Bio 169 Respiratory System Study Guide
Spring Semester 2005
Learning Objectives, Topics, Key Words
Readings: Martini, Chapter 23
1. Know the organs of the respiratory system and understand their functions
upper respiratory system
nose
naris (plural = nares; external and internal)
paranasal sinuses
conchae (also called, turbinates) --> spinning of air (recall: turbine)
warms, moistens, filters
epithelium : pseudostratified ciliated with goblet cells
olfaction
affects speech
pharynx -- 3 regions
nasopharynx (above palate)
oropharynx (also digestive)
laryngopharynx (below epiglottis)
lower respiratory system
larynx (voice box)
anchored superiorly to hyoid bone
made mostly of hyaline cartilages (e.g.,thyroid, cricoid)
glottis (see p. 805)
epiglottis (elastic cartlilage)
keeps solids and liquids out
vocal folds (vocal "cords")
trachea (windpipe)
hyaline cartilage (hold trachea open, C-shaped rings accommodate esophagus)
ciliated mucous pseudostratifed (beat upwards)
tracheostomy
intubation
lungs
apex, base
pleura (visceral (covers lung), parietal (chest wall))
intrapleural space (a potential space what is the pressure in here?)
hilus
lobes (3 right, 2 left)
fissures
segments (9 or 10/lung)
bronchial tree (trachea --> bronchioles)
bronchiole histology changes as gets smaller: cartilage decreases, smooth muscle increases
[conducting portion = "dead space"]
(upper respiratory system included in conducting portion)
primary bronchus (plural, bronchi)
branch from trachea at carina
secondary bronchi (lobar)
tertiary bronchi (segmental)
bronchioles
smooth muscle layer relatively thicker
progressively lose goblet cells, then cilia
terminal bronchioles
ANS control of smooth muscle (PS constricts, S dilates)
asthma (how do certain asthma drugs work?)
bronchoscopy
[respiratory portion = gas exchange surfaces]
respiratory bronchioles
alveolar ducts
alveoli (the bottom line!)
squamous epithelium (type I)
elastic basement membrane
Type II alveolar cells
secrete surfactant
alveolar macrophages (dust cells)
fibroblasts -- in interstitium (space surrounding alveoli)
make elastic and reticular fibers
blood supply to the lungs
dual
deoxygenated blood from right ventricle
oxygenated blood to bronchial tree from branches off aorta
2. Understand the components of the respiratory membrane (also called, alveolar-capillary membrane)
gas exchange surface
diffusion
oxygen in
carbon dioxide out
Type I cells
basement membrane of alveolus
basement membrane of capillary
capillary endothelium
(RBC membrane)
3. Understand the mechanics of pulmonary ventilation (breathing)
bulk flow
pressure difference
inspiration (inhalation)
Boyles Law (increasing volume --> decreasing pressure)
inspiration (inhalation)
muscles of inspiration
diaphragm
external intercostal muscles
accessory muscles (sternocleidomastoid, scalenes)
intrapleural pressure (always subatmospheric)
intrapleural space has thin layer of serous fluid
alveolar pressure (cycles above and below atm. pressure)
eupnea
expiration (exhalation)
muscles = internal intercostals (+ abdominals)
tissue elasticity
alveolar surface tension
surfactant reduces
preemies may lack surfactant
collapse of alveoli = atelectasis
atelectic lung doesnt contribute to gas exchange
compliance (= change in volume ÷ change in pressure; opposite of "stiffness")
compliance determines the work of ventilation
decreased in restrictive lung disease, e.g. interstitial fibrosis --> decr. compliance
increased in obstructive lung disease, e.g., chronic obstructive pulmonary disease (COPD) e.g., like emphysema
4. Understand the pulmonary volumes and pulmonary capacities
typical rate = 12 breaths/min
6 liters/minute ("minute volume")
spirometer -- used to perform pulmonary function tests (volumes, rates of gas flow)
volumes
tidal volume (resting TV ~500 ml)
alveolar ventilation = tidal volume anatomic dead space (~150 ml)
expiratory reserve volume (ERV)
inspiratory reserve volume (IRV)
residual volume (RV)
capacities (sums of different volumes)
inspiratory capacity (IC=TV + IRV)
functional residual capacity (FRC=RV + ERV)
(forced) vital capacity (FVC= IRV + TV + ERV)
total lung capacity (sum of all volumes)
5. Understand the chemistry of the exchange of oxygen and carbon dioxide
Daltonss Law
total pressure = sum of partial pressures of a gas mixture
partial pressure = mole fraction x total pressure
pO2 (e.g., 0.21 x 760 mmHg = 160 mmHg)
Henrys law
concentration of dissolved gas is proportional to partial pressure
bends
hyperbaric chamber
6. Understand external and internal respiration
gas transport is driven by difference in partial pressures
external respiration = gas exchange between alveolus and capillary
pO2 (105 mmHg alveolus vs ~40 mmHg in venous blood)
pCO2 (40 mmHg vs 45 mmHg)
depends on surface area (~70 meters2)
diffusion distance (thinner alveolar-capillary membrane --> faster)
rate and depth of alveolar ventilation
internal respiration = gas exchange between capillary and cells
same laws, opposite direction of gradient in partial pressures
7. Understand the transport of oxygen and carbon dioxide by the blood
Oxygen
problem: O2 not very soluble in water
most transported bound to hemoglobin (to iron atoms in heme groups)
20 ml oxygen/100 ml arterial blood (=100% saturation)
alveolar pO2 determines saturation
% saturation vs pO2 is S-shaped relation
flat at very high pO2
very steep at low pO
2 favors unloading in tissuespH affects binding
pCO
2 affects bindingCO
2 promotes O2 dissociation under tissue conditions (pCO2, low pO2)Hb F (fetal) higher O
2 affinity than Hb A (maternal)Carbon Dioxide
v. soluble in water
mostly in plasma
reacts with water
carbonic anhydrase
bicarbonate ion (most)
some binds to hemoglobin (globin)
carbaminohemoglobin (form of hemoglobin with CO
2 bound to it)8. Understand the control of ventilation by the nervous system
brain stem (see diagram, p. 863)
medullary rhythmicity center
dorsal respiratory group (DRG) = inspiratory center)
ventral respiratory group (VRG) = expiratory center)
intrinsic rhythmic neural network sets the basic pattern of inspiration
apneustic center (pons)
stimulates DRG (during inspiratory phase)
pneumotaxic center (pons)
inhibits apneustic center (promotes exhalation)
for fast breathing
"higher centers" influence brain stem
e.g., can stop breathing voluntarily (for a bit; WHAT FORCES YOU TO BREATHE?)
speech
exercise (experience and upper motor neuron output are inputs to lower centers)
hypothalamus for temperature regulation (panting)
chemical sensation
peripheral chemoreceptors
aortic body
carotid body
sense pCO2, pO2, pH
central chemoreceptors
neurons in medulla -- sense pH
hypercapnia and hypocapnia
hypoxia increases sensitivity to hypercapnia
hypoxia
mild hypoxia stimulates ventilation
hypercapnia increases sensitivity to hypoxia
"positive feedback" at very low pO2
decreased ventilation because respiratory neurons are oxygen starved
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Last updated 24 March 2005