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x1 - Respiratory > Physiology > Flashcards

Physiology Flashcards

1
Q

functions of the respiratory system

A

*Gas exchange
acid base balance
protection from infection
communication via speech

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2
Q

type 1 pneumocytes

cell type + function

A

simple squamous epithelium

for gas exchange

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3
Q

type 2 pneumocytes

cell type + function

A

Cuboidal epithelium

produce surfactant

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4
Q

muscles for inspiration

A

diaphragm (contracts + lowers)

external intercostal muscles (pull ribs up)

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5
Q

muscles for forced expiration

A

internal intercostal muscles (force ribs down)

abdominal muscles

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6
Q

Boyle’s law

+ relation to breathing

A

the pressure exerted by a gas is inversely proportional to its volume

*When you increase the volume in the lungs/ intrapleural cavity, the pressure decreases

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7
Q

steps of inspiration

A
  1. contraction of muscles
  2. decrease in intrapleural pressure
  3. lungs expand
  4. decrease in alveolar pressure
  5. air flows into lungs
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8
Q

Alveolar pressure (P (subscript)A)

A

pressure inside lungs

changes from slightly +ve to slightly -ve with breathing cycle

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9
Q

intrapleural pressure (P (subscript)ip)

A 
pressure inside pleural cavity
always negative (and less than alveolar pressure*) in health due to elastic recoil of lungs and chest wall away from each other

*If not, the lungs would collapse

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10
Q

transpulmonalry pressure (P (subscript)T)

A

alveolar pressure - intrapleural pressure

always positive in health. if negative, the lungs would collapse due to their elastic recoil.

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11
Q

respiratory minute volume/ pulmonary ventilation

A

the volume of air inhaled or exhaled from a persons lungs per minute

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12
Q

mechanical factors affecting respiratory minute volume

A
  1. difference between atmospheric and alveolar pressures

2. airway resistance (mostly determined by radii of airways)

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13
Q

Alveolar ventilation

A

volume of fresh air getting to the alveoli (and so available for gas exchange) per minute

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14
Q

alveolar PO2

A

100mgHg

13.3kPa

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15
Q

Arterial PO2

A

75mgHg

10kPa

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16
Q

Alveolar PCO2

A

40mgHg

5.3kPa

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17
Q

Arterial PCO2

A

46mgHg

6.1kPa

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18
Q

The role of pulmonary surfactant

A

reduces surface tension on the alveolar surface membrane which…

reduces tendency for alveoli to collapse
increases lung compliance (stretchability)
makes breathing easier

is more effective in smaller alveoli as is more concentrated

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19
Q

surface tension

A

the attraction between water molecules that occurs at any air-water interface

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20
Q

The law of Laplace

A

P = 2T/r

P = inwardly directed pressure
T = surface tension (reduced by surfactant)
r = radius of alveoli
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21
Q

significance of the law of laplace

A

inwardly directed pressure is equalised in differently sized alveoli

As inwardly directed pressure is greater in smaller alveoli but surfactant is more effective as it’s more concentrated

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22
Q

2,3-DPG

A

A sugar produced by RBCs in hypoxic conditions. This shifts the oxyhamoglobin dissociation curve to the right (decreases Hb affinity for O2) for more oxygen delivery

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23
Q

factors that affect gas exchange

A

the partial pressure gradient
gas solubility
available surface area

the thickness of the membrane
distance

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24
Q

the ventilation:perfusion ratio should be…

A

1 in a healthy lung

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25
Q

ventilation-perfusion ratio in the apex of the lung

A

ventilation > perfusion

because alveolar pressure is greater than arterial pressure so arterioles are compressed

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26
Q

alveolar dead space

A

Alveoli that are not perfused

ventilation > perfusion

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27
Q

shunt

A

ventilation < perfusion

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28
Q

response to ventilation > perfusion (alveolar dead space)

A

increase in alveolar PO2 –> pulmonary vasodilation (increases perfusion)

decrease in alveolar PCO2 –> mild bronchial constriction (decreases ventilation)

ratio balances

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29
Q

response to ventilation < perfusion (shunt)

