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Flashcards in The respiratory system Deck (59):
1

Respiratory quotient

Ratio of CO2: O2 - depends on food consumed

2

Trachea and bronchi

Rigid tubes - rings of cartilage avoid collapse

3

Bronchioles

No cartilage, smooth muscle walls, sensitive to some hormones/chemicals

4

Alveoli

Thin walled inflatable sacs
Pulmonary capillaries around each alveolus for good blood supply
Large SA and thinner - efficient gas exchange 0.5 microm

5

Type I alveolar cells

1 cell layer thick - flattened

6

Type II alveolar cells

Secrete surfactant (phospholipid)

7

Alveolar macrophages

Guard lumen to prevent infection

8

Pores of Kohn

Airflow between neighbouring alveoli - collateral ventilation
Lined with ciliated epithelia and bathed in mucous - much-ciliatory escalator

9

Pleural sac

Double-walled, closed sac separating from thoracic wall
Pleural cavity = interior
Intracellular sac secreted by pleura surfaces - lubrication, protection

10

Diaphragm

Skeletal muscle separating thoracic and abdominal cavity

11

Function of respiratory system

Exchange of gases in air/blood, homeostatic regulation of pH, defence against inhaled pathogens, vocalisation, thermoregulation, water loss

12

Pressures in the respiratory system

Atmospheric (barometric) pressure
Intra-alveolar pressure (intrapulmonary)
Intrapleural pressure (intrathoracic)
Alveolar pressure atmospheric = air out of lungs

13

Boyle's Law

Any constant temperature, the pressure exerted by a gas varies inversely with the volume of gas

14

Lung mechanics

No muscles, relies on difference in pressure (transpulmonary pressure = Palv - Pip) and compliance (stretch)
Respiration muscles attached to chest wall and contract and real to change chest dimensions, causing TP change

15

Inspiration

Diaphragm domed -> phrenic nerve -> contracts and flattens
Intercostal muscles -> intercostal nerve
Expansion of thoracic cavity decrease in intrapleural pressure - increasing ling volume and lowers intra-alaveolar pressure than atmospheric so air enters

16

Expiration

Relaxation of inspiratory muscles - diaphragm and chest wall muscles decrease chest cavity size
Intrapleural pressure increases, compresses lungs, intra-alveolar pressure increases - above atmospheric -> air out
Contraction of expiration muscles -> abdominal wall and internal intercostal

17

Elastic recoil of alveoli

Highly elastic connective tissue, alveolar surface tension

18

Lung compliance

Effort to stretch lungs
Change in volume to given force/pressure = change in V/Change in P
Ease with with volume can be changed
Reciprocal of elastane
High compliance = easy chest expansion

19

Law of LaPlace

Surface tension P=2T/R
P in large alveolus > smaller - small may collapse
Sufacant lowers surface tension o liquid lining alveoli so pressure to hold alveoli open = reduced

20

Airway resistance, R

R proportional to Ln/r^4
Upper airways diameter constant
Mucus accumulation can increase resistance
Bronchioles - collapsible tubes increase R
Bronchoconstriction (asthma) and dilation can occur

21

Tidal volume, TV

Volume of air/breath

22

Inspiratory reserve, IRV

Extra volume that can be maximum inspired

23

Inspiratory capacity, IC

= IRV + TV

24

Expiratory reserve, ERV

Extra volume that can be expired by max contraction beyond normal

25

Residual volume, RV

Minimal volume remaining in lungs after max expiration

26

Functional residual capacity, FRC

Volume of air in runs after normal expiration
= ERV + RV

27

Vital capacity, VC

Max volume of air in single breath maximum inspired
IRV + TV + ERV

28

Total lung capacity, TLC

Mac volume lungs can hold
VC + RV

29

Forced expiratory volume in 1 second, FEV

Volume of air during first second of expiration in VC determination

30

Anatomical dead space

Conducting airways, no gas exchange occurs ~150ml

31

Physiological dead space

Anatomical dead space + alveolar dead space
Alveolar dead space = non-functioning alveoli e.g. absence of blood flow

32

Minute ventilation

Volume breathed in per min

33

Pulmonary ventialton

Tidal volume x respiratory rate

34

Alveolar ventialtion

TV-dead space x respiratory rate

35

Pulmonary circulation

Conc O2 + CO2 in arterial blood is contents, O2 in same rate as consumers, CO2 out same rate as produced

