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MS1422017S2 > Respiratory System > Flashcards

Respiratory System Flashcards

1
Q

What is external respiration?

A

The process in the lungs by which oxygen is absorbed from the atmosphere into blood within the pulmonary capillaries and carbon dioxide is excreted.

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2
Q

What is internal respiration?

A

The exchange of gasses between blood in the systemic capillaries and the tissue fluid and cells

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3
Q

What is pulmonary ventilation?

A

The bulk movement of air in/out of lungs. The ventilatory pump comprises the rib cage with its associated muscles and the diaphragm

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4
Q

Describe the conducting part of the respiratory system and give examples:

A

A series of cavities and thick walled tubes which conduct air between the nose and the deepest recesses of the lungs and in doing so warm, humidify and clean it. The conducting airways are in the nasal cavities, larynx, trachea, bronchi and bronchioles i.e no gas exchange

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5
Q

Describe the respiratory part of the respiratory system and give examples:

A

Comprises tiny thin walled airways where gasses are exchanged between air and blood. The airways are respiratory bronchioles, alveolar ducts and sacs and alveoli. They have large surface areas for gas exchange

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6
Q

What is the upper respiratory tract?

A

Nasal cavity to larynx

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7
Q

What is the lower respiratory tract?

A

Trachea to alveoli

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8
Q

What are the 3 things that need to happen in the nasal cavity?

A
  1. Air needs to be warmed to 37 degrees
  2. Filter/cleaned
  3. Humidify the air by saturating with H2O
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9
Q

Where is the first place where the air is filtered in the nasal cavity?

A

In the nares (nostrils) by vibrissae

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10
Q

What is the function of the mucus membrane and what is it made up of in the nasal cavity?

A

To humidify and warm the air. It is made up of respiratory epithelia and a layer of mucus. There are ciliated cells and mucus cells (goblet cells) that are sticky to capture the dirt.

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11
Q

What does smoking do to the nasal cavity?

A

Paralyses the cilia so they need to constantly blow their nose or cough etc.

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12
Q

What is under the mucus membrane in the nasal cavity?

A

A rich blood supply for heat exchange and warming. There are also serous gland that secrete a watery secretion

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13
Q

What is on the lateral surface of the nasal cavity and what is their function?

A

There are 3 sloping shelves (conchae) which increase the surface area of the mucus membrane . They are made up of turbante bones for turbulance

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14
Q

Describe the sinuses:

A

They are air filled and open the cavity. They lighten the face and add resonance to the voice.

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15
Q

What is on the roof of the nasal cavity?

A

This is where the olfactory epithelium is found. Turbulance caused by sniffing carries the air up into the epithelium.

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16
Q

What are the 3 parts of the pharynx and do they carry food or air?

A
  1. Nasopharynx - air
  2. Oropharynx - air and food
  3. Laryngopharynx - air and food

They each have an anterior opening

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17
Q

Describe the epiglottis:

A

Points up when it is open and down and posteriorly when its closed. Its made of elastic cartilage

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18
Q

As there is ______ branching, the diameter of tubes _______ and surface area _________

A

Increased, decreased, increased

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19
Q

Describe the structure of the trachea:

A

Supported by C shaped rings of cartilage. Free ends of the cartilage are connected by trachealis muscle (smooth), where contraction narrows the diameter of the trachea.

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20
Q

Describe the cell layers of the trachea and their functions:

A

Lined with ciliated epithelium (pseudostratified coloumnar) the cilia transports a mucus sheet upwards to the nasopharynx (muscocillary escalator) mucus comes up.

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21
Q

Where does the esophagus sit in relation to the trachea?

A

The esophagus sits immediately posterior to the trachea, lying in the small groove formed by the trachealis muscle

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22
Q

What is an asthma attack and what can you take to stop one?

A

Constriction of smooth muscle in bronchioles where there is no cartilage so the airways shut. Can take a bronchodilator e.g salbutonol, which relaxes the smooth muscle.

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23
Q

What are the sources of mucus in the bronchus?

A

Mucus glands and goblet cells

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24
Q

Name the cell layers in the bronchus:

A

Cilia - pseudostratified columnar epithelium and goblet cells - smooth muscle - mucus glands - catilage plates (moon shaped) - bronchus wall (leads to alveoli)

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25
Q

Name the cell layers of bronchioles:

A

Cilia - club cells (watery secretions to keep the airways hydrated) and ciliated simple columnar epithelium goes to cuboidal transition - smooth muscle (leads to alveoili)

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26
Q

What are alveolar sacs?

