Case 3 - respiratory system structure and function

Question 1

how many times does the airway tree divide?

Answer 1

23 times

Question 2

functions of the respiratory system?

Answer 2

*Gaseous Exchange
*Acid-Base Balance
*Phonation
*Warming, humidification, filtration of gas
*Defense against airborne pathogens

Question 3

what do the first 16 divisions of the airway tree make?

Answer 3

conducting zone/conducting airways

Question 4

what do the remaining/last 7 divisions of the airway tree make?

Answer 4

respiratory zone

Question 5

what do alveolar sacs contain?

Answer 5

each alveolar sac contains many alveoli

Question 6

what is dead space gas?

Answer 6

When you exhale, first you have to
breathe out the volume of the
conducting airways (about 150-200ml) BEFORE you exhale alveolar gas. This is
sometimes called dead space gas

Question 7

similarities b/w right and left lung

Answer 7

oblique fissure
superior and inferior lobes

Question 8

differences b/w right and left lung

Answer 8

Right lung has:
2 fissures - oblique and horizontal fissures
3 lobes - sup., inf., middle lobes
right lung is shorter, wider, heavier

Left lung has:
only 1 fissures - oblique fissure
only 2 lobes - sup., inf.
lingula
presence of cardiac notch
left lung is longer, narrower, smaller, lighter

Question 9

Right lung is considered to be ______ than left lung whereas left lung is considered to be ______ than right lung

Answer 9

1) shorter
2) smaller

Question 10

name the accessory inspiratory muscles

Answer 10

scalenus, trapezius, sternomastoid/sternocleidomastoid

Question 11

name the accessory muscles of inspiration and their roles

Answer 11

scalenes group - elevates ribs
trapezius
pectoralis minor
sternomastoid/sternocleidomastoid - elevates sternum

Question 12

name the principal muscles of inspiration and their roles

Answer 12

external intercostal muscles - elevates ribs
interchondral part of internal intercostal muscles - elevates ribs
diaphragm - dome of diaphragm descends, thus increasing vertical dimension of thoracic cavity; also elevates lower ribs

Question 13

how does quiet breathing of expiration occur?

Answer 13

expiration results from passive, elastic recoil of the lungs, rib cage and diaphragm

Question 14

name the muscles of expiration active breathing and their roles

Answer 14

internal intercostal muscles except the interchondral parts - pulls the ribs down
abdominal muscles - pulls ribs down, compresses abdominal contents thus pushing diaphragm up
quadratus lumborum - pulls ribs down

Question 15

define breathlessness (NICE)

Answer 15

Breathlessness is a subjective, distressing sensation of difficulty with breathing
(NICE).

Question 16

how is breathlessness measured?

Answer 16

breathlessness is measured using a scale: the MRC dyspnoea scale.

Question 17

what are the signs and symptoms of inadequate breathing (name 3)?

Answer 17

nasal flaring
cyanosis
chest tightness
excessive use of accessory muscles
numbness, tingling in hands and feet
pursed lips on exhalation
coughing, crowing, high-pitched bark
respiratory noise - wheezing, rattling
impaired mentation (mental activity)
unconsciousness - dizziness, restlessness, anxiety, confusion, combativeness

Question 18

where do the 2 layers of the pleura (the visceral pleura and parietal pleura) fuse?

Answer 18

The two layers (the visceral pleura and parietal pleura) fuse at the hilum of the
lung.

Question 19

what makes the intra-alveolar pressure fall

Answer 19

During inspiration the increase
in the size of the lungs makes
the intra-alveolar pressure fall
(Boyle’s Law).
The decrease in
alveolar pressure during
inspiration in quiet breathing is
SMALL; only about 1mmHg.

Question 20

what is expiration?

Answer 20

Expiration is a normally a passive
process involving no muscle work.
It is brought about by the relaxation of
inspiratory muscles.
The chest wall and stretched lungs
recoil to their pre-inspiratory size
because of their elastic properties

Question 21

what makes the intra-alveolar pressure rise above atmospheric?

Answer 21

The recoil of the lungs makes the
intra-alveolar pressure rise above
atmospheric, but again, only by 1
mm Hg.

Question 22

In expiration, how does the intra-alveolar pressure become equal to atmospheric
pressure?

Answer 22

Expiration is brought about by the relaxation of inspiratory muscles.
The chest wall and stretched lungs
recoil to their pre-inspiratory size,
because of their elastic properties
The recoil of the lungs makes the
intra-alveolar pressure rise above
atmospheric, but again, only by 1
mm Hg.
The air then leaves the lungs
down its pressure gradient until
the intra-alveolar pressure
become equal to atmospheric
pressure

Question 23

what does the diaphragm and external intercostals do when you breathe in/inspire?

