gas exchange Flashcards
gaseous exchange system
A gaseous exchange like this circulatory system with the atmosphere
the gaseous exchange system is adapted to
- clean and warm the air that enters during breathing
- maximize the surface area for diffusion of oxygen , carbon dioxide between the blood and atmosphere
- minimize the distance for this diffusion
- maintain the adequate gradients for this diffusion
gas exchange in single celled organisms
single-celled organisms, the oxygen simply diffuses from the fluid outside the cell, through the cell surface membrane and into the cytoplasm
oxygen and CO2 are
nonpolar molecules, and they can cross the phospholipid bilayer
gaseous exchange in multicellular organisms requires
a special gas exchange surface - example: alveoli in the human lungs
Alevoli collectively have a large/huge surface area , probably traveling around 20m^2 in adults- therefore gas exchange of oxygen and carbon dioxide.
greater the surface area, greater the rate of diffusion
lungs seen in
thoratic ( chest ) activity
lungs surrounded by
the plural membranes which enclose an airtight space
this space contains a small quantity of fluid ( plural fluid ) to allow friction-free movement as the lungs are ventilated by the movement of the diaphragm and ribs
air pathway
nostrils- nasal cavity - pharynx - larynx - bonchi - terminal bronchiole - respiratory bronchiole - alveolar duct- alveoli ( gas exchange occurs)
the beating of the cilia in the airways
carries mucus upwards towards the larynx at a speed of about 1cmmin^-1
what happens to air inside the nasal chamber?
the nasal chamber is lined with hairs, mucus glands and richly supplied with blood vessels, the air flowing through the nose is warmed to body temperature and moistened by evaporation from the lining, for protecting the delicate surface inside lungs from dessication( drying out), particles smaller than 5-10 micro metre are trapped by nose hairs
mucus lining the nasal cavity traps the germs and suspended matter in the air and moistens the air, in the trachea and bronchi, the mucus produced by the goblet cells
Mucus-
mucin - glycoprotein- golgi bodies
glycoprotein process happening in
golgi body
trachea position
comes anterior to the oesophagus
cross-section of trachea
the lining is compressed of ciliated epithelium which rests on a basement made up of protein fibers
in between the ciliated cells are goblet cells
beneath the epithelium is an area of loose tissue with blood vessels and mucous glands
the trachea as a whole is supported by 15-20 C- shaped in complete rings of cartilage ( completely posteriorly by the trachealis muscle )
structure and function of golgi bodies
produce mucus to trap dust and pathogens, mucus must contain mucin, which is a glycoprotein. therefore, the number of golgi bodies are so high in goblet cells
structure and function of mucous glands
produce mucus to trap dust and pathogens , mucuc contains mucin which is a glycoprotein
structure and function of elastic fibres
they stretch during respiration and recoil ( to push air out) during expiration
structure and function of cillia
beats to push mucus to the throat, so that it could be swallowed
structure and function of C-cartillage
keep the aiways open , thus lowring resistance to air. provides support and keeps the trachea from colla[somh due to changes in air pressure
structure and function of smooth muscle
airways widen when smooth muscle relaxes ( for example during exercise) when it contracts the airways constricts
structure and function of trachealis muscle
found in the posterior wall allows the trachea to contract and decrease its diameter
steps involved in the production of mucus from goblet cells
- transcription: production of mRNA
- transalation: protein chains produced
- lumen of E.R- enzymes modify the secondary folding
- transport vesicles formed
- binds with golgi body- glucose is added
- tertiary or quaternary folding, if necessary
- exocytosis
- mucin with water
bronchi singular
bronchus
bronchi
a major branch of the trachea that extends to the lungs
at the base of the trachea are 2 bronchus which subdivide and branchial “tree” in each lung
cartilage in the trachea and bronchi keeps the airways open and air resistance low, and prevents them from collapsing or bursting as the air pressure changes during breathing
cross-section of bronchi
ciliated epithelium is the inner lining of bronchi. between which goblet cells are present
the number of goblet cells is less compared to that of the trachea.
