Respiratory System II

Question 1

internal vs external respiration

Answer 1

external: exchange between pulmonary capillaries and alveoli
internal: exchange between systemic capillaries and surrounding cells

Question 2

factors affecting external respiration

Answer 2

lipid solubility of gases
partial pressure gradients
surface area, thickness and structure of the respiratory membrane
airflow perfusion and rate of blood flow

Question 3

why does lipid solubility of gases effect respiration

Answer 3

affects ability to pass through lipid membranes

Question 4

atmospheric pressure at sea level

Answer 4

760 mmHg

Question 5

what is the combined partial pressure of respiratory gases equivalent to

Answer 5

atmospheric pressure
each gas has a partial pressure proportional to its composition of the atmosphere

Question 6

partial pressure of each gas and how is it calculated

Answer 6

proportion of the atmosphere made up of gas * atmospheric pressure (760 mmHg)

O2:
CO2:
N2:
H2O:

Question 7

what happens to partial pressure of each gas at high altitude
why

Answer 7

decreases
atmospheric pressure decreases with altitude
composition of gases stays the same

Question 8

Henry’s Law

Answer 8

amount of gas that dissolves in a liquid depends on partial pressure and solubility of the gas

Question 9

does O2 or CO2 has greater solubility in water

Answer 9

with the same pressure at a given temperature
more CO2 dissolves into liquid

Question 10

partial pressures in alveoli

Answer 10

PO2 = 104 mmHg
PCO2 = 40 mmHg
PH2O = 47 mmHg

Question 11

humidification of inhaled air

Answer 11

air moving along the airways gets humidified, picks up water molecules and increases the pp of water

Question 12

mixing of old and new air

Answer 12

air is not completely expelled from the alveoli at the end of each breath

Question 13

O2 loading and CO2 unloading

Answer 13

O2 diffuses along its pp gradient from the alveolus into the blood

CO2 diffuses along its pp gradient from the blood into the alveolus

until equilibrium is reaches

Question 14

diffusion barriers at alveoli
what does thicker barrier cause

Answer 14

alveolar epithelium
basement membranes
capillary endothelium

thicker barrier -> slower diffusion

Question 15

diffusion at alveoli only occurs if

Answer 15

alveoli are ventilated and perfused

Question 16

decreased difference in pp
abnormal thickening of barrier
decreased alveolar volume or number
examples

effect of these on diffusion

Answer 16

decrease

decreased difference in pp: high altitude
abnormal thickening of barrier: fibrosis, oedema
decreased alveolar volume or number: pneumonia

Question 17

effect of blood flow cessation on gas exchange
example

Answer 17

blood flow ceases -> no gas exchange
pulmonary embolism

Question 18

what is the effect of severe exercise in gas exchange at alveoli

Answer 18

rate of breathing and blood flow increases
may not be enough time for gas exchange

Question 19

how long does it normally take for PO2 of blood to reach PO2 of alveoli

Answer 19

0.25 s
(1/3 of its way along capillary)

Question 20

factors affecting internal respiration

Answer 20

surface area in tissues
pp gradients
rate of blood flow
metabolic rate of the tissue

Question 21

why is PO2 of blood entering systemic capillaries lower than alveolar PO2

Answer 21

imperfect ventilation perfusion coupling at the lungs

Question 22

PO2 of blood entering systemic capillaries vs alveolar PO2

Answer 22

100 mmHg
104 mmHg

Question 23

pulmonary ventilation

Answer 23

process of air exchange between lungs and the atmosphere
physiological process involving muscles and volume/pressure changes

Question 24

Boyle’s law

Answer 24

in a closed system the pressure that gas molecules exert is related to the volume they occupy

Question 25

inspiration muscles

Answer 25

contraction of diaphragm and external intercostal muscles increases the volume and decreases pressure within the thoracic cavity and air flows in

Question 26

movement of external intercostal muscles and diaphragm

Answer 26

external intercostal muscles: elevate rib cage; the sternum moves anteriorly diaphragm: flattens and moves interiorly

Question 27

expiration muscles

Answer 27

relaxation of diaphragm and external intercostal muscles decreases the volume and increases pressure within the thoracic cavity and air flows out

Question 28

what accessory muscles are involved in deep inspiration

Answer 28

scalene muscles sternocleidomastoids forceful contraction of normal respiratory muscles

Question 29

what accessory muscles are involved in deep expiration

Answer 29

internal intercostal muscles external obliques rectus abdominus internal obliques transversus abdominus

Question 30

intrapleural pressure factors that affect it

Answer 30

usually negative to intrapulmonary and atmospheric pressure surface tension of alveolar fluid elasticity of the lung elasticity of thoracic wall

Question 31

pleural fluid

Answer 31

acts as a suction to keep lungs inflated

Question 32

intrapleural pressure during inspiration and expiration

Answer 32

inspiration: decreases due to thoracic wall moving outwards and increasing volume expiration: returns to 756 mmHg due to thoracic wall recoiling and decreasing volume

Question 33

why is pleural space usually a potential space

Answer 33

intrapleural pressure < atmospheric pressure

Question 34

what can cause pleural space to expand examples

Answer 34

if filled with: - excess fluid (pleural effusion - fluid leaking from capillaries) (pleural haemothorax - blood leaking from injured vessels) - excess air (pneumothorax - from puncture)