9) Gas Exchange Flashcards
what gases are exchanged & by what process do they move through the alveolar and capillary wall?
- O2 & CO2
- Diffusion
definition of diffusion
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
what is the gas exchange system adapted to do
- 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
tracheal walls are made of ?
- smooth muscle
- ciliated epithelium lining
- goblet cells
- supported by C shaped cartilage
bronchus walls made of ?
- 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
bronchiole walls made of ?
- smooth muscle
- lined w epithelial cells
- some cilia getting less and less
- no cartilage
alveoli walls made of ?
- collagen
- elastic fibres
- lined w single layer of squamous epithelial cells
- no cartilage
capillary network walls made of ?
- single layer of endothelial cells
what do goblet cells do
- 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
what is mucus and where is it made and stored before being secreted ?
- slimy solution of mucin
- made in goblet cells found in ciliated epithelium / mucus glands beneath ciliated epithelium
- stored in vesicles at top of cell
what does mucus do
- traps and inhales sticky particles + bacteria & viruses
- made of glycoproteins w many carbohydrates
how is mucus removed from the body
- 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
as air ways get smaller, what happens to cilia, goblet cells, columnar cells
- cilia become less
- goblet cells become less (none in bronchioles)
- columnar cells become more cuboidal
where does gas exchange occur
alveolus
what is 02 exchanged between
alveolus –> blood in lung capillaries
what is CO2 exchanged between
blood in lung capillaries –> air in alveolus
what factors increase the rate of diffusion, and how are alveoli adapted for this ?
- large surface area : elastic fibres to stretch & recoil
- steep concentration gradient : ventilation & movement of blood
- short diffusion distance : thin cells forming walls
adaptions of alveoli - large surface area
- 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
which fibres support and stop the alveoli from bursting ?
collagen
adaptations of the alveoli - short diffusion distance
- 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
adaptations of the alveoli - steep concentration gradient
- 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
Explain how the structure of the capillary wall is related to its functions
- one cell thick wall = short distance for diffusion
- endothelial cells
- endothelial pores = for passage of small molecules
what happens if cartilage is damaged on bronchi
bronchi may collapse / lose structural support
Describe the function of smooth muscle in the bronchus
- smooth muscle contracts
- changes diametre of the airway
- helps to regulate airflow into/away from gas exchange surface
role of elastic fibres during ventilation
- stretch in inhalation
- recoil to help exhalation
- prevent alveoli from overstretching/bursting on inhalation
why do some cells appear darker than others in bronchial epithelium?
- 2 types : goblet & ciliated epithelial cells
- use of stains give diff colours
- diff density
give 3 differences between bronchi cartilage & smooth muscle in function and structure
- 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
explain why respiratory bronchioles (smallest bronchioles closest to alveoli) do not have any goblet cells
- mucus can prevent gas exchange
- respiratory bronchioles have few/no cilia so cannot difficult to move mucus
- mucus increases distance for diffusion of gases
differences between the epithelium of bronchioles and the epithelium of
alveoli
- (bronchioles) have columnar, epithelium / cells ;(bronchioles) have ciliated, epithelium (epithelial) cells
- (alveoli) have squamous, epithelium / cells ;
