Respiratory System

Question 1

Explain mechanics of inspiration in the mammal

Answer 1

1. Diaphragm contracts, moves caudally and flatters, expands size of thorax
2. external intercostal muscles that run caudoventrally from rib in front to rib behind pull back rib forwards and out
3. increases thorax size resulting in a drop in pressure in alveoli so breath in

Question 2

Describe the mechanisms of active expiration

Answer 2

internal intercostal muscles that pull ribs back and in and abdominal wall muscles

Question 3

What is the respiratory rate and what is it in most domestic species and horses

Answer 3

number of breaths in 1 min.
DS = 20-30 bpm
Horses = slower resting resp rate of about 10-12bpm

Question 4

What is:

1. Normal resting breathing
2. Increases resp rate
3. Increases resp depth
4. Laboured brething
5. Absence of breath

Answer 4

1. Eupnoea
2. tachypnoea
3. Hyperpnoea
4. Dyspnoea
5. apnoea

Question 5

What direction do external intercostal muscles run and where do they lift ribs

Answer 5

caudoventrally. lift ribs out adn cranially

Question 6

What occurs during active expiration

Answer 6

1. abdominal muscles push abdominal contents cranially forcing relaxed diaphragm to dome up into thorax
2. costal portions of intercostal muscles which slope cranioventrally oull ribs caudally and inwards
3. overall reduces size of the thorax, increasing pressure in alveoli

Question 7

what is compliance?

Answer 7

the degree to whihc a change in transpulmonary pressure causes a change in volume of lung

Question 8

what is compliance dependent on?

Answer 8

1. elasticity in lung tissue and thoracic cage

2. surface tension in alveoli

Question 9

what is surface tension and what deos it do in alevoli

Answer 9

1. the interface between fluid lining the respiratory bronchioles, alveolar ducts and alveolar sacs and air forms H bonds, creating surface tension.
2. it tends to reduce surface area, thus ST in alveoli will resist expansion of the lung which reduces compliance of the lung.

Question 10

how is surface tension resistance counteracted in the alveolus

Answer 10

1. by type 2 alveolar cells producing surfactant- a mixture of phospholipids, proteins adn Ca2+ which reduces the formation of H bonds between water molecules and hence reduces ST inside alveolus

Question 11

how does surfactant counteract the alveolar resistance

Answer 11

1. reduces the formation of H bonds between water molecules as hydrophilic heads of phospholipids dissolce in liquid linign alveolus and philic tails remain on inside preventing H bonds

Question 12

What is one of the reasons premature neonates struggle to survive. what can this lead to and what deos it present as?

Answer 12

1. due to their inadequate production of surfactant

2. leads to respiratory distress syndrome, which presents with severe dyspnoea (laboured breathing)

Question 13

Why is sighing important with surfactant production? What could occur during prolonged general anaesthesia if inadequate ventilation is provided

Answer 13

1. signing can stimulate release of surfactant

2. develop atelectasis = collapse of alveoli

Question 14

What is pressure in alveolus dependent on? Equation

Answer 14

1. radius
2. surface tension
   P = 𝟐𝐓/r

Question 15

If a smaller alveolus has a higher internal pressure than a larger why don’t they collapse as air moves down p gradient into larger alveoli

Answer 15

Amount of surfactant is the same in every alveoli so smaller alveoli have higher conc

Question 16

What is airway resistance governed by?

Answer 16

1. length and radius of the tube
2. viscosity of the substance travelling through
3. turbulence of the air in the airway

Question 17

How does turbulence change as air moves through respiratory system?

Answer 17

1. declines with each division of the airway becuase the total cross sectional area of the airways increases with each division

Question 18

What is the smooth muscle in the walls of the airways innervated by?

Answer 18

autonomic nervous system

Question 19

What effect does activation of the sympathetic ANS on smooth muscle cells thus on ventilation?

Answer 19

relax due to stimulation of beta 2 adrenoreceptors, causing an increase in the radius of the airways, therefore a reduction in resistance to flow and increased lung ventilation to allow for an increases oxygen demand

Question 20

Definition of tidal volume. what is normal tidal volume in domestic species

Answer 20

1. volume of air moved during a respiratory cycle (normal volume)
2. normal = around 10-15 ml/kg

Question 21

how to calculate minute ventilation

Answer 21

multiplying tidal volume by number of breaths

Question 22

What is residual volume. What is it due to

Answer 22

volume of air that remains after a full expiration. Due to limitations in compressibility of the thoracic wall

Question 23

What is functional residual capacity

Answer 23

Expiratory reserve volume + residual volume = total amount of air left in lungs after normal expiration at rest

Question 24

What is FO2.

What is partial pressure

Answer 24

FO2 = 0.21 = proportion of gas mixture that is made up of O2
Pa = pressure exerted by an individual gas within a gas mixture

Question 25

DEscribe how gas exchange occurs at the alveolus

Answer 25

1. blood entering lung caps from RV with have low pa O2 and high pa CO2
2. so CO2 will diffuse into alveolar air and O2 with doffuse into blood until eq is reached

Question 26

Talk about ventilation:perfusion in the alveolus

Answer 26

1. Ideal ventilation: perfustion are matched = enabled full equilibrium of gases to be achieved = correct transfer of gases
2. In reality ratio mismatched. If low ventilation but normal perfusion

Question 27

What is dead space

Answer 27

areas which are ventilated but don’t aprticipate in gas exchange e.g. anatomical (airways) unperfused alveoli = functional dead space

Question 28

1. what 2 factors deos alveolar compliance depend on

Answer 28

1. Surface tension

2. Elasticity

Question 29

what effect will stimulation of beta 2 adrenoreceptors have on resistance to movement of air through the airways

Answer 29

decrease because causes relaxation and dilation of smooth muscle airway

Question 30

Why is alveolar paO2 lower than pO2 in room air

Answer 30

1. constant exchange of oxygen at alveolus and not replacing all of that air every time
2. water vapour in gas mixture so everything has reduced partial pressure