7 Mammalian Gas Exchange

Question 1

what is the need for a gas exchange system (GES) in multicellular organisms?

Answer 1

low SA:vol ratio

large diffusion distance

high metabolic rate

∴ diffusion rate too low to sustain aerobic respiration

Question 2

what is the definition of a tissue?

Answer 2

a group of one or more cell types that are specialised and working together for a particular function

Question 3

what is the definition of an organ?

Answer 3

a group of one or more tissue types that are specialised to carry out specific function(s)

Question 4

what is the definition of an organ system?

Answer 4

a collection of organs with particular function

Question 5

what are the component parts of the GES?

Answer 5

lungs, trachea, bronchi, bronchioles, larynx, mouth, diaphragm

Question 6

why is a rich blood supply required for the lungs?

Answer 6

maintains a steep concentration gradient for gas exchange of O(2) and CO(2)

Question 7

what is the diameter of an alveolus?

Answer 7

~ 200 - 300 um

Question 8

what is the purpose of surfactant in the alveoli?

Answer 8

makes the lining moist ∴ reduces surface tension and prevents the alveoli sticking together during exhalation

easier for O(2) to dissolve and diffuse into the blood

Question 9

what is the purpose of smooth muscle in the bronchi and bronchioles?

Answer 9

to control the diameter of the lumen during inhalation and exhalation

Question 10

what is the purpose of ciliated epithelial cells?

Answer 10

to keep the airway free of debris by wafting mucus and its contents up the trachea to be swallowed or expelled as sputum

Question 11

what is the purpose of goblet cells?

Answer 11

to secrete mucus (a glycoprotein) to trap pathogens and other foreign objects

Question 12

what is the purpose of cartilage in the trachea?

Answer 12

to provide support to keep the airway open during inhalation as the pressure in the thorax decreases

Question 13

what happens during inhalation?

Answer 13

intercostal muscles: contract

ribcage: up and out
diaphragm: contracts and flattens

thorax pressure: decreases

thorax volume: increases

Question 14

what happens during exhalation?

Answer 14

intercostal muscles: relax

ribcage: down and in
diaphragm: relaxes and domes

thorax pressure: increases

thorax volume: decreases

Question 15

name three factors that contribute to lung size

Answer 15

body size (and ∴ gender)

physical activity level

general health

Question 16

what is roughly the capacity of the lungs?

Answer 16

~ 6 dm^3

Question 17

what is the definition of tidal volume?

Answer 17

the volume of air that moves in and out of the lungs during a normal breath

Question 18

what is the definition of vital capacity?

Answer 18

the maximum amount of air that can be forcibly expelled from the lungs following breathing as deeply as possible

~ 3 - 5 dm^3

Question 19

what is the definition of residual volume?

Answer 19

the volume of air remaining in the lungs after a maximal expiratory effort

Question 20

what is the definition of dead space?

Answer 20

the volume of non-exchange surfaces in the breathing system

Question 21

what is definition of pulmonary ventilation?

Answer 21

the amount of air exchanged with the environment per minute

Question 22

how is pulmonary ventilation calculated?

Answer 22

p.v. = tidal volume x breathing rate

Question 23

what is FEV(1)?

Answer 23

{forced expiratory volume}

the volume of air that can be breathed out in the first second of forced exhalation

Question 24

how is FEV(1) calculated?

Answer 24

FEV(1) = (4.3 x height - 0.029 x age) - 2.49

Question 25

what is PEFR?

Answer 25

{peak expiratory flow rate}

the maximum rate of forcing air out through the mouth

Question 26

what is the use of PEFR?

Answer 26

used to diagnose pulmonary disorders

Question 27

what can cause respiratory arrest?

Answer 27

obstruction of trachea or bronchi

drug overdose

asthma attack

severe pneumonia

severe shock

heart attack

Question 28

how is respiratory arrest treated?

Answer 28

expired air resuscitation

then CPR