A

Bunch of alveolis together (grapes)

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27
Q

What are alveolar ducts?

A

Tubes made up of alveoli sacs

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28
Q

What are alveoli covered in?

A

Capillaries - pulmonary

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29
Q

What are the 3 types of cells found in alveoli and what are their functions?

A
  1. Squamous pneumocytes - flat and skinny
  2. Surfactant cell - secretes surfactant that helps to reduce surface tensions. Reduces work of breathing by keeping alveoli open
  3. Alveolar macrophage - wandering cell - last defence mechanism
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30
Q

What is in between the alveolar air and a RBC i.e the capillary?

A

Squamous pneumocyte
Basement membrane which is fused to minimise diffusion space
Capillary endothelium

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31
Q

Describe the 3 subdivisions of the lung:

A

Primary bronchi - left and right mainstem bronchi supplying each lung
Secondary bronchi - lobar bronchi supplying the lobes (2 on th eleft and 3 on the right)
Tertiary bronchi - segmental bronchi that supply segments of th elungs (8 on the left, 10 on the right) each segment has its own blood supply

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32
Q

What is each segment of the lung enclosed by?

A

Connective tissue - allows it to have its own blood supply

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33
Q

What is the hilum?

A

Where the pulmonary vessels and the primary bronchi enter/exit

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34
Q

Describe the pleurae and pleural space:

A

A smooth membrane (pleura) covers each lung and also lines the thoracic cavity where the lung sits. The 2 membranes are continuous at the root of the lung (hilum). A thin film of fluid separates the 2 pleurae allowing them to slide past each other without friction and prevents the 2 from being separated. When the thoracic wall moves in or out, the lungs must follow. Or when the diaphragm moves up or down, the lungs must follow

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35
Q

List the orders of layers between the lung and muscles:

A 
Lung
Visceral pleura
Pleural space filled with pleural fluid
Parietal pleura
Muscles (intercostal/diaphragm)
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36
Q

Describe quiet breathing:

A

Movement of the ribcage is only responsible for about 25% of air movement in and out of the lungs. Inspiration is active it requires the contraction of external intercostal muscles which run obliquely between ribs. Expiration is passive. The ribcage returns to its position without requiring muscular action.

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37
Q

Describe breathing during exercise

A

Both sets of intercostal muscles are active. Externals for inspiration and internals for expiration

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38
Q

Describe the structure and location of the diaphragm:

A

A dome shaped platform which forms the floor of the thorax and roof of the abdomen. Its central part is a thin layer of connective tissue called the central tendon. The lateral margins are fast acting skeletal muscular and innervated by the phrenic nerve

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39
Q

What does contraction of the diaphragmatic muscle cause?

A

Flattening of the diaphragm, pulling its central dome downwards which increases the volume of the thorax and causes inspiration

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40
Q

What does the passive relaxation of the diaphragm cause?

A

The diaphragm lifts back down towards the thorax, reducing thoracic volume (expiration)

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41
Q

Movement of what is responsible for 75% os bulk flow of air during quiet breathing?

A

Diaphragm

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42
Q

Tidal volume?

A

Volume of one breath (500ml)

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43
Q

What is the range of values for a tidal volume?

A

Residual volume to total lung capacity

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44
Q

Functional residual capacity

A

The amount of air in the lungs at the end of a normal relaxed expiration

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45
Q

What is the L/min at rest and exercise?

A

6l/min rest

20L/min exercise

46
Q

Air is a fluid. In order for it to move, there must be a pressure gradient caused by what?

A

Air will only enter the lungs if the alveolar pressure is less than that of atmospheric (barometric). Alveolar pressure becomes sub - atomospheric when thoracic volume increases which is achieved by descent of the diaphragm and elevation of the rib cage (inspiration)

47
Q

The bulk flow rate of air (volume per unit time) of air entering or leaving the lungs is proportional to…..

