Transport in Animals

Question 1

Describe how the structure of an artery is adapted for its function

Answer 1

• Thick collagen wall - resists bursting
• Thick elastic layer - stretches and recoils to maintain pressure
• Thick smooth muscle layer - contracts/relaxes to constrict/dilate the lumen to control blood flow
• Smaller lumen than veins to maintain pressure

Question 2

Explain the structure of arterioles

Answer 2

• Relatively thicker muscle layer and lumen compared to arteries
• But arteries have a thicker elastic layer to withstand high pressures

Question 3

Explain the structure of venules

Answer 3

• Smaller in diameter and have thinner walls than veins
• Both have valves

Question 4

Describe the formation of tissue fluid

Answer 4

• Formed when high hydrostatic pressure at the arteriole end of a capillary forces plasma out of the capillary and into the interstitial spaces surrounding cells
• Returns to the circulatory system at the venule end of the capillary when oncotic pressure (from plasma proteins) is higher

Question 5

What are the differences in composition of blood, tissue fluid and lymph?

Answer 5

• Blood - RBC’s, WBC’s, platelets and plasma
• Tissue fluid - like plasma with fewer proteins, doesn’t contain red blood cells but may contain some white blood cells
• Lymph - similar to tissue fluid, but contains less oxygen and nutrients and contains many fatty acids and white blood cells

Question 6

Compare the structure of the atria and ventricles

Answer 6

Atria are smaller and have thinner walls as they only need to pump blood to the ventricles

Question 7

Compare the structure of the right and left ventricle

Answer 7

• Left ventricle has a thicker muscular wall as it pumps oxygenated blood to the entire body, requiring more force

Question 8

What are ectopic heartbeat and atrial fibrillation?

Answer 8

• Ectopic heartbeat - extra heartbeats with abnormal rhythm
• Atrial fibrillation - rapid electrical impulses are generated in the atria, causing them to contract fast but not effectively

Question 9

How is carbon dioxide transported in the bloodstream?

Answer 9

• Some dissolves in plasma
• Some binds to haemoglobin in red blood cells to form carbaminohaemoglobin
• Some reacts with water, catalysed by carbonic anhydrase to form carbonic acid, which dissociates to form hydrogen carbonate ions and hydrogen ions
• Plasma transports these ions and red blood cells to the lungs, where they’re converted to carbon dioxide and exhaled

Question 10

Describe the formation of haemoglobinic acid and its importance

Answer 10

• Formed when haemoglobin binds to hydrogen ions
• One way that haemoglobin helps maintain the pH of the blood when the concentration of carbon dioxide is high