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Question 1

why do most animals need specialised transport systems?

Answer 1

• high metabolic activity of cells
• distance between cells and oxygen supply is too large foe effective diffusion
• the bigger the organism the bigger the SA:V ratio so gases cant be exchanged fast enough

Question 2

Explain SA:V ratio

Answer 2

• The bigger the organism, the smaller the surface areas to volume ratio. This means oxygen has further to travel to reach respiring cells and it is harder for the oxygen required to be absorbed by the available surface area.

Question 3

How is level of activity related to oxygen and glucose demand?

Answer 3

• Higher activity levels means cells respire more and this means a higher demand for oxygen and glucose.

Question 4

Explain surface area and volume.

Answer 4

• The greater the volume, the greater the need for oxygen by respiring cells. the greater the surface area, the greater the supply of oxygen being absorbed. As animals get bigger, the SA:V ratio decreases, meaning the oxygen supplied by the surface area is not enough to meet the demands of the organism and its’ volume. Larger organisms therefore require adaptions in order to deliver enough oxygen to all their respiring cells.

Question 5

Why can’t diffusion alone meet the oxygen demands for multi-cellular organism?

Answer 5

• Distance between cells and the oxygen supply is too great for effective diffusion so gases cannot be exchanged fast enough. Diffusion is still necessary in order to exchange gases between the transport medium and respiring cells.

Question 6

Define Mass Flow
Diffusion
Circulatory system 
Haemolymph
Single circulatory system 
Double Circulatory system 
Pulmonary circulation
Systematic circulation

Answer 6

• movement of fluid in one direction
• passive movement of substances through a partially permeable membrane, down a concentration gradient.
• the transport system of an animal
• The transport medium for insects which transports nitrogenous waste and nutrient around the body (not CO2 and O2)
• Blood passes through the heart once for each complete circuit of the body.
  Blood passes through the heart twice for every complete circuit of the body.
• part of the circulatory system where deoxygenated blood is pumped to the lungs and oxygenated blood is returned.
• part of the circulatory system where blood is pumped to the entire body and returns to the heart.

Question 7

State examples of animals with each type of circulatory system.

Answer 7

• Single = fish, worms

- Double = birds and mammals.

Question 8

What is a closed system and an open system.

Answer 8

• Closed system = blood is contained in blood vessels

- Open systems = transport medium is in direct contact with the cells.

Question 9

What is the limitation of a singular circulatory system?

Answer 9

Blood pressure drops once blood has passed through the capillaries so return to the heart is low. This has an impact on activity levels.

Question 10

Why is the single circulatory system not a problem for fish?

Answer 10

counter-current flow of blood through gills enables them to pick up more O2 which means higher rate of respiration which means more ATP and this enables them to be more active.

Question 11

What is the main advantage of a double circulatory system?

Answer 11

Higher blood pressure, meaning greater activity levels.

Question 12

Order of blood vessels when leaving the heart.

Answer 12

Arteries, arterioles, capillaries, venules, veins

Question 13

What is the lumen?

Answer 13

The space within the walls of blood vessels where blood flows.

Question 14

What are the layers of blood vessels?

Answer 14

Lumen, tunica intima, tunica media, tunica externa.

Question 15

State the components of blood vessel walls and it’s function.

Answer 15

Tunica intima = endothelium - layer of endothelial cells what regulates what leaves and enters the blood vessel.
Tunica media = Elastin Tissue = contains elastin and provides vessels with flexibility.
= Smooth muscle = contacts and releases to change size of lumen which changes blood flow (vasodilation/constriction).
Tunica externa = contains collagen and provides structural support to maintain shape and volume.

Question 16

Which has the most smooth muscle and why does it need it?

Answer 16

Arteriole as the muscle constricts to prevent blood flowing into the capillary bed.

Question 17

Which has the most elastin tissue?

Answer 17

Arteries. it allows them to withstand force of the blood being pumped away from the heart?

Question 18

Describe the structure of veins and venules.

Answer 18

Walls contain a lot of collagen and relatively little elastin fibre. The lumen is wide and lined with endothelium so the blood flows easily.

Question 19

Describe the structure of arteries and arterioles.

Answer 19

Artery walls have thick layers of elastic tissue in order to withstand pressure. They also have endothelium, smooth muscle and fibrous tissue.
Arterioles have more smooth muscle and elastin then arteries. The smooth muscle contracts in order to restrict blood flow into capillaries and control blood flow in individual organs.

