9) Gas Exchange

Question 1

what gases are exchanged & by what process do they move through the alveolar and capillary wall?

Answer 1

• O2 & CO2
• Diffusion

Question 2

definition of diffusion

Answer 2

net movement of particles/ions from a higher concentration to lower concentration down a concentration gradient as a result of the random movement of particles

Question 3

what is the gas exchange system adapted to do

Answer 3

• clean & warm the air that enters during breathing
• maximise surface area for diffusion of 02 & CO2 between blood and atmosphere
• minimise diffusion distance
• maintain adequate concentration gradients for diffusion

Question 4

tracheal walls are made of ?

Answer 4

• smooth muscle
• ciliated epithelium lining
• goblet cells
• supported by C shaped cartilage

Question 5

bronchus walls made of ?

Answer 5

• smooth muscle & elastic fibre
• ciliated epithelium lining
• goblet cells (fewer than trachea)
• supported by irregular blocks of cartilage that gets less and less as the bronchi gets smaller

Question 6

bronchiole walls made of ?

Answer 6

• smooth muscle
• lined w epithelial cells
• some cilia getting less and less
• no cartilage

Question 7

alveoli walls made of ?

Answer 7

• collagen
• elastic fibres
• lined w single layer of squamous epithelial cells
• no cartilage

Question 8

capillary network walls made of ?

Answer 8

• single layer of endothelial cells

Question 9

what do goblet cells do

Answer 9

• PRODUCE MUCUS
• mucus forms a layer over ciliated epithelium
• sticks to bacteria/pathogen
• mucus moved away back to mouth
• mucus prevents pathogens reaching epithelial cells

Question 10

what is mucus and where is it made and stored before being secreted ?

Answer 10

• slimy solution of mucin
• made in goblet cells found in ciliated epithelium / mucus glands beneath ciliated epithelium
• stored in vesicles at top of cell

Question 11

what does mucus do

Answer 11

• traps and inhales sticky particles + bacteria & viruses
• made of glycoproteins w many carbohydrates

Question 12

how is mucus removed from the body

Answer 12

• continuous beating of cilia sweep mucus (w particles and pathogens) away from lungs and back up to larynx
• at the top of the trachea, the mucus is swallowed & any pathogens killed by acid in stomach

Question 13

as air ways get smaller, what happens to cilia, goblet cells, columnar cells

Answer 13

• cilia become less
• goblet cells become less (none in bronchioles)
• columnar cells become more cuboidal

Question 14

where does gas exchange occur

Answer 14

alveolus

Question 15

what is 02 exchanged between

Answer 15

alveolus –> blood in lung capillaries

Question 16

what is CO2 exchanged between

Answer 16

blood in lung capillaries –> air in alveolus

Question 17

what factors increase the rate of diffusion, and how are alveoli adapted for this ?

Answer 17

• large surface area : elastic fibres to stretch & recoil
• steep concentration gradient : ventilation & movement of blood
• short diffusion distance : thin cells forming walls

Question 18

adaptions of alveoli - large surface area

Answer 18

• elastic fibres can stretch and recoil
• when air is breathed into lungs, elastic fibres stretch
• this increases SA of walls allowing more gases to be exchanged at once
• elastic fibres then recoil (exhalation), helping to expel air from alveoli

Question 19

which fibres support and stop the alveoli from bursting ?

Answer 19

collagen

Question 20

adaptations of the alveoli - short diffusion distance

Answer 20

• gases need to pass through alveolus & capillary, whose walls v tightly pressed against each other
• wall of alveolus = squamous epithelium cells
• single layer c& very thin cells
• wall of capillaries = endothelial cells
• also single layer & thin

Question 21

adaptations of the alveoli - steep concentration gradient

Answer 21

• inhaling brings air of high concentration of O2 into lungs & exhaling removes higher concentration of CO2 from lungs
• ventilation keeps O2 concentration high & CO2 concentration low in lungs/alveolus

blood flow
- blood arriving is deoxygenated
- newly oxygenated blood is constantly removed
- movement of blood keeps O2 concentration low & CO2 concentration high in capillary surrounding alveolus

Question 22

Explain how the structure of the capillary wall is related to its functions

Answer 22

• one cell thick wall = short distance for diffusion
• endothelial cells
• endothelial pores = for passage of small molecules

Question 23

what happens if cartilage is damaged on bronchi

Answer 23

bronchi may collapse / lose structural support

Question 24

Describe the function of smooth muscle in the bronchus

Answer 24

• smooth muscle contracts
• changes diametre of the airway
• helps to regulate airflow into/away from gas exchange surface

Question 25

role of elastic fibres during ventilation

Answer 25

• stretch in inhalation
• recoil to help exhalation
• prevent alveoli from overstretching/bursting on inhalation

Question 26

why do some cells appear darker than others in bronchial epithelium?

Answer 26

• 2 types : goblet & ciliated epithelial cells
• use of stains give diff colours
• diff density

Question 27

give 3 differences between bronchi cartilage & smooth muscle in function and structure

Answer 27

• cartilage does not have smooth muscle
• cells closer together in smooth muscle
• cells elongated in smooth muscle, but round in cartilage
• smooth muscle changes diametre of airways + contracts
• cartilage prevents collapse of bronchus

Question 28

explain why respiratory bronchioles (smallest bronchioles closest to alveoli) do not have any goblet cells

Answer 28

• mucus can prevent gas exchange
• respiratory bronchioles have few/no cilia so cannot difficult to move mucus
• mucus increases distance for diffusion of gases

Question 29

differences between the epithelium of bronchioles and the epithelium of
alveoli

Answer 29

• (bronchioles) have columnar, epithelium / cells ;(bronchioles) have ciliated, epithelium (epithelial) cells
• (alveoli) have squamous, epithelium / cells ;