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MEDSCI 142 > Respiratory System > Flashcards

Respiratory System Flashcards

1
Q

function of conchae

A
  • increases surface area of mucus that air is exposed to
  • create turbulence → swirls air around/slows air down→ particles stick to mucus
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2
Q

how does the nasal cavity prepare air for respiration?

A
  • thick hairs (i.e. vibrissae) at entrance → filters/cleans air
  • lined with respiratory epithelium (i.e. pseudostratified ciliated columnar epithelium + goblet cells + basal cells) → particles stick to wet/warm mucus → humidifies and heats air
  • very rich blood supply under epithelium → heat from blood into air → warms air
  • glands under epithelium → secrete water → humidifies air
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3
Q

olfactory epithelium

A
  • at roof of nasal cavity
  • sniffing → causes turbulence → carries air up to olfactory epithelium
  • axons of olfactory receptor cells → through perforations in overlying bone (i.e. cribriform plate) → brain
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4
Q

impairments to mucocilliary escalator

A
  • allergies, bronchitis, colds → excess mucus, cilia cannot cope → mucus is not cleared → coughing, increased risk of infection
  • smoking → toxins paralyse cilia (disappear with long term smoking), makes mucus thicker → mucus is not cleared → coughing, increased risk of infection
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5
Q

order of conductive airways

A

nasal cavities → pharynx → larynx → trachea → main stem bronchi → lobar bronchi → segmental bronchi → smaller bronchi → terminal bronchioles

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6
Q

order of respiratory airways

A

nasal cavities → pharynx → larynx → trachea → main stem bronchi → lobar bronchi → segmental bronchi → smaller bronchi → terminal bronchioles

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7
Q

generations of respiratory tree

A
  • trachea → 0
  • main stem bronchi → 1
  • lobar bronchi → 2
  • segmental bronchi → 3
  • smaller bronchi → 4-9
  • bronchioles → 10-15
  • terminal bronchioles → 16-19 (i.e. the point at which risk of critical infection transitions from low → high)
  • respiratory bronchioles → 20-23
  • alveolar ducts → 24-27
  • alveolar sacs → 28
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8
Q

features of bronchial wall

A
  • cartilage, smooth muscle → keeps the bronchi open
  • ciliated columnar epithelium + goblet cells, mucus glands → secrete and move mucus, condition air for gas exchange
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9
Q

features of bronchiolar wall

A
  • smooth muscle → controls flow of air
  • ciliated cuboidal epithelium, club cells → move/destroy particles that haven’t been filtered, condition the air for gas exchange
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10
Q

features of alveolar wall

A
  • type I pneumocyte → squamous epithelium, very thin cytoplasm
  • type II pneumocyte → cuboidal epithelium, secretes surfuctant
  • alveolar macrophages → last minute defence, ingests particles
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11
Q

lung segments

A
  • divisions of the lungs with each division supplied by a segmental bronchus
  • each has its own air/blood supply and connective tissue capsule
  • damage in one segment will not impact the others
  • generally 8 on the left, 10 on the right
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12
Q

responsibility of ribs in quiet breathing

A

ribs responsible for ~25% of air movement in/out of lungs

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13
Q

responsibility of diaphragm in quiet breathing

A
  • responsible for ~75% of air movement in/out of lungs in quiet breathing
  • smaller proportion during exercise
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14
Q

structure of diaphragm

A
  • dome-shaped platform, forms floor of thorax
  • central part → thin sheet of connective tissue/aponeurosis (i.e. central tendon)
  • lateral margins → fast acting skeletal muscle, innervated by phrenic nerve
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15
Q

innervation of respiratory muscles

A
  • internal intercostal muscles → internal intercostal nerves (T1-L1)
  • external intercostal muscles → external intercostal nerves (T7-L1)
  • diaphragm → phrenic nerve (C3-C5)
  • abdominal muscles → abdominal nerve (T7-L1)
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16
Q

residual volume

A
  • volume remaining in the lungs following maximal expiration
  • some air remains trapped in small airways, prevents airways from fully collapsing
  • cannot be measured with spirometer
  • assessed by dilution method involving breathing helium gas
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17
Q