Question 20

Describe the structure of capillaries.

Answer 20

Small lumen and walls made up endothelial cells.
Their adaption include:
- provide large surface area for diffusion of substances.
- Blood flow slows because the diameter is smaller than in the arterioles and as a result there is more time for diffusion to take place.
- Walls are one-cell thick for easy diffusion.

Question 21

How does the body move blood back to the heart against gravity?

Answer 21

• one-way valves
• contraction of muscles squeezes the veins and forces blood back top the heart.
• breathing movements in the chest change the pressure and the squeezing motion moves the blood in the veins in the chest and abdomen towards the heart.

Question 22

How does vasodilation/constriction work?

Answer 22

Arterioles have lots of smooth muscle and the when the muscle constricts the size of the lumen is changed and this limits the blood flow to the capillaries.

Question 23

Components of the liquid part of blood

Answer 23

55% - Plasma = Glucose, amino acids, glycerol, fatty acids, ions, urea, vitamins, plasma proteins.

Question 24

Components of the cellular part of blood

Answer 24

45% - red blood cells, leucocytes, platelets.

Question 25

State the functions of red blood cells, leucocytes and platelets.

Answer 25

Red blood cells - carrying oxygen and aiding with the transportation of carbon dioxide.
Leucocytes - several types of white blood cells which are part of the immune response.
Platelets - fragments of larger cells called megakaryocytes in bone marrow, involved in blood clotting.

Question 26

What does blood transport?

Answer 26

• oxygen to and from respiring cells,
• digested food from the small intestine
• nitrogenous waste from cells to excretory organs
• hormone
• food molecules from storage compounds to cells
• platelets to damaged areas
• cells and antibodies involved in the immune system

Question 27

Other the transport what are the functions of he blood?

Answer 27

• keeps a steady body temperature

- act as a buffer to minimise pH changes

Question 28

Define the terms blood plasma, tissue fluid and lymph.

Answer 28

Blood plasma = the main part and liquid part of the blood, carrying dissolved substances and blood cells.
Tissue fluid = the solution surrounding the cells of multi-cellular animals.
Lymph = modified tissue fluid collected in the lymph system. It is the tissue fluid that does not return to the capillaries (10%)

Question 29

Explain how tissue fluid is made?

Answer 29

Hydrostatic pressure forces fluid out of the capillaries which surrounds the cells. This is called tissue fluid.

Question 30

What makes up tissue fluid?

Answer 30

The liquid part of blood without plasma proteins or red blood cells.

Question 31

What makes up lymph?

Answer 31

Similar to blood plasma/tissue fluid but with fewer nutrients and less oxygen. I also has fatty acids from the small intestine.

Question 32

Diameter and wall thickness of arteries.

Answer 32

Diameter - 4mm

Wall thickness - 1mm

Question 33

Diameter and wall thickness of arterioles

Answer 33

Diameter - 30 micrometres

Wall thickness - 20 micrometres

Question 34

Diameter and wall thickness of capillary

Answer 34

Diameter - 8 micrometres

Wall thickness - 1 micrometre

Question 35

Diameter and wall thickness of venules

Answer 35

Diameter - 20 micrometres

Wall Thickness - 2 micrometres

Question 36

Diameter and wall thickness

Answer 36

Diameter - 5 mm

Wall Thickness - 0.5 mm

Question 37

Define hydrostatic pressure

Answer 37

As flood flows through arterioles into the capillaries, it is still under pressure from the surge of blood that occurs everytime the heart contracts.

Question 38

Define oncotic pressure

Answer 38

The tendency of water to move into the blood by osmosis. This is because plasma proteins give blood a low water potential.

Question 39

Define filtration pressure

Answer 39

The net driving force which pushes fluid into tissue spaces and out of vascular sites.

Question 40

Describe how the oncotic pressure and hydrostatic pressure varies across the circulatory system.

Answer 40

Hydrostatic pressure = 4.6 kPa
Oncotic pressure = 3.3kPa
Arteriole end of capillary bed = 4.6 - 3.3 = 1.3 kPa - net flow of fluid out of the capillaries.
Venule end of capillary end = hydrostatic pressure falls to 2.3 kPa.
2.3 - 3.3 = - 1.0 kPa - fluid moves back into the blood

Question 41

Describe how oncotic pressure in capillaries is produced.

Answer 41

Water moves into capillaries due to its low water potential. This is due to plasma proteins which means a high solute concentration.