18 - anatomy of ventilation Flashcards

1
Q

pulmonary ventilation definition:

A

the physical movement of air into and out of the respiratory tract

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2
Q

function of breathing:

A

to ensure constant supply of oxygen

to prevent build up of CO2 and therefore maintain pH

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3
Q

inspiration

A

expiration

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4
Q

inhilation

A

exhalation

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5
Q

what two principles does pulmonary ventilation rely on?

A
  • Boyles law (pressure of a gas is inversley proportional to its volume (and so the containers volume) at a constant temperature)
  • Air flows from an are of low pressure to an area if high pressure
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6
Q

In a syringe

A
  • plunger pulled back
  • volume inside increases
  • pressure decreases
  • fluid/gas moves in
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7
Q

air will enter the lungs when

A

atmospheric pressure is greater than pressure within the lungs (intraalveolar pressure or intrapulmonary pressure)

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8
Q

air will leave the lungs when

A

atmospheric pressure is less than pressure in the lungs

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9
Q

how do we change the pressure in the lungs?

A

by changing the volume of the lungs and thoracic cavity

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10
Q

atmospheric pressure is

A

760mmHg

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11
Q

pressure in the lungs differs by how many mmHg during inspiration and expiration

A

-1=759

+1=761

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12
Q

Thoracic volume can be increased by:

A

-increasing the vertical diameter (diaphragm)
-increasing the anterior posterior diameter (ribs)
-increasing the transverse diameter (up and out) (ribs)
not horizontal diameter

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13
Q

contracting the diaphragm

A
  • flattens the diaphragm
  • causes vertical diameter to increase
  • increases thoracic capacity by 75%
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14
Q

Elevation of the ribs

A
  • increases the AP diameter and the transverse diameter

- responsible for 25% of thoracic capacity increase

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15
Q

How is AP diameter increased

A
  • pump handle action of the ribs

- elevation of the ribs at the sternal end causes them to become horizontal instead of B\F

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16
Q

How is the transverse diameter increased

A

The bucket handle - ribs tend to dip in the middle like a sagging bucket handle - during inspiration pick the bucket handle up so its horizontal - this increases the diameter from left to right

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17
Q

How does the thoracic cavity size effect lung size?

A

The parietal pleura is stuck to the thoracic wall and diaphragm.
the visceral pleura is stuck to the surface of the lungs and moves with the parietal pleura due to surface tension cause by the serous fluid (fills cavities) in the cavity between the two membranes

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18
Q

the pressure in the pleural cavity is

A

always lower than atmospheric and intrapulmonary pressure because the elastic fibres in the lung tissue are always trying to pull back and cause recoil, causing negative pressure in the pulmonary cavity

19
Q

If air gets between lung and _____ pleura

A
  • parietal pleura the lung will succeed on pulling back and come free from the pleura and collapse - pneumothroax
  • occurs as a result of injury - disease or puncture wound
20
Q

what causes pneumothorax

A
  • accumulation of air in pleural cavity resulting from disease or puncture wound
  • loss of negative intrapleural pressure
  • lung collapse
21
Q

on x-rays what is

  • black
  • white
  • imbetween
A
  • air is black
  • connective tissues come up faintly grey
  • if the whole lung space is a solid black colour the lung has collapsed
  • bone is white
  • everything else is imbetween
22
Q

when one lung collapses

A

it can push the mediastinum to the other side and cause the other lung to collapse

23
Q

what to do when someones lung collapses

A

put a tube into the pleural cavity and put the other end of the tube into water so the air from the space will start bubbling into the water and the lung will re-inflate

24
Q

what is used in quiet inspiration

A

active process

  • diaphragm 75%
  • external intercostal muscles 25%
25
Q

what is used in forced inspiration

A
  • pectoralis major
  • pectoralis minor
  • scalenes
  • serratus anterior
  • sternacloidamastoids

-used by unhealthy people as normal inspiration

26
Q

external intercostal muscles

A

go downwards and forwards. start on one rib and go down onto the next one. lift the ribs like you would lift weights from squats

27
Q

pec minor

A

pec minor is attached on the shoulder and comes down to the ribs - it pulls ribs 3-5 up and down to help with AP diameter

28
Q

scalenes

A

are in the neck come from the cervical vertebra onto the ribs
fixes the first rib in place so the external intercostal muscles can work more effectively

29
Q

serratus anterior

A

comes round the side from the spine and helps pull ribs out at the side

30
Q

sternocleidomastoid

A

is between the sternum and the clavicle

helps fix the first rib and pulls the sternum out at the front

31
Q

pec major

A

fixes your humorous so you can move the ribs up and out

32
Q

whats used in quiet expiration

A

nothing its a passive process

relax the diaphragm and external intercostal muscles

33
Q

whats used in forced expiration

A
  • active process
  • internal intercostal muscles
  • abdominal muscles - compress contents of abdomen and therefore push them up against the diaphragm to force air out
34
Q

neural control of ventilation

A

chemoreceptors

-central and peripheral

35
Q

chemoreceptors

A
  • detect changes in pH ppO2 and ppCO2

- send information via afferent pathways to the brain via the vagus nerve and glossopharyngeal nerves

36
Q

where do the signals from the chemo receptors get sent

A
  • through afferent pathways through vagus and glossopharangeal nerve
  • to the respiratory centres in the brain stem
  • down the efferent pathways down the the phrenic and intercostal nerves
37
Q

which nervous system controls the diaphragm

A

signals sent to skeletal muscle so somatic nervous sytsem

38
Q

central chemo receptors

A
  • respond to changes in pH and CO2
  • DONT RESPOND TO O2
  • found in the medulla in the brain stem
39
Q

peripheral chemoreceptors

A
  • respond to ppO2 ppCO2 and pH
  • found near baroreceptors
  • some called aortic bodies found in aortic arch
  • stimulate? vagus nerve
  • some called carotid bodies found in the common carotid artery
40
Q

groups of neurons in the respiratory centres

A
  • medullary rhythmicity area

- pneumotaxic area (pons)

41
Q

medullary rhythmicitary area

A

dorsal (back) respiratory group - sets rhythm, stimulates muscles of quiet inspiration
ventral (front) respiratory group - involved in forced expiration and inspiration

42
Q

pneumotaxic area

A

influences the dorsal respiratory group by regulating the duration of inspiration

43
Q

Hering breuer reflex

A

prevents the over inflation of the lungs

  • stretch receptors in the visceral pleura, bronchioles and alveoli
  • impulses sent to the pneumotaxic area via the vagus nerve
  • duration of inspiration shortened