3.2 Transport in animals

Question 1

Why do multicelllular organisms need transport systems ?

Answer 1

• They have a low surface area to volume ratio
• They have higher metabolic rate
• They are relatively big
• They are very active (large number of cells respiring very quickly)

Question 2

What is the transport system in mammals and what does it carry ?

Answer 2

• In mammals they use the circulatory system which uses blood to carry glucose and oxygen around the body. It also carries hormones,antibodies (to fight disease) and waste like co2.

Question 3

What are the different types of circulatory systems ?

Answer 3

• Single circulatory systems
• Double circulatory systems
• Closed circulatory systems
• Open circulatory systems

Question 4

What circulatory system do fish have ?

Answer 4

• Fish have single circulatory system

Question 5

What is the difference between single and double circulatory systems?

Answer 5

• In a single circulatory system the blood only passes through the heart once to complete a circuit of the body.
• In a double circulatory system the blood passes through the heart twice for each complete circuit of the body.

Question 6

Explain circulatory system in fish .

Answer 6

-Fish have single circulatory system
- In fish the heart pumps blood to the gills ( to pick up oxygen ) and then through the rest of the body (to deliver oxygen) in a single circuit.

Question 7

Explain circulatory system in mammals.

Answer 7

• Mammals have a double circulatory system.
• The heart is divided down the middle
• The right side of the heart pumps oxygenated blood to the lungs (to pick up oxygen) - pulmonary system
• The left side of the heart , pumps blood to the rest of the body - systematic system
• When blood returns to the heart, it enters the right side again

Question 8

Explain closed circulatory system.

Answer 8

• The blood is enclosed into the vessels
• The heart pumps into the arteries.These branch into millions of capillaries.
• Substances like oxygen and glucose diffuse from the blood capillaries into the body cells but the blood stays inside the blood vessels as it circulates.
• Veins take the blood back into the heart.

Question 9

Explain open circulatory system

Answer 9

• Some invertebrates have an open circulatory system - blood inst enclosed into the blood vessels all the time
• It flows freely through the body cavity .
• The blood flows around the insects organs ,gradually making its way back into the heart segments through the series of valves.
• It supplies the insects cells with nutrients and transport things like hormones in the body. It doesnt supply the insects cells with oxygen though - this is done by a system called the tracheal system.

Question 10

What do blood vessels transport around the body ?

Answer 10

• Blood vessels transport substances around the body.

Question 11

What are the arteries ?

Answer 11

• They carry blood from the heart to the rest of the body.
• Their walls are thick and muscular and have elastic tissue to strech and recoil as the heart beats, which helps maintain the high pressure.
• The endothelium is folded allowing the artery to expand- this also helps maintain high blood pressure.
• All arteries carry oxgenated blood expect for the pulmonary ateries which carry oxygenated blood.

Question 12

What are arterioles ?

Answer 12

• Arteries branch into arterioles, which are mucch smaller
• They also have a smooth muscle layer which allows them to expand or contract , thus controlling the amount of blood flowing into the tissues.

Question 13

What are capillaries ?

Answer 13

• They are the smallest blood vessel
• Substances like glucose and oxygen are exchanged between cells and capillries,so they are adapted for efficient diffusion, e.g their walls are only one cell thick.
• They connect to venules

Question 14

What are venules ?

Answer 14

• They have think walls that contain muscle cells. The venules join together to form veins.

Question 15

What are veins?

Answer 15

• Carry blood from the organs of the body towards the heart.
  -Blood is flowing at a much lower pressure so veins have a large lumen and much thinner walls containing little elastic fibres or muscle tissue.
• Valves prevent the slow-moving blood from flowing backwards.
• The contraction of nearby body muscles helps blood to flow through veins.
• All veins carry deoxgenated blood , exxecpt the pulmonary veins which carry oxgenated blood to the heart from the lungs.

Question 16

What is tissue fluid ?

Answer 16

• Tissue fluid is the fluid that surround cells in the tissues.
• Its made from substances that leave the blood plasma e.g. oxygen,water and nutrients.
• Unlike blood , it doesnt contain red blood cells or big proteins , because they are too large to be pushed out through the capillary walls.
• Cells take in oxygen and nutrients from the fluid and release metabolic waste into it.

Question 17

How do substances move out of the capillaries ?

Answer 17

They move by pressure filtration

Question 18

Explain pressure filtration

Answer 18

1) At the start of the capillary bed,nearest the arteries hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid. This difference in hydrostatic pressure reduces in the capillaries and into the spaces around the cells forming tissue fluid.
2) As the fluid leaves,the hydrostatic pressure reduces in the capillaries- so the hydrostatic pressure is much lower at the end of the capillary bed that’s nearest to the venules.
3) There is another form of pressure - oncotic pressure which is generated by plasma proteins present in capillaries which lowers water potenial.
4) At the venule end of the capillary bed , the water potential is lower than the water potntial in the tissue fluid due to fluid loss form capilliaries and high oncotic pressure.This means some water re-enters the capillaries from the tissue fluid at the venule end by osmosis.

Question 19

What happens to excess tissue fluid that doesn’t get to re-enter the capillaries ?

Answer 19

• The excess tissue fluid drains into lymph vessels.
• It eventually gets returned to the blood through the lymphatic system.

Question 20

Explain lymphatic system.

Answer 20

• The smallest lymph vessels are the lymph capillaries
• Excess tissue fluid passes onto lymph vessels. Once inside, its called lymph
• Valves in the lymph vessels stop the lymph going backwards.
• Lymph gradually moves towards the main lymph vessels in the thorax (chest cavity). Here it is returned to the blood, near the heart.