A

The difference between atmospheric and alveolar pressure

48
Q

Describe the forces (and what causes them to arise), that contribute to the balancing of forces in the lungs:

A
  1. The lungs experience a force FL that causes a tendency for them to collapse. This force arises from the elastic recoil of stretched elastic fibres and surface tension of wet alveolar cells.
  2. The chest wall (ribcage and muscles) experiences a force FCW that tends to cause it to spring outwards thereby increasing the volume. The force arises from stretched tissues in the sterno-costal and costo-vertebral joints.
49
Q

Describe a pneumothorax:

A

When a penetrating injury of the chest wall creates a connection between the atmosphere and the intrapleural space, the balance of forces which normally occurs in the lungs is destroyed on the affceted side. This is because the adhesive forces between water molecules are interrupted and this allows the lungs to collapse and in response the chest wall to recoil out

50
Q

Lungs are entirely devoid of muscles under voluntary control - how do we voluntarily breath?

A

Under normal resting conditions, they fill by indirect action of skeletal muscle and they empty via their elastic recoil

51
Q

Describe the pressure volume relations during respiration:

A

Immediately before inspiration, alveolar pressure is equal to atmospheric pressure. There is no air flow because there is no driving pressure from the atmosphere to the lungs. Inspiration starts with contraction of the diaphragm, enlarging the thoracic cavity. As thoracic volume increases, the intrapleural pressure becomes more subatmospheric and the lungs expand. This increase in lung volume causes a weaker pressure to decrease and air moves into the lungs. Airflow ceases when alveolar pressure returns to atmospheric pressure. When inspiration terminates, the diaphragm relaxes, intrapleural pressure rises and the lungs recoil.

52
Q

During expiration, why is the alveolar pressure higher than atmospheric?

A

Because the gases are compressed which elevates alveolar pressure above atmospheric, driving air from the lungs out to the atmosphere

53
Q

What are the 5 factors affecting exchange of air?

A
  1. Muscular effort
  2. Compliance
  3. Resistance
  4. Dead space
  5. Diffusion
54
Q

What is compliance?

A

Change of V per change of P. Inverse is elasticity/stiffness. It is the distensibilty of the lungs and chest wall.

55
Q

What does greatly increased compliance lead to?

A

Loss of elastic fibres can lead to emphysema

56
Q

Describe the pressure volume loop (hysteresis) and when saline filled:

A

At low volumes, the lungs are not compliant because the alveoli have collapsed so a relatively large pressure is required to overcome the surface tension in order to reopen them. Once they are open, the lungs distend relatively easily until they are near full inflation. The deflation curve differs from the inflation curve because of surface tension. Much less effort is required to inflate the lungs when they are filled with saline rather than air.

57
Q

Where in the airways is the resistance the greatest?

A

The secondary bronchi

58
Q

As total cross sectional area increases in the smaller respiratory airways, resistance….

A

Decreases

59
Q

What is anatomic dead space?

A

The volume of the conducting airways. No exchange of gases occurs in this volume. Its presence dilutes tidal inspiration with alveolar air remaining from the previous expiration
Hence Vt = 1/3 alveolar air + 2/3 fresh air

60
Q

Give an example of anatomic dead space if 150mL of fresh air is inspired:

A

Before inspiration there is 150mL of old air. During inspiration 300mL of fresh air comes in and 150mL stays out. At the end of inspiration the air has mixed. At the end of expiration, first the fresh comes back out (150mL) followed by the 300mL of old air

61
Q

Describe gas exchange by diffusion in the lungs:

A

Oxygen and carbon dioxide move between the alveoli and pulmonary capillary blood and from systemic capillary blood back into the cells by diffusion

62
Q

The volume of gas transported across a membrane such as the alveolar pulmonary capillary interface per unit time is related to:

A

The driving pressure or difference in partial pressure of the gas across the membrane. It is inversely related to the length of diffusion pathway and the square root of the molecular weight of the gas

63
Q

What is respiratory distress syndrome?

A

The absence of pulmonary surfactant, much greater muscular effort required to generate a negative intrapleueral pressure to inflate the lungs. This causes distress/fatigue

64
Q

What is emphysema?

A

Destruction of elastic peribronchial and interalveolar tissue which normally holds open the small bronchiols during expiration. This makes the lungs more compliant. Passive deflation is impaired because upon expiration the bronchiols collapse, trapping air downstream in the alveoli. As a consequence, functional residual capacity increases

65
Q

What is pulmonary edema?

A

Water on the lung. Causes increased diffusion distance. Diminished gaseous change and is a consequence of streptococus pneumoniae

66
Q

Describe the partial pressure of gas in solution (henrys law)

A

The concentration of a dissolved gas varies directly with its partial pressure. The constant of proportionality is solubility. The solubility of a gas depends on solvent (Oxygen is more soluble in water than oil. And inversely the temperature. Carbon dioxide is 24 times more soluble in blood than oxygen. The partial pressure of a dissolved gas is that externally applied pressure required to prevent it coming out of solution.