A

decreased alveolar PO2
causes pulmonary vasoconstriction –> blood diverted to a better ventilated alveoli

increased alveolar PCO2 –> mild bronchial dilation (slight increase in ventilation)

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30
Q

anatomical dead space

A

air in the airways that does not reach the alveoli so is not available for gas exchange

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31
Q

physiological dead space

A

alveolar dead space + anatomical dead space

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32
Q

difference between partial pressure and gas content

A

partial pressure refers only to gas in solution.

gas content includes the gas in other forms, e.g. O2 bound to haemoglobin

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33
Q

concentration of oxygen in systemic arterial blood

A

200ml/L

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34
Q

static spirometry

A

measures the volume exhaled

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35
Q

dynamic spirometry

A

measures the time taken to exhale a certain volume

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36
Q

FEV1 / FVC

A 
FEV1 = forced expiratory volume in 1 second
FVC = forced vital capacity

= 80% in healthy males

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37
Q

Compliance in obstructive and restrictive lung diseases

A 
obstructive = compliance normal
restrictive =  compliance decreased
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38
Q

FEV1 / FVC in obstructive and restrictive lung diseases

A

obstructive = lowered as rate of expiration is most affected

restrictive = normal/ higher as the volume of air in the lungs which can be exhaled is reduced

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39
Q

Tidal volume

A

volume usually breathed in/out

500ml

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40
Q

Residual volume

A

Volume of air that cannot be exhaled

1200ml

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41
Q

Inspiratory reserve volume

A

extra volume which can be inhaled on top of tidal volume

3000ml

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42
Q

expiratory reserve volume

A

volume which can be exhaled after tidal volume has been exhaled
1100ml

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43
Q

Total lung capacity

A

5800ml

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44
Q

inspiratory capacity

A

tidal volume + inspiratory reserve volume

3500ml

45
Q

vital capacity

A

total volume that can be exhaled

4600ml

46
Q

functional residual capacity

A

volume left in lungs after exhaling tidal volume.
residual volume + expiratory reserve volume
2300ml

47
Q

significance of the plateau of the oxygen-haemoglobin dissociation curve

A

even at only 60mmHg, haemoglobin is still 90% saturated.

this allows for relatively normal O2 uptake when alveolar PO2 is reduced.

48
Q

result of the oxygen-haemoglobin dissociation curve shifting LEFT

A

higher affinity = less O2 delivery

holds on tighter

49
Q

result of the oxygen-haemoglobin dissociation curve shifting RIGHT

A

lower affinity = more O2 delivery

lets go easily

50
Q

causes of the oxygen-haemoglobin dissociation curve shifting LEFT

A

low temperature
low PCO2
low 2,3-DPG
high pH

51
Q

causes of the oxygen-haemoglobin dissociation curve shifting RIGHT

A

high temperature
high PCO2
high 2,3-DPG
low pH

52
Q

foetal haemoglobin O2 affinity

A

higher than adult haemoglobin to be able to extract O2 from the mother
(oxygen-haemoglobin dissociation curve to the left)

53
Q

myoglobin O2 affinity

A

higher than haemoglobin. as myoglobin exists in skeletal muscle, it must be able to extract O2 from arterial blood when exercising.
(oxygen-haemoglobin dissociation curve to the left)

54
Q

forms in which CO2 is carried in the blood

A

7% dissolved in plasma

23% combines with deoxyhaemoglobin to form carbamino compounds

70% as bicarbonate ions in plasma or H ions bound to deoxyhaemoglobin (carbonic anhydrase)

55
Q

the role of carbonic anhydrase

A
  1. 70% of CO2 enters RBCs
  2. it combines with water and forms carbonic acid - catalysed by CARBONIC ANHYDRASE
  3. carbonic acid dissociates into bicarbonate and H ions

CO2 + H2O H2CO3 HCO3- H+

  1. bicarbonate ions move into the plasma in exchange for Cl- ions. H+ ions bind to deoxyhaemoglobin
56
Q

factors that influence ventilation*

*Respiratory drive, rate and depth of breathing

A

*chemoreceptor input
mechanosensory input (thorax stretch reflex)
voluntary over-ride via higher centres in the brain
Emotion via the limbic system

57
Q

where are central chemoreceptors located?