minimal volume

A

volume of air remaining in the lungs after a complete collapse of the lung

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18
Q

functional residual capacity

A

expiratory reserve volume + residual volume

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19
Q

vital capacity

A

inspiratory reserve volume + tidal volume + expiratory reserve volume

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20
Q

respiratory frequency

A
  • number of times you breathe in a minute
  • ~12 breaths/min
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21
Q

dead space ventilation

A
  • dead space volume (0.15L) x respiratory frequency
  • ~1.8L/min
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22
Q

alveolar ventilation

A
  • (tidal volume - dead space) x respiratory frequency
  • ~4.2 L/min
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23
Q

minute ventilation

A
  • tidal volume x respiratory frequency
  • dead space volume + alveolar volume
  • ~6.0 L/min
  • hyperventilation → >6 L/min
  • hypoventilation → <6 L/min
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24
Q

FEV1

A
  • forced expiratory volume in 1 second
  • ~4.0L
  • smaller FEV1 indicates increased resistance
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25
Q

FVC

A
  • forced vital capacity
  • ~5.0L
26
Q

FEV1/FVC

A
  • ~80% in healthy lung
  • lower/higher indicates problem
27
Q

elasticity

A
  • ability to recover original size and shape after deformation
  • due to elastin and collagen in lung tissue
  • forms a matrix that supports airways, alveoli, and vessels
  • in inhalation → fibres stretch → outwards pulling force (i.e. radial traction) → opens airways → reduces resistance to airflow
  • in exhalation → inwards pulling force → passively returns stretched airways to resting state
28
Q

compliance

A
  • term used in respiratory physiology (i.e. not elasticity)
  • compliance = 1/elasticity = change in volume/change in pressure
  • how much pressure required to pull apart, stiffness
  • more pressure required → less compliant
  • less pressure required → more compliant
29
Q

Laplace’s law

A
  • measures the surface tension induced pressure within the alveoli
  • P = 2T/R
  • P → pressure, T → surface tension, R → radius of alveolus
  • the smaller the radius, the greater the deflating pressure
30
Q

COPD

A
  • chronic obstructive pulmonary disease
  • increased compliance → less pressure required to inflate lungs
  • at FRC, lung is somewhat inflated, diaphragm is flattened, mid-sternal space reduced
  • cannot take deep breaths → limited inspiratory reserve volume
  • caused by smoking → loss of elastic fibres
31
Q

Fibrosis

A
  • decreased compliance → more pressure required to inflate lungs
  • at FRC, lungs are deflated, mid-sternal space widened
  • fluffy white matter (i.e. fibrotic tissue) at bottom of lung
  • caused by toxins/contaminants (e.g. coal mining) → inflammation → scar tissue
32
Q

dead space

A
  • formed by conducting zone (i.e. trachea, main stem bronchi, lobar bronchi)
  • volume of air that fills conducting airways, does not participate in gas exchange
  • ~150 mL per breath
  • ~2.2 mL per kg
  • causes contamination of freshly inhaled air, diluting oxygen content
33
Q

funnel effect

A
  • air flow ∝ 1/cross-sectional area
  • cross-sectional area increases from trachea → alveoli by 500x
  • conducting zone → fast and turbulent air flow
  • respiratory zone → slow and laminar (i.e. in smooth, parallel layers) air flow
34
Q

parasympathetic control of airflow

A
  • innervated by branches of vagus nerve
  • bronchoconstriction
  • releases acetylcholine
  • acts on muscarinic receptor → smooth muscle constriction
35
Q

sympathetic control of airflow

A
  • innervated by sympathetic nerves from thoracic spinal segment
  • bronchodilation
  • releases noradrenaline
  • acts on beta-adrenoceptors → smooth muscle relaxation
36
Q

