Extended response questions

Question 1

Why are the lungs so well suited to their function of gas exchange?

Answer 1

• Many alveoli and convoluted structure = large surface area, meaning large amounts of gas can be exchnaged quickly
• Each alveoli is covered by capillaries, meaning blood is close to the air in alveolus and so gases don’t have to travel very far
• Walls of alveoli and capillaries are only 1 cell thick, means gases don’t have to travel very far in and out of blood
• lungs are deep inside body, prevents excessive evaportaion of the fluids that cover the alveoli surfaces
• the lung volume can be changed by movements of the muscles so air flows in and out of the lungs. this ensures there is always a concentration difference of the gases

Question 2

What are the steps in inspiration?

Answer 2

• Diaphragm contracts moving downwards
• Intercostal muscles contract moving up and outwards
• This increases lung volume
• Which decreases air pressure inside lungs
• Air flows into lungs from a higher pressure (outside body) to a lower pressure (inside lungs) until pressure becomes equal

Question 3

What are the steps in expiration?

Answer 3

• Diaphragm relaxes moving upwards
• Intercostal muscles relax moving down and inwards
• This decreases lung volume
• Which increases air pressure inside lungs
• Air flows out of lungs from a higher pressure (inside lungs) to a lower pressure (outside body) until pressure becomes equal

Question 4

What are the 3 stages of blood clotting?

Answer 4

Stage 1: Vasoconstriction of blood vessels

Stage 2: Platelet Plug

Stage 3: Coagulation

Question 5

what is vasoconstriction of blood vessels

Answer 5

when smooth muscles in walls of vessels that have beeen damaged or injured constrict to reduce the diameter of the lumen which reduces blood flow through them

Question 6

how is a platelet plug formed?

Answer 6

• inside of vessel walls are damaged causing them to become rough
• platelets stick to the rough wall of the vessel, then all platelets stick together forming a platelet plug at the site
• Platelets also release substances that act as vasoconstrictors on the walls of the vessel, which enhances and prolongs vasoconstriction

Question 7

What are all the things that occur in coagulation?

Answer 7

• Activity of clotting factors in the blood plasma increases
• A series of reactions results in the formation of a thread-like protein called FIBRIN
• The fibrin threads create a MESH network
  around the platelet plug covering it’s surface
  and sealing the inside of the wound.
• More erythrocytes, leucocytes, platelets and plasma get
  trapped by this network of fibrin.
• This build up of material is called a blood clot
  (THROMBUS).
• The threads stick to the damaged blood vessel
  and hold the clot in place.
• After the clot is formed, the network of threads
  contracts, pulling the edges of the damaged vessel
  together. This is known as CLOT RETRACTION.
• As the clot retracts, a fluid called SERUM is squeezed out of the cut.
• The serum dries and a scab is formed over the
  wound to prevent entry of micro-organism

Question 8

List points about arteries

Answer 8

Always carry blood away from the heart

Carry oxygenated blood, except for the pulmonary artery

Have thick, muscular and elastic walls to pump and accommodate blood

They carry blood under variable pressure; pressure increases when blood is pumped through artery and then decreases as the ventricles relax again