36

Gas exhange

Simple diffusion of O2/CO2 down partial pressure gradients
pp exerted by each gas in mixture = total pressure x fractional composition of gas in mixture
Diffusion gradients in lungs and tissue affected by conc grad, SA and permeability

37

Dalton's law

P total = P1 + P2....
Air --- becomes moist ---> alveoli --> water vapour reduced N2/O2 levels

38

Establishment of gradients

P(air) = PN2, PO2, PH2O, PCO2
Air through conducting zone - humidified to saturation

39

Solubility of gases

Any pp cones of dissolved gases differ - some more soluble

40

Henry's law

C = kP (pp in atmosphere)

41

Air flows down conc gards

Air -> alveoli PO2 down
PCO2 down
Due to continuous gas exchnage alveoli/capillaries, air mixes with alveoli air, alveoli air saturated water vapour

42

Exchange of O2 and CO2

In alveoli = rapid
In tissue = diffusion grads. PCO2 depends on metabolic activity and blood flow to tissue. Large grads = more exchange
Venous blood active tissue, down PO2 and up PCO2
Venous blood right atrium mixed PCO2 and PO2 average

43

Determinants of alveolar PO2 and PCO2

PO2 and PCO2 in inspired air, minute ventilation, rate respiration tissue consumes O2/produces CO2 - alveolar ventilation exceeds demands of tissue: PO2 up and PCO2 down

44

Matching ventilation to perfusion

Ratio alveolar ventilation to pulmonary blood flow (Va/Q - 0.8 av)
Upright = gravity increases pulmonary arterial hydrostatic pressure at base than apex - alveolar ventilation varies in same direction as blood flow
Ventilated alveoli close to perfused capillaries ideal for gas changes.
Top blood flow not as good - middle = best
Airway obstruction - V/Q = 0 no ventilation
Vascular obstruction - V/Q = infinity = no perfusion

45

Perfusion

Delivery of blood to tissue

46

Haemoglobin

Hb + O2 HbO2 - each carries 4 O2 molecules
PO2 100mgHg (normal) = Hb 98% sat

47

O2/Hb dissociation curve

ppO2 high (lungs) sat high
ppO2 low (tissue) sat low - dissociation
Plateau where ppO2 high - lungs
Steep - systemic Hb unloads O2 to tissues
Sigmoidal curve
1O2 bound increase affinity for Hb for next O2
O2 binding = conformational changes
Lower affinity shifts curve right - higher pO2 to achieve saturation
Higher affinity shift to left - lower PO2 to achieve sat
Temp increase - to right
pH acidity up, affinity down, to left

48

Myoglobin

O2 binding protein in skeletal muscle - higher affinity for O2 than Hb
Low pO2 50% saturated
Liberates O2 when pO2 to 10mmHg

49

Foetal Hb

PaO2 20mmHg low sat - 60% sat

50

Co2 combined with water

Bicarbonate ion -> carbonic acid

51

Hypoventilate

PCO2 and H+ ions up, lower pH, inc HCO3- respiratory acidosis - kidneys conserve HCO3-
PO2 down stimulates increase in breaths and depth

52

Hyperventilate

PCO3 and H+ ions down, higher pH, decrease in HCO3- - respiratory alkalosis - renal compensation excretes HCO3
APO2 up - reduced lack of CO2 - decrease breaths and depth

53

'Black box' control of breathing

Respiratory neurons in medulla inspiration and expiration
Neurons in pons modulate ventilation
Rhythmic pattern breathing
Ventilation modulated chemical factors and higher brain centres

54

What controls breathing rhythm

Medulla oblongata
Dorsal respiration group - in region in nucleus tracts solitairus (NTS)
Vagus nerve and higher brain centres alter DRG/VRG

55

Chemoreceptors

Monitor PO2, PCO2, in carotid and aortic bodies

56

Type I peripheral chemoreceptors

Contact blood - afferent nerves - NT

57

Type II peripheral chemoreceptors

Glial cell like - repair and nutrient supply

58

Central chemoreceptors

Ventral surface medulla - H+ ions stimuli pH change cerebrospinal fluid
H+ don't cross, CO2 does

59

Chemoreceptor reflex

Central and peripheral respond PCO2 changes