Week 20: (A) Respiratory Physiology

Question 1

What branches are the conductive zone?

Answer 1

1-16

Question 2

What branches are the respiratory zone (acinus)?

Answer 2

17-23

Question 3

How do we measure how much of a gas is in a space?

Answer 3

partial pressure

Question 4

What is partial pressure?

Answer 4

The notional pressure of a constituent of gas if it alone occupied the entire volume of the original mixture at the same temp.

Question 5

What percent room air is oxygen?

Answer 5

0.21/ 21%

Question 6

What is the pressure of air at room temp?

Answer 6

760mm Hg

Question 7

Does concentration of oxygen change with what state the has is in?

Answer 7

YES, room air has a higher concentration that water and blood (both the same)

Question 8

Why do we use partial pressure?

Answer 8

Partial pressure refers to a number of gasses in an area

Tells us the direction which has moves, Conc does not!

Question 9

Is partial pressure and Concentration proportional?

Answer 9

YES

Question 10

What is the partial pressure exchange when O2 enter the alveolus?

Answer 10

atmospheric pressure = 156mm Hg to alveolar 100 mmHg

Question 11

Where does the O2 in the airways dissolve?

Answer 11

Airway surface liquid (ASL) lining the alveolus

Question 12

What is the O2 solubility in the ASL?

Answer 12

0.003ml O2/100ml/1mmHg

Question 13

What is PO2 at 100mmHg in the ASL?

Answer 13

0. 003ml X 100

0. 3ml O2/100ml ASL

Question 14

how much oxygen does blood contain?

Answer 14

contains 0.003ml O2/100ml/1mmHg Po2
PLUS
All the O2 bound to haemoglobin (1.39ml O2/g Hb x Hb conc x %Hb saturation/ 100)

Question 15

What is the PO2 of mixed venous blood that arrives at the lungs?

Answer 15

40 mmHg

Question 16

What is the O2 conc of mixed venous blood arriving at the lungs with PO2 40mmHg ?

Answer 16

(40 x 0.003) + (1.39 x 15 x 75/ 100) = 0.12 + 15.64

–> 15.8 ml O2/100ml blood

Question 17

What has higher O2 concentration, venous or ASL?

Answer 17

venous
venous= 15.8 ml
ASL = 0.3 ml

Question 18

What has higher partial pressure, ASL or venous?

Answer 18

ASL
ASL= 100 mmHg
Venous = 40 mmHg

Question 19

What would happen if O2 moved according to Conc gradients?

Answer 19

move from bloods to ASL out of the body.

Question 20

what is the pathway of O2 entering the body? from dry room air to Cytochrome C oxidase…

Answer 20

Dry room air- 159
Tracheal gas- 149
Alveolar gas- 100
Pulmonary venous blood-98
Systemic arterial blood-96
mixed venous- 40 
mitochondria-2 
Cytochrome C oxidase -~0

Question 21

What drives the surface area of alveoli?

Answer 21

the number of alveoli

Question 22

What percent of the lungs is the respiratory zone?

Answer 22

95%

Question 23

What is the surface area of the respiratory zone?

Answer 23

130m^2 packed into a 6L volume

Question 24

What are 2 consequences to airway branching for lung function?

Answer 24

1) increase SA for gas exchange

2) Dissipates resistance to airflow as airway diameter narrows towards the respiratory zone

Question 25

Why is it that we are able to respire as the airway diameter decreases? down generations...

Answer 25

According to Poiseuille's Law It is about the total surface area for has exchange not just the individual alveolus Combined cross-sectional area of the airways

Question 26

Compare branch generation 1 to branch generation 17 about; No. of airways, total cross-sectional area (cm2) and Airflow Resistance factor (&)?

Answer 26

BG 1; 1, 2.5, 100*% | BG 17; 23630, 300, 0.9%

Question 27

What is the upper airways ?

Answer 27

Nose, nasal cavity, pharynx

Question 28

What is the lower airways?

Answer 28

Larynx; trachea, bronchial tree and the lungs

Question 29

What is a definition of Poiseuille's Law?