below the epithelium are elastic fibers
a layer of smooth muscles comes in between the submucosa and cartilage blocks
in bronchi there are irregular blocks of cartilage
Bronchiole
each bronchus divides many times to form smaller bronchioles. terminal bronchiole divided to form even narrower respiratory bronchioles that supply the alveoli with air. bronchioles are surrounded by smooth muscle, which can contract or relax to adjust the diameter of these tiny airways. during exercise, the muscles relax to allow a greater flow of air to the alveoli, the absence of cartilage makes these adjustments possible
terminal bronchiole
after the bronchus comes the terminal bronchiole
terminal bronchiole has no cartilage or goblet cells
smooth muscles and ciliated cells present
size- 1mm in diameter
Respiratory bronchiole
comes after terminal bronchiole
no cartilage , goblet cells or smooth muscle
a few cillia are present
size-0.5mm in diameter
cross section of bronchiole
inner layer of ciliated epithelium followed by smooth muscle
there is no cartilage in bronchus
elastic fibers are seen
alveolar duct
size: 400 micro meter in diameter
ni cartilage, goblet cells, smooth muscles or cillia
alveolar duct is also a site of gas exchange
alveolus is made up
of squamous epithelial cells- single, flat cells
alveolus size
250 micro meter in diameter
alveoli contain
elastic fibers which stretch during inspiration and recoil during expiration to help force air out
Alveoli fully expanded- increases surface area for diffusion
example: during exercise
blood capilaries with thin
single celled walls ( endothelial) are seen very close to the alveoli
macrophage ( dust cells):
phagocytes usually found in blood. some migrate through the capilaries and clear debris, dust particles, bacteria and fungal spores from the alveolus called visiting phagocytes
surfactant
moist lining formed by the mixture of lipoproteins and phospholipids. it helps in easy diffusion. prevents alveoli from sticking together, surfactant reduces the surface of the fluid so that alveolus does not collapse, gases dissolve and diffuse
adaptations of gas exchange surface/ alveoli
1) one cell thick: made up of squamous epithelial cells- for easy diffusion
2) walls have elastic fibers ( elastin ) : that stretch and recoil during inhilation and exhalation
3)moist surface: so gases can diffuse dissolved
4)large surface area:many alveoli
5)short diffusion distance: because of thin layers of alveolus wall ( epithelium) and capillary wall ( endothelium)
6) surrounded by many capilaries- to maintain a steep concentration gradient for diffusion, blood is slowed in capilaries, good ventilation in lungs and good circulation of blood maintain a good concentration gradient
O2 and CO2 molecules diffuse
( high to low con. gradient) quickly between the air and blood because the distance is very small
a steep con. gradient must be maintained in alveoli
made by breathing and circulation of blood
breathing supplies
fresh air into the lungs, with a relatively high O2 con. (PO2 = 13.9kPa) and a relatively low CO2 con.(PCO2=5.3kPa)
blood is brought to the lungs
with a relatively high O2 (PO2=5.3kPa) and a high con. of CO2 (PCO2= 6.0kPa) than the air in the alveoli
O2 therefore
diffuses down its concentration gradient from the air in the alveoli to the blood, and CO2 diffuses down in con. gradient in the opposite direction
Partial pressure
the pressure excreted by a single component a mixture of gases of gases commonly expressed in mmg
if O2 has to move from alveoli into RBC
it must cross 5 cell membranes layers. this means 10 phospholipid layers
it it must just enter the capilary
it has to cross 4 cell membrane layers
if CO2 has to cross from RBC to alveoli
it must cross 5 cell membrane layers
if CO2 has to cross from capillary
to alveoli it must cross 4 cell membrane layers
trachea number
1
teachea approx diameter
1.8cm
trachea cartilage
yes
trachea goblet cells
yes
trachea smooth muscle
yes
bronchus number
2
bronchus approx diameter
1/2cm
bronchus cartilage
yes
bronchus goblet cells
yes
bronchus smooth muscle
yes
terminal bronchiole number
48000
terminal bronchiole approx diameter
1mm
terminal bronchiole cartilage
no
terminal bronchiole gobelt cells
no
terminal bronchiole smooth muscle
yes
respiratory bronchiole number
300k
respiratory bronchiole approx diameter
0.5mm
respiratory bronchiole cartilage
no
respiratory bronchiole goblet cells
no
respiratory bronchiole SM
no
alveolar duct number
9 X 10^6
alveolar duct approx diameter
400 micro meter
alveolar duct cartilage
wrong
alveolar duct goblet cells
no
alveolar duct SM
no
alveoli number
3x10^9
alveoli approx diameter
250 micro meter
alveoli cartilage, goblet cells and SM
no
main limiting factor on the amount of work done that muscles can
perform during aerobic exercise?