A

the medulla

58
Q

where are peripheral chemoreceptors located?

A

in the aorta and carotid arteries

59
Q

what stimulus activates central chemoreceptors?

A

[H+] in the plasma
which directly reflects PCO2 as only CO2 can travel through the capillary wall into the CSF

Central chemoreceptors provide the primary ventilatory drive

60
Q

equation determining plasma pH

A

CO2 + H2O H2CO3 H+ + HCO3-

61
Q

activity of peripheral chemoreceptors

A

Fire APs in response to high [H+]* or significantly low PO2 in the plasma

Provide the secondary ventilatory drive

*H+ from any source - so regulates acid-base imbalance

62
Q

VRG

A

Ventral Respiratory Group of neurons,

supplies the tongue, pharynx, larynx and expiratory muscles

63
Q

DRG

A

Dorsal Respiratory Group of neurons

supplies the inspiratory muscles via the phrenic and intercostal nerves

64
Q

Respiratory centres

A

e.g. VRG and DRG
groups of neurons that fire bursts of APs, setting an automatic rhythm of breathing which is ajusted in response to stimuli

65
Q

response to acidosis

A

an increase in [H+]

stimulates an increase in ventilation to blow off CO2 and shift the equation:

CO2 + H2O H2CO3 H+ + HCO3-

to the left

66
Q

response to alkalosis

A

a decrease in [H+]

stimulates a decrease in ventilation to retain CO2 and shift the equation:

CO2 + H2O H2CO3 H+ + HCO3-

to the right

67
Q

response to hypoxia

A

significantly low [O2]

stimulates an increase in ventilation to increase O2 content in the blood

68
Q

sperm formation

A

1 spermatogonium with 46 chromosomes forms 4 sperms with {22 + Y/X} chromosomes.

starts at adolescence and happens continuously

69
Q

ovum formation

A

1 oogonium with 46 chromosomes forms 1 ovum with {22 + X} chromosomes.

Meiosis I is completed before birth. Meiosis II occurs once each month

70
Q

stages of embryology

A 
Pre-embryonic = 0-3 weeks
Embryonic = 4-8 weeks
Foetal = 9-40 weeks
71
Q

Formation of the placenta and placental villi

process + timing

A

Can start by day 6

when the chorion is formed it forms villi which burrow into the endometrium and help implantation.

later the chorion forms the placenta and the villi provide maximum contact area with the maternal blood.

Matures by 18-20 weeks

72
Q

functions of the placenta

A

foetal nutrition
transport of waste and gas
immune function

73
Q

structures derived from the ectoderm

A

epidermis of skin

neural tube

74
Q

structures derived from the mesoderm

A

PARAXIAL: dermis of skin, muscles, bone

INTERMEDIATE PLATE: urogenital system

LATERAL PLATE: peritoneum, pleura, body cavities

75
Q

structures derived from the endoderm

A

gut

respiratory system

76
Q

steps of fertilization

A
  • several sperms surround the ovum
  • one penetrates
  • the pronucleus of the sperm fuses with the pronucleus of the ovum forming a diploid cell = ZYGOTE
77
Q

the laryngotracheal groove grows out of the…

A

foregut

78
Q

the oesophagus and trachea are separated by the…

A

oesophagotracheal septum

79
Q

outer cells of the blastocyst

A

trophoblast

80
Q

layers of the bilaminar disc

A 
top = epiblast
bottom = hypoblast

Formed from the inner cell mass of the blastocyst

81
Q

cavities around the bilaminar disc

A 
top = amniotic cavity
bottom = yolk sac
82
Q

morula

A

a solid mass of cells formed by mitotic division of the zygote

83
Q

the axis of the embryo is formed by the…

A

primitive streak (in the midline of the epiblast)

