Download Lower Respiratory System a. larynx (voice box)

Lower Respiratory System
a.
larynx (voice box) - mucous membranes are composed of ciliated columnar
.epithelial cells
b. trachea (windpipe) - air passageway extending from the larynx; it divides into
right and left primary bronchi; mucous membranes are composed of ciliated
.columnar epithelial cells; windpipe is supported by hyaline cartilage rings
c.
bronchi - the trachea divides in to a right primary bronchus (goes to right lung)
and a left primary bronchus (goes to left lung); bronchi are similar in structure to the
trachea; upon entering each lung the primary bronchi divide to form smaller bronchi
- the secondary bronchi; secondary bronchi continue to branch into smaller bronchi,
called tertiary bronchi, that then divide into bronchioles, which divide into even
.smaller terminal bronchioles
As the tubes get smaller, several structural changes
:occur
Cartilage rings are replaced by cartilage plates and then the cartilage
.disappears all together
¨
The mucous membrane changes from ciliated columnar epithelium to cuboidal
¨
epithelium (any debris reaching these smaller tubes must now be removed by white
.)blood cells
As the cartilage decreases the amount of smooth muscle increases during
¨
asthma attacks the muscles go into spasm and because there is no supporting
cartilage the spasms close off the air passageways - asthma medication such as
.)albuterol targets this smooth muscle tissue
d. lungs - lobes contain lobules (small compartments in the lungs); each lobule
contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal
bronchiole; terminal bronchioles subdivide into microscopic branches called
respiratory bronchioles, which subbdivide into several alveolar ducts; around each
alveolar duct are alveolar sacs containing alveoli (cup-shaped projections lined with
epithelium); the exchange of respiratory gases between the lungs and blood takes
place by diffusion across the alveolar and capillary walls; the lungs are surrounded by
.a membrane called the pleura
B. Defenses & Normal Flora
Defenses .1
a.
mucociliary defenses in upper respiratory system, larynx, trachea, & bronchi
.(cilia on that columnar epithelial cells whips up mucous
.b.
macrophages in the bronchioles & alveoli
.c. IgA (antibody) protects mucous membranes
Normal Flora - includes species of streptococci, lactobacilli, & some Gram
.2
negatives in the upper respiratory system; the lower respiratory system (as well as
.the sinuses & middle ear) is normally sterile
C. Clinical Syndromes
.Rhinitis - nasal inflammation; most common of all respiratory syndromes
Adenoiditis - infection of adenoid tonsil
.1
.2
Pharyngitis - infection of the throat; called tonsillitis if tonsils are primarily
.3
infected; symptoms include sore throat, sometimes fever, throat may be covered by
.a milky white exudate, ulcers, blisters, or even a grayish membrane
.Sinusitis - sinuses fill with fluid & become infected
.4
Otitis media - middle ear infection; middle ear fills with fluid & becomes
.infected
.5
Epiglottitis - infection of the epiglottis; can cause the epiglottis to swell to
.6
many times its normal size; can cut off respiration and cause sudden death; on rare
occasions laryngitis (infection of the larynx) & laryngotracheobronchitis (croup produces a barking cough) may also cause this to occur; a severe airway narrowing
near the epiglottis or the larynx causes stridor (whistling sound heard as the person
.)breathes in
Bronchitis - infection of the bronchi; produces a thick, infected mucous; cough
.7
brings up infected phlegm; fever is another symptom; complete obstruction does not
.occur because the bronchi are so numerous
Bronchiolitis - infection of the bronchioles; inflammation narrows these tiny
.8
collapsible airways; air can enter, but has difficulty getting out; clinical signs include
.)wheezing (musical noise heard during expiration) & trachyapnea (rapid breathing
Pneumonia - infection of the lungs, with fluid & microbes replacing the air that
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normally fills the alveoli; normal gas exchange cannot take place; clinical signs
include fever, trachyapnea, labored breathing, & a cough that may produce infected
secretions; if pneumonia involves the pleura, it causes pleurisy, associated with
.painful breathing; caused by bacteria, viruses, and fungi
II. Upper Respiratory Infections
A. Bacterial Causes of URI's (Bacteria are the most virulent of the u.r. pathogens,
)!but the great thing is that they can be treated with antibiotics
