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THE MAMMALIAN
TRANSPORT SYSTEM

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Learning outcomes
To explain the relationship between the structure and
function of arteries, veins and capillaries
To describe the structure of red blood cells, phagocytes
and lymphocytes and explain the differences between
blood, tissue fluid and lymph
Describe the role of haemoglobin in carrying oxygen and
carbon dioxide
To describe and explain the significance of the
dissociation curves of adult oxyhaemoglobin at different
carbon dioxide levels (the Bohr effect)
To describe and explain the significance of the increase
in the red blood cell count of humans at high altitude
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Transport systems
Functionally connect body cells with the organs of
exchange
Circulatory system ensures no substance has to
diffuse far to enter or leave a cell
E
...
oxygen from inhaled air diffuses across a thin
epithelium and into the blood while carbon dioxide
diffuses in opposite direction
Circulatory system carries oxygen-rich blood to
other parts of the body
3

gastrovascular cavity
Hydra and other cnidarians, invertebrates
body wall only 2 cells thick encloses
gastrovascular cavity (digestion and distribution
of substances throughout body)
Exchange materials with the environment
through a single opening

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5

Open & closed circulatory
systems
1
...
g
...
Closed circulatory system blood is confined
to vessels & distinct from interstitial fluid
The heart pumps blood into large vessels that
branch into smaller coursing through the
organs
The blood exchange materials between
interstitial fluid bathing the cells
E
...
earthworm, squids, octopuses and
vertebrates

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Adaptations of
vertebrates
1
...
Amphibian
3-chambered heart, 2 atria & 1 ventricle (2
circuits of blood flow: pulmonary & systemic)
Pulmonary circuit leads to the lung and skin,
blood picks up O2 as it flow through capillaries;
O2-rich blood returns to left atrium of heart, and it
is pumped to systematic circuit
Systemic circuit carries blood to all organ except
lungs; returns the blood to right atrium via veins

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Double circulation ensures vigorous flow of blood to
the brain, muscles and other organs as the blood is
pumped 2nd time after it losses pressure in the
capillary beds of the lung
Mixing of O2-rich with O2-poor blood in single
ventricle
3
...
Mammalian or bird
4-chambered, 2 atria & 2 completely separated
ventricles
Double circulation; heart keeps O2-rich blood fully
separated with O2-poor blood
Left side of heart handles only O2-rich blood; rightO2poor blood
Delivery of O2 to all parts of body enhanced as
a) No mixing of O2-rich with O2-poor blood
b) Double circulation restores pressure after blood has
passed through lung capillaries
The Circulatory System - AS Biology Revision - OCR (Unit
1
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2)
...
flv
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Ѱ higher in tissue fluid addition of ‘plasma’ without
plasma protein by ultrafiltration
The difference of Ѱ allows osmosis to take place
~ 90% of the plasma which left capillary returns to
blood at venule end
Remaining tissue fluid drains into tubes called
lymphatic vessels
Functions of tissue fluid provide materials; remove
waste; keep compositions and temperature around cells
constant; moisture allows gas exchange into and out
cells

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LYMPH
The escape tissue fluid: lymph (same composition
as tissue fluid except contains fat droplets)
Lymphatic system drains into circulatory system
near the shoulders
Accumulation/ failure of return to blood by lymphatic
system tissue and body cavity swollen/ edema
(e
...
severe dietary protein deficiency)
have valves (prevent backflow of fluid towards
capillaries)
Depend on movement of skeletal muscles to
squeeze fluid along
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Along lymph vessel are specialized
swellings : lymph nodes
Lymph nodes filter the lymph and attacking
viruses and bacteria (body defense with
white blood cells)
When body fighting an infection, cells
multiply rapidly lymph nodes become
swollen and tender
Functions of lymphatic system:
- Body defense
- Maintains fluid level and [protein] in the
blood
- Transports fats absorbed from the intestine
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STRUCTURE OF BLOOD
Blood consists of
1
...
Cell fragments (platelets)
3
...
Maintains osmotic balance of blood;
2
...
4 in human;
3
...
Maintain blood viscosity
5
...
Transport nutrients (albumin)
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platelets
Formed as a result of breaking up of large cells in
bone marrow, then enter blood
~2-3 µm in diameter
No nuclei
Involved in blood clotting; stop loss of blood from
a wound
~300000 platelets per µl

