lung physiology 1 Flashcards
1
Q
what is the respiratory pump
A
consists of abdominal and thoracic structures that are important in the expansion and contraction of the lungs
2
Q
where is the respiratory pump
A
between the head and abdomen
3
Q
define venous return
A
the return of blood to the right side of the heart via the vena cava
4
Q
what does respiratory pump do
A
when muscles contract and relax during the inspiration and expiration process,
pressure changes occur in the thoracic and abdominal cavities.
these pressure changes compress the nearby veins and assist blood return to the heart
5
Q
what are the 2 muscles of respiration
A
inspiration
expiration
6
Q
what do inspiratory muscles do
A
expand the thoracic cavity
help in inhalation
due to diaphragm and external intercostal muscles contracting
largely quiet
7
Q
what do expiratory muscles do
A
compress the thoracic cavity
induce exhalation
8
Q
what are the primary inspiratory muscles
A
diaphragm
external intercostals
9
Q
is expiration passive or active and why
A
passive during quiet breathing
because of the elastic recoil of the lungs and surface tension
10
Q
which muscles are involved in expiration
A
internal intercostals
intercostalis intimi
subcostals
abdominal muscles.
11
Q
what do inspiration muscles do to the the ribs and sternum
A
elevate them
12
Q
what do expiration muscles do to the ribs and sternum
A
depress them
13
Q
describe inspiration process
A
- phrenic nerve stimulated
- diaphragm contracts - flattens, extending the superior/inferior dimension of the thoracic cavity
- external intercostal muscles contract - elevates the ribs and sternum, extending the anterior/posterior dimension of the thoracic cavity
- results in an increase in the volume of the thoracic cavity
- as the lungs are held against the inner thoracic wall by the pleural seal, they also undergo an increase in volume
- results in a decrease in the pressure within the lungs.
- pressure of the environment external to the lungs is now greater than the environment within the lungs
- air moves into the lungs down the pressure gradient
14
Q
innervation of diaphragm
A
phrenic nerves (C3-C5)
15
Q
is inspiration active or passive
A
active
16
Q
what happens during breathing
A
the contraction and relaxation of muscles change the volume of the thoracic cavity.
as the thoracic cavity and lungs move together, this changes the volume of the lungs
in turn changing the pressure inside the lungs
17
Q
what is inspiration
A
the phase of ventilation in which air enters the lungs.
18
Q
what is expiration
A
the phase of ventilation in which air is expelled from the lungs.
19
Q
what is inspiration initaited by
A
by contraction of the inspiratory muscles - diaphragm & external intercostal muscles
20
Q
what is expiration initiated by
A
by relaxation of the inspiratory muscles
21
Q
process of expiration
A
- diaphragm relaxes to return to its resting position - reducing the superior/inferior dimension of the thoracic cavity
- external intercostal muscles relax to depress the ribs and sternum - reducing the anterior/posterior dimension of the thoracic cavity
- results in a decrease in the volume of the thoracic cavity
- the elastic recoil of the previously expanded lung tissue allows them to return to their original size.
- results in an increase in the pressure within the lungs
- pressure inside the lungs is now greater than in the external environment
- air moves out of the lungs down the pressure gradient.
22
Q
what is the pleural space
A
the space between the outer surface of the lungs and inner thoracic wall - usually filled with pleural fluid
23
Q
what does pleural fluid do
A
forms a seal which holds the lungs against the thoracic wall by the force of surface tension.
this seal ensures that when the thoracic cavity expands or reduces, the lungs undergo expansion or reduction in size accordingly.
24
Q
what are the layers of pleura
A
includes two thin layers of tissue that protect and cushion the lungs
inner layer - visceral pleura
outer layer - parietal pleura
25
where is visceral pleura
wraps around the lungs and is stuck so tightly to the lungs that it cannot be peeled off
26
where is parietal pleura
lines the inside of the chest wall
27
what is forced breathing/expiration
an active mode of breathing which utilises additional muscles to rapidly expand and contract the thoracic cavity volume. It most commonly occurs during exercise.
28
what are accessory muscles
muscles other than the diaphragm and intercostal muscles that may be used for breathing
all of these muscles act to increase the volume of the thoracic cavity
29
what are the accessory muscles involved in active inspiration (5)
Scalenes- elevates the upper ribs.
