Transport in Humans

Question 1

What is a double circulation?

Answer 1

• blood passes through the body twice in a complete circuit around the body,
• made up of pulmonary circulation and systemic circulation

Question 2

What are the advantages of a double circulation?

Answer 2

• efficient circulatory system as,
• oxygenated and de-oxygenated blood are separated
• body cells receive oxygenated blood at a faster rate
• reduced blood pressure in the lungs
• blood moving at a slower rate to allow more time for gaseous exchange

Question 2

What is the structure of arteries?

Answer 2

• thick, muscular and elastic walls
• narrow lumen
• valves are absent

Question 2

What is the structure of capillaries?

Answer 2

• one-cell thick walls that are partially permeable
• narrow lumen
• extensively branched

Question 2

What is the structure of veins?

Answer 2

• thin, less muscular and less elastic walls
• wide lumen
• contains semi-lunar valves

Question 3

What is the function of the elastic walls of arteries?

Answer 3

Elastic walls help to withstand high pressure blood forced out from the heart –> stretches and recoils to push blood out in spurts

Question 3

What is the function of the thick and muscular walls of the arteries?

Answer 3

muscular contractions help to push out blood
- when arteries constricts, lumen narrows and less blood flows
- when arteries dilate, lumen widens and more blood flows

Question 4

What is the function of capillary walls being one-cell thick that are partially permeable?

Answer 4

• allows for diffusion of substances across the capillary walls
• increase rate of diffusion/ efficient exchange of substances

Question 4

What is the function of the capillaries having a narrow lumen?

Answer 4

slows down flow of blood to allow more time for exchange

Question 4

What is the function of the capillaries being extensively branched?

Answer 4

it provides large surface area + lowers blood pressure, to slow down flow of blood –> more time for exchange of substances

Question 5

What is the function of veins?

Answer 5

• carries low blood pressure back to the heart
• semi- lunar valves prevents backflow of blood –> when muscles contract and squeeze, blood is pushed past the open valves. When muscles relax, blood that has been pushed cannot flow back

Question 5

What is blood and what does it contain?

Answer 5

Blood is a “fluid tissue” as it consists of a fluid in which different blood cells and platelets are suspended in. Blood contains blood cells, platelets and plasma

Question 5

What is the structure and function of plasma?

Answer 5

it is pale yellowish liquid, composed mostly of water, plasma transports dissolved substances e.g. nutrients (glucose, amino acids), waste products, soluble proteins, hormones, CO2, excretory products (urea)

Question 5

What is the structure of red blood cells?

Answer 5

• contains haemoglobin
• small and flexible
• flattened and biconcave shape
• no nucleus

Question 6

What is the function of red blood cells?

Answer 6

• the haemoglobin RBCs contain is a protein that contains iron, and binds with oxygen
• able to squeeze through narrow capillaries due to them being small and flexible
• flattened and biconcave shape increases surface area to volume ratio for faster rate of diffusion of oxygen
• having no nucleus allows RBCs to contain more haemoglobin

Question 6

What is the function and structure of phagocytes?

Answer 6

• colourless, contains a lobed nucleus, and granular cytoplasm
• carries out phagocytosis, to engulf/ ingest and destroy foreign particles e.g. bacteria

Question 7

What is the structure and function of lymphocytes?

Answer 7

they are colourless and contain a large, round nucleus, they produce antibodies which protects the body by
- recognising foreign particles
- destroying bacteria and viruses
- clumping bacteria together for easy ingestion by phagocytes
- neutralize toxins by bacteria