Respiratory System - Paper <=1998
1998_2nd
semester_Q5_Part_A
For
an essay format answer, click here.
The Major Points are described below.
Major
Points: Tissues produce CO2 >
gradient means CO2 travels into blood >
hydration occurs here in the presence carbonic anhydrase >
carbonic acid is very unstable and quickly dissociates >
hydrogen ions act as a buffering mechanism >
Bohr Effect >
bicarbonate ions are produced >
electrochemical gradient forces this outside into plasma >
as a result to chemical electrical equilibrium, Cl- flows into the cell >
known as chloride shift.
1998_2nd
semester_Q5_Part_B
For
a full blown answer please click here.
The Major Points are described below.
Major Points: Central chemoreceptors > location > BBB > Hydrogen buffer is substandard > Hydrogen diffuses into cell > increase in partial pressure of carbon dioxide in solution only > Peripheral Chemoreceptors > types and location > innervation > hypercapnic response > only provide 25% but fast response is important.
1997_2nd
semester_Q5_Part_A
P50
= occurs at PO2 of 25mmHg. Also at about 40mmHg, saturation is about 70%.
Max saturation is about 98%. Sigmoid shape (Do you know why?).
1997_2nd
semester_Q5_Part_B
Four
factors (Major Points):
Temperature
> increase right
shift, decrease left shift >
explain the functional implications
PH
>
increase right shift, decrease left shift >
Bohr effect >
explain the functional implications
CO2
>
increase right shift, decrease left shift >
Haldane effect à
explain the functional implications
2,3
biphosphoglycerate >
increase right shift, decrease left shift > produced by red blood cells >
binds to hemoglobin – beta chain > fetal biphosphoglycerate >
gamma chains >
greater affinity >
left shift
Tip: When given an opportunity to choose always choose temperature and ph because you can functionally relate this to increased exercise routine. The others are a little difficult, although carbon dioxide can also be related to exercise.
1997_2nd
semester_Q4_Part_B
Forced
Vital Capacity and Forced Expiratory volume are dynamic values which are
measured using times spirometry. A vitallograph is used to measure these
volumes. Forced Vital Capacity relates to the amount of air which can be expired
by the person and the time taken to do so. This should be done in minimum time
as the rate of flow of air is also taken into account. The forced vital
capacity, theoritically speaking should be the same as the vital capacity which
is a static value. The forced expiratory volume, on the other hand, is related
to forced vital capacity in that this is the amount of air which is expired by
the person in the first 1 second of expiration. This should account to about 80%
of forced vital capacity. These two are useful clinically because they can be
used to determine restrictive or obstructive pulmonary disorders.
Restrictive
disorders are ones where the lung’s compliance is reduced, therefore it is not
able to expand well hence affecting the volume of air which can be taken in and
stored. That is the capacity of the lung is reduced. Obstructive disorders are
cause normally due to increased resistance offered by the respiratory
passageways. This resistance can be due to the presence of excess mucous or
chronic constriction of the respiratory passageways.
Thus
measuring a low Forced Vital Capacity will indicate a restrictive disorder. That
is less air is now able to be occupied inside the lungs. This means that the
ratio of FEV1:FVC is higher. Measuring a low FEV1 means that the air is not able
to be expired in a quick time, indication some sort of resistance. This is
classic sign of obstructive disorders. Thus the ratio is decreased.
Major
Points: FVC > meaning
> FEV1 > meaning > dynamic or static > what is restrictive and
obstructive diseases > what does each measurement indicate > what does it
mean clinically?
1996_2nd
semester_Q5
Carbon
dioxide is produced in the tissues of the body and so is carried by the blood to
be excreted into the alveolus, that is then expired into the atmosphere. There
are three mechanism of carbon dioxide storage and these are: in plasma solution,
bound to hemoglobin, as bicarbonate ions in plasma.
Carbon
dioxide is highly lipid soluble and also highly soluble in aqueous solution. Due
to this, a small portion is dissolved in the plasma solution. Out of total
carbon dioxide storage amount, only 5% is present in plasma completely dissolved
and out of the alveolar contributions, 10% is derived from dissolved plasma
supplies.