Answer 29

A doubling of total airway diameter at each branch generation reduces resistance 16 fold.

Question 30

What drives the bulk gas into the conductive zone?

Answer 30

Driven by difference in net pressure caused by the expansion and relaxation of chest cavity

Question 31

What is the movement of gas form the atmosphere to airways?

Answer 31

CONVECTION

Question 32

What is the movement of gas from the airways to the blood called?

Answer 32

DIFFUSION

Question 33

What is required for gas to move into the airways from the atmosphere?

Answer 33

Open airways | Will move into lung if pressure is below the atmospheric

Question 34

What is needed for has to move out of the lungs to the atmosphere?

Answer 34

relaxation; lung deflated shape due to the elastic recoil this causes the pressure on the walls of alveoli This causes the pp of the lungs to be above atmospheric CONVECTION OCCURS

Question 35

What is the alveolar pressure the sum of?

Answer 35

elastic recoil pressure (airways collapsing) | Also, variable by muscular effect (Pleural P)

Question 36

What muscles are used in inspiration of the lungs?

Answer 36

external intercostal muscles between rib cages

Question 37

What direction do the ribs move in inspiration?

Answer 37

upwards and outwards

Question 38

What happens when the diaphragm contracts?

Answer 38

diaphragm moves down, pressure decreases inside airways, creating more space --> gas moves into airways

Question 39

What are the 3 categories of the main inspiratory muscles?

Answer 39

Diaphragm External intercostals Accessory muscles

Question 40

what are the key features of the diaphragms during inspiratory?

Answer 40

- dome shaped, sits above liver - Phrenic nerves, C3-5 - Flattens on contraction - Moves 1cm in quiet breathing, up to 10cm

Question 41

what are the accessory muscles and key features?

Answer 41

sternocleidomastoid, scalene, plus some others | Chest expands, intrapleural pressure falls

Question 42

How do the lungs expire air?

Answer 42

mostly by elastic recoil (at rest)

Question 43

What muscles in the lungs cause expiration?

Answer 43

internal intercostal muscles (slope down riband back)- exercise

Question 44

What way motion do the lungs move when expiration occurs?

Answer 44

depressing lower rib. against lung

Question 45

When does forced expiration occur?

Answer 45

exercise, voluntary (cough, sneeze, defection)

Question 46

What are the main expiratory muscles used in forced expiration occurs?

Answer 46

abdominal wall - push guts up against diaphragm | internal intercostals

Question 47

define partial pressure

Answer 47

The pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture. Example: Atmospheric Pressure = 760mmHg Pressure of air we breathe therefore = 760mmHg 21% of air we breath = O2 Partial pressure of O2 in air we breath = 21% x 760mmHg = 160mmHg

Question 48

Calculate the partial pressure... O2 = 21% Atmospheric pressure = 760 mmHg

Answer 48

percent of Oxygen X atmospheric pressure 760 mmHg 21 x 760 = 160 mmHg

Question 49

Why is the partial pressure of oxygen lower in the alveolar space compared to atmospheric pressure (160mmHg)

Answer 49

diluted by anatomical dead space and residual volume saturated by water vapour, needs to be in solution. It is constant equilibrium with gas in the blood

Question 50

What is the normal partial pressure of CO2 in the alveoli?

Answer 50

40mmHg 5.3 kPa

Question 51

In health, are the partial pressure of CO2 and O2 the same in the alveoli and systemic arterial blood?

Answer 51

yes

Question 52

What are the values of alveolar ventilation in hypo-ventilation?

Answer 52

PO2 falls to 30 mmHg and PCO2 rises to 100 mmHg.

Question 53

What are the values of alveolar ventilation in hyper-ventilation?

Answer 53

PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg.

Question 54

What is the alveolar partial pressure of oxygen?

Answer 54

100mmHg 13.3 kPa

Question 55

For any given change in pressure in the lung, where has the biggest change in volume?

Answer 55

at the base of the lung and less at the apex alveolar ventilation greatest at the base.

Question 56

Where is compliance greatest in the lung?

Answer 56

most compliance at the base