Hering-Breuer Reflex

A
  • mechanoreceptors in bronchioles detect stretch → activates vagus afferents (i.e. sensory nerves of vagus nerve) → signal sent to medulla oblongata respiratory centres
  • activates sympathetic efferents → signal sent to NA-β-adrenoceptor (i.e. noradrenaline) on bronchioles → bronchodilation
37
Q

pulse pressure

A

systolic pressure - diastolic pressure

38
Q

pulmonary pressure

A
  • systolic/diastolic → 22/10 mmHg
  • mean → 14mmHg
  • low pressure system
  • only has to pump blood to one organ (i.e. lungs)
39
Q

tracheobronchial circulation

A
  • branch of aorta delivers oxygenated blood → tracheobronchial tree
  • deoxygenated blood from tracheobronchial tree → branch of vena cava and branch of pulmonary vein
  • branch to pulmonary vein (i.e. anatomical shunt/design fault) delivers deoxygenated blood into left side of heart, contaminates oxygenated blood
40
Q

regional variations

A

top of lung → hydrostatic pressure is the lowest (i.e. poorly perfused), P(A) > P(a) > P(v)
middle of lung → hydrostatic pressure is greater, P(a) > P(A) > P(v)
bottom of lung → greatest hydrostatic pressure (i.e. best perfused), P(a) > P(v) > P(A)
- P(a) → pulmonary blood pressure/hydrostatic pressure
- P(v) → arterial venous difference, driving force for blood flow
- P(A) → alveolar pressure

41
Q

pulmonary hypertension

A
  • hypoxia → vasoconstricton → increased pulmonary vascular resistance → increased afterload to overcome
  • increased pulmonary arterial pressure → strain on right ventricle → right heart failure → stretched, baggy, weak
42
Q

pulmonary oedema

A
  • left ventricular myocardial infarction (e.g. due to blood clot), right heart normal → congestion → increased pulmonary venous pressure
  • increased hydrostatic pressure → oedema → systemic hypoxia (i.e. not enough oxygen to the body) → tired, weak, breathlessness (i.e. dyspnoea)
43
Q

PO2 differential across tissue

A
  • alveoli → 100mmHg
  • capillary → 40mmHg
  • 60mmHg difference
  • diffuses into capillaries
  • large driving force (i.e. 10x bigger than CO2)
44
Q

PCO2 differential across tissue

A
  • alveoli → 40mmHg
  • capillaries → 46mmHg
  • 6mmHg difference
  • diffuses into alveoli
  • small driving force
45
Q

carrying capacity of blood for oxygen

A
  • 1L of blood (i.e. 150g Hb) carries 200mLs of oxygen
  • 1g of Hb can transport 1.39mL of oxygen when fully saturated
  • at PO2 of 80mmHg, 1L of blood carries 0.2mL of aqueous oxygen
46
Q

oxygen transport in blood

A
  • binds with haemoglobin (predominantly)
  • dissolves in solution
47
Q

carbon dioxide transport in blood

A
  • dissolves in solution (20x more soluble in blood than O2)
  • as HCO3- (i.e. predominantly, 85% of carbon dioxide, catalysed by carbonic anhydrase, 60% diffused into plasma, 20% in red blood cells, 5% in plasma (i.e. not enzymatically regulated))
  • combines to amine groups (i.e. NH2) of proteins (CO2 + Hb-NH2 ↔ Hb-NHCOO- (i.e. carbamino protein) + H+)
  • as H2CO3 and CO3- ions (low levels)
48
Q

oxygen dissociation curve - saturation

A
  • sigmoidal relationship due to cooperative binding
  • at lower PO2 → smaller percent oxygen saturation of haemoglobin, lower affinity, tissues have lower PO2 (i.e. due to oxygen consumption) → encourages oxygen release
  • at higher PO2 → higher percent oxygen saturation of haemoglobin, higher affinity, alveoli have higher PO2 (i.e. due to oxygen rich air entering) → encourages oxygen uptake
  • ~25% reduction in saturation from lungs to tissues
  • independent of amount of Hb present
49
Q

why does Hb’s affinity for oxygen change?