The
second major form of carbon dioxide carriage by blood is by binding to the
hemoglobin molecule. The hemoglobin molecule is made of four polypeptide chains
each with a iron complex in the middle, called a heme complex. Each of the
polypeptide chain can be broken up into a alpha and a beta chain. The carbon
dioxide molecule can bind to the globin portion (polypeptide portion) of the
hemoglobin molecule. The saturation of hemoglobin (due to oxygen loading) has an
effect on the binding of carbon dioxide, called the Haldane effect. As the
saturation of the hemoglobin rises, the affinity of hemoglobin towards carbon
dioxide decreases. Thus in the situation of the tissues, where excess carbon
dioxide is produced, oxygen is needed for delivery so therefore oxygen is
offloaded, therefore carbon dioxide has a high affinity towards hemoglobin.
About 5-10%is stored in this way and 20-30% of the alveolar contribution is from
this form.
The
third major form of carbon dioxide storage is as bicarbonate ion in the plasma.
This contributes to about 80-90% of the total carriage of carbon dioxide, and
contirbutes to about 60-70% of the alveolar contribution. The mechanism is
described next. When carbon dioxide is produced by the tissues, it travels
straight into the blood due to the gradient present. In the blood, in the
presence of carbonic anhydrase, the hydration of CO2 occurs. This hydration
forms carbonic acid, which quickly dissociates into Hydrogen ions and
bicarbonate ion. The hydrogen ion is a good buffer and weaks oxygen-hemoglobin
bond à
called the Bohr effect à
and the bicarbonate ion moves into plasma due to concentration gradient. To
compensate for the electrical imbalance, choride ions move in à
called chloride shift.
Thus
together these three mechanisms contribute to carbon dioxide storage in blood.
Major Points: Carbon dioxide > in solution > contribution in terms of percentages > bound to hemoglobin > which portion > structure of hemoglobin > Haldane effect > functional significance > as bicarbonate ions in plasma > mechanism > Bohr effect > chloride shift
1998_2nd
semester_Q4
Major
Points (Subdivisions): vocal cords >
glottis > Trachea > primary bronchi > to each lung > secondary
bronchi > to each lobe of each lung > tertiary bronchi > to each
bronchopulmonary segment of each lung > diameter decrease > < 1mm >
called bronchioles > repiratory bronchioles (contain alveolus on each side)
> alveolar ducts > alveolus > gas exchange takes place here
Major
Points (Structural differences): epithelial changes from pseudostratified
columnar to low columnar, cuboidal, squamous >
decrease in cilia > decrease in goblet cells > same concentration of
elastic fibres > smooth muscle increases > cartilage decreases >
alveolar macrophages present > structure of an alveolar wall
Major
Points (Functional Implications): squamous cells allow for easy gas exchange
due to thinness > cilia sweep
away the mucus with dust particles towards upper airway > goblet cells
secrete mucus which attract dust particles, therefore keeping airways clean >
decrease in cilia means dust can still be swept away > no goblets cells means
macrophages need to be active > cartilage decrease means, increase elasticity
of passageways > more smooth muscle means constriction therefore increase
resistance.
1996_2nd semester_Q4_Part_A
Major
points (Alveolar Wall): alveolar epithelium >
connective tissue (sometimes) > blood vessels >
alveolar epithelium > holes present to allow gases to pass between alveolus
Major
Points (Respiratory Membrane): capillary endothelium >
fused basal laminas >
alveolar epithelium > sometimes connective tissue > pulmonary fibrosis
(altering of collagen fibres within connective tissue) > pulmonary oedema (accumulation
of fluid in the connective tissue due to large imbalances of the capillary
hydrostatic and plasma oncotic pressure).
Major Points: Concentration gradient > maintenance > bulk flow of blood and air > energy from right vent of heart and respiratory muscles > surface area > thinness of the respiratory membrane > give examples when air is breathed in, partial pressures of O2 and CO2 in mixed venous blood.
1995_2nd
semester_Q4_Part_A
Major
points (trachea): Where is trachea located? >
what type of epithelium > structural features of epithelium > cartilage
rings present > ligamentous membrane > smooth muscle > elastic fibres
Major
Points (alveolus): Where is alveolus located? >
what type of epithelium > structural features of alveolus > types of cells
present > surfactant function > macrophages present > no cartilage >
sometimes a little bit of connective tissue > some
elastic fibres
Major
Points: Talk about function of epithelia of the trachea >
function of the thinness of epithelia of the alveolus > function of cartilage
in trachea > function of smooth muscle in trachea > function of elastic
fibres (stretch recoil properties) > function of alveolar cells >
particularly of surfactant secreting cells > alveolar macrophages >
function of holes present in alveolar walls connecting two alveoli together.