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Respiratory System - Loz > Lecture 9 - Mechanics of Ventilation 1 > Flashcards

Lecture 9 - Mechanics of Ventilation 1 Flashcards

1
Q

what is the thoracic cavity lined by?

A

pleura

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2
Q

what is the thoracic cavity bound by?

A
  • ribcage and intercostal muscles
  • sternum
  • thoracic vertebrae
  • diaphragm
  • thoracic inlet
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3
Q

how is the thoracic cavity flattened?

A

laterally

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4
Q

what is the pleura?

A

serous membranes covering all surfaces within the thoracic cavity, forms mediastinum between two plural cavities

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5
Q

what is the pulmonary or visceral plura?

A

covers surface of all organs and vessels in the thorax

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6
Q

what is the parietal plura?

A

lines inner walls of thoracic cavity
named according to region eg/ diaphragmatic plura
continuous with pulmonary plura

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7
Q

what is the sternopericardial ligament?

A

folds of pleura attaching heart to sternum

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8
Q

with is the place venue cavae?

A

fold of pleura suspending caudal vena cava

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9
Q

what are the pleural cavities?

A

two complete sacs (L and R)

airtight cavities containing small amount of fluid

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10
Q

what does the mediastinum enclose and what are the three devisions?

A

mediastinum encloses thymus, heart, trachea, oesophagus, major thoracic vessels and nerves.
the three divisions are:
- cranial mediastinum = cranial to the heart
- middle mediastinum = containing heart
- caudal mediastinum = caudal to the heart

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11
Q

inspiration requires active muscular contraction, what is the principle muscle of inspiration (during normal breathing)

A

the diaphragm

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12
Q

what does the diaphragm seperate

A

the thoracic cavity from the abdomen

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13
Q

what are the three attachments of the diaphragm?

A

transverse processes of the first 2-3 lumbar vertebrae
internal aspect of ribs near coastal arch
caudal end of the sternum

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14
Q

what muscles are used for forced inspiration

A

the external intercostal and scalenus muscles

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15
Q

how do they external intercostal and scalenus muscles contribute to forced inspiration

A

draw rib cranially and laterally = expansion of the thorax

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16
Q

where do the external intercostal muscles run?

A

caudoventrally between adjacent ribs

17
Q

where does the scalenus muscle originate and where does it insert?

A

on transverse process of cervical vertebrae and inserts on first few ribs

18
Q

what muscles are required for normal expiration?

A

NONE = normal expiration is PASSIVE
utilises elastic recoil of the lung
expulsion of air until contraction of thorax reaches equilibrium between elastic recoil and resistance to stretch of insp muscles.

19
Q

what muscles are required for forced/active expiration

A

internal intercostal and abdominal muscles

20
Q

when is active expiration required?

A

when the requirement for ventilation is elevated

21
Q

how do the internal intercostal and abdominal muscles contribute to forced expiration

A

reduce the volume of the thorax below equilibrium volume

22
Q

where do the internal intercostal muscles rn

A

caudodorsally between adjacent ribs and collapse thoracic cavity

23
Q

what nerve innervates the diaphragm

A

the phrenic nerve, originates from spinal cord in 5th-7th cervical nerves

24
Q

what does the intercostal nerve innervate

A

external and internal intercostal muscles
scalenus muscle
abdominal muscle

25
Q

what is the alveolar pressure

A

760mmHg (Same as atmospheric)
when the muscles of ventilation are relaxed or fixed and the glottis is open.
transient changes: decreases w/ insp, increases with/ exp

26
Q

what is the sub atmospheric pressure within intrathoracic/pleural pressure and how is it formed?

A
  • parietal and visceral pleura adhere to each other due to fluid in film
  • elastic recoil of lung and intercostal muscles appose each other
27
Q

describe airflow during inspiration incl. the ventilation pressures

A

contraction of the diaphragm –> expansion of thorax –> DROP in pressure of thoracic cavity (754mmHg) , expansion of lungs drop in alveolar pressure (759mmHg) –> airflow DOWN pressure gradient into lungs.

28
Q

describe airflow during inspiration incl. the ventilation pressures

A

relaxation of inspiratory muscles –> decrease in lung and thoracic volume = thoracic pressure goes back to 756 –> increased alveolar pressure (761mmHg) –> airflow DOWN pressure gradient OUT of lungs

29
Q

what changes to normal inspiration occur with forced inspiration?

A

contraction of accessory muscles increases the thoracic pressure above resting inspiratory volume = greater pressure drop = greater pressure gradient

30
Q

what changes to normal inspiration occur with forced expiration?

A

reduction in thoracic volume and lung volume below resting volume = greater increase in intralveolar pressure = greater pressure gradient = faster and more complete emptying of lung

31
Q

how does lung collapse occur?

A

via hole in thoracic wall or hole in lung leading to equalisation of atmospheric pressure within the lung, intrapleural (thoracic) space and the atmosphere

32
Q

where is respiratory dead space, how can it be categorised?

A

volume of airways that does not participate in gas exchange
can be anatomical or physiological

due to existence of dead space not all air breathed in is available for ventilation

33
Q

what is anatomic dead space?

A

not anatomically adapted for gas exchange

eg/ all airways from nose to the terminal bronchi

34
Q

what is physiological dead space?

A

total volume of air not participating in case exchange, includes any anatomical dead space plus any alveoli with inadequate circulation

35
Q

what is tidal volume?

A

volume of air breathed in or out in a single breath in ml/breath

36
Q

what is pulmonary minute ventilation?

A

tidal volume (ml/breath) x respiratory rate (breath/min)

37
Q

what is alveolar ventilation?

A

(tidal volume - dead space volume) x resp rate

eg/ alveolar ventilation is volume of air entering alveoli in one minute

Respiratory System - Loz (19 decks)

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