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Bio 169 Respiratory System Study Guide
Spring Semester 2005

Learning Objectives, Topics, Key Words



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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)

Boyle’s 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 doesn’t 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

Daltons’s 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)

Henry’s 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 pO2 favors unloading in tissues

pH affects binding

pCO2 affects binding

CO2 promotes O2 dissociation under tissue conditions (pCO2, low pO2)

Hb F (fetal) higher O2 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 CO2 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