Transport System
Page 1 of 27
,Transport system in animals
An animals transport system moves substances such as:
- O2 and CO2
- Nutrients
- Waste products
- Hormones
- Antibodies
However
In SMALL simple structured animals and unicellular protozoa, a small/thin body provides a
large surface area:volume ratio. Therefore substances can simply diffuse from cell
to cell.
What is surface area to volume ratio?
in this diagram, cube 1 is an example of a small animal/
protist, and cube 3 is an example of a larger animal
where a transport system is required, rather than a
diffusion process.
Characteristics of a transport system
(commonly referred to as a circulatory system)
- Blood: transports substances
- Blood vessels: structures in which blood flows
- Heart: pumps blood through blood vessels to various body parts
- Valves: (in heart and blood vessels) ensure blood flows in one direction
Soon we will explore the heart, and another part of the circulatory system, the lymphatic
system.
Page 2 of 27
,Types of circulatory systems
1. OPEN BLOOD SYSTEM 2. CLOSED BLOOD SYSTEM
Many invertebrates e.g. insects, Larger animals e.g. segmented snails,
crustaceans worms, vertebrates, sea urchins
Blood pumped at low pressure Blood pumped under high pressure
Blood pumped from heart into main Blood pumped from heart into blood body
cavity i.e. haemocoel vessels
Blood bathes all internal organs Blood contained within blood vessels
Blood moves slowly through tissues Blood travels rapidly to body cells
System inefficient - small animals only System efficient for large animals
Blood only Blood in blood vessels and tissue fluid
between blood vessels and cells, in event of
leakage
Note - open blood systems are mainly found in invertebrates because the blood flows
slowly with low pressure and it is not a very efficient blood system; the invertebrates that
even have blood systems, are very small, and therefore do not require much pressure for
blood to be transported because organs are in close range.
high pressure
=
fast delivery
Page 3 of 27
, Transport system in humans
- A closed circulatory system (see qualities above)
- Usually called the cardiovascular system.
- A double circulatory system i.e. blood flow through two distinct circulations, the
pulmonary circuit and the systemic circuit.
Double circulatory system
Pulmonary circuit:
from right side of heart (when it leaves, blood has a high
CO2 concentration and low oxygen levels)
→lungs (CO2 delivered to lungs and O2 absorbed)
→left side of heart receives oxygenated blood
Pulmonary basically means lungs/breathing system, so we
can say the purpose of this system is to take deoxygenated
blood to the lungs where the blood gets oxygenated, and
then return it to the left side of the heart.
Systemic circuit:
from left side of heart (carries oxygenated blood - low CO2,
high O2)
→ rest of body (as blood passes through the organs it provides O2 to body cells and
used for cellular respiration, while CO2 diffuses from the body cells into the blood)
→ right side of heart (blood is now deoxygenated)
This pathway takes blood to all the other systems in the body (eg digestive, reproductive),
but NOT the lungs. The systemic circuit is much bigger and more important as its purpose
is to provide O2 to more systems.
Advantages of the double circulatory system
Pulmonary circuit: blood pumped to lungs for gaseous exchange i.e. blood absorbs O₂
and releases CO₂
Systemic circuit: blood pumped under high pressure to all parts of body
Nutrients,O₂ provided to cells and CO₂, wastes removed from body cells.
High pressure of blood: - Allows tissue fluid to form
- Allows O₂ to be carried quickly to all body cells.
NOTE refer to sides of heart as if someone is facing you, use THEIR left and right.
Page 4 of 27
Page 1 of 27
,Transport system in animals
An animals transport system moves substances such as:
- O2 and CO2
- Nutrients
- Waste products
- Hormones
- Antibodies
However
In SMALL simple structured animals and unicellular protozoa, a small/thin body provides a
large surface area:volume ratio. Therefore substances can simply diffuse from cell
to cell.
What is surface area to volume ratio?
in this diagram, cube 1 is an example of a small animal/
protist, and cube 3 is an example of a larger animal
where a transport system is required, rather than a
diffusion process.
Characteristics of a transport system
(commonly referred to as a circulatory system)
- Blood: transports substances
- Blood vessels: structures in which blood flows
- Heart: pumps blood through blood vessels to various body parts
- Valves: (in heart and blood vessels) ensure blood flows in one direction
Soon we will explore the heart, and another part of the circulatory system, the lymphatic
system.
Page 2 of 27
,Types of circulatory systems
1. OPEN BLOOD SYSTEM 2. CLOSED BLOOD SYSTEM
Many invertebrates e.g. insects, Larger animals e.g. segmented snails,
crustaceans worms, vertebrates, sea urchins
Blood pumped at low pressure Blood pumped under high pressure
Blood pumped from heart into main Blood pumped from heart into blood body
cavity i.e. haemocoel vessels
Blood bathes all internal organs Blood contained within blood vessels
Blood moves slowly through tissues Blood travels rapidly to body cells
System inefficient - small animals only System efficient for large animals
Blood only Blood in blood vessels and tissue fluid
between blood vessels and cells, in event of
leakage
Note - open blood systems are mainly found in invertebrates because the blood flows
slowly with low pressure and it is not a very efficient blood system; the invertebrates that
even have blood systems, are very small, and therefore do not require much pressure for
blood to be transported because organs are in close range.
high pressure
=
fast delivery
Page 3 of 27
, Transport system in humans
- A closed circulatory system (see qualities above)
- Usually called the cardiovascular system.
- A double circulatory system i.e. blood flow through two distinct circulations, the
pulmonary circuit and the systemic circuit.
Double circulatory system
Pulmonary circuit:
from right side of heart (when it leaves, blood has a high
CO2 concentration and low oxygen levels)
→lungs (CO2 delivered to lungs and O2 absorbed)
→left side of heart receives oxygenated blood
Pulmonary basically means lungs/breathing system, so we
can say the purpose of this system is to take deoxygenated
blood to the lungs where the blood gets oxygenated, and
then return it to the left side of the heart.
Systemic circuit:
from left side of heart (carries oxygenated blood - low CO2,
high O2)
→ rest of body (as blood passes through the organs it provides O2 to body cells and
used for cellular respiration, while CO2 diffuses from the body cells into the blood)
→ right side of heart (blood is now deoxygenated)
This pathway takes blood to all the other systems in the body (eg digestive, reproductive),
but NOT the lungs. The systemic circuit is much bigger and more important as its purpose
is to provide O2 to more systems.
Advantages of the double circulatory system
Pulmonary circuit: blood pumped to lungs for gaseous exchange i.e. blood absorbs O₂
and releases CO₂
Systemic circuit: blood pumped under high pressure to all parts of body
Nutrients,O₂ provided to cells and CO₂, wastes removed from body cells.
High pressure of blood: - Allows tissue fluid to form
- Allows O₂ to be carried quickly to all body cells.
NOTE refer to sides of heart as if someone is facing you, use THEIR left and right.
Page 4 of 27