Question 21

What does the blood contain ?

Answer 21

• RBC (are too big to get through capillary walls into tissue fluid)
  -WBC ( mostly in the lymph system, they only enter tissue fluid when there’s an infection)
• Platelets -(Only present in tissue fluid if capillaries are damage)
• Proteins - (Mostly too big to fit through capillary walls
• Water - (tissue and lymph have a higher water potential in the blood)
• dissolved solutes - solutes can move freely between all)

Question 22

What does tissue fluid contain ?

Answer 22

• RBC
• very few WBC
• very few proteins
• water
  dissolved solutes

Question 23

What does lymph contain ?

Answer 23

-WBC
-only protein - antibodies
- water
- dissolved solutes

Question 24

What is the function of the heart ?

Answer 24

• The heart consists of two muscular pumps
• The right side of the heart pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood to the rest of the body.

Question 25

Describe the external structure of the heart.

Answer 25

It consists of :
- Superior vena cava
- Inferior vena cava
- Aorta
- Right atrium
- Coronary artery
- Right ventricle
- Left ventricle
- Pulmonary veins
- Left atrium
- Pulmonary artery

Question 26

Describe the internal structure

Answer 26

-It consists of :
- Superior vena cava
- Inferior vena cava
- Aorta
- Right atrium
- Coronary artery
- Right ventricle
- Left ventricle
- Pulmonary veins
- Left atrium
- Pulmonary artery
- Semi-lunar valve
-Atrioventricular valve

Question 27

What are the function of valves ?

Answer 27

• Valves in the heart prevent backflow - prevent blood flowing the wrong way.

Question 28

What are the types of valves and where ?

Answer 28

• Atrioventricular valves - they link the atria to the ventricles.
• Semi-lunar valves - they link the ventricles to the pulmonary artery and aorta.

Question 29

How do the valves function ?

Answer 29

1) The valves are only open one way - whether they are open or closed depends on the relative pressure of the heart chambers.
2) If there’s high pressure behind a valve its forced open
3) If pressure is higher in front of the valve, its forced shut.

Question 30

Explain how the heart works.

Answer 30

• The chambers at the top are called atria and these chambers receive the blood from the veins supplying the heart. Blood flows from the atria to the ventricles, which are separated from the atria by atrioventricular valves to prevent blood flowing in the opposite direction. There are another set of valves between the ventricles and the arteries which are called the semi-lunar valves as they look like little half-moons.
• The main artery which takes oxygenated blood from the left side of the heart to the rest of the body is called the aorta whereas the artery which delivers deoxygenated blood between the right side of the heart and the lungs is called the pulmonary artery. The major vein which returns blood from the body to the right side of the heart is the vena cava and the vein which ferries blood from the lungs to the heart is called the pulmonary vein.

The heart muscle itself also needs its own blood supply, so that it can get plenty of oxygen and glucose to keep respiring and keep pumping - these are called the coronary arteries. It’s a blockage in these coronary arteries which leads to a heart attack.

Question 31

How do you correctly carry out a heart dissection ?

Answer 31

-

Question 32

What is the cardiac cycle ?

Answer 32

• It is an ongoing sequence of contraction and relaxation of the atria and ventricles that keep blood continuously circulating round the body .
• The volumes of the atria and ventricles change as they contract and relax, altering the pressure in each chamber
• This causes valves to open and close, which directs blood flow through the heart.

Question 33

What are the three stage of the cardiac cycle ?

Answer 33

• Ventricles relax ,atria contract
• Ventricles contract, atria relax
• Ventricles relax, atria relax

Question 34

What happens in first stage ?
- Ventricles relax ,atria contract

Answer 34

• Ventricles are relaxed. The atria contracts which decreases their volume and increases their pressure.
• This pushes the blood into the ventricles through the atrioventricular valves. There’s a slight increase in ventricular pressure and volume as the ventricles receive the ejected blood from the contracting atria.

Question 35

What happens in the second stage ?
- Ventricles contract, atria relax

Answer 35

• The atria relax. The ventricles contract decreases their volume and increases their pressure.
• The pressure becomes higher in the ventricles than the atria , which forces the atrioventricular valves shut to prevent backflow.
• The high pressure in the ventricles opens the semi-lunar valves- blood is forced out into the pulmonary artery and aorta.

Question 36

What happens in the third stage ?
- Ventricles relax, atria relax

Answer 36

• The ventricles and the atria both relax. The higher pressure in atrioventricular valves forced open the pulmonary artery and aorta causes the semi-lunar valves to
  close, preventing back-flow.
• The atria fill with blood (increasing their pressure) due to the higher pressure in the vena cava and pulmonary vein.
• As the ventricles continue to relax, their pressure falls below the pressure in the atria.
• This causes the atrioventricular valves to open and blood flows passively (withoutbeingpushed by atrial contraction) into the ventricles from the atria.The atria contract,and then the whole process begins again.

Question 37

How does the blood flow in the heart ?

Answer 37

• Dexoxygenated blood flows into the posterior and anterior vena cava
• Then it enters into right atrium and it contracts pushing the blood to the right ventricle
• The ventricle contracts pushing the blood through the semi-lunar valves into the pulmosry artery
• The blood reaches the lungs and picks up oxygen , this oxygenated blood goes via pulmonary veins to left atrium sending blood to left atrioventricular valves towareds the left ventricle.
• The left ventricle contracts back to aorta.

Question 38

How do you calculate cardiac output ?

Answer 38

• This is the volume of blood pumped by the heart by the per minute.
• ## Cardiac ouput = heart rate x stroke volume.