Topic 8 – Exchange and Transport in Animals- The circulatory system

Question 1

What is the circulatory system?

Answer 1

● Network of organs and vessels

● Enables the flow of blood and transport of oxygen, carbon dioxide, nutrients and other molecules around the body

Question 2

What are the main components of blood?

Answer 2

● Red blood cells
● White blood cells
● Platelets
● Plasma

Question 3

What are red blood cells also known as?

Answer 3

Erythrocytes

Question 4

What is the function of red blood cells?

Answer 4

● Transport O2 from lungs to tissues

● Transport CO2 from tissues to lungs

Question 5

How do red blood cells transport oxygen to body cells?

Answer 5

● Lungs, haemoglobin in RBCs binds reversibly with oxygen to form oxyhaemoglobin
● Tissues, oxyhaemoglobin breaks down to form haemoglobin and oxygen which diffuses into cells

Question 6

How are red blood cells adapted to their function?

Answer 6

● Biconcave disk gives large SA/V ratio, increasing diffusion rate
● Lack nucleus, allowing more space for haemoglobin molecules (increases oxygen carrying capacity of the cell)
● Small and flexible so they can squeeze through capillaries
● Thin giving a short diffusion distance

Question 7

What is the function of white blood cells?

Answer 7

Provide immunological protection

Question 8

Name two types of white blood cell

Answer 8

● Phagocytes

● Lymphocytes

Question 9

What are phagocytes?

Answer 9

● Type of WBC

● Engulf pathogens and digest them in a process known as phagocytosis

Question 10

What are lymphocytes?

Answer 10

● Type of WBC
● Produce antibodies specific to a pathogen
● Produce antitoxins to neutralise toxins

Question 11

What is the function of platelets?

Answer 11

Role in blood clotting

Question 12

What is plasma?

Answer 12

● Pale-yellow liquid portion of the blood

● Contains proteins, nutrients, waste products, hormones, antibodies etc.

Question 13

How is plasma adapted to its function?

Answer 13

Plasma consists mainly of water. This acts as a solvent, enabling the transport of materials around the body.

Question 14

What are the three main types of blood vessel?

Answer 14

● Arteries
● Capillaries
● Veins

Question 15

What is the function of the arteries?

Answer 15

Carry blood away from the heart under high pressure

Question 16

Describe how the arteries are adapted to their function (6)

Answer 16

● Narrow lumen maintains high pressure
● Thick wall to withstand high pressure
● Thick layer of smooth muscle provides strength
● Thick layer of elastic fibres allow stretch and recoil
● Smooth inner lining to reduce friction
● No valves

Question 17

What is the function of the veins?

Answer 17

Return blood to the heart under low pressure

Question 18

Describe how the veins are adapted to their function (4)

Answer 18

● Large lumen eases blood flow
● Thin wall as blood at low pressure
● Thin layer of smooth muscle and elastic fibres
● Valves prevent backflow of blood

Question 19

What is the function of the capillaries?

Answer 19

Allow the exchange of materials at tissues

Question 20

Describe how the capillaries are adapted to their function (4)

Answer 20

● Form large network ∴ greater surface area for diffusion
● Walls one cell thick giving a short diffusion distance
● Walls permeable allowing the exchange of substances ● Narrow lumen decreases diffusion distance

Question 21

Describe the double circulatory system in humans

Blood flows through the heart twice in two circuits:

Answer 21

● Pulmonary circuit

● Systemic circuit

Question 22

What is the pulmonary circuit?

Answer 22

● Part of the circulatory system involving the right side of the heart
● Deoxygenated blood is transported to the lungs
● Gaseous exchange occurs between the alveoli and capillaries in the lungs
● Oxygenated blood is returned to the left side of the heart

Question 23

What is the systemic circuit?

Answer 23

● Part of the circulatory system involving the left side of the heart
● Oxygenated blood is pumped to tissues and organs around the body
● Exchange of materials occurs at tissues
● Deoxygenated blood returns to the right side of the heart

Question 24

Name the four chambers of the heart

Answer 24

● Left atrium
● Left ventricle
● Right atrium
● Right ventricle

Question 25

Describe the pathway of blood around the body, naming the structures of the heart

Answer 25

Pulmonary vein → Left atrium → Left ventricle → Aorta → Body → Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs

Question 26

Why is the left ventricle thicker than the right ventricle?

Answer 26

● It pumps blood a further distance

● It must generate a greater force of contraction so blood can be pumped at a higher pressure

Question 27

What is the function of valves in the heart?

Answer 27

Prevent the backflow of blood

Question 28

What is cardiac output?

Answer 28

The volume of blood pumped out of a ventricle in one minute

Question 29

What is stroke volume?

Answer 29

The volume of blood pumped out of a ventricle in one contraction

Question 30

What is heart rate?

Answer 30

The number of times the heart contracts in one minute

Question 31

How is cardiac output calculated?

Answer 31

cardiac output = heart rate × stroke volume (cm3 min-1) (bpm) (cm3)