Sternocleidomastoid - elevates the sternum.
Pectoralis major and minor- pulls ribs outwards.
Serratus anterior - levates the ribs (when the scapulae are fixed).
Latissimus dorsi- elevates the lower ribs.
30
what do scalenes do
elevates the upper ribs
31
what does sternocleidomastoid do
elevates the sternum
32
what do pectoralis major and minor do
pull the ribs outwards
33
what do serratus anterior do
elevates the ribs
(when the scapulae are fixed)
34
what does latissimus dorsi do
elevates the lower ribs
35
what is active inspiration
involves the contraction of the accessory muscles of breathing (in addition to those of quiet inspiration, the diaphragm and external intercostals). All of these muscles act to increase the volume of the thoracic cavity
36
what is active expiration
utilises the contraction of several thoracic and abdominal muscles. These muscles act to decrease the volume of the thoracic cavity
37
which muscles are involved in active expiration
anterolateral abdominal wall
Internal intercostal
Innermost intercostal
38
what do anterolateral abdominal wall muscles do
increases the intra-abdominal pressure, pushing the diaphragm further upwards into the thoracic cavity
39
what do internal intercostal muscles do
depresses the ribs.
40
what do Innermost intercostal do
depresses the ribs
41
what determines airway resistance
tube length
tube radius
flow type
42
what is gas exchange
the process by which oxygen and carbon dioxide move between the bloodstream and the lungs.
this is the primary function of the respiratory system.
it is essential to ensure a constant supply of oxygen to tissues, as well as removing carbon dioxide to prevent its accumulation
43
define ventilation
flow of air into and out of the alveoli
44
define perfusion
total volume of blood reaching the pulmonary capillaries in a given time period
45
what is V/Q mismatch
ventilation/perfusion
when blood is going to poorly ventilated parts of lung
46
what is dead space
volume of air not contributing to ventilation
47
what affects rate of diffusion of gases (3)
1. concentration gradient: The greater the gradient, the faster the rate
2. surface area for diffusion: The greater the surface area, the faster the rate
3. length of the diffusion pathway: The greater the length of the pathway, the slower the rate
48
what is the sensory nerve supply to the diaphragm
phrenic nerve to central tendon and lower 6 or 7 intercostal nerve to peripheral parts.[8]
49
what are the 7 layers of gas exchange
1. alveolar epithelium
2. tissue interstitium
3. capillary endothelium
4. plasma layer
5. red cell membrane
6. red cell cytoplasm
7. Hb binding
50
what are homeostatic responses to V/Q mismatch
to divert blood away from poorly ventilated areas (HPVC)
or
divert to better perfused lung areas (LBC)
51
what are homeostatic responses to V/Q mismatch
to divert blood away from poorly ventilated areas (HPVC)
or
divert to better perfused lung areas (LBC)
52
why is it important to have matching ventilation and perfusion of the lungs
it ensures continuous delivery of oxygen and removal of carbon dioxide from the body
53
define ventilation rate
refers to the volume of gas inhaled and exhaled from the lungs in a given time period, usually a minute
54
define ventilation rate
refers to the volume of gas inhaled and exhaled from the lungs in a given time period, usually a minute
55
what is the ideal V/Q ratio
1 for maximally efficient pulmonary function
however, the ratio varies depending on the part of the lung concerned
56
why are there different V/Q ratios for different areas of the lungs
due to the relation of the area to the heart.
areas of lung below the heart have increased perfusion relative to ventilation due to gravity, reducing the V/Q ratio.
as such the overall value in the average human lung is closer to 0.8.