Answer 23

When you breathe in, your diaphragm descends and the external intercostals
contract to enlarge the thoracic cavity

Question 24

what causes the respiratory zone airways to expand?

Answer 24

the lungs are ‘glued’ to the inner side of the thoracic cavity by the two layers of the pleura - this causes the respiratory zone airways to expand.

Question 25

What keeps the lungs kept ‘glued’ to the inside of the thoracic wall?

Answer 25

Two forces hold the thoracic wall and the lungs in close opposition: 1) The intrapleural fluid cohesiveness - water molecules in the intrapleural fluid are attracted to each other and resist being pulled apart. This means that the pleural membranes tend to stick together; also pleural fluid may contain molecules which increase the surface tension of the fluid. 2) The negative intrapleural pressure - the sub-atmospheric intrapleural pressure creates a pressure gradient between the lung wall and the chest wall. This holds the outer surface of the lung against the inner surface of the thorax

Question 26

in lung disease, when the potential space is filled with each of these, what do we call it: Air? Fluid? Blood? Chyle? Pus?

Answer 26

Potential space can be filled with * Air (pneumothorax) * Fluid (pleural effusion) * Blood (haemothorax) * Chyle (Chylothorax, thoracic duct) * Pus (Empyema)

Question 27

cell type of Type I Pneumocyte?

Answer 27

Simple squamous epithelial cells

Question 28

cell type of Type II Pneumocyte?

Answer 28

Simple cuboidal cells

Question 29

primary function of Type I Pneumocyte?

Answer 29

Gas exchange

Question 30

primary function of Type II Pneumocyte?

Answer 30

Production of surfactant

Question 31

what is the chief structural cell of the alveolar wall?

Answer 31

Type I Pneumocytes

Question 32

what does surfactant do?

Answer 32

surfactant reduces the surface tension in the alveoli and stops the alveoli collapsing during expiration. Surfactant binds to water molecules within the alveoli and pushes these molecules apart.

Question 33

role of surfactants containing lipoproteins B&C?

Answer 33

Surfactants containing lipoproteins B&C (the ‘classic’ form) reduces surface tension and ensure proper lung function.

Question 33

role of surfactants containing lipoproteins A&D?

Answer 33

Surfactants containing lipoproteins A & D coat bacteria and viruses and help the immune system deal with them. (surfactant D deficiency is a particular risk factor for pulmonary tuberculosis)

Question 34

Respiratory Distress Syndrome of the New Born?

Answer 34

Foetal lungs are unable to synthesise surfactant until late in pregnancy Premature babies (before ~28 weeks) may not have enough pulmonary surfactant This causes respiratory distress syndrome (RDS) of the new born; lungs are hard to inflate and some alveoli may fail to open at all during inspiration The baby has to make very strenuous inspiratory efforts in an attempt to overcome the high surface tension and inflate the lungs.

Question 35

summary of surfactant?

Answer 35

Pulmonary surfactant is a complex mixture of lipid and protein, secreted by the type II pneumocytes It lowers alveolar surface tension by spreading out between the water molecules lining the alveoli This prevents the smaller alveoli from collapsing and emptying their air contents into the larger alveoli. With surfactant, alveoli shrink evenly during expiration

Question 36

According to the Fick principle, gas transfer from alveoli to capillaries is reduced when there is:

Answer 36

reduced surface area increased thickness of alveolar membrane reduced oxygen concentration inadequate time for gas transfer

Question 37

what value is SaO2 (arterial oxygen saturation) to be considered hypoxaemia?

Answer 37

An SaO2 (arterial oxygen saturation) value below 90% is hypoxaemia

Question 38

what does a pulse oximeter measure?

Answer 38

The proportion of haemoglobin that is bound to oxygen is called percent saturation and written as % Hb saturation or often for arterial blood as SaO2

Question 39

Healthy individuals at sea level should show oxygen saturation values between?

Answer 39

Healthy individuals at sea level usually show oxygen saturation values between 96% and 99%, and should be above 94%.

Question 40

what is FRC?

Answer 40

Functional residual capacity (FRC) is the volume remaining in the lungs after a normal, passive exhalation.

Question 41

What is RV?

Answer 41

Residual volume (RV) is the amount of air that remains in the lungs after a person has exhaled as much as they can. It's normal to have some air left in the lungs after exhaling to keep them from collapsing.

Question 42

what does FRC represent?

Answer 42

Functional residual capacity (FRC) represents the point of the breathing cycle where the lung tissue elastic recoil and chest wall outward expansion are balanced and equal