Transcript Transport in Humansx

Transport in Humans
Blood vessels
Cross section of an artery
Structure vs
function
Cross section of a vein
• Structure
vs
function
Cross section of a capillary
• Structure vs
function
Red Blood Cells (erythrocytes)
Bi-concave shape increases surface area and keeps the
haemoglobin as close as possible to the membrane
Shape makes them flexible to squeeze along capillaries.
No nucleus or mitochondria, so more room for
haemoglobin.
Cannot reproduce, and die after 3 months, so are
manufactured in liver, spleen and bone marrow.
White Blood Cells (Leucocytes)
Generally larger that erythrocytes, and have a nucleus. Despite having
a nucleus, they are short lived (a few days) and are reproduced in the
bone marrow.
Are capable of amoeboid movement, so they can squeeze through
pores in capillary walls to reach tissues and sites of infection.
Visible when stained, using a light microscope, and fall into two groups.
Granulocytes (having granules in the cytoplasm) and are
polymorphonuclear * (?)
Agranulocytes (no visible granules) and are mononuclear, ** (?)
* Looking as though they have more than one nucleus
** Having one definite nucleus
GRANULOCYTES
Neutrophils
70% of all white blood cells.
They squeeze between cells in the capillary wall, and
wander through the intercellular spaces.
The move to infection sites in the body, where they
engulf and digest disease causing bacteria. (they are
phagocytic)
GRANULOCYTES
Eosinophils.
They represent 1.5% of all white blood cells, and
get their name from their granules that turn red
when stained by Eosine dye
They increase in number in allergic conditions such
as asthma or hayfever, and they possess antihistamine properties.
Their numbers are controlled by stress of various
kinds (ie the result of an asthma attack)
GRANULOCYTES
Basophils
They represent 0.5% of all white blood cells and
their granules stain blue with dyes such as methylene
blue.
The cells produce histamine, a chemical found in
damaged tissues. Histamine stimulates repair of
damaged tissues, so is important, but over production
can occur in allergic reactions (and so needs to be
controlled)
AGRANULOCYTES
Monocytes
They are formed in the bone marrow, and have a bean
shaped nucleus.
They only last 30 hours or so in the blood, after which
they leave the capillaries and enter the tissues.
Here they become Macrophages
AGRANULOCYTES
Macrophages
These are phagocytic, and engulf bacteria and other
large particles, such as damaged tissue.
They are also involved in the immune system (to be
covered later)
Macrophages and Neutrophils (discussed earlier) both
act as a first line of defence against bacteria.
LYMPHOCYTES
These make up 24% of all white blood cells, and
develop from cells that originate in the bone marrow
(although the lymphocytes themselves develop in a
gland called the Thymus, and also in lymph tissue (to
be discussed later).
There are two types of Lymphocyte, T Cells and B cells
that are involved in immune reactions, such as
antibody production, graft rejection and killing tumour
cells.
Their lifespan ranges from a few days to 10 years or
more.
Summary: Create a chart showing the name,
function of the cell, and a picture of it
Blood cells
BLOOD PLASMA
This is the fluid that the cells are surrounded
by. It contains
Nutrients
Waste Products,
Plasma Proteins
Tissue fluid
• Cells are bathed in tissue fluid
• Source of nutrients and oxygen
• Blood at the arterial end is under high pressure which
forces water and small molecules out into interstitial
spaces (ultrafiltration)
• Proteins are too big to move so they create an osmotic
effect which keeps some fluid in the capillary.
• The pressure at the venous end is low so water, waste
and carbon dioxide move back in to the capillary.
Lymphatic system
• Not all tissue fluid circulates
back into the capillary
• Some drains into the lymphatic
system
• Similar in composition to tissue
fluid but has more fatty
substances
• Works in defence system as well.
Body Fluids: A Comparison
The relationship
between Blood,
Tissue Fluid and
Lymph
Haemoglobin (recap)
It is made up of 4 polypeptide chains
(Quaternary structure)
Each chain is a globin molecule, and there are 2
chains of alpha-globin, and 2 chains of betaglobin.
Molecule is nearly spherical.
Hydrophobic R-groups point inwards, and
hydrophilic R groups point outwards making it
soluble.
Haemoglobin (recap)
Interactions of the hydrophobic R groups help
hold the molecule into it’s 3-dimentional
shape.
In Sickle cell anaemia, a glutamic acid
molecule (an amino-acid) near the surface of a
globin molecule is replaced by valine, which
has a hydrophobic R group.
The hydrophobic R group makes the whole
molecule less soluble and prevents it
functioning correctly.
Haemoglobin (recap)
Each polypeptide chain contains a haem
group.
Haem is not made of amino acids, and is called
a prosthetic group.
Each haem group contains an iron atom, which
can bind with an oxygen molecule, 02
Each haemoglobin molecule can therefore
carry 8 atoms of oxygen.
