Exchange and transport - CIRCULATION/TISSUE FLUID

Question 1

What makes a good transport system?

Answer 1

• A suitable medium to carry materials
• A form of mass transport
• A closed system of vessels to transport medium
• Mechanisms for transporting medium within vessels

Question 2

What is an open circulatory system?

Answer 2

Transport medium is not enclosed within the transport vessels

Question 3

What is a closed circulatory system?

Answer 3

• Blood is confined to the vessels
• Passes through the heart twice in each complete circuit of the body
• Transport medium is enclosed within the transport vessels

Question 4

What is a single circulatory system?

Answer 4

• Blood is pumped from the heart to the gas exchange organ then directly back to the rest of the body
• Only passes through the heart once in a complete circuit

Question 5

What is a double circulatory system?

Answer 5

• Blood is pumped from the heart to the gas exchange organ, back to the heart then to the rest of the body
• Passes through the heart twice in one complete circuit

2 parts:
- Pulmonary circuit where medium is circulated to the lungs to be oxygenated
- Systemic circuit where medium is circulated to the rest of the body to unload oxygen

Question 6

What is the tunica intima?

Answer 6

Endothelial cells + elastic layer

Question 7

What is the tunica media?

Answer 7

Smooth muscle layer

Question 8

What is the tunica externa?

Answer 8

Thick outer fibrous layer

Question 9

Structure related to function of arteries?

Answer 9

• Lumen is narrow to maintain high blood pressure
• Elastic layer stretches (systole) and recoils (diastole) to maintain high blood pressure
• Thick outer layer stops vessel from bursting
• No valves due to pressure forcing blood in one direction

Question 10

Structure related to function of arterioles?

Answer 10

• Lumen is narrow to maintain blood pressure
• No need for thick elastic layer as blood pressure is lower
• Muscle layer is relatively thicker than in arteries to allow greater contraction and therefore restriction of blood flow to control the movements of blood flowing into capillaries

Question 11

Structure related to function of veins?

Answer 11

• Small muscle layer (constriction/dilation cannot control flow of blood so no need for it to be thick)
• Thin elastic layer as blood pressure is too low to create a recoil action
• Thinner outer layer as pressure is too low to burst vessel
• Valves to prevent backflow of blood due to low blood pressure

Question 12

Structure to function of capillaries?

Answer 12

• Thin epithelial layer for shorter diffusion distance
• Lots of them (highly branched) for increased SA
• Narrow diameter so no cell is far from a capillary, hence short diffusion distance
• Narrow lumen therefore RBCs squeezed through so even closer to the cells
• Spaces between the epithelial cells allow WBCs to escape into tissue

Question 13

Suggest two changes that will be made to the blood by the arterioles and explain why these changes are necessary?

Answer 13

• Decreased rate of blood flow to increase time for diffusion to occur
• Decreased pressure to prevent high pressure bursting the capillaries

Question 14

What is tissue fluid formed of?

Answer 14

• Glucose
• Amino acids
• Fatty acids
• Ions in solution
• Oxygen

Question 15

What is homeostasis and why is it important in regards to tissue fluid?

Answer 15

• The regulation of internal conditions in response to stimuli
• Important to maintain tissue fluid as it is the immediate environment of cells
• Important to maintain temperature, pH and water potential

Question 16

What is hydrostatic pressure and where is it highest?

Answer 16

• Pressure exerted by the water inside the capillaries
• Highest at the arterial end and lowest at the venule end

Question 17

How is tissue fluid formed?

Answer 17

• High hydrostatic pressure at the arterial end
• Causes tissue fluid to move out of blood plasma from the capillary into tissue fluid surrounding cells
• Area of high hydrostatic pressure to area of low hydrostatic pressure

Question 18

High blood pressure leads to an accumulation of tissue fluid. Explain how. (PPQ 3 marks)

Answer 18

• High blood pressure causes high hydrostatic pressure at arteriole end
• Forcing water out capillaries and into the tissue surrounding the cells
• More tissue fluid formed then is reabsorbed

Question 19

The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriole end of the capillary. Explain why. (PPQ 3 marks)

Answer 19

• Water has left the capillary
• Proteins are too large to leave the capillary
• Increases concentration of blood proteins, hence decreasing water potential