67
Q

What are the 2 ways that oxygen is carried in the blood?

A
  1. In simple solution - (only 3mL os oxygen per L of plasma because O2 has low solubility)
  2. As oxyhemoglobin in erythrocytes (197mL/L)
    200mL of Oxygen per L of plasma
68
Q

What is the normal pressure in the veins and what happens when we exercise?

A

40mmHg at 70% saturated

When exercising, we can drop this down to 25% without losing too much pressure

69
Q

Does the curve shift to the left or right when there is low blood pH/ high blood PCO2?

A

Right

70
Q

Does the curve shift to the left or right when there is high blood pH/ low blood PCO2?

A

Left

71
Q

Describe the effect of anaemia on O2 transport:

A

For the anaemia curve, hemoglobin is reduced to 60mL/L which is less than half of normal (200mL/L). As a result, total oxygen bound is substantially reduced despite the fact that hemoglobin remains 98% saturated.

72
Q

Describe the effect of carbon monoxide on oxygen transport:

A

Binding of oxygen to hemoglobin is blocked off by carbon monoxide which has a higher affinity than oxygen for hemoglobin. This causes a reduction in oxyhemoglobin saturation

73
Q

How is carbon dioxide transported in the blood?

A
  1. 9% in simple solution as CO2 (high solubility)
  2. 13% as HbCO2 - carbaminohemoglobin
  3. As bicarbonate
  4. 78% as carbonic acid
74
Q

How is carbon dioxide eliminated?

A
  1. From the blood - as CO2 in lungs and as HCO3- by kidney

2. From the body - by exhalation or urination

75
Q

What is alveolar ventiltion?

A

The amount of gas that reaches the alveoli during 1 breath

76
Q

What is pulmonary ventilation?

A

The total volume of gas taken into the respiratory system during 1 breath. This includes both the alveolar ventilation and deadspace ventilation

77
Q

Describe the function of alveolar ventilation:

A

It replenishes the supply of O2 that has been removed from the blood by the tissues while excreting from the alveoli CO2 that has been added to the blood by the tissues. It is regulated to maintain effectively constant the partial pressures of O2 and CO2 in the arterial blood. In consequence, pulmonary O2 intake matches O2 tissue consumption and elimination of CO2 matches CO2 production.

78
Q

Any change in alveolar ventilation relative to metabolism will alter the levels of ______?

A

O2 and CO2 in the arterial blood

79
Q

What happens during hyperventilation?

A

There is an accumulation of O2 in the alveoli. This increases the PAO2 and PaO2. There is a decrease of CO2 in the alveoli. This means there is a decrease of PACO2 and PaCO2 and an increase in arterial pH. This causes respiratory alkalosis and eventually an alkalotic coma.

80
Q

What happens during hypoventilation?

A

There is diminished O2 in the alveoli. This decreases the PAO2 and PaO2. There is an accumulation of CO2 in the alveoli. This means there is a increase of PACO2 and PaCO2 and a decrease in arterial pH. This causes respiratory acidosis and eventually an acidotic coma

81
Q

Describe respiratory control by the CNS:

A

Respiratory rhythm occurs in the brainstem. The basic rhythm is generated by 2 groups of neurons in the medulla oblongata. These medullar centres are the dorsal respiratory group (DRG). The neurons are primarily active during ventilation and the ventral respiratory group (VRG) some during inspiration, some expiration and some during the transition. The rythmic drive in the brainstem is transmitted to motor neurons in the barinstem (cranial) and spinal chord which in turn drive the muscles involved in breathing

82
Q

Describe the feedback from the bronchioles/bronchi:

A

There are slow adapting stretch fibres that are located in the walls of the bronchi and bronchioles and they send signals via myelinated fibres in the vagus nerve to the brainstem respiratory centre. Activation of these receptors by lung inflation stops inspiration.

83
Q

Describe the feedback from the airways:

A

There are irritant sensors in the airways that send signals via myelinated and unmyelinated C fibres in the vagus nerve that respond to

  1. Noxious mechanical and chemical stimuli e.g smoke, food down
  2. Histamine/prostaglandins produced in response to inflammation/allerg
  3. Lung hyperinflation

Activation of these receptors causes reflex constriction of bronchioles (smooth muscle), coughing, rapid shallow breathing, increased mucus secretion.