Oxygen dissociation curve
• Degree of oxygenation of haemoglobin is
determined by the partial pressure of oxygen
in the immediate surroundings.
• Partial pressure of a gas is the pressure
exerted by that gas in a volume of air.
• At sea level the total atmospheric pressure is
101.3kPa.
• Atmosphere has 21% oxygen so the partial
pressure of oxygen is 21% of 101.3kPa, or
21.3kPa.
The curve shows how much haemoglobin is saturated by
oxygen at different partial pressures of oxygen
• Note that the curve is sigmoidal because
• There is high affinity by each haem group and
oxygen at high partial pressures.
• This means that in the lung tissue, where
there is a lot of oxygen, it quickly combines
with the haemoglobin
• There is low affinity between each haem
group and oxygen at low partial pressures.
• This means that in muscle tissue, where the
body needs the haemoglobin to give up its
oxygen it will do so easily.
Carbon dioxide
• 5% carbon dioxide is transported in
solution
• 10% combines with some of the amino
acids in haemoglobin to form
carbaminohaemoglobin.
• 85% carried as hydrogencarbonate ions.
• CO2 diffuses into red blood cells and it is
changed into carbonic acid by an enzyme
called carbonic anyhydrase
• Carbonic acid dissociates to form H+ and
hydrogen-carbonate ions.
Write the formulae for these two reactions
on p110 of your textbook.
• HCO3- (hydrogencarbonate) ions can
diffuse out of the cell and are then
transported in the plasma.
• Chloride ions move in to the red blood cell
from the plasma, to maintain electrical
neutrality by replacing the hydrogencarbonate irons that have moved out.
• This is referred to as the Chloride Shift.
• H+ are taken up by the haemoglobin to form
haemoglobinic acid (HHb)
• Haemoglobin is therefore acting as a buffer
to keep blood from being too acidic by
preventing a build-up of H+ ions.
• This also forces haemoglobin to release
their oxygen molecules,
Summary of whole process
Bohr Effect
• Oxygen dissociation
curve is shifted to the
right due to the presence
of CO2
• CO2 reduces the affinity
of haemoglobin for
oxygen
• This means the more CO2
there is, the more O2 is
released from the
Haemoglobin
Explained in more
detail………..
Graph:
(a) The partial pressure of
oxygen in the tissue
(b) At Pco2 = 3kPa Hb has
50% unloaded its oxygen.
(c) At Pco2= 4kPa Hb has
approx 80% unloaded its
oxygen.
(d) At Pco2= 6kPa Hb has
approx 90 % unloaded its
oxygen.
• Adaptations to altitude:
• Prolonged time at altitude results in the following
adaptations for the individual
1) Increased vascularisation of the muscle
2) Increases in the concentration of myoglobin (single
chain globular protein containing haem, found in
muscles)
3) Increased red cell number in blood
Red blood cell count at high altitude
• At high altitudes there is lower atmospheric pressure
of oxygen.
• The current number of red blood cells in the body
cannot meet the cells demands for oxygen.
• Polycythemia occurs, which is an increase in the bodies
red blood cell count.
• It means there is more haemoglobin available to bond
with oxygen molecules meaning more oxygen can be
transported to the cells in the body, therefore helping
to meet the oxygen demands of the body even with
less oxygen in the air.
More adaptations to altitude:
4) Greater number of mitochondria per muscle
cell
5) Increases in the concentration of respiratory
enzymes
6) Improved buffering of pH and utilisation of
lactate ions, (the product of anaerobic
respiration). This is called lactate clearance.
• An interesting observation in sports medicine
has been the realisation that athletes do not
need to train at altitude to achieve these
effects.
• Rather the key is to recover at altitude which
means recovering and sleeping either at
altitude or in a hypobaric chamber which can
simulate high altitude. It is during recovery
that the body adapts to the stresses of
exercise and under high altitude recovery
conditions it they recover with the above list
of 6 adaptations.
The Heart
The heart
Closed,
double
circulation
Thickness
of the walls
is related
to their
functions
The cardiac cycle
Atrial systole
• atrium contracts
• blood flows from
atrium to the
ventricle
Ventricular Systole
• Ventricles contract
• Atrioventricular
valves close
• Semi lunar valves
open
Diastole
• whole heart is
relaxed
• Electrical impulses
control the pace.
• These impulses are
provided by two
electrical nodes:
the sinoatrial (SA)
node and
the atrioventricular
(AV) node.
• Called the
natural pacemakers of
the heart.
Diastole
no electrical activity during this phase
Atrial Systole
Sinoatrial node fires an electrical impulse ,
it spreads throughout the right and left atria,
causing the muscle to contract and push blood
into the ventricles.
Towards the end of the atrial systole the
electrical impulse reaches and triggers the
atrioventricular node.
• Ventricular Systole
• The atrioventricular node (after a short delay)
fires an impulse,
• it spreads throughout the thick ventricular
muscle,
• causing contraction from the bottom of the
ventricles,
• pushing blood through the lungs and body.