june 2019- paper 3

Question 1

how does ultrafiltration occur? (4)

Answer 1

• high hydrostatic pressure
• water, urea, and ions move out
• through gaps in the endothelium
• and through capillary basement membrane

Question 2

how does the AV valve maintain unidirectional flow of blood? (2)

Answer 2

• opens when pressure in atrium is higher than ventricle

- closes when pressure in ventricle is higher than in atrium