Haemophilus influenzae .1
a. General
G(-) rod
¨
needs a growth factor present in human red blood cells - hence the name
)"Haemophilus ("blood loving
¨
!!)”once thought to cause influenza - IT DOES NOT CAUSE INFLUENZA (“the flu
.major cause of virulence is the production of a capsule
¨
¨
:b. URI's
epiglottitis - caused by H. influenzae type B (encapsulated) – adults produce ).1
Ab's, but young children are at risk; ampicillin not effective due to plasmid-borne
antibiotic resistance; conjugate vaccine (Hib) now available; babies are routinely
.immunized against this pathogen
sinusitis - caused by H. influenzae (nonencapsulated) strains ).2
otitis media (middle ear infection) - caused by H. influenzae (nonencapsulated)
.strains
).3
:c. H. influenzae type B (encapsulated) also causes
meningitis - infection of membranes covering the brain & spinal cord; before
the vaccine this bacterium was the leading cause of meningitis and mental
.retardation in children
).1
.cellulitis - infection of skin & subcutaneous tissues ).2
)conjunctivitis (pink eye ).3
Streptococcus pyogenes .2
:a. General
G(+) cocci
¨
"pyogenes means "pus forming
¨
)do not produce the enzyme catalase (distinguishes them from the Staphs
¨
medically important strains are classified by their hemolytic & serological
¨
properties [see lab manual for beta vs. alpha hemolysis; S. pyogenes is usually beta
]hemolytic - clear zones of hemolysis
:b. URI's
pharyngitis (strep throat) - transmitted by respiratory droplets or contaminated ).1
food/drink; clinical signs: severe sore throat, fever, chills, headache, inflamed
pharynx, tender lymph nodes in neck; whitish exudate on tonsils; diagnosis: latex
.agglutination kit that detects Ag in throat swab
:c. Complications of strep throat
scarlet fever - some strains produce an erythrogenic exotoxin that causes ).1
scarlet fever; the toxin kills cells and causes intense inflammation; was once a life.)threatening illness; today's cases are mild (due to a decrease in virulence
septicemia - bacteria spread to into the blood stream ).2
rheumatic fever - occurs after the infection is over (postinfection complication); ).3
causes inflammation of joints, skin, brain, heart valves (endocarditis); leading cause
of heart disease among children in developing countries; bacteria have an Ag similar
to that on heart cells – wbc’s become sensitized to the bacterial Ag, then attack the
heart cells; disease can be prevented if strep throat is treated with penicillin within
first 10 days; r.f. patients should receive a monthly penicillin injection - they are in
.danger if they contact another strep infection
:d. Other diseases caused by Streptococci
Impetigo (pyoderma) – highly contagious; occurs almost exclusively in children;
usually different strain than those that cause strep throat; easily treated with
).1
penicillin; usually heals without scarring, but pigment can be permanently lost; also
.caused by staphylococci
Corynebacterium diphtheriae .3
:a. General
G(+) irregular rod
¨
produce an exotoxin; gene for exotoxin is carried by a temperate
¨
bacteriophage, so only strains infected by this virus can produce toxin & cause
.diphtheria; toxin interferes with protein synthesis in eukaryotic cells
b.
Diphtheria
transmission: respiratory droplets; bacteria is noninvasive, but deeper tissues
are affected because they absorb the toxin
¨
clinical signs: infected throat swells & becomes covered by a tough, grayish
¨
pseudomembrane composed of dead human cells & microbes [membranous
pharyngitis]; swollen tissue & pseudomembrane can obstruct airway, leading to
death by suffocation; fatal complications can also result if toxin enters the blood
stream and damages other organs; treatment: horse antitoxin (serum sickness is a
)potential risk
prevention: toxoid vaccine - produced by treating toxin with formaldehyde ¨
part of DPT (diphtheria-pertussis-tetanus) series given to infants; immunization does
!not confer lifelong immunity - adults should have a booster every 10 years
Bacterial causes of the common cold: Mycoplasma pneumoniae, Coxiella .4
.burnetii
.Remember that most colds are viral
B. Viral Causes of URI's - more common & less serious than bacterial infections;
treatment is a challenge (antibiotics are worthless). (See Chapter 10 on these groups
)of viruses
Rhinoviruses .1
a. General
RNA viruses
¨
"named for portal of entry - rhino means "nose
¨
.primary cause of commn cold - causes 1/4 to 1/2 of colds
about 100 different serotypes (have different antigens
¨
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