A
  • Hb4 (i.e. deoxyhaemoglobin) + O2 → Hb4O2 + O2 → Hb4O4 + O2 → Hb4O6 + O2 → Hb4O8 (i.e. oxyhaemoglobin, fully saturated)
  • CO2 + H2O ↔ H2CO3 (i.e. carbonic acid) ↔ H+ HCO3- (i.e. bicarbonate)
    • CO2 + H2O ↔ H2CO3 catalysed by carbonic anhydrase, highly concentrated in red blood cells, can go in either direction
  • at tissues → more CO2, more H+, lower pH → causes conformational changes that decrease haemoglobin affinity for oxygen → oxygen release
  • at lungs → less CO2, less H+, higher pH → causes conformational changes that increase haemoglobin affinity for oxygen → oxygen uptake
50
Q

oxygen dissociation curve - content

A
  • dependent on PO2 and amount of haemoglobin present
  • less capacity for carrying oxygen
  • anaemia (i.e. reduced blood cells, haemoglobin) → saturation may be 100%, but blood oxygen content is reduced
51
Q

carbon dioxide dissociation curve - content

A
  • two curves since HbO2 has less affinity for CO2 than Hb (i.e. deoxyHb)
  • HbO2/arterial blood → displaced to the right (i.e. Haldane shift)
  • actual curve is steeper than expected since arterial and venous points are joined
  • cannot be saturated → dependent on PCO2, high CO2 solubility and methods of transport
52
Q

Bohr shift

A
  • Bohr shift → for a given PO2, haemoglobin has a lower affinity for oxygen, less saturated, more oxygen given up
  • represented by a rightward shift
  • e.g. at tissues
  • increased CO2, increased [H+] (i.e. lower pH), increased temperature (i.e. heat generated by metabolism), increased DPG (i.e. diphosphoglycerate, product of metabolism, binds to Hb, contributes to offloading of O2)
53
Q

chloride shift

A
  • HCO3- moves out/into of cell down its concentration gradient
  • entrance/exit of Cl- ions maintains cellular electroneutrality
    at tissue -> HCO3- moves out of cell, Cl- ions enter cell
    at lung -> HCO3- moves into of cell, Cl- ions exit cell
54
Q

fetal haemoglobin

A
  • leftward shift in oxygen dissociation (saturation) curve
  • higher affinity for oxygen than adult haemoglobin at a given PO2
  • O2 saturation within maternal blood entering the placenta is low
  • helps movement of oxygen across placenta to foetus
  • prevents hypoxia in foetus
55
Q

myoglobin

A
  • leftward shift in oxygen dissociation (saturation) curve
  • functions as O2 store within muscle tissue
  • higher affinity for oxygen than haemoglobin at a given PO2
  • only binds one O2
56
Q

location of peripheral chemoreceptors

A
  • outside central nervous system
  • located in aortic bodies (i.e. at aortic arch) carotid bodies (i.e. at bifrucation of carotid artery)
  • connected to brain stem via vagal and glossopharyngeal nerves (i.e. C5/C6)
57
Q

stimulants of peripheral chemoreceptors

A
  • hypoxia (i.e. reduced PO2)
  • hypercapnia (i.e. increased PCO2)
  • combination of hypoxia and hypercapnia (i.e. very effective)
  • haemorrhage (i.e. loss of blood and ability to carry oxygen)
  • acidosis (i.e. decreased blood pH)
  • increased sympathetic activity (i.e. decreased blood supply to carotids)
  • sodium cyanide (i.e. mimics lack of oxygen)
58
Q

reflex response of peripheral chemoreceptors

A
  • fast response time
  • increases rate and depth of breathing (i.e. minute volume increases)
59
Q

location of central chemoreceptors

A
  • inside central nervous system
  • located within the medulla oblongata
  • three chemo-sensitive regions on ventral surface
  • neurons and/or astrocytes <0.5mm beneath the surface
  • close to basilar artery
60
Q

stimulants of central chemoreceptors

A

H+ ions liberated when CO2 diffuses across the blood brain barrier and dissolves in CSF

61
Q

reflex response of central chemoreceptors

A
  • slow response time as protons cannot cross blood-brain barrier, and low levels of carbonic anhydrase in CSF
  • increases minute volume
  • hypercapnia (i.e. increased PCO2) increases minute volume in a non-linear manner (i.e. dog leg effect)

MEDSCI 142 (6 decks)

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