Chapter 8: transport in mammals Flashcards
Define the term “closed circulatory system”
A circulatory system in which the blood pumped
by the heart is contained within blood vessels.
The blood does not come into direct contact with
the cells. Closed circulatory systems are found in
animals, e.g. vertebrates.
Describe the journey of blood through the human
circulatory system with reference to the 4 major blood
vessels of the heart.
heart (r) → pulmonary artery → lungs →
pulmonary vein → heart (l) → aorta →
body → vena cava → heart (r)
Define the term “double circulatory system”.
A circulatory system in which the blood flows through the
heart twice in two circuits. Blood is pumped from the
heart to the lungs before returning to the heart. It is then
pumped around the body, after which it returns to the
heart again. Double circulatory systems are found in
mammals.
What are the advantages of a closed system?
● Lower blood volume required to keep
system moving
● Blood pressure can be controlled and
maintained
What are the advantages of a double circulatory
system?
● Maintains blood pressure around the whole body
● Uptake of oxygen is more efficient
● Delivery of oxygen and nutrients more efficient
● BP can differ in pulmonary and systemic systems
Relate the structure of arteries to their function.
● Thick, muscular walls to withstand high pressure
● Elastic tissue allows them to stretch and recoil to prevent
pressure surges
● Narrow lumen to maintain pressure
● Smooth muscle which enables them to vary blood flow
● Lined with smooth endothelium to reduce friction and ease
flow of blood
Relate the structure of veins to their function.
● Wide lumen eases blood flow
● Thin walls eases compression by skeletal muscles
● Require valves to prevent backflow of blood
● Less muscular and elastic tissue as they don’t have
to control blood flow
Relate the structure of capillaries to their function.
● Walls only one cell thick giving a short diffusion pathway
● Narrow lumen, red blood cells squeeze through,
decreasing the diffusion distance
● Numerous and highly branched, providing a large
surface area
Relate the structure of arterioles and venules to their
function.
● Branch off arteries and veins in order to feed blood into
and take blood away from the capillaries
● Smaller than arteries and veins so that the change in
pressure is more gradual as blood passes through
increasingly small vessels
Draw and describe the structure of an erythrocyte.
● Diameter- 6.2-8.2μm ● Thickness- 2-2.25μm ● Large surface area to volume ratio ● Form biconcave discs ● No nucleus and no large organelles to maximise O2 carrying ability
- Cell surface membrane
- Cytoplasm - appear dark at edges, becoming lighter in the centre (pink gradient stain under light microscope)
Draw and describe the structure of neutrophils.
● Lobed nucleus for flexibility
within blood vessels
● Granulocyte
- Cell surface membrane
- Cytoplasm (appears granular) stains light blue
- Lobed nucleus- varies from 3-5 lobes- stains deep blue
Draw & describe the structure of lymphocytes.
● Very large nucleus
● Small amount of cytoplasm
● Agranulocyte
- Cell surface membrane
- Cytoplasm- stains pale purple
- Circular nucleus- stains dark purple
What is tissue fluid?
A fluid surrounding cells and tissues that
contains glucose, amino acids, oxygen and
other nutrients. It supplies these to the cells,
while also removing any waste materials.
Outline the different pressures involved in the
formation of tissue fluid.
● Hydrostatic pressure - higher at arterial end of capillary
than venous end
● Oncotic pressure - changing water potential of the
capillaries as water moves out, induced by proteins in the
plasma
How is tissue fluid formed?
As blood is pumped through increasingly smaller vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of the capillaries. It then exchanges substances with the cells.
Why does blood pressure fall along the capillary?
● Friction
● Lower volume of blood
What happens at the venous end of the capillary?
● Oncotic pressure is greater than
hydrostatic pressure
● Fluid moves down its water potential gradient
back into the capillaries
How is tissue fluid removed?
● Tissue fluid drains into the lymphatic
system where it is referred to as ‘lymph’
● The lymph returns to the blood via the
subclavian veins
Give some examples of intracellular and extracellular
body fluids in which water is the primary component.
Water is a component of: ● Blood plasma (for the transport of substances) ● Cytoplasm ● Tissue fluid (bathes cells) ● Lymph ● Urine for excretion ● Serum
*Why is water important in body fluids?
● Water acts as a solvent in order to transport material in
biofluids
● Water has a high specific heat capacity - a large amount of
energy is required to change its temperature - facilitating the
maintenance of homeostatic conditions
Describe the role of haemoglobin.
Present in red blood cells. Oxygen molecules
bind to the haem groups and are transported
around the body. They are released where
oxygen is needed in respiring tissues.
How does partial pressure of oxygen affect
oxygen-haemoglobin binding?
Haemoglobin has variable affinity for oxygen depending on the
partial pressure of oxygen, p(O2):
● At high p(O2), oxygen associates to form oxyhaemoglobin
● At low p(O2), oxygen dissociates to form deoxyhaemoglobin
How is carbon dioxide carried from respiring cells to
the lungs?
● Transported in aqueous solution in the plasma
● As hydrogen carbonate ions in the plasma
● Carried as carbaminohaemoglobin in the blood
What is the chloride shift?
● Process by which chloride ions move into the
erythrocytes in exchange for hydrogen carbonate
ions which diffuse out of the erythrocytes
● One-to-one exchange
Why is the chloride shift important?
It maintains the electrochemical
equilibrium of the cell.
What is the function of carbonic anhydrase?
Catalyses the reversible reaction
between water and carbon dioxide to
produce carbonic acid.
Write equations to show the formation of hydrogen
carbonate ions in the plasma.
Carbonic anhydrase enzyme catalyses:
CO2 + H2O ⇌ H2CO3 (carbonic acid)
Carbonic acid dissociates:
H2CO3 ⇌ HCO3 - (hydrogen carbonate ions) + H+
State the Bohr effect.
The loss of affinity of haemoglobin for
oxygen as the partial pressure of carbon
dioxide increases.
Explain the role of carbonic anhydrase in the Bohr
effect.
● Carbonic anhydrase is present in red blood cells
● Catalyses the reaction of carbon dioxide and water to form
carbonic acid, which dissociates to produce H+ ions
● H+ ions combine with the haemoglobin to form haemoglobinic acid
● Encourages oxygen to dissociate from haemoglobin
Why is a higher concentration of erythrocytes important
for human populations living at high altitudes?
● High altitude, low p(O2), oxygen saturation in
erythrocytes will decrease
● To carry an equal volume of O2 in blood, a
higher concentration of erythrocytes is required
What is plasma?
● Main component of the blood (yellow liquid) that
carries red blood cells
● Contains proteins, nutrients, mineral ions,
hormones, dissolved gases and waste. Also
distributes heat
Describe and explain the shape of a dissociation
curve for adult haemoglobin.
Sigmoidal curve (S-shaped):
● When first O2 molecule binds, it changes the tertiary structure of
haemoglobin so that it is easier for the second and third molecules to
bind
● Third molecule changes the tertiary structure of haemoglobin so that
it is more difficult for the fourth molecule to bind
Draw a diagram of the human heart,
including the names of chambers,
vessels, and valves.
see pmt memorize this
Describe what happens during cardiac diastole.
The heart is relaxed. Blood enters the atria,
increasing the pressure and opening the
atrioventricular valves. This allows blood to flow into
the ventricles. Pressure in the ventricles is lower
than in the arteries, so semilunar valves remain
closed.
Describe what happens during atrial systole.
The atria contract, forcing the
atrioventricular valves open. Blood flows
into the ventricles.
Describe what happens during ventricular systole.
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries.
Explain how the heart contracts
● SAN initiates and spreads impulse across the atria, so they contract.
Thick fibrous walls prevent impulse spreading directly to ventricles
● AVN receives, delays, and then conveys the impulse down the bundle
of His
● Impulse travels into the Purkinje fibres which branch across the
ventricles, so they contract from the bottom up.
The walls of the chambers of the heart vary in
thickness - explain this.
● Walls of both atria relatively thin, only have to cap blood in
ventricles as ventricles fill mostly passively
● Left ventricle wall significantly thicker than right, left must
provide pressure for systemic flow, right only has to supply
pulmonary system. Both are thicker than the atria