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erythrocytes
red blood cells (RBCs); most numerous blood cells
8
...
Contains hemoglobin (respiratory pigment-250
million molecules/cell); collects O2 easily at
lungs & releases at respiring tissues
2
...
Contains enzyme carbonic anhydrase (needed
for transport of CO2)
4
...
Flexible cell surface membrane (helps cell to be
squeezed through narrow capillaries; resist bursting
due to changes of volume)
6
...
Thin cell surface membrane (short diffusion distance)
8
...
g
...
g
...
g
...
Oxyhemoglobin (red blood cells)~ 98
...
Dissolved gases in blood plasma ~1
...
flv
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A hemoglobin has 4 polypeptide chains; each chain
1 heme group; able to bind 4 O2 to Fe ion; weakly
bound
Active tissues rich in H+ that will bind to Hb
molecules; weaken bonding of O2 +Hb
O2 releases to be used in tissues
Binding of H+ to Hb will produce reduced
hemoglobin/ hemoglobin acid
H+ + Hb
HHb
(deoxyhemoglobin)
at
tissues

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TRANSPORT OF CO2 IN
MAMMALS
CO2 is transported in blood stream in 3 forms:
a
...
Carbaminohemoglobin (red blood cells)~23%
c
...
34-7
...

O2 + HHb produce oxyhemoglobin and H+, H+ will
used by bicarbonate ion to produce carbonic acid
Amount of CO2 inversely proportional with degree of
O2 saturation; more CO2 can be carried
(carbaminohemoglobin) as partial pressure of O2
drops (Haldane effect)  encourage gases
exchange in lung tissue
http://www
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com/watch?v=Qrvrs6RXxwY

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Oxygen dissociation curve
Unit for [gas] usually stated in terms of pressure
Partial pressure [gas], Pgas
[gas] increases, partial pressure of gas increases
Hb has a high affinity (attractive force) for O2 where there
is high [O2]
The affinity of Hb for O2 at different partial O2 pressure is
shown by oxygen dissociation curve of Hb
S-shaped (binding of 1st O2, facilitate 2nd, 3rd and 4th) and
vice versa

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BOHR EFFECT
As partial pressure CO2
mounts, oxygen
dissociation curve of hemoglobin shifts to the
right (Bohr shift/ Bohr effect)
Definition: partial pressure CO2
in tissue
increases (pH level lowered), affinity of
hemoglobin for oxygen is lowered
Thus, O2 dissociation from hemoglobin is
dependent on partial pressure of O2 & CO2
Oxygen Dissociation_Bohr Effect_Chloride Shift
Revision Video
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of red blood cells per unit volume will increase with
time
Due to low partial pressure of O2 stimulates
secretion of more erythropoietin hormone,
stimulates bone marrow produce more red blood
cells
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60

Fetal hemoglobin has an oxygen dissociation curve
to the left compared to maternal hemoglobin; fetal
hemoglobin has higher affinity towards oxygen,
allows to pick up O2 from mother’s blood

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Mammals such as sea lion, dolphins and whales
have certain adaptations to enable them dive deep
into ocean:
a
...
High [myoglobin] in muscle tissues
c
...
Spontaneous ability to lower heartbeat rate when
diving

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FACTORS INFLUENCING o2
saturation in hemoglobin
Temperature
Concentration of hydrogen ions in blood
Presence of diphosphoglycerate/ diphosphoglyceric
acid (product of glycolysis)
Partial pressure of CO2

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