84
Q

Where are the peripheral receptors and what do they sense?

A

They are in the carotid (found at biforcation of common carotid arteries) and aortic bodies (aortic arch and subdivision arteries) and they sense arterial PO2 and PCO2 informing the central respiratory centre if more ventilation is required to maintain appropriate levels of gas in the blood.

85
Q

Describe the feedback from carotid bodies:

A

They are located at the biforcation of the common carotid arteries. They are highly vascularised, having a very high blood flow in relation to their metabolic needs and are well suited to sense the O2 nd CO2 levels in the blood. They respond to decreased PaO2 or increases in the PaCO2. Afferents from the carotid bodies travel in the carotid sinus nerve (along with the baroreceptors) which joins the glossopharnygeal crainial nerve as it enters the medulla.

86
Q

Describe the feedback from the aortic bodies:

A

They are found in the aortic arch and subdivision arteries. Their afferents travel in the vagus nerve

87
Q

Describe feedback from the central chemoreceptors:

A

They are located on the ventral surface of the medulla and are sensitive to the pH of CSF.

88
Q

PaCO2 is sensed by:

A
  1. Peripherally - carotid bodies (glossopharyngeal nerve) and aortic (vagus nerve)
  2. Central chemoreceptors
89
Q

Describe the responsiveness to pH

A
  1. Centrally - on the ventral medulla bathed by CSF (not blood). CO2 is readily soluble in CSF and can readily cross the blood brain barrier . Subdiffuge of protons across the barrier by the formation of HCO3- by carbonic acid (water + CO2). Ventilation is sensitive to ventral medullary pH
90
Q

Ventilation is most sensitive to….

A

Peripheral PaCO2

Central pH

91
Q

What is residual volume?

A

The volume of air remaining in the lungs after a forceful exhale

92
Q

What s inspiratory capacity?

A

Max amount of air inspired including tidal volume

93
Q

What is functional residual capacity?

A

The volume of air present in the lungs after a passive expiration

94
Q

What is vital capacity?

A

The greatest volume of air that can be expelled from the lungs after taking a maximal inspiratory breath

95
Q

What is inspiratory reserve volume?

A

The maximum amount of additional air that can be drawn into the lungs above tidal volume

96
Q

What is expiratory reserve volume?

A

The maximum amount of additional air that can be expired from the lungs below tidal volume

97
Q

When is there the greatest tidal volume in the lungs and what is it?

A

After 2 seconds in between the inspiration and expiration and it is about 0.4 L

98
Q

When drawing a fake lung, name the layers from trachea to total lung capacity:

A

Trachea, residual volume, functional residual capacity, tidal volume, total lung capacity

99
Q

When your lungs are floppy, how does it affect inflation/deflation?

A

Easy to inflate, hard to deflate

100
Q

When your lungs are rigid, how does it affect inflation/deflation?

A

Hard to inflate, easy to deflate

101
Q

Compliance _______ as volume _______ up to a certain point. At high lungs volumes compliance ______ which leads to deflation:

A

Increases
Increases
Decreases

102
Q

Describe the changes in intrapleural pressures during an inspiration and expiration:

A

Starts at -3mmHg, decreases to -7mmHg during inspiration then rises to -4mmHg during exhalation

103
Q

Describe the changes in alveolar pressures during an inspiration and expiration:

A

Starts at 0 drops to -ve 1 then back to 0

Starts at 0 rises to +1 then back to 0

104
Q

What is daltons law?

A

The total pressure of gas is the sum of the pressures exerted by each individual constituent

105
Q

What is the normal pressure of PvO2 (oxygen in the veins)?

A

100mmHg at 70% saturated

106
Q

What is the normal HbO2 content in mlO2/L plasma?

A

200

107
Q

What is the Carbon monoxide poisoning HbO2 content in mlO2/L plasma?

A

80

108
Q

What is the anemic HbO2 content in mlO2/L plasma?

A

50

109
Q

What is the normal HbCO2 content in mlCO2/L plasma?

A

600 (3x that of O2)

110
Q

After 5 seconds of hyperventilation, how much has PACO2 pressures dropped?

A

From 60 - 40 mmHg and can go as low as 10mmHg

MS1422017S2 (8 decks)

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