beneath nail
g.
nail groove—furrow between nail fold & bed in eponychium (cuticle)
a.
growth occurs from proximal end of bed, on avg. about 1
mm/week; slower in toe nails
Applications to health
A.
Acne—inflammation of sebaceous glands resulting in comedones (blackheads)
1.
acne vulgaris—common acne
a.
affects almost 80% of teenagers
b.
most common in ages 14-25
2.
acne cosmetica—most common in adults (chin area)
a.
caused mostly by birth control pills, oily cosmetics, stress, iodides (from
salt water or shellfish
3.
Causes
a.
increased hormones (usu. testerone) which stimulates sebaceous cell
production & secretion (sebum)
b.
follicles become colonized by bacteria (usu. Staphylococcus or Priopionibacteria)
i.
pinching/squeezing may cause the compromised epidermal cells
to become displaced, resulting in permanent scarring
4.
Types of Acne lesions (of increasing severity)
a.
comdeones (open blackheads, closed whiteheads [pimples])
b.
papules
c.
pustules
d.
cysts
B.
Impetigo—superficial skin infection caused by Staphylococci and Streptococci
a.
characterized by pustules that become crusted and rupture
b.
occurs principally around mouth, nose and hands
C.
D.
E.
F.
G.
H.
i.
most common in children
ii.
a common nursery epidemic
SLE (Systemic Lupus Erythematosus)—“lupus”
1.
an autoimmune inflammatory disease of the onnective tissue
2.
cause unknown (not thought to be hereditary)
a.
rheumatoid arthritis & rheumatic fever do tend to occur in
relatives of SLE victims; these are also autoimmune disorders
3.
symptoms include: low-grade fever, aches, fatigue, “butterfly rash” across
Cheeks and nose
4.
Triggers: penicillin, sulfa drugs or tetracycline drugs; excessive sunlight, injury,
emotional upset, infection, stress
Psoriasis—chronic, sometimes acute skin condition affecting 6-8 million people in the
U.S.
1.
exhibit patchy scales of skin; involves a high rate of mitosis
Warts
1.
usually benign (noncancerous)
2.
caused by papoviruses, which cause uncontrolled cell growth
3.
may be spread by contact-transfer
Cold sores (fever blisters)
1.
caused by Herpes simplex virus (type I), which can lay dormant for long periods
Of time
2.
most infections occur during infancy but remain subclinical
a.
recur periodically throughout lifetime
b.
may be triggered by UV radiation, hormonal changes, emotional upset
c.
may be transmitted by oral or respiratory routes
d.
Herpes type 2 (HSV-2) responsible for genital herpes, spread through
sexual contact
3.
no treatment for herpes (cure); antivirals help send it back into remission
Sunburn
1.
occurs 208 hours after exposure to UV light
2.
pain & redness maximal in about 12 hours; dissipates in 72-96 hours
3.
one of the most dangerous skin afflictions
a.
causes inhibition of DNA or RNA, leading to cell death
b.
can also damage blood vessels, nerves, & other dermal structures
4.
extreme burns may produce sunstroke
a.
is a disruption of thermoregulatory processes
b.
results in fever, collapse, convulsions, coma & death
Skin cancer
1.
everyone is a potential victim
2.
occurs in nonpigment-producing cells of epidermis
a.
carcinomas—most common
i.
looks like warts
ii.
high cure rate, especially when caught early
b.
melanomas—occurs in melanocytes
i.
spread easily to other parts of the body (metastasis)
ii.
low survival rate
iii.
grows very fast; by the time many people think to have it
checked, it has already spread
iv.
3.
appears as an irregular mole, and is usually dark in color as opposed
to carcinomas, which may be white, pink, red, etc.
Prevention
a.
PABA, which binds to epidermal cells
b.
better yet, avoid exposure
c.
Stay out of tanning beds! They are cancer coffins! But you’ll look
great at your funeral!