57
how does gravity triggers changes in ventilation and perfusion
1. pleural pressure
2. hydrostatic pressure
58
effect of pleural pressure on ventilation
is increased at the base of the lungs, resulting in more compliant alveoli and increased ventilation
59
effect of hydrostatic pressure on perfusion
is decreased at the apex of the lung, resulting in decreased flow and decreased perfusion
60
what happens when ventilation is good but perfusion is poor
V/Q value increases
dead space
leads to embolism (pulmonary)
(blood clot)
61
what happens when perfusion is good but ventilation is poor
V/Q value decreases
shunt
leads to pulmonary oedema
(collapsed alveoli due to fluid build up)
62
homeostatic response for when ventilation is good but perfusion is poor
local bronchoconstriction
air diverted to better ventilated areas
63
response when perfusion is good but ventilation is poor
hypoxic pulmonary vasoconstriction
blood diverted to better perfused areas
64
impact of inadequeate ventilation on gas exchange
- inadequate ventilation
- V/Q reduces,
- gas exchange within the affected alveoli is impaired
- the capillary partial pressure of oxygen (pO2) falls and the partial pressure of carbon dioxide (pCO2) rises
65
what is hypoxic vasoconstriction
homeostatic mechanism
causes diversion of blood to better ventilated parts of the lung.
However, in most physiological states the haemoglobin in these well ventilated alveolar capillaries will already be saturated
this means that red cells will be unable to bind additional oxygen to increase the pO2.
so the pO2 level of the blood remains low, which acts as a stimulus to cause hyperventilation
resulting in either normal or low CO2 levels.
66
what can cause V/Q mismatch
due to either reduced ventilation of part of the lung
or
reduced perfusion.
67
what is grahams law
the rate of diffusion is inversely proportional to the square root of its molar mass at identical pressure and temperature
68
what is henrys law
the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid”.
69
how do gasses diffuse through gases
the smaller the mass of a gas, the more rapidly it will diffuse.
70
how do gasses diffuse through liquids
the more soluble a gas is, the faster it will diffuse.
71
how do gasses diffuse through liquids
the more soluble a gas is, the faster it will diffuse.
72
does carbon dioxide diffuse faster or slower than oxygen in liquids
faster
because it is more soluble than oxygen,
73
describe membrane thickness of lungs
the thinner the membrane, the faster the rate of diffusion.
the diffusion barrier in the lungs is extremely thin,
74
what conditions can cause thickiening of diffusion barrier in lungs (2)
1. Fluid in the interstitial space (pulmonary oedema)
2. Thickening of the alveolar membrane (pulmonary fibrosis)
75
describe membrane surface area of lungs
the larger the surface area, the faster the rate of diffusion.
the lungs normally have a very large surface area for gas exchange due to the alveoli
76
which condition reduces lung surface area
emphysema
leads to the destruction of the alveolar architecture
this causes the formation of large air-filled spaces known as bullae.
this reduces the surface area available and slows the rate of gas exchange
77
what is surfactant
a phospholipoprotein that lines the alveolar walls over the water film and reduces the surface tension, keeping the alveoli open so that we can breathe properly
78
define respiratory epithelium
pseudostratified ciliated columnar epithelium with goblet cells
79
what can disruption of acid base balance lead to (2)
arrhythmias and seizures
80
what is buffering
the ability of blood to be resistant to small changes in pH
this is due to the basal levels of bicarbonate and hydrogen ions in blood
81
why does body maintain close control of ph
to ensure optimal control eg for enzyme controlled reactions in cells
82
normal pH
7.4
83
normal H+ concentration
40 nmol
84
what happens if V/Q mismatch
hypoxia - oxygen deficiency at tissues
85
what is hypoventilation
breathing that is too shallow or too slow to meet the needs of the body.
86
what causes hypoventilation
increased CO2 level
increase H+ level
87
what does hypoventilation lead to
build up of acid and too little oxygen in blood
- respiratory acidosis
88
what is respiratory acidosis
a condition that occurs when your lungs can't remove all of the carbon dioxide produced by your body
89
what is hyperventilation
rapid and deep breathing
90
what causes hyperventilation
decreased CO2 level
decreased H+ level
91
what does hyperventilation lead to
respiratory alkalosis
92
what is respiratory alkalosis
occurs when high levels of carbon dioxide disrupt the blood's acid-base balance
93
how does the respiratory system contribute to balance of acids and bases
by regulating the blood levels of carbonic acid
CO2 in the blood readily reacts with water to form carbonic acid, and the levels of CO2 and carbonic acid in the blood are in equilibrium
94
carbonic acid equilibrium equation
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3
95
how to offset acidosis
by ‘blowing off CO2'
or
the kidneys secrete more HCO3
96
how to offset alkalosis
by retaining CO2
or
secreting less HCO3
97
what is type 1 resp failiure
occurs when the respiratory system cannot adequately provide oxygen to the body, leading to hypoxemia
Low PaO2, normal PaCO
98
what is type 2 resp failiure
occurs when the respiratory system is unable to adequately remove carbon dioxide from the body, leading to hypercapnia, and can be caused by respiratory pump failure and increased carbon dioxide production
Low PaO2, high PaCO2
99
what does the henderson - hasselbalch equation do
relates the pH to the ratio between the concentration of bicarbonate and the partial pressure of carbon dioxide.
100
what is the henderson - hasselbalch equation
pH = 6.1 + log10[[HCO3-] / [0.03 X PCO2]]
101
what happens if you increase bicarbonate levels
the pH will rise and turn more alkaline
102
what happens if you increase the partial pressure of carbon dioxide
the pH of blood will fall and turn acidic
103
how does respiratory system restore blood pH
alters the respiratory rate, to change the concentration of carbon dioxide in the blood,
104
what does the oxygen dissociation curve show
shows the rate at which oxygen associates, and also dissociates, with haemoglobin at different partial pressures of oxygen (pO2)
105
what is partial pressure of oxygen
refers to the pressure exerted by oxygen within a mixture of gases; it is a measure of oxygen concentration
106
what does haemoglobin saturation mean
when all of its oxygen binding sites are taken up with oxygen; so when it contains four oxygen molecules
107
what is haemoglobins affinity for oxygen
The ease with which haemoglobin binds and dissociates with oxygen
108
what does it mean when haemoglobin has a high affinity
it binds easily and dissociates slowly
109
what does it mean when haemoglobin has a low affinity for oxygen
it binds slowly and dissociates easily
110
why is oxygen dissociation a curve and not a line
oxygen binds with haemoglobin at different rates as the pO2 changes
It can be said that haemoglobin's affinity for oxygen changes at different partial pressures of oxygen
111
why does oxygen dissociation curve have a sigmoid shape
It can be said that haemoglobin's affinity for oxygen changes at different partial pressures of oxygen
Co-operative binding means that haemoglobin has a greater ability to bind oxygen after a subunit has already bound oxygen
112
what happens at high partial pressures
haemoglobin binds to oxygen to form oxyhaemoglobin. All of the red blood cells are in the form of oxyhaemoglobin when the blood is fully saturated with oxygen
113
what does a right shift of ODC indicate
decreased oxygen affinity of haemoglobin allowing more oxygen to be available to the tissues.
114
what does a left shift of ODC indicate
increased oxygen affinity of haemoglobin allowing less oxygen to be available to the tissues.
115
how does pH affect ODC
A decrease in the pH shifts the curve to the right - the Bohr effect
an increase in pH shifts the curve to the left. - This occurs because a higher hydrogen ion concentration causes an alteration in amino acid residues that stabilises deoxyhaemoglobin in a state (the T state) that has a lower affinity for oxygen.
116
how does CO2 affect ODC
a decrease in CO2 shifts the curve to the left
an increase in CO2 shifts the curve to the right
CO2 affects the curve in two ways:
1. the accumulation of CO2 causes carbamino compounds to be generated, which bind to oxygen and form carbaminohaemoglobin. Carbaminohaemoglobin stabilizes deoxyhaemoglobin in the T state.
2. the accumulation of CO2 causes an increase in H+ ion concentrations and a decrease in the pH, which will shift the curve to the right
117
how does temperature affect ODC
an increase in temperature shifts the curve to the right - denatures the bond between oxygen and haemoglobin, which increases the amount of oxygen and haemoglobin and decreases the concentration of oxyhaemoglobin.
a decrease in temperature shifts the curve to the left
temperature does not have a dramatic effect but the effects are noticeable in cases of hypothermia and hyperthermia
118
how do organic phosphates affect OFC
2,3-Diphosphoglycerate (2,3-DPG) is the main primary organic phosphate.
a increase in 2,3-DPG shifts the curve to the right
a decrease in 2,3-DPG shifts the curve to the left.
2,3-DPG binds to haemoglobin and rearranges it into the T state, which decreases its affinity for oxygen.
119
what are the 3 ways co2 is transported in the blood
1. dissolved in plasma - 1-%
2. bound to haemoglobin - carbaminohemoglobin - 23%
3. as HC03- - 65%