84
Q

formation of the trilaminar disc

A

epiblast cells…

  1. migrate between the epiblast and hypoblast forming the mesoderm.
  2. displace the hypoderm forming the endoderm

The epiblast is now called the ectoderm:

ECTOderm
MESOderm
ENDOderm

85
Q

notochord formation

A

ectoderm cells sink to between the mesoderm and endoderm to form a solid tube

86
Q

neural tube formation

A

the notochord induces ectoderm cells to sink to between the ectoderm and mesoderm and form the neural tube

87
Q

3 sections of the mesoderm

A

(outside to inside:)

lateral plate mesoderm
intermediate plate mesoderm
paraxial mesoderm

88
Q

somites

A

bilaterally paired sections of the paraxial mesoderm, each is innervated by a spinal nerve pair.
they subdivide into a dermatome, myotome and sclerotome.

89
Q

space between the slanchnic and somatic lateral plate mesoderms

A

intra-embryonic coelom

90
Q

Week 1 embryo development

A

blastocyst formation

blastocyst moves to uterine cavity

91
Q

Week 2 embryo development

A

bilaminar disc formed
implantation
placenta formation

92
Q

Week 3 embryo development

A

gastrulation
nurulation
somite formation
Lateral folding begins

93
Q

Week 4 embryo development

A

lateral folding completes (gut tube forms)
Head + Tail folding
organogenesis

94
Q

gastrulation

A

formation of germ layers

95
Q

nurulation

A

formation of neural tube

96
Q

Pneumocytes

A

Alveolar cells

97
Q

Conducting airways

A

Trachea
Primary bronchi
Smaller bronchi

98
Q

Respiratory airways

A

Bronchioles

Alveoli

99
Q

Function of pleural fluid

A

“sticks” the pleura together. This sticks the lungs to the rib cage and diaphragm so the lungs inflate when the chest expands

100
Q

Compliance definition

A

Stretchability

NOT elasticity

101
Q

Transport of O2 in the blood

A

O2 dissolves into the plasma and then binds to Hb, this maintains the partial pressure gradient that continues to “suck” O2 out of the alveoli.

Hb + O2 HbO2

At normal PO2, Hb becomes ~98% saturated, this saturation is reduced when PO2 is reduced

102
Q

Significance of the shape of the oxyhaemoglobin dissociation curve for O2 unloading in the tissues

A

At 40mmHg (a resting cell) only 25% O2 is extracted from haemoglobin

However as PO2 falls in an exercising cell, the % saturation of Hb rapidly falls to greatly increase O2 delivery

103
Q

Blastocyst development

A

As the morula grows, getting nutrition to the central core of cells becomes difficult do a blastocystic cavity develops.

This forms a blastocyst consisting of an inner cell mass inside an outer lining of cells (trophoblast)

104
Q

Blastocyst implantation

A

at ~7 days the blastocyst begins to burrow into the endometrium (uterine wall)
The trophoblast forms the chorion which develops villi which help to burrow

105
Q

Development of the lung bud

A
  1. The laryngotracheal groove grows from the anterior foregut (at 4 weeks)
  2. This diverticulum grows out into the splanchnic mesoderm and enlarges forming lung buds
106
Q

Development of the bronchial tree

A
  1. the oesophagotracheal septum separates the oesophagus and trachea
  2. Lung buds “punch” into the splanchnic mesoderm forming airways
  3. Lung buds expand, pushing the splanchnic and somatic mesoderms together
107
Q

Formation of alveoli

A

Alveolar sacs form at the end of terminal bronchioles

They progressively divide into smaller subunits leading to alveoli.
~95% of alveoli are formed post-natally

108
Q

Pericardialperitoneal canals

A

Gap between the splanchnic and somatic mesoderm (Visceral and parietal pleura)
Will form the pleural cavity

x1 - Respiratory (3 decks)

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