AQA A-Level Biology - Mass Transport, Mass Transport A level Biology
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1. Single Circulatory System A system where blood is not con-
fined to blood vessels and only
passes through the heart once,
smaller animals have this system
2. Mass Transport System This system exists when organ-
isms have:
- A large surface area to volume
ratio (simple diffusion cannot ac-
commodate for the organisms)
- A large activity of the organism
(require more substances at one
time than smaller organisms)
3. Arteries Vessels that carry blood away from
the heart and to arterioles at a high
pressure. Most layers are thick so
that they can function correctly and
efficiently
4. Arterioles Vessels that control blood flow
from arteries to capillaries. Layers
are thinner than arteries due to
lower blood pressure
5. Capillaries Tiny vessels that link arterioles to
veins. These have branched net-
works to allow for a larger total sur-
face area across the body, as they
are so thin but have a vast network,
no cell is too far away from one
6. Veins Vessels that carry blood towards
the heart from capillaries. Layers
are very thin with a large lumen to
ensure pressure is very low
7. Basic Structure of Arteries, Arterioles Consist of:
and Veins - Tough fibrous outer layer which
, AQA A-Level Biology - Mass Transport, Mass Transport A level Biology
Study online at https://quizlet.com/_ejg0za
resists internal and external pres-
sure changes
- Muscle layer which can contract
to control blood flow
- Elastic layer which maintains
blood pressure by stretching and
springing back (recoiling)
- Endothelium which is a smooth
layer that reduces friction
- Lumen which is the central cavity
9. Fluid in Circulatory System These are all associated with the
circulatory system:
1) Blood
2) Tissue fluid
3) Lymph
10. Tissue Fluid A fluid that allows cells to receive
the contents of blood and utilise
these products to stay alive and
functioning. It is formed due to hy-
drostatic pressure and osmosis
11. Capillary Network Where tissue fluid is formed
12. Hydrostatic Pressure The pressure of the blood as
the heart beats. This forces fluid
and nutrients from the capillaries.
, AQA A-Level Biology - Mass Transport, Mass Transport A level Biology
Study online at https://quizlet.com/_ejg0za
A small amount of this pressure
forces some fluid back into the net-
work. But the net movement is out
of the capillary network
13. Osmotic Pressure The pressure that occurs due to
sudden changes in water potential,
moving water back into the cap-
illary network via osmosis, where
the water potential is lower
14. Lymph Vessel The location where excess tissue
fluid is drained, this is where tissue
fluid is converted into lymph
15. Swelling If you have fewer lymph nodes,
then there is a lower likelihood of
you being able to drain tissue fluid
which could lead to this problem.
The only way to heal this is by giv-
ing the body time to drain the tissue
fluid
16. Xylem The part of a plant which brings
water up through the roots of the
plant and transports the water and
nutrients to different parts of the
plant; mainly to the leaves
17. Transpiration The loss of water from a leaf via the
stomata (evaporation)
18. Cohesion What allows for water to "stick
together" and form unbroken
columns across the mesophyll lay-
er
19. Transpiration Pull The reason water is pulled up
through the plant when the plant
has undergone transpiration
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