the amount of oxygen delivered to the muscles is limited by the volume
of blood flowing to them. The more popular answer was that the limitation is due to the speed of dissociation of oxyhaemoglobin.Evidently it is not generally appreciated how quickly dissociation occurs.
moist walls does not effect efficiency of gas exchange
oxygen can diffuse about one thousand times more slowly in water than
it can in air. Therefore although oxygen has to be dissolved before it can
cross the alveoli cell membranes, having moist walls does not increase
efficiency of gaseous exchange.
why is the inner lining of the bronchiole folded
to allow for expansion during breathing
maintaining conc gradient for co2 and o2
- ventilation of the lungs would maintain the concentration gradients
by reducing the carbon dioxide concentration in the alveoli, whilst
increasing the oxygen concentration. - blood flow past alveoli
- flow of blood through the lungs
- breathing movement exhcanging air
- blood arrives in the lungs w lower o2 conc and higher co2 conc than
alveolar air - NOT THIN LINING IN ALVEOLI
how is the collapse of alveoli prevented (qs81)
epithelial cells secrete a chemical that reduces cohesion in water [
surfactant ]
surfactant reduces surface tension in the lungs
which organelle is present in large quantities in ciliated epithelial cells?
mitochondira
^preference over golgi, rer and lysosomes
a disease damages alveoli. effects
surface area - decreases
volume of lungs - no change
max volume of air breathed out - decreases [im guessing because
efficiency of diffusion decreased]
to plasme
4 membrances
/ to rbc
5 membrances (for o2 and co2)
most o2 absorbed =
breathing rate * tidal volume
during exercise,
breaths r shorter and faster so vital capacity decreases
vital capacity =
lung volume at full inspiration - lung volume at full
expiration
an epidermis would not be seen in the photomicrograph of the wall of a
trachea (elastic fibres and smooth muscle can be seen)
the bronchus contains both
ciliated cells and goblet cells; it is the bronchiole that contains ciliated cells, but very few goblet cells. [look out for this word for bronchioles]
absence of cartilage in small bronchioles allows them to
expand
bronchioles may contain ciliated epithelium or goblet cells (its just that
not all bronchioles contain them, the ones that do so are in v small quantities)
there is no endothelium or epithelium in
bronchioles
process of gaseous exchange
Goblet cells found in
trachea and bronchus/bronchiole.
Smooth muscle is found
trachea, bronchus, bronchiole
Role of mucus in the gas exchange system:
- Lines surface (of epithelium);
- Sticky;
- Traps, dust/spores/bacteria/AW;
- Moved by cilia;
- Towards throat/away from lungs;
- Protects, alveoli/gas exchange surface.
Mucus is sticky and therefore helps to
trap dust and bacteria thereby protecting the alveoli against damage and pathogens. The cilia sweeps out the mucus away from the lungs.
Smooth muscle in the trachea and in the bronchi relaxes during
strenuous exercise.
Suggest the advantages of relaxing this smooth muscle during periods of strenuous exercise
I more air can enter unqualified
more air / oxygen, reaches the, alveoli / gas exchange surface ;
more gas exchange / greater absorption of oxygen / excretes more carbon
dioxide ; AW
A maximises oxygen obtained
satisfies increased demand for oxygen / AW ;
trachea / bronchi / airways, widen / AW ;
e.g. dilate / expand / enlarge A diameter of lumen increases
reduces resistance to air flow ; R rate of air flow increases
Describe process of gas exchange between alveoli and blood
Carbon dioxide diffuses out of blood and oxygen diffuses into blood
By diffusion; From an area of high concentration to an area of low concentration down the gradient
Across the squamous epithelium cells of alveoli
And endothelial cells of capillary walls A squamous cells but must be made clear this is for capillaries
Oxygen binds to RBCs I oxygen binds to Hb
Steep concentration gradient maintained by good air ventilation/uptake by haemoglobin/blood carries oxygen away / blood arrives with carbon dioxide / deoxygenated blood